CENTRE DE DOCUMENTATION DE L’INSTITUT GEOGRAPHIQUE NATIONAL centrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededo cumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentatio ndel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNce SELECTION D’ARTICLES SIGNALES entre le 1 ER MARS et le 30 AVRIL 2011 6 MAI 2011 bulletin 56 centrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededo CENTRE DE DOCUMENTATION DE L'INSTITUT GEOGRAPHIQUE NATIONAL 6/8 Avenue Blaise Pascal - Cité Descartes - Champs sur Marne 77455 Marne la Vallée cedex 2 Tél. : 01.64.15.32.80 Télécopie : 01.64.15.32.84 Mél : [email protected]Site Web : http://www.ensg.ign.fr centrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededocumentationdel'IGNcentrededo
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CENTRE DE DOCUMENTATION DE L’INSTITUT GEOGRAPHIQUE NATIONAL
_______________________________________________________________________________________Articles signalés entre le 1er mars et le 30 avril 2011 par le Centre de Documentation de l’IGN – p. 2
Acquisition d'image
Titre Spectroscopic calibration correlation of field and lab-sized fluorescence LIDAR systems
SPECTRALE, SIGNATURE SPECTRALEN° notice A2010-573Résumé d’auteur A method has been developed to correlate spectral signatures obtained with various
fluorescence LIght Detection And Ranging (LIDAR) systems. A calibrated fluorescence reference target was used to calibrate the spectral response of the LIDAR transmitter channels and obtain their transfer functions. Two LIDAR systems have been spectrally characterized, and corrected signatures for two bioaerosols are presented. The first LIDAR system is the Standoff Integrated Bioserosol Active Hyperspectral Detection field LIDAR developed by Defence R&D Canada. This standoff system uses a 351-nm pulsed laser in a monoaxial design. The second system is a lab-sized aerosol chamber designed to characterize fluorescent aerosols under controlled environmental conditions. The chamber was designed according to classical short-range biaxial LIDAR principles, with the purpose of duplicating the results obtained with field LIDAR systems. Aerosols generated within the chamber are probed by a 355-nm pulsed laser, and autofluorescence spectra are measured with a spectrometer and an intensified charge-coupled device camera. This chamber is used to collect the reference spectra of various fluorescing aerosols and simulants of biological agents. One of the main objectives in using this chamber is to produce and compile a library of instrument-free fluorescing spectra that can be transferred to other LIDAR-based bioaerosol sensors with known optical transfer functions.
Titre Structured Light Scanners: Working Principles, Performance and AccuracyAuteur(s) GEORGOPOULOS (A.), IOANNIDIS (C.) et VALANIS (A.)Source GIM INTERNATIONAL, vol 25, n° 2, [01/02/2011], pp 25 - 27Langue AnglaisMots clés TELEMETRE LASER TERRESTRE, TEST DE PERFORMANCEN° notice A2011-038Résumé d’auteur Laser technology is the flagship for producing accurate digital 3D representations of
objects, but other techniques are also widely used, one of which is structured light scanning. The authors discuss the characteristics of this accurate measuring technique, used primarily for indoor, close-range applications. They also tested a commercially available structured light camera and found the accuracy in line with the manufacturer’s claim of 50 micrometres.
STEREOSCOPIQUE, LASERGRAMMETRIE, LOGICIEL DE TRAITEMENT D'IMAGE, MODELE 3D DE L'ESPACE URBAIN, ORTHOIMAGE INTEGRALE
N° notice A2011-062Résumé d’auteur In cooperation with Diamond Airborne Sensing, the Tiltan company has developed a
highly integrated airborne image data acquisition and photogrammetric processing system. This utilizes digital frame images that have been acquired employing the step framing principle in a convergent oblique mode to produce its stereo-coverage of the terrain. The overlapping stereo-images can then be used to produce true orthophotos and 3D urban models using highly automated photogrammetric image processing techniques.
Titre It's all about elevation: Radar satellites cover our Earth in 3DAuteur(s) RIEGLER (G.)Source GEOINFORMATICS, vol 14, n° 2, [01/03/2011], pp 16 - 14Langue Anglais
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Mots clés IMAGE RADAR MOIREE, IMAGE TANDEM-X, IMAGE TERRASAR-X, INTERFEROMETRIE PAR RADAR A ANTENNE SYNTHETIQUE, MNS TERRASAR-TANDEM-X, MODELE NUMERIQUE DE TERRAIN
N° notice A2011-061Résumé d’auteur With the successful launch of the German radar satellite TanDEM-X on june 21st, 2010, a
new era of global digital elevation information provision has commenced. Together with TerraSAR-X, TanDEM-X forms a high-precision radar interferometer acquiring the data basis for a global homogeneous Digital Elevation Model of unprecedented quality, accuracy, and coverage. This unique dataset will be available for the entire land surface of the Earth from 2014 onwards.
Analyse spatiale
Titre OpenModeller: a generic approach to species’ potential distribution modellingAuteur(s) DE SOUZA MUNOZ (M.), DE GIOVANNI (R.), DE SIQUEIRA (M.) et al.Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 111 - 135Langue AnglaisMots clés DISTRIBUTION SPATIALE, ESPECE VEGETALE, LOGICIEL LIBRE, NICHE ECOLOGIQUE,
POPULATION ANIMALEN° notice A2011-030Résumé d’auteur Species’ potential distribution modelling is the process of building a representation of the
fundamental ecological requirements for a species and extrapolating these requirements into a geographical region. The importance of being able to predict the distribution of species is currently highlighted by issues like global climate change, public health problems caused by disease vectors, anthropogenic impacts that can lead to massive species extinction, among other challenges. There are several computational approaches that can be used to generate potential distribution models, each achieving optimal results under different conditions. However, the existing software packages available for this purpose typically implement a single algorithm, and each software package presents a new learning curve to the user. Whenever new software is developed for species’ potential distribution modelling, significant duplication of effort results because many feature requirements are shared between the different packages. Additionally, data preparation and comparison between algorithms becomes difficult when using separate software applications, since each application has different data input and output capabilities. This paper describes a generic approach for building a single computing framework capable of handling different data formats and multiple algorithms that can be used in potential distribution modelling. The ideas described in this paper have been implemented in a free and open source software package called openModeller. The main concepts of species’ potential distribution modelling are also explained and an example use case illustrates potential distribution maps generated by the framework.
Titre Crime analysis through spatial areal aggregated density patternsAuteur(s) PHILLIPS (P.) et LEE (I.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 49 - 74Langue AnglaisMots clés AGREGATION SPATIALE, ANALYSE SPATIO-TEMPORELLE, DENSITE, DISTRIBUTION
SPATIALE, INFRACTION, MODELE DE DENSITEN° notice A2011-028Résumé d’auteur Intelligent crime analysis allows for a greater understanding of the dynamics of unlawful
activities, providing possible answers to where, when and why certain crimes are likely to happen. We propose to model density change among spatial regions using a density tracing based approach that enables reasoning about large areal aggregated crime datasets. We discover patterns among datasets by finding those crime and spatial features that exhibit similar spatial distributions by measuring the dissimilarity of their density traces. The proposed system incorporates both localized clusters (through the use of context sensitive weighting and clustering) and the global distribution trend. Experimental results validate and demonstrate the robustness of our approach.
Titre Computational method for the point cluster analysis on networksAuteur(s) SUGIHARA (K.), OKABE (A.) et SATOH (T.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 167 - 189Langue Anglais
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Mots clés ANALYSE DE GROUPEMENT, APPROCHE HIERARCHIQUE, DISTANCE EUCLIDIENNE, RESEAU, TACHE CLAIRE
N° notice A2011-032Résumé d’auteur We present a general framework of hierarchical methods for point cluster analysis on
networks, and then consider individual clustering procedures and their time complexities defined by typical variants of distances between clusters. The distances considered here are the closest-pair distance, the farthest-pair distance, the average distance, the median-pair distance and the radius distance. This paper will offer a menu for users to choose hierarchical clustering algorithms on networks from a time complexity point of view.
Titre Interpreting motion events of pairs of moving objectsAuteur(s) GOTTFRIED (B.)Source GEOINFORMATICA, vol 15, n° 2, [01/04/2011], pp 247 - 271Langue AnglaisMots clés ANALYSE SPATIALE, DONNEES LOCALISEES, LANGAGE DE MODELISATION, OBJET
GEOGRAPHIQUE PONCTUEL, OBJET MOBILE, RAISONNEMENT SPATIALN° notice A2011-086Résumé d’auteur When accumulating large quantities of positional data with ubiquitous positioning
techniques, methods are required that can efficiently make use of these data. This work proposes a representation that approximates motion events of pairs of objects. It is shown how the employment of formal grammars enables the interpretation of such motion events. This is accomplished by composing motion patterns into specific qualitative features. In particular, the change of relative directions defines characteristic motion events.
Titre Qualitative change detection using sensor networks based on connectivity information
DONNEES SPATIOTEMPORELLES, EXPLOITATION DE CAPTEURS WEB, GAZ, RESEAU DE CAPTEURS, TRAITEMENT DE DONNEES
N° notice A2011-087Résumé d’auteur The research reported in this paper uses wireless sensor networks to provide salient
information about spatially distributed dynamic fields, such as regional variations in temperature or concentration of a toxic gas. The focus is on deriving qualitative descriptions of salient changes to areas of high-activity that occur during the temporal evolution of the field. The changes reported include region merging or splitting, and hole formation or elimination. Such changes are formally characterized, and a distributed qualitative change reporting (QCR) approach is developed that detects the qualitative changes simply based on the connectivity between the sensor nodes without location information. The efficiency of the QCR approach is investigated using simulation experiments. The results show that the communication cost of the QCR approach in monitoring large-scale phenomena is an order of magnitude lower than that using the standard boundary-based data collection approach, where each node is assumed to have its location information.
Applications de géodésie spatiale
Titre The distress alerting satellite system: Taking the search out of search and rescueAuteur(s) AFFENS (D.), DREIBELBIS (R.), MENTALL (J.) et THEODORAKOS (G.)Source GPS WORLD, vol 22, n° 1, [01/01/2011], pp 72 - 79Langue AnglaisMots clés BALISE, CONSTELLATION GALILEO, CONSTELLATION GLONASS, CONSTELLATION GPS,
IMAGE SAR, MEDECINE HUMAINE, POSITIONNEMENT PAR GNSS, RADAR A ANTENNE SYNTHETIQUE, URGENCE
N° notice A2011-054Résumé d’éditeur In 1997, a Canadian government study determined that an improved search and rescue
system would be one based on medium-Earth orbit satellites, which can provide full global coverage, can determine beacon location, and would need fewer ground stations.
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This month's column examines the architecture of the GPS-based Distress Alerting Satellite System and takes a look at early test results.
Titre LBS : le marché tant attenduAuteur(s) BLOMAC (F. DE)Source SIG LA LETTRE, n° 125, [01/03/2011], pp 2 - 6Mots clés APPAREIL PORTABLE, NAVIGATION AUTOMOBILE, NAVIGATION PEDESTRE, SERVICE
FONDE SUR LA POSITIONN° notice A2011-082Résumé d’auteur Le marché des LBS fourmille d'idées et d'applications nouvelles chaque jour. Il est
désormais bien loin le temps où TomTom régnait en maître absolu avec les PND de voiture (personal navigation device ou portable navigation device). Désormais, l'heure est à l'innovation tous azimuts. Mais le marché reste en grande partie à construire dans un univers en perpétuelle évolution.
SPECTRALE, SOUS-BOISN° notice A2011-046Résumé d’auteur This paper attempts to quantify soil moisture in various canopy cover conditions using n-
dimensional spectral signatures, including land surface temperature, vegetation index, albedo, and others. First, the feature vector between the pixels and various moisture contents was indentified. Normalization of the varying distance from a user-defined initial state to any pixel location, and coefficients related with n-dimensional spectral feature space were calculated, assigning weights to each parameter. Then, a soil moisture index was developed using a linear combination of the first order polynomials. The Extended Fourier Amplitude Sensitivity Test (eFAST) was used to calculate the relative variance contribution of model input parameters to the variance of soil moisture predictions. Results derived from satellite data including Enhanced Thematic Mapper Plus (ETM+) and the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery demonstrated significant correlations between the index and soil moisture obtained for different ecosystems and vegetation cover. The best agreement, the coefficient of determination (R2), between the index and soil moisture were 0.58 and 0.65 for ETM+ and MODIS data, respectively. eFAST sensitivity analysis indicates that land surface temperature might be the most determinant factor in soil moisture estimation, then albedo, followed by NDVI.
IMAGE RADAR, IMAGE SPATIALE, OUTIL D'AIDE A LA DECISION, RISQUE NATUREL, SECURITE CIVILE, SYSTEME D'INFORMATION GEOGRAPHIQUE
N° notice A2011-060Résumé d’auteur Today, geospatial imagery is a valuable source about the world around us. Its widespread
availability provides us with timely and accurate data about virtually anything occurring on the Earth's surface, from natural phenomena and disasters to events caused by human activity, such as military operations. The use of imagery is far reaching, in both private industry and government applications - its value now being additionally enhanced as it becomes an effective source of input to GIS, allowing like never before the ability to verify the validity or quantity of field work, justify investment expenses and aid in decision making.
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Applications photogrammétriques
Titre Using aerial imagery and GIS in automated building footprint extraction and shape recognition for earthquake risk assessment of urban inventories
Auteur(s) SAHAR (L.), MUTHUKUMAR (S.) et FRENCH (S.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 48, n° 9, [01/09/2010], pp 3511 -
3520Langue AnglaisMots clés EXTRACTION AUTOMATIQUE, IMAGE AERIENNE, RECONNAISSANCE DE FORMES,
RECONSTRUCTION 2D DU BATI, RECONSTRUCTION AUTOMATIQUE, RISQUE NATUREL, SEISME, SYSTEME D'INFORMATION GEOGRAPHIQUE, TRAITEMENT AUTOMATIQUE DE DONNEES
N° notice A2010-572Résumé d’auteur Earthquakes cause massive loss of property and lives, and mitigating their potential
effects requires accurate modeling and simulation of their impacts. Earthquake building damage modeling and risk assessment applications require accurate accounts of inventories at risk and their attributes such as structure type, usage, size, number of stories, shape, year built, value, etc. This paper describes the development of algorithms for automatically extracting and recognizing 2-D building shape information using integrated aerial imagery processing and Geographic Information Systems data. We use vector parcel geometries and their attributes to simplify the building extraction task by limiting the processing geography. Extraction is significantly improved by innovatively weighting the histograms. Extracted buildings are cleaned, simplified, and run through 2-D shape recognition routines that classify the footprint. We discuss reasons for successes and failures in both extraction and recognition.
Titre 3D City Models: Supporting Tool for Urban Planning and DesignAuteur(s) PARMEHR (E.), AFARY (A.) et BASIRI (B.)Source GIM INTERNATIONAL, vol 25, n° 2, [01/02/2011], pp 29 - 31Langue AnglaisMots clés 1:500, CARTE TOPOGRAPHIQUE, DONNEES LOCALISEES 2D, DONNEES LOCALISEES 3D,
IMAGE AERIENNE, MODELE 3D DE L'ESPACE URBAIN, PLANIFICATION URBAINEN° notice A2011-039Résumé d’auteur Abasabad in the north of Tehran has been designated a development area to serve the
millions of people living in the metropolis. In order to progress from general zoning plan to detailed designs of buildings, roads, green zones and playgrounds, accurate and detailed geo-data was required, preferably in the form of large-scale digital maps and 3D city models. The authors describe how they produced this type of 2D and 3D geo-data using high-resolution digital aerial imagery and scale 1:500 maps.
Titre City model enrichmentAuteur(s) SMART (P.), QUINN (J.) et JONES (C.)Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 223 -
234Langue AnglaisMots clés DONNEES LOCALISEES LIBRES, MODELE 3D DE L’ESPACE URBAIN, POINT D'APPUI,
POLYGONE, RECONSTRUCTION 3D DU BATI, WEB 2.0N° notice A2011-075Résumé d’auteur The combination of mobile communication technology with location and orientation aware
digital cameras has introduced increasing interest in the exploitation of 3D city models for applications such as augmented reality and automated image captioning. The effectiveness of such applications is, at present, severely limited by the often poor quality of semantic annotation of the 3D models. In this paper, we show how freely available sources of georeferenced Web 2.0 information can be used for automated enrichment of 3D city models. Point referenced names of prominent buildings and landmarks mined from Wikipedia articles and from the OpenStreetMaps digital map and Geonames gazetteer have been matched to the 2D ground plan geometry of a 3D city model. In order to address the ambiguities that arise in the associations between these sources and the city model, we present procedures to merge potentially related buildings and implement fuzzy matching between reference points and building polygons. An experimental evaluation demonstrates the effectiveness of the presented methods.
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Titre Acquisition of the 3D boundary of the Triglav glacier from archived non-metric panoramic images
PANORAMIQUE, DONNEES LOCALISEES 3D, GLACIER, MODELE NUMERIQUE DE SURFACE, MONTAGNE, NUMERISATION DE PHOTOGRAPHIE, PHOTOGRAPHIE ARGENTIQUE, VOLUME (grandeur)
N° notice A2011-079Résumé d’auteur A panoramic, non-metric, Horizont camera has been used for regular, monthly, close-
range photography of the rapidly retreating Triglav glacier in Slovenia since 1976. The unfavourable geometry of the convergent images taken from the two camera stations has made any direct stereoscopic observation and recording impossible. The aim of this research was to define the most useful method for acquiring 3D data from these panoramic, convergent images. The Horizont camera was calibrated and three methods were then tested: the generation of pseudo-orthophotographs, the application of 2D clinometry and the interactive orientation of a detailed digital elevation model (DEM) on the images. The third turned out to be the only method suitable for determining the boundary of the Triglav glacier. The interactive orientation of a detailed DEM on the Horizont images is described in detail. The 3D glacier boundary can be acquired from individual Horizont images (camera stations A and B) enabling the computation of the glacier’s area and theoretical volume. By repeating the glacier boundary acquisition for different orientation parameters, the standard deviations of the glacier area and theoretical volume were computed. Because of the more precise average area and volume measurements achieved with the camera station B images, only these were chosen for the glacier disappearance study. Every third year between 1976 and 2005 the Horizont images were used to compute the changes in the area and volume of the glacier. The glacier area was found to have reduced to 8% of its earlier size, from 15 ha in 1976 to 1·2 ha in 2000. However, owing to harsher than average winters since then the decline in the glacier area was found to have slowed in the past decade (2000 to 2009). The glacier’s theoretical volume decreased roughly exponentially from 1976 to 2005
Titre Minimising systematic error surfaces in digital elevation models using oblique convergent imagery
Auteur(s) WACKROW (R.) et CHANDLER (J.)Source PHOTOGRAMMETRIC RECORD, vol 26, n° 133, [01/03/2011], pp 16 - 31Langue AnglaisMots clés ANGLE DE PRISE DE VUE, DEFORMATION DE SURFACE, ERREUR SYSTEMATIQUE,
INONDATION, MODELE NUMERIQUE DE SURFACE, PHOTOGRAMMETRIE TERRESTREN° notice A2011-076Résumé d’auteur There are increasing opportunities to use consumer-grade digital cameras, particularly if
accurate spatial data can be captured. Research recently conducted at Loughborough University identified residual systematic error surfaces or domes discernible in digital elevation models (DEMs). These systematic effects are often associated with such cameras and are caused by slightly inaccurate estimated lens distortion parameters. A methodology that minimises the systematic error surfaces was therefore developed, using a mildly convergent image configuration in a vertical perspective. This methodology was tested through simulation and a series of practical tests. This paper investigates the potential of the convergent configuration to minimise the error surfaces, even if the geometrically more complex oblique perspective is used. Initially, simulated data was used to demonstrate that an oblique convergent image configuration can minimise remaining systematic error surfaces using various imaging angles. Additionally, practical tests using a laboratory testfield were conducted to verify results of the simulation. The need to develop a system to measure the topographic surface of a flooding river provided the opportunity to verify the findings of the simulation and laboratory test using real data. Results of the simulation process, the laboratory test and the practical test are reported in this paper and demonstrate that an oblique convergent image configuration eradicates the systematic error surfaces which result from inaccurate lens distortion parameters. This approach is significant because by removing the need for an accurate lens model it effectively improves the accuracies of digital surface representations derived using
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consumer-grade digital cameras. Carefully selected image configurations could therefore provide new opportunities for improving the quality of photogrammetrically acquired data.
Applications SIG
Titre Du bruit des infrastructures au plan de prévention du bruit dans l'environnement : Bruit : comment agir?
Auteur(s) GARCIA (C.)Source TECHNI.CITÉS, n° 198, [08/11/2010], 7 pMots clés BRUIT AUDITIF, CARTOGRAPHIE DU BRUIT, DIRECTIVE EUROPEENNE, LUTTE CONTRE LE
BRUIT, SURVEILLANCE SANITAIRE, SYSTEME D'INFORMATION GEOGRAPHIQUEN° notice A2010-389Résumé d’auteur L'aménagement du territoire et les progrès technologiques ont permis aux Français de
réduire les distances géographiques tout en favorisant l'accès à la voiture. Conséquence, en dix ans, le nombre de points noirs bruit n'a pas vraiment diminué, 200 000 logements étant toujours exposés à des niveaux sonores importants. La directive européenne sur l'évaluation du bruit dans l'environnement marque toutefois un tournant dans l'évaluation des politiques publiques. De nouvelles stratégies, de nouveaux moyens émergent peu à peu.
Titre SIG et 3D au service des villes vertesAuteur(s) NEDEY (F.)Source GAZETTE DES COMMUNES (LA), vol 2010, n° 43, [15/11/2010], pp 64 - 66Mots clés AMENAGEMENT URBAIN, CARTE DE LA VEGETATION, DONNEES LOCALISEES 3D, OUTIL
D'AIDE A LA DECISION, SIMULATION 3D, SYSTEME D'INFORMATION GEOGRAPHIQUEN° notice A2010-570Résumé d’auteur Les SIG et la simulation 3D sont des moyens d'expertise pour les projets
d'aménagement. Des cadastres verts numériques sont élaborés.
Titre Optimal routefinding with unlimited possible directions of movementAuteur(s) DEAN (D.)Source TRANSACTIONS IN GIS, vol 15, n° 1, [01/02/2011], pp 87 - 107Langue AnglaisMots clés BASE DE DONNEES LOCALISEES, CALCUL D'ITINERAIRE, DONNEES MAILLEES, METHODE
N° notice A2011-059Résumé d’auteur Finding optimal paths through raster databases is limited by the very nature of the raster
data itself. This limitation restricts the possible directions of movement through the database from the infinite possibilities found in the real world to a finite number of possibilities defined by the cell-to-cell movement that characterizes raster databases. A Triangulated Irregular Network (TIN)-based alternative optimization model that allows unlimited possible directions of movement is presented. While not without its own limitations, this new approach offers a viable alternative to raster-based optimal routefinding.
Titre AAM modelling aids Brisbane floods crisisAuteur(s) BLACKBURN (J.)Source GEO:GEOCONNEXION INTERNATIONAL, vol 10, n° 4, [01/04/2011], pp 32 - 33Langue AnglaisMots clés ACQUISITION DE DONNEES, INONDATION, MEDIA, MODELE DE SIMULATION, SIMULATION
3DN° notice A2011-091Résumé d’auteur AAM floods simulation models in 3D highlight Brisbane flood conditions for media.
Titre Flood mapping system for FlandersAuteur(s) SIGGISSource GEO:GEOCONNEXION INTERNATIONAL, vol 10, n° 4, [01/04/2011], pp 34 - 35Langue AnglaisMots clés ARCGIS, CARTOGRAPHIE DES RISQUES, INONDATION, SERVICE WEB GEOGRAPHIQUEN° notice A2011-090
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Résumé d’éditeur SIGGIS developped a mapping web application to provide a flood mapping system for the Flemish environmental society (Vlalmse milieu maatschappij), complete with editing functions - within one week - and completed it with an ArcGis based model for perimeter corrections.
Base de donnees localisées
Titre Modelling and analysing 3D buildings with a primal/dual data structureAuteur(s) BOGUSLAWSKI (P.), GOLD (C.M.) et LEDOUX (H.)Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 188 -
197Langue AnglaisMots clés BATI, CITYGML, DUALITE DE POINCARE, GRAPHE, MODELE TOPOLOGIQUE DE DONNEES,
MODELISATION 3D, STRUCTURE DE DONNEES LOCALISEESN° notice A2011-072Résumé d’auteur While CityGML permits us to represent 3D city models, its use for applications where
spatial analysis and/or real-time modifications are required is limited since at this moment the possibility to store topological relationships between the elements is rather limited and often not exploited. We present in this paper a new topological data structure, the dual half-edge (DHE), which permits us to represent the topology of 3D buildings (including their interiors) and of the surrounding terrain. It is based on the idea of simultaneously storing a graph in 3D space and its dual graph, and to link the two. We propose Euler-type operators for incrementally constructing 3D models (for adding individual edges, faces and volumes to the model while updating the dual structure simultaneously), and we also propose navigation operators to move from a given point to all the connected planes or polyhedra for example. The DHE also permits us to store attributes to any element. We have implemented the DHE and have tested it with different CityGML models. Our technique allows us to handle important query types, for example finding the nearest exterior exit to a given room, as in disaster management planning. As the structure is locally modifiable the model may be adapted whenever a particular pathway is no longer available. The proposed DHE structure adds significant analytic value to the increasingly popular CityGML model.
Titre Aggregation of LoD 1 building models as an optimization problemAuteur(s) GUERCKE (R.), GOTZELMANN (T.), BRENNER (C.) et SESTER (M.)Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 209 -
DU BATI, MODELISATION 3D, RECONSTRUCTION 3D DU BATIN° notice A2011-074Résumé d’auteur 3D city models offered by digital map providers typically consist of several thousands or
even millions of individual buildings. Those buildings are usually generated in an automated fashion from high resolution cadastral and remote sensing data and can be very detailed. However, not in every application such a high degree of detail is desirable. One way to remove complexity is to aggregate individual buildings, simplify the ground plan and assign an appropriate average building height. This task is computationally complex because it includes the combinatorial optimization problem of determining which subset of the original set of buildings should best be aggregated to meet the demands of an application. In this article, we introduce approaches to express different aspects of the aggregation of LoD 1 building models in the form of Mixed Integer Programming (MIP) problems. The advantage of this approach is that for linear (and some quadratic) MIP problems, sophisticated software exists to find exact solutions (global optima) with reasonable effort. We also propose two different heuristic approaches based on the region growing strategy and evaluate their potential for optimization by comparing their performance to a MIP-based approach.
Titre A multiple representation data structure for dynamic visualisation of generalised 3D city models
Auteur(s) MAO (B.), BAN (Y.) et HARRIE (L.)
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Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 198 - 208
Langue AnglaisMots clés REPRESENTATION MULTIPLE, STRUCTURE DE DONNEES LOCALISEES, VISUALISATION
DYNAMIQUEN° notice A2011-073Résumé d’auteur In this paper, a novel multiple representation data structure for dynamic visualisation of
3D city models, called CityTree, is proposed. To create a CityTree, the ground plans of the buildings are generated and simplified. Then, the buildings are divided into clusters by the road network and one CityTree is created for each cluster. The leaf nodes of the CityTree represent the original 3D objects of each building, and the intermediate nodes represent groups of close buildings. By utilising CityTree, it is possible to have dynamic zoom functionality in real time. The CityTree methodology is implemented in a framework where the original city model is stored in CityGML and the CityTree is stored as X3D scenes. A case study confirms the applicability of the CityTree for dynamic visualisation of 3D city models.
Titre Connectivity in the regular polytope representationAuteur(s) THOMPSON (R.) et VAN OOSTEROM (P.)Source GEOINFORMATICA, vol 15, n° 2, [01/04/2011], pp 223 - 246Langue AnglaisMots clés ALGEBRE DE BOOLE, BASE DE DONNEES LOCALISEES, CONNECTIVITE, OBJET
GEOGRAPHIQUE, RAISONNEMENT SPATIAL, RELATION TOPOLOGIQUE, TRAITEMENT GEOMETRIQUE DE DONNEES
N° notice A2011-088Résumé d’auteur In order to be able to draw inferences about real world phenomena from a representation
expressed in a digital computer, it is essential that the representation should have a rigorously correct algebraic structure. It is also desirable that the underlying algebra be familiar, and provide a close modelling of those phenomena. The fundamental problem addressed in this paper is that, since computers do not support real-number arithmetic, the algebraic behaviour of the representation may not be correct, and cannot directly model a mathematical abstraction of space based on real numbers. This paper describes a basis for the robust geometrical construction of spatial objects in computer applications using a complex called the “Regular Polytope”. In contrast to most other spatial data types, this definition supports a rigorous logic within a finite digital arithmetic. The definition of connectivity proves to be non-trivial, and alternatives are investigated. It is shown that these alternatives satisfy the relations of a region connection calculus (RCC) as used for qualitative spatial reasoning, and thus introduce the rigor of that reasoning to geographical information systems. They also form what can reasonably be termed a “Finite Boolean Connection Algebra”. The rigorous and closed nature of the algebra ensures that these primitive functions and predicates can be combined to any desired level of complexity, and thus provide a useful toolkit for data retrieval and analysis. The paper argues for a model with two and three-dimensional objects that have been coded in Java and which implement a full set of topological and connectivity functions which is shown to be complete and rigorous.
Cadastre ancien
Titre Un cadastre de province méconnu : le cadastre d'Alsace (1760-1764)Auteur(s) TSCHAEN (L.)Source XYZ, n° 126, [01/03/2011], pp 43 - 56Mots clés CADASTRE ANCIEN, HISTOIRE DE LA CARTOGRAPHIEN° notice A2011-099Résumé d’auteur Vers le milieu du XVIIIe siècle a été réalisé dans la province d'Alsace rattachée au
royaume de France par les traités de Westphalie de 1648, un cadastre fiscal méconnu des ouvrages modernes qui font autorité en matière de cadastre français. Ceci est notamment le cas de l'ouvrage de base sur le "Cadastre français" édité en 1953. Il en est de même d'un ouvrage plus récent sur son histoire et sa rénovation qui, lui, date de 1990. Puis, un récent article sur le cadastre napoléonien paru dans cette revue cite, comme réussite technique antérieure, le cadastre de la généralité de l'Ile-de-France en ignorant le cadastre de la province d'Alsace tout aussi performant, mais qui lui est antérieur d'une quinzaine d'années et a peut-être servi de modèle. Pourtant, ce cadastre
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exécuté en un temps record de 1760 à 1764, à l'initiative de l'intendant d'Alsace, Jacques Pineau baron de Lucé, en vue de parvenir à une plus juste répartition de la charge fiscale, a été réalisé avec l'agrément du roi "avant qu'il ne s'agisse de pareille opération pour la totalité du royaume". Il a ainsi été commencé quelques années avant la publication de l'édit d'avril 1763 ordonnant le dénombrement des biens-fonds du royaume et la déclaration du roi du 21 décembre suivant concernant le cadastre général qu'il comptait entreprendre dans son royaume en vue "d'exclure tout arbitraire et toute inégalité dans la répartition des impositions... " Seule Mireille Touzery cite dans cette revue l'existence de ce cadastre, il est vrai, avec une petite erreur de date.
Cadastre étranger
Titre Customary tenure and good governanceAuteur(s) ARKO-ADJEI (A.)Source GIM INTERNATIONAL, vol 25, n° 3, [01/03/2011], pp 27 - 31Langue AnglaisMots clés ACCES AUX DONNEES LOCALISEES, AMENAGEMENT DU TERRITOIRE, COUTUME, DROIT
COUTUMIER, GESTION FONCIERE, INSTITUTION ADMINISTRATIVEN° notice A2011-066Résumé d’auteur Although customary tenure institutions come under considerable strain and their functions
tend to be weakened by existence of a statutory institutional framework, many people in peri-urban areas continue to rely on such arrangements for land delivery. These institutions maintain their traditional power and social responsability for allocating the right to use land, resolve conflicts, and carry out overall management of customary land. Yet little attention has been paid to whether or not the activities of these indigenous institutions meet good governance objectives in land administration. The issue has been studied in Ghana.
Cartographie
Titre La saga des CassiniAuteur(s) BEZES (B.) et DURANTHON (M.)Source L'ALPE, n° 52, [01/03/2011], pp 66 - 75Mots clés CARTE DE CASSINI, TOPONYMIE LOCALE, TRIANGULATION DES CASSININ° notice 10894Résumé d’auteur Depuis la fin du 17e siècle jusqu'au début du 19e siècle, les Cassini ont dessiné le
territoire de la France avec une précision inégalée jusqu'alors. Ces trésors scientifiques et artistiques sont conservés à la Cartothèque de l'Institut Géographique National.
Titre Du manuel au numérique pour la cartographie aux moyennes échelles : L'exemple des cartes au 1/100 000 en France
Auteur(s) LECORDIX (F.)Source BULLETIN DES SCIENCES GÉOGRAPHIQUES INCT, n° 25, [01/06/2010], pp 42 - 51Mots clés 1:100.000, BD CARTO, CARTE TOP 100, CHAINE DE PRODUCTION, GENERALISATION
CARTOGRAPHIQUE AUTOMATISEE, MISE A JOUR AUTOMATIQUE, MOYENNE ECHELLE, PLACEMENT AUTOMATIQUE DES ECRITURES
N° notice A2010-577Résumé d’auteur L'Institut Géographique National (France) produit depuis de nombreuses années une
série de cartes au 1/100 000 sur l'ensemble de la France. Historiquement réalisée par des procédés manuels, cette série a pu basculer en mode numérique grâce aux recherches que l'IGN a lancé, à partir des années 1990, pour automatiser la production de ses cartes par dérivation, des bases de données géographiques, comme la BD Carto® de l'IGN. Après une phase de recherche de 10 ans sur la généralisation, le placement des écritures et la mise à jour automatique, l'IGN est passé à une phase d'industrialisation des recherches par l'intermédiaire du projet Carto2001 qui a permis, en 2004, d'obtenir une chaîne de production de la nouvelle Top 100 au 1/100 000. Après un passage de relais au service de production, cette chaîne a permis de produire une base cartographique France entière au 1/100 000 et d'extraire les 76 feuilles de cette nouvelle série qui ont toutes été réalisées avant fin 2009. Désormais, cette phase cartographique et ces feuilles sont mises à jour par un mécanisme de propagation des mises à jour effectuées dans la BD Carto®. Ce texte permet de suivre l'évolution de l'arrivée de cette
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nouvelle chaîne de production numérique qui transforme radicalement les processus de production cartographique utilisés jusqu'alors.
Titre 100 ans d'"Atlas mondial suisse" et nouvel "Atlas mondial suisse interactif"Auteur(s) CRON (J.), HABERLING (C.), HURNI (L.) et MOLL (P.)Source GÉOMATIQUE SUISSE, vol 109, n° 1, [01/01/2011], pp 8 - 10Mots clés ATLAS NATIONAL, ATLAS NUMERIQUE, CARTE THEMATIQUE, CARTE TOPOGRAPHIQUEN° notice A2011-055Résumé d’auteur L'Atlas mondial suisse fête son centenaire par une nouvelle édition. La version imprimée
traditionnelle a été réactualisée pour l'occasion et se double désormais d'un "Atlas mondial suisse interactif", novateur et à base Internet.
Titre Genealogy that counts: using content analysis to explore the evolution of persuasive cartography
CONCEPTION CARTOGRAPHIQUE, HISTOIRE DE LA CARTOGRAPHIE, PROPAGANDE, SEMIOLOGIE GRAPHIQUE
N° notice A2011-089Résumé d’auteur Maps are often used for persuasive purposes. Yet little is known about whether or not
different persuasive map producers use similar cartographic techniques or about how such techniques have evolved through time. This article explores the genealogy of persuasive map design by analyzing 256 such maps published since 1800. Quantitative content analysis is used to break down each map among 190 contextual, data, design, and layout variables. Cross-tabulations and descriptive statistics are used to test whether and how the characteristics of persuasive maps have changed over time and differ by type of producer. The results illustrate that although some persuasive techniques have changed over time and by producer, most techniques are recurring and used by all types of producers. The results imply that different techniques of persuasive cartography are largely timeless, regardless of producer or medium. It is also argued that content analysis may prove a useful method for other research in map genealogy.
Géodésie spatiale
Titre Analyse des séries temporelles SLR du géocentre et des EOP basées sur les mesures des satellites LAGEOS1/2 et Starlette
Auteur(s) GOURINE (B.), KAHLOUCHE (S.) et GHEZALI (B.)Source BULLETIN DES SCIENCES GÉOGRAPHIQUES INCT, n° 25, [01/06/2010], pp 2 - 13Mots clés ANALYSE DIACHRONIQUE, DONNEES TLS, ELEMENT D'ORIENTATION EXTERNE,
GEOCENTRE, LAGEOS, SERIE TEMPORELLE, STARLETTE, TELEMETRIE LASER SUR SATELLITE, VARIANCE
N° notice A2010-576Résumé d’auteur L'objectif de cet article est d'étudier l'impact des mesures laser (SLR) du satellite bas
Starlette dans la détermination précise des produits geodésiques (EOP et géocentre), sur une période de 14 ans (1993-2007). Les résultats ont montré que la précision sur les trois composantes de la translation (Mouvement du géocentre), est de l'ordre de 4 à 5 mm pour les solutions LAGEOS1/2 et Starlette, respectivement. Concernant les EOP, les écarts-types des solutions LAGEOS1/2 et Starlette sont respectivement de l'ordre de 0.14 et 0.20 mas (~4-6mm) en coordonnées du pôle, et de 0.01 et 0.02 ms (~5-10 mm) en temps (UTI et LOD). L'analyse des résultats est basée d'une part, sur l'analyse fréquentielle, et d'autre part, sur l'étude du bruit des séries temporelles des paramètres d'intérêt. Des termes saisonniers sont estimés, de l'ordre de quelques mm, sur les composantes du géocentre en comparaison avec des modèles géodynamiques. Le type de bruit dominant est le bruit blanc, avec un niveau de l'ordre de 2mm. Le signal périodique des EOP est décomposé en termes interannuel, annuel et courtes périodes. Le bruit de scintillation est le bruit caractérisant des séries temporelles des EOP avec un niveau de l'ordre de 4 et 15 mm en coordonnées du pôle et en LOD, respectivement, pour la solution Starlette.
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Titre Integer least-squares theory for the GNSS compassAuteur(s) TEUNISSEN (P.)Source JOURNAL OF GEODESY, vol 84, n° 7, [01/07/2010], pp 433 - 447Langue AnglaisMots clés ALTITUDE, AMBIGUITE ENTIERE, DONNEES GNSS, METHODE DES MOINDRES CARRES,
POSITIONNEMENT PAR GNSS, RESOLUTION D'AMBIGUITEN° notice A2010-569Résumé d’auteur Global navigation satellite system (GNSS) carrier phase integer ambiguity resolution is
the key to high precision positioning and attitude determination. In this contribution, we develop new integer least-squares (ILS) theory for the GNSS compass model, together with efficient integer search strategies. It extends current unconstrained ILS theory to the nonlinearly constrained case, an extension that is particularly suited for precise attitude determination. As opposed to current practice, our method does proper justice to the a priori given information. The nonlinear baseline constraint is fully integrated into the ambiguity objective function, thereby receiving a proper weighting in its minimization and providing guidance for the integer search. Different search strategies are developed to compute exact and approximate solutions of the nonlinear constrained ILS problem. Their applicability depends on the strength of the GNSS model and on the length of the baseline. Two of the presented search strategies, a global and a local one, are based on the use of an ellipsoidal search space. This has the advantage that standard methods can be applied. The global ellipsoidal search strategy is applicable to GNSS models of sufficient strength, while the local ellipsoidal search strategy is applicable to models for which the baseline lengths are not too small. We also develop search strategies for the most challenging case, namely when the curvature of the non-ellipsoidal ambiguity search space needs to be taken into account. Two such strategies are presented, an approximate one and a rigorous, somewhat more complex, one. The approximate one is applicable when the fixed baseline variance matrix is close to diagonal. Both methods make use of a search and shrink strategy. The rigorous solution is efficiently obtained by means of a search and shrink strategy that uses non quadratic, but easy-to-evaluate, bounding functions of the ambiguity objective function. The theory presented is generally valid and it is not restricted to any particular GNSS or combination of GNSSs. Its general applicability also applies to the measurement scenarios (e.g. single-epoch vs. multi-epoch, or single-frequency vs. multi-frequency). In particular it is applicable to the most challenging case of unaided, single frequency, single epoch GNSS attitude determination. The success rate performance of the different methods is also illustrated.
Titre Bilan de journée de la géodésie à l'IGN : première partieAuteur(s) DUQUENNE (F.)Source XYZ, n° 125, [01/12/2010], pp 17 - 17Mots clés GEODESIE SPATIALEN° notice A2010-579Résumé d’auteur Le 14 octobre 2010, l'IGN et le bureau des longitudes ont organisé à Saint-Mandé une
rétrospective des cinquante dernières années de géodésie qui, malgré les problèmes de transport, a réuni 150 personnes. Les participants pourront, comme ceux qui ont manqué l'évènement visualiser le film des conférences et télécharger les présentations en allant sur le site Internet htt://geodesie.ign.fr (informations / nouveautés).
Titre DORIS system: the new ageAuteur(s) AURIOL (A.) et TOURAIN (C.)Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1484 - 1496Langue AnglaisMots clés BALISE DORIS, DORIS, INSTRUMENT EMBARQUE, INTERNATIONAL DORIS SERVICE,
JASON, MESURAGE DE PHASE, ORBITE PRECISE, ORBITOGRAPHIE, PSEUDO-DISTANCE, RECEPTEUR DGXX
N° notice A2010-562Résumé d'auteur The boarding of the first DGXX DORIS instrument on Jason-2 mission gives us the
opportunity to present the improvements that have been implemented on the DORIS system. The goal of this paper is to present information about the new capacities of the DORIS system and to give the current status of its components. An overview of the DORIS system, the International DORIS Service and the Jason-2 satellite mission are first presented. Then the new characteristics of the on-board instrument are detailed. The capacity to track up to seven ground beacons simultaneously dramatically increases the number of measurements performed: a factor of three increase over Jason-1 is observed
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at the altitude of 1330 km. It also increases the diversity of directions of observation and allows low elevation measurements from 0°. The new phase measurements capability allows now phase processing. The instability of the Jason-1 USOs (Ultra-Stable Oven-controlled quartz oscillator) while crossing the South Atlantic Anomaly has been solved by decreasing the sensitivity to radiation by a factor of 10. New features of the on-board software enhance the coastal and inland water altimetry and increase the robustness of the data. The new software also improves the real time orbit accuracy for operational altimetry. The improvements introduced concurrently on the ground segment have also significantly enhanced capability. The new RINEX exchange formats provide simultaneous phase and pseudo-range measurements. The maintenance of the DORIS Beacons Network and the work done by the DORIS Signal Integrity monitoring team lead to an increased availability of the Network from 75% to 90% and so to a more homogenous orbit coverage. All these improvements including the lessons learned during the past 20 years of operations have pushed the DORIS system forward to a New Age.
Titre An inter-comparison of zenith tropospheric delays derived from DORIS and GPS data
DONNEES GPS, ERREUR SYSTEMATIQUE, PROPAGATION TROPOSPHERIQUE, STATION DORIS, STATION GPS, TRAITEMENT DU SIGNAL
N° notice A2010-568Résumé d’auteur Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) and Global
Positioning System (GPS) techniques are similarly affected by propagation delays in the neutral atmosphere (troposphere) and hence make use of similar data processing strategies for reducing this effect. We compare Zenith Tropospheric Delays (ZTDs) estimated from 52 DORIS and GPS station pairs co-located at 35 sites over the 2005–2008 period. We find an overall systematic negative mean bias of -4 mm and a median bias of -2 mm, with a large site-to-site scatter and especially stronger biases over South America, potentially linked to remaining problems related to the South Atlantic Anomaly (SAA) in the current DORIS data processing. The standard deviation of ZTD differences is in the range 4–12 mm over the globe (8 mm on average), with larger values located in the southern hemisphere. The spatial variability of differences is consistent with previous work but remains largely unexplained. DORIS is shown to be much less sensitive to instrumental changes than GPS (only the switch from Alcatel to Starec antenna at Toulouse is detected as an offset of -4 mm in the ZTD time series). On the opposite, discontinuities and spurious annual signals are found in the GPS ZTD solutions. A discontinuity of +5 mm is found on 5 November 2006, linked to the switch from relative to absolute GPS antenna models used in the data processing. The use of modified GPS antennas (e.g. at GODE) or improved antenna models is shown to reduce the spurious annual signal (e.g. from 5 mm to 2 mm at METS). Overall, the agreement between both techniques is good, though DORIS shows a significantly larger random scatter. The high stability and good spatial and temporal coverage make DORIS a potential candidate technique for meteorology and climate studies as long as reasonable time averaging can be applied (e.g. differences are reduced from 8.6 to 2.4 mm with 5-day averages) and no real-time application is considered. This technique could be considered as a potential contributor to Global Geodetic Observing System (GGOS) for climatology.
Titre Refining DORIS atmospheric drag estimation in preparation of ITRF2008Auteur(s) GOBINDDASS (M.L.), WILLIS (P.), MENVIELLE (M.) et DIAMENT (M.)Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1566 - 1577Langue AnglaisMots clés CHAMP GEOMAGNETIQUE, DONNEES DORIS, INTERNATIONAL TERRESTRIAL REFERENCE
FRAME, MODELE ATMOSPHERIQUE, MOUVEMENT DU POLE, SERIE TEMPORELLE, TRAITEMENT DU SIGNAL
N° notice A2010-565Résumé d’auteur In preparation of ITRF2008, all geodetic technique services (VLBI, SLR, GPS and
DORIS) are generating new solutions based on combination of individual analysis centers solutions. These data reprocessing are based on a selection of models, parameterization and estimation strategy unique to each analysis center and to each technique. While a good agreement can be found for models between groups, thanks to the existence of the
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IERS conventions, a great diversity still exist for parameter estimation, allowing possible future improvements in this direction. The goal of this study is to focus on the atmospheric drag estimation used to generate the new DORIS/IGN ignwd08 time series prepared for ITRF2008. We develop here a method to inter-compare different processing strategies. In a first step, by analyzing single-satellite solutions for a few weeks of data but for a large number of possible analysis strategies, we demonstrate that estimating drag coefficient more frequently (typically every 1–2 h instead of previously every 4–8 h) for the lowest DORIS satellites (SPOTs and Envisat) provides better geodetic results for station coordinates and polar motion. This new processing strategy also solved earlier problem found when processing DORIS data during intense geomagnetic events, such as geomagnetic storms. Differences between drag estimation strategies can mostly be found during these few specific periods of extreme geomagnetic activity (few days per year). In such a case, when drag coefficient is only estimated every 6 h or less often for single-satellite solution, a significant degradation in station coordinate accuracy can be observed (120 mm vs. 20 mm) and significant biases arose in polar motion estimation (5 mas vs. 0.3 mas). In a second step, we reprocessed a full year of DORIS data (2003) in a standard multi-satellite mode. We were able to provide statistics on a more reliable data set and to strengthen these conclusions. Our proposed DORIS analysis is easy to implement in all software packages and is now already used by several analysis centers of the International DORIS Service (IDS) when submitting reprocessed solutions for ITRF2008.
Titre Towards development of a consistent orbit series for TOPEX, Jason-1, and Jason-2Auteur(s) LEMOINE (F.), ZELENSKY (N.), WILLIS (P.), ZIEBART (M.), SIBTHORPE (A.), BOY (J.),
LUCERY (V.) et al.Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1513 - 1540Langue AnglaisMots clés DONNEES DORIS, FORCE DE GRAVITATION, IERS TERRESTRIAL REFERENCE FRAME,
INTERNATIONAL TERRESTRIAL REFERENCE FRAME, JASON, ORBITOGRAPHIE, TOPEX-POSEIDON
N° notice A2010-564Résumé d’auteur The TOPEX/Poseidon, Jason-1 and Jason-2 set of altimeter data now provide a time
series of synoptic observations of the ocean that span nearly 17 years from the launch of TOPEX in 1992. The analysis of the altimeter data including the use of altimetry to monitor the global change in mean sea level requires a stable, accurate, and consistent orbit reference over the entire time span. In this paper, we describe the recomputation of a time series of orbits that rely on a consistent set of reference frames and geophysical models. The recomputed orbits adhere to the IERS 2003 standards for ocean and earth tides, use updates to the ITRF2005 reference frame for both the SLR and DORIS stations, apply GRACE-derived models for modeling of the static and time-variable gravity, implement the University College London (UCL) radiation pressure model for Jason-1, use improved troposphere modeling for the DORIS data, and apply the GOT4.7 ocean tide model for both dynamical ocean tide modeling and for ocean loading. The new TOPEX orbits have a mean SLR fit of 1.79 cm compared to 2.21 cm for the MGDR-B orbits. These new TOPEX orbits agree radially with independent SLR/crossover orbits at 0.70 cm RMS, and the orbit accuracy is estimated at 1.5–2.0 cm RMS over the entire TOPEX time series. The recomputed Jason-1 orbits agree radially with the Jason-1 GDR-C orbits at 1.08 cm RMS. The GSFC SLR/DORIS dynamic and reduced-dynamic orbits for Jason-2 agree radially with independent orbits from the CNES and JPL at 0.70–1.06 cm RMS. Applying these new orbits, and using the latest altimeter corrections for TOPEX, Jason-1, and Jason-2 from September 1992 to May 2009, we find a global rate in mean sea level of 3.0 + 0.4 mm/yr.
Titre IDS contribution to ITRF2008Auteur(s) VALETTE (J.J.), LEMOINE (F.), FERRAGE (C.), ALTAMIMI (Z.), WILLIS (P.), YAYA (P.)
et SOUDARIN (L.)Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1614 - 1632Langue AnglaisMots clés ANALYSE DIACHRONIQUE, CORRECTION TROPOSPHERIQUE, DONNEES DORIS, DORIS,
INTERNATIONAL TERRESTRIAL REFERENCE FRAME, MODELE DE GRAVITE TERRESTRE, ORBITOGRAPHIE
N° notice A2010-566
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Résumé d’auteur For the first time, the International DORIS Service (IDS) has produced a technique level combination based on the contributions of seven analysis centers (ACs), including the European Space Operations Center (ESOC), Geodetic Observatory Pecny (GOP), Geoscience Australia (GAU), the NASA Goddard Space Flight Center (GSFC), the Institut Géographique National (IGN), the Institute of Astronomy, Russian Academy of Sciences (INASAN, named as INA), and CNES/CLS (named as LCA). The ACs used five different software packages to process the DORIS data from 1992 to 2008, including NAPEOS (ESA), Bernese (GOP), GEODYN (GAU, GSC), GIPSY/OASIS (INA), and GINS (LCA). The data from seven DORIS satellites, TOPEX/Poseidon, SPOT-2, SPOT-3, SPOT-4, SPOT-5, Envisat and Jason-1 were processed and all the analysis centers produced weekly SINEX files in either variance–covariance or normal equation format. The processing by the analysis centers used the latest GRACE-derived gravity models, forward modelling of atmospheric gravity, updates to the radiation pressure modelling to improve the DORIS geocenter solutions, denser parameterization of empirically determined drag coefficients to improve station and EOP solutions, especially near the solar maximum in 2001–2002, updated troposphere mapping functions, and an ITRF2005-derived station set for orbit determination, DPOD2005. The CATREF software was used to process the weekly AC solutions, and produce three iterations of an IDS global weekly combination. Between the development of the initial solution IDS-1, and the final solution, IDS-3, the ACs improved their analysis strategies and submitted updated solutions to eliminate troposphere-derived biases in the solution scale, to reduce drag-related degradations in station positioning, and to refine the estimation strategy to improve the combination geocenter solution. An analysis of the frequency content of the individual AC geocenter and scale solutions was used as the basis to define the scale and geocenter of the IDS-3 combination. The final IDS-3 combination has an internal position consistency (WRMS) that is 15 to 20 mm before 2002 and 8 to 10 mm after 2002, when 4 or 5 satellites contribute to the weekly solutions. The final IDS-3 combination includes solutions for 130 DORIS stations on 67 different sites of which 35 have occupations over 16 years (1993.0–2009.0). The EOPs from the IDS-3 combination were compared with the IERS 05 C04 time series and the RMS agreement was 0.24 mas and 0.35 mas for the X and Y components of polar motion. The comparison to ITRF2005 in station position shows an agreement of 6 to 8 mm RMS in horizontal and 10.3 mm in height. The RMS comparison to ITRF2005 in station velocity is at 1.8 mm/year on the East component, to 1.2 mm/year in North component and 1.6 mm/year in height.
Titre Efficient estimation of variance and covariance components: A case study for GPS stochastic model evaluation
Auteur(s) LI (B.), SHEN (Y.) et LOU (L.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 49, n° 1, [01/01/2011], pp 203 -
210Langue AnglaisMots clés COVARIANCE, MODELE STOCHASTIQUE, MATRICE DE COVARIANCE, POSITIONNEMENT
PAR GPS, VARIANCEN° notice A2011-049Résumé d’auteur The variance and covariance component estimation (VCE) has been extensively
investigated. However, in real application, the bottleneck problem is the huge computation burden, particularly when many variance and covariance components are involved for many heterogeneous observations. The objective of this paper is to develop a new method allowing the efficient estimation of variance and covariance components. The core of the new method is to construct an orthogonal complement matrix of the coefficient matrix in a Gauss-Markov model using only the coefficient matrix itself. Therefore, the constructed matrix and the computed discrepancies of measurements with each other, which are the essential inputs for the VCE, are invariant in the iterative procedure of computing the variance and covariance components. As a result, the computation efficiency is significantly improved. As a case study, we apply the new method to evaluate the GPS stochastic model with 15 variance and covariance components demonstrating its superior performance. Comparing with the traditional VCE method, the equivalent results are achievable, and the computation efficiency is improved by 34.2%. In the future, much more sensors will be available, and plentiful data can be acquired. Therefore, the new method will be very promising to efficiently estimate the variance and covariance components of the measurements from the different sensors and reasonably balance their contributions to the fused solution, benefiting the higher time-resolution solutions.
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Titre EGNOS gets to workAuteur(s) BOULLETE (F.), KENNES (B.) et al.Source GPS WORLD, vol 22, n° 2, [01/02/2011], pp 34 - 39Langue AnglaisMots clés CORRECTION, CORRECTION DU SIGNAL, EUROPEAN GEOSTATIONARY NAVIGATION
OVERLAY SERVICE, PRECISION DU POSITIONNEMENT, SIGNAL GPS, TELEPHONIE MOBILE, TRAITEMENT DU SIGNAL
N° notice A2011-057Résumé d’auteur GPS corrections from the European Geostationary Navigation Overlay Service can
improve the positioning accuracy and user experience of GPS-enabled mobile phones, even if EGNOS satellites are not visible and even when the GNSS chipset in the phone does not support satellite-based augmentation systems.
Titre Evaluation of the impact of atmospheric pressure loading modeling on GNSS data analysis
Auteur(s) DACH (R.), BOHM (J.), LUTZ (S.), STEIGENBERGER (P.) et BEUTLER (G.)Source JOURNAL OF GEODESY, vol 85, n° 2, [01/02/2011], pp 75 - 91Langue AnglaisMots clés ANALYSE DE DONNEES, DONNEES GNSS, IMPACT SUR LES DONNEES, INTERNATIONAL
GLOBAL NAVIGATION SATELLITE SYSTEMS SERVICE, PRESSION ATMOSPHERIQUE, SIGNAL GNSS
N° notice A2011-067Résumé d’auteur In recent years, several studies have demonstrated the sensitivity of Global Navigation
Satellite System (GNSS) station time series to displacements caused by atmospheric pressure loading (APL). Different methods to take the APL effect into account are used in these studies: applying the corrections from a geophysical model on weekly mean estimates of station coordinates, using observation-level corrections during data analysis, or solving for regression factors between the station displacement and the local pressure. The Center for Orbit Determination in Europe (CODE) is one of the global analysis centers of the International GNSS Service (IGS). The current quality of the IGS products urgently asks to consider this effect in the regular processing scheme. However, the resulting requirements for an APL model are demanding with respect to quality, latency, and—regarding the reprocessing activities—availability over a long time interval (at least from 1994 onward). The APL model of Petrov and Boy (J Geophys Res 109:B03405, 2004) is widely used within the VLBI community and is evaluated in this study with respect to these criteria. The reprocessing effort of CODE provides the basis for validating the APL model. The data set is used to solve for scaling factors for each station to evaluate the geophysical atmospheric non-tidal loading model. A consistent long-term validation of the model over 15 years, from 1994 to 2008, is thus possible. The time series of 15 years allows to study seasonal variations of the scaling factors using the dense GNSS tracking network of the IGS. By interpreting the scaling factors for the stations of the IGS network, the model by (2004) is shown to meet the expectations concerning the order of magnitude of the effect at individual stations within the uncertainty given by the GNSS data processing and within the limitations due to the model itself. The repeatability of station coordinates improves by 20% when applying the effect directly on the data analysis and by 10% when applying a post-processing correction to the resulting weekly coordinates compared with a solution without taking APL into account.
Titre GNSS and the Ionosphere: What's in Store for the Next Solar Maximum?Auteur(s) JENSEN (A.) et MITCHELL (C.)Source GPS WORLD, vol 22, n° 2, [01/02/2011], pp 40 - 48Langue AnglaisMots clés DEGRADATION DU SIGNAL, IONOSPHERE, PERTURBATION IONOSPHERIQUE, QUALITE DU
SIGNAL, SIGNAL ALEATOIRE, SIGNAL GNSS, VENT SOLAIREN° notice A2011-058Résumé d’éditeur Although the sun can become disturbed at any time, solar activity is correlated with the
approximately 11-year cycle of spots on the sun's surface. We are just coming out of a minimum in the solar cycle and headed for the next maximum, predicted to occur around the middle of 2013. How significantly will GNSS users be affected? In this month's column, two ionosphere experts tell us what might be in store.
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Titre U-GPS : un prolongement du système GPS sous terreAuteur(s) CAVERNE (J.B.)Source XYZ, n° 126, [01/03/2011], pp 27 - 36Mots clés ELECTROMAGNETISME, LEVER SOUTERRAIN, POSITIONNEMENT PAR GNSS, PROTOTYPE,
SPELEOLOGIEN° notice A2011-097Résumé d’auteur Le GPS devenu un outil pratique et usuel pour de nombreuses applications, aussi bien
en topographie que dans d'autres domaines. Cependant, nécessitant une communication avec les satellites, il n'est pas utilisable en sous-sol. Ainsi dans les mines, les grottes, les tunnels et d'autres cavités, il faut se passer de ses services. Ce navrant constat pour les professionnels du monde souterrain a amené l'Institut Suisse de Spéléologie et de Kartstologie (ISSKA) à décider de mettre sur pied un moyen de positionnement direct de points en souterrain. Ensuite, grâce à des partenaires experts en microtechnique, l'U-GPS a pu voir le jour, rendant possible le suivi en temps réel, depuis la surface sur ordinateur, d'un émetteur se déplaçant dans une grotte. Afin de gagner en efficacité et en précision, ce tout nouvel outil a fait l'objet de tests, qui ont permis de mieux comprendre quels sont les facteurs source d'erreur. Ces expériences doivent encore se poursuivre. En plus, avec la pratique, des protocoles d'utilisation se mettent en place. Mais l'ampleur des possibilités offertes fait de ce système novateur, une technologie très prometteuse.
Titre Bilan de journée de la géodésie à l'IGN : deuxième partieAuteur(s) DUQUENNE (F.)Source XYZ, n° 126, [01/03/2011], pp 14 - 15Mots clés GLOBAL NAVIGATION SATELLITE SYSTEM, INTERNATIONAL TERRESTRIAL REFERENCE
SYSTEM, NIREF, NOUVELLE TRIANGULATION DE LA FRANCE, SYSTEME DE REFERENCE GEODESIQUE, TRANSIT
N° notice A2011-094Résumé d’auteur Le n°125 d'XYZ ayant rapporté les contributions des premiers intervenants à la Journée
de la géodésie du 14 octobre 2010, le n°126 complète le compte rendu en proposant à l'attention du lecteur le condensé des exposés d'Alain Harmel, Zuheir Altamini et de l'auteur de ses lignes.
Géomatique
Titre A framework for regional association rule mining and scoping in spatial datasetsAuteur(s) DING (W.), EICK (C.), YUAN (X.), WANG (J.) et NICOT (J.P.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 1 - 28Langue AnglaisMots clés ANALYSE DE GROUPEMENT, DECOUVERTE DE CONNAISSANCES, EXPLORATION DE
DONNEES GEOGRAPHIQUES, REGLE D'ASSOCIATIONN° notice A2011-026Résumé d’auteur The motivation for regional association rule mining and scoping is driven by the facts that
global statistics seldom provide useful insight and that most relationships in spatial datasets are geographically regional, rather than global. Furthermore, when using traditional association rule mining, regional patterns frequently fail to be discovered due to insufficient global confidence and/or support. In this paper, we systematically study this problem and address the unique challenges of regional association mining and scoping: (1) region discovery: how to identify interesting regions from which novel and useful regional association rules can be extracted; (2) regional association rule scoping: how to determine the scope of regional association rules. We investigate the duality between regional association rules and regions where the associations are valid: interesting regions are identified to seek novel regional patterns, and a regional pattern has a scope of a set of regions in which the pattern is valid. In particular, we present a reward-based region discovery framework that employs a divisive grid-based supervised clustering for region discovery. We evaluate our approach in a real-world case study to identify spatial risk patterns from arsenic in the Texas water supply. Our experimental results confirm and validate research results in the study of arsenic contamination, and our work leads to the discovery of novel findings to be further explored by domain scientists.
Titre Les marchés publics : l'envers du miroirAuteur(s) HALBOUT (H.)Source GÉOMATIQUE EXPERT, n° 78, [01/01/2011], pp 46 - 49
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Mots clés APPEL D'OFFRES, DROIT PUBLIC, DONNEES LOCALISEES, MARCHE PUBLICN° notice A2011-044Résumé d’auteur Rédiger un appel d'offre est souvent un dilemme pour les petites ou moyennes
collectivités. Comment éviter les pièges, et que penser du document, édité en juin dernier par le Service des Achats de l'Etat, intitulé Bonnes pratiques achat du SAE.
Titre TIDES, a new descriptor for time series oscillation behaviorAuteur(s) MARIOTE (L.), MEDEIROS (C.), DA SILVA TORRES (R.) et al.Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 75 - 109Langue AnglaisMots clés EXPLORATION DE DONNEES GEOGRAPHIQUES, OSCILLATION, SERIE TEMPORELLEN° notice A2011-029Résumé d’auteur Sensor networks have increased the amount and variety of temporal data available,
requiring the definition of new techniques for data mining. Related research typically addresses the problems of indexing, clustering, classification, summarization, and anomaly detection. There is a wide range of techniques to describe and compare time series, but they focus on series’ values. This paper concentrates on a new aspect—that of describing oscillation patterns. It presents a technique for time series similarity search, and multiple temporal scales, defining a descriptor that uses the angular coefficients from a linear segmentation of the curve that represents the evolution of the analyzed series. This technique is generalized to handle co-evolution, in which several phenomena vary at the same time. Preliminary experiments with real datasets showed that our approach correctly characterizes the oscillation of single time series, for multiple time scales, and is able to compute the similarity among sets of co-evolving series.
Titre Le plus beau des périplesAuteur(s) SEITE (J.M.) et THOMAS (M.)Source GÉOMATIQUE EXPERT, n° 78, [01/01/2011], pp 24 - 38Mots clés ACQUISITION D'IMAGES, AUTOCAD MAP, CAMERA VIDEO, CARTE MARINE, DONNEES
LOCALISEES, LITTORAL, MONUMENT HISTORIQUE, NAVIRE, PHARE, PHOTOGRAPHIE, POSITIONNEMENT PAR GPS, PRECISION METRIQUE, PROTECTION DE L'ENVIRONNEMENT, RECENSEMENT, SITE ARCHEOLOGIQUE, SITE CLASSE, SYSTEME D'INFORMATION GEOGRAPHIQUE, TRAIT DE COTE
N° notice A2011-042Résumé d’auteur Protéger le littoral de l'une des plus belles îles de la Terre, la Corse, passe avant tout par
sa connaissance exhaustive. Dans ce but, l'expédition Kallisté Péripli, pilotée par Jean-Marie Séïté, a réalisé un tour complet de l'île, filmant et photographiant chaque détail. Récit d'un tour de Corse en bateau placé sous les auspices de l'histoire, de l'image et de la géomatique.
Titre Influence of street reference data on geocoding qualityAuteur(s) ZANDBERGEN (P.)Source GÉOCARTO INTERNATIONAL, vol 26, n° 1, [01/02/2011], pp 35 - 47Langue AnglaisMots clés BASE DE DONNEES D’ADRESSES, DONNEES LOCALISEES DE REFERENCE, EXHAUSTIVITE
DES DONNEES, GEOCODAGE PAR ADRESSE POSTALE, PRECISION DU POSITIONNEMENT, REPETABILITE, RESEAU ROUTIER
N° notice A2011-035Résumé d’auteur Repeatability of street geocoding was characterized in terms of completeness and
positional accuracy by using different street network datasets to geocode the same address input file. Match rates were highest for local street centrelines followed by StreetMap USA 2005 and TIGER 2000 data. Positional accuracy was highest for local street centrelines, while StreetMap USA 2005 and TIGER 2000 were nearly identical. Rural addresses were geocoded less accurately than urban addresses. Multi-family residential and commercial, institutional or industrial addresses were geocoded less accurately than urban single family residential addresses. The enhancement of TIGER 2000 data by commercial firms resulted in higher match rates but not in improved positional accuracy. The study has also highlighted the unique nature of multi-family and non-residential addresses in terms of the quality of their street geocoded locations. When such addresses are of specific interest alternatives to traditional street geocoding may need to be considered.
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Géomatique web
Titre Evaluating selected visualization methods for exploring VGIAuteur(s) FEICK (R.) et DEPARDAY (V.)Source GEOMATICA, vol 64, n° 4, [01/12/2010], pp 427 - 437Langue AnglaisMots clés DONNEES LOCALISEES LIBRES, FILTRAGE D'INFORMATION, INFORMATION
GEOGRAPHIQUE VOLONTAIRE, LOGICIEL DE CARTOGRAPHIE, UTILISATEUR CIVIL, VISUALISATION CARTOGRAPHIQUE
N° notice A2010-574Résumé d’auteur The increasing prevalence of user-generated, or volunteered, geographic information is
changing established practices of spatial data production and use in ways that were largely unanticipated in nature or in scope. This paper investigates one dimension of VGI use that has received relatively little attention to date, namely the influence of different cartographic visualisation methods on citizens' ability to explore and understand VGI. Following a brief review of key challenges related to VGI use, the paper describes a web-based software prototype that was designed to allow users to compare several simple geovisualisation and data filtering techniques for VGI exploration. Next, attention is directed to a specific study context where citizens used the software tool to explore a rich data set of locally-produced VGI related to community assets. The paper concludes with a discussion of the results from this experiment.
Titre Functional description of geoprocessing services as conjunctive datalog queriesAuteur(s) FITZNER (D.), HOFFMANN (J.) et KLIEN (E.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 191 - 221Langue AnglaisMots clés APPARIEMENT DE DONNEES LOCALISEES, DECOUVERTE DE CONNAISSANCES,
PROGRAMMATION EN LOGIQUE, REQUETE SPATIALE, SERVICE WEB GEOGRAPHIQUE, WEB PROCESSING SERVICE, WEB SEMANTIQUE
N° notice A2011-033Résumé d’auteur Discovery of suitable web services is a crucial task in Spatial Data Infrastructures (SDI).
In this work, we develop a novel approach to the discovery of geoprocessing services (WPS). Discovery requests and Web Processing Services are annotated as conjunctive queries in a logic programming (LP) language and the discovery process is based on Logic Programming query containment checking between these descriptions. Besides the types of input and output, we explicitly formalize the relation between them and hence are able to capture the functionality of a WPS more precisely. The use of Logic Programming query containment allows for effective reasoning during discovery. Furthermore, the relative simplicity of the semantic descriptions is advantageous for their creation by non-logics experts. The developed approach is applicable in the Web Service Modeling Framework (WSMF), a state-of-the-art semantic web service framework.
Titre HIS: Golden Horn GISAuteur(s) ALKAN (R.), KALKAN (Y.) et ERDOGAN (C.)Source GIM INTERNATIONAL, vol 25, n° 3, [01/03/2011], pp 21 - 25Langue AnglaisMots clés ACQUISITION DE DONNEES, BASE DE DONNEES LOCALISEES, POSITIONNEMENT
CINEMATIQUE EN TEMPS REEL, POSITIONNEMENT PAR GPS, SIG NOMADE, SYSTEME D'INFORMATION GEOGRAPHIQUE, WEBSIG
N° notice A2011-065Résumé d’auteur As part of an ongoing project to bring to city managers, citizens, tourists and other geo-
data of the Golden Horn area of Istanbul, Turkey, the authors designed a geo-database accessible both via desktop computers connected to the internet and wireless handheld mobile GIS devices used in the field.
Infrastructure de données
Titre Potential of VGI as a resource for SDIS in the north/south contextAuteur(s) GENOVESE (E.) et ROCHE (S.)Source GEOMATICA, vol 64, n° 4, [01/12/2010], pp 439 - 450Langue Anglais
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Mots clés INFORMATION GEOGRAPHIQUE VOLONTAIRE, INFRASTRUCTURE NATIONALE DES DONNEES LOCALISEES, INTEGRATION DE DONNEES
N° notice A2010-575Résumé d’auteur New on-line services that support user generated and user modified maps are emerging
at a rapid pace and a vast amount of information has been created. Anyone with Internet access via computer or mobile devices now has the ability to display geospatial data and voluntarily add information without the help of a GIS expert. This user created geospatial content has been named Volunteered Geographic Information (VGI) by Goodchild [2007a]. The concept and its implementation present a combination of potential and risks, which now must be considered. This study aims primarily at detecting, and presenting schematically, the strengths and weaknesses, opportunities and threats of VGI as a resource for Spatial Data Infrastructures (SDIs) in the North and South contexts. We explore how the integration of VGI with official information can be a powerful source of novel data that can be included in SDIs. We analyse the VGI potential in developing countries, especially in areas where reliable spatial data is scarce and the digital divide is more delineated. We suggest that the use of VGI technology can be capitalised upon by building SDIs, and we conclude with a number of suggestions for further research.
Titre L'Afigéo dresse son bilan géomatique 2010Auteur(s) SIMIAR (M.)Source GÉOMÈTRE, n° 2076, [01/12/2010], pp 14 - 15Mots clés FORMATION, INFORMATION GEOGRAPHIQUEN° notice A2010-578Résumé d’auteur De façon traditionnelle, l'Association française pour l'information géographique dresse
chaque année le bilan du secteur de la géomatique en France.
GEOPORTAIL, INSPIRE, MODELISATION 3D, PHOTOGRAMMETRIE AERIENNE, REFERENTIEL A GRANDE ECHELLE
N° notice A2011-040Résumé d’auteur Crée à l'aube de la Seconde guerre mondiale du désir de sauvegarder le patrimoine
cartographique - jusqu'alors militaire - menacé de tomber aux mains de l'armée allemande, l'Institut Géographique National a évolué d'un simple "dépôt" de cartes papier pour devenir l'un des pôles internationaux de compétence dans le domaine de la géodésie, de la topographie, de la géomatique et de la géodésie. 2010 était l'occasion de revenir sur toute cette histoire.
Titre How to achieve consistency for 3D city modelsAuteur(s) GROGER (G.) et PLUMER (L.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 137 - 165Langue AnglaisMots clés CITYGML, COHERENCE DES DONNEES, CONTRAINTE DE COHERENCE, GEOMETRIE
ALGOIRITHMIQUE, MODELE 3D DE L'ESPACE URBAIN, SOLIDE, SURFACE (GÉOMÉTRIE)N° notice A2011-031Résumé d’auteur Consistency is a crucial prerequisite for a large number of relevant applications of 3D city
models, which have become more and more important in GIS. Users need efficient and reliable consistency checking tools in order to be able to assess the suitability of spatial data for their applications. In this paper we provide the theoretical foundations for such tools by defining an axiomatic characterization of 3D city models. These axioms are effective and efficiently supported by recent spatial database management systems and methods of Computational Geometry or Computer Graphics. They are equivalent to the topological concept of the 3D city model presented in this paper, thereby guaranteeing the reliability of the method. Hence, each error is detected by the axioms, and each violation of the axioms is in fact an error. This property, which is proven formally, is not guaranteed by existing approaches. The efficiency of the method stems from its locality: in most cases, consistency checks can safely be restricted to single components, which are defined topologically. We show how a 3D city model can be decomposed into such components which are either topologically equivalent to a disk, a sphere, or a torus, enabling the modeling of the terrain, of buildings and other constructions, and of bridges and tunnels, which are handles from a mathematical point of view. This enables a
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modular design of the axioms by defining axioms for each topological component and for the aggregation of the components. Finally, a sound, consistent concept for aggregating features, i.e. semantical objects like buildings or rooms, to complex features is presented.
Titre Infrastructure de données spatiales et ingénierie territoriale : une approche empirique à partir du SIG Pyrénées
N° notice A2011-043Résumé d’auteur L'infrastructure de données spatiales (IDS) développée par l'APEM, support de
l'observatoire socio-économique du massif pyrénéen, a permis de consolider une démarche collective au service du développement économique montagnard.
Titre Un nouveau CNIG très inspiréAuteur(s) BLOMAC (F. DE)Source SIG LA LETTRE, n° 124, [01/02/2011], pp 01 - 01Mots clés INFORMATION GEOGRAPHIQUE, INSPIREN° notice A2011-064Résumé d'auteur Le décret tant attendu, relatif au Conseil national de l'information géographique (CNIG) a
été publié le 31 janvier dernier. Il recentre les activités de cette commission consultative sur la directive INSPIRE. Sa composition laisse une large part aux représentants des collectivités locales. Mais ses moyens concrets seront assurés par l'IGN.
Titre Adresses et numéros de parcelles : le décret qui préciseAuteur(s) BLOMAC (F. DE)Source SIG LA LETTRE, n° 125, [01/03/2011], pp 1 - 1Mots clés ADRESSE POSTALE, INFRASTRUCTURE NATIONALE DES DONNEES LOCALISEES,
PARCELLAIREN° notice A2011-084Résumé d’auteur Un décret a été pris le 1er mars précisant la définition des notions de parcelles et
d'adresses, librement constituables en bases de données et diffusables par l'Etat et les collectivités. Même s'il n'apporte aucune surprise, ce décret met fin à de lourdes procédures et devrait faciliter la mise en place de flux de données géographiques, qui seront rapidement obligatoires dans le cadre d'INSPIRE.
Titre RGE gratuit, quelques précisionsAuteur(s) BLOMAC (F. DE)Source SIG LA LETTRE, n° 125, [01/03/2011], pp 9 - 11Mots clés DIFFUSION DE DONNEES, DONNEES LOCLAISEES DE REFERENCE, REFERENTIEL A
GRANDE ECHELLEN° notice A2011-083Résumé d’auteur Le 22 février, l'IGN a rassemblé une centaine de clients et partenaires à Montpellier pour
présenter en détails sa nouvelle politique commerciale autour du référentiel à grande échelle (RGE) en Languedoc-Roussillon, avec l'aide de l'association SIG-LR. Réponses à quelques questions que nombre de nos lecteurs doivent se poser.
Titre Standards in practice: metadata for INSPIREAuteur(s) LEKKERKERK (H.)Source GEOINFORMATICS, vol 14, n° 2, [01/03/2011], pp 46 - 47Langue AnglaisMots clés DIRECTIVE EUROPEENNE, INFRASTRUCTURE EUROPEENNE DES DONNEES LOCALISEES,
INSPIREN° notice A2011-063Résumé d’auteur The 3rd of december 2010 was deadline for member states of the EU to publish their
Annex I & II metadata to their national geoportal. With this deadline behind us, now is a good time to investigate what is available and how we can use it.
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Lasergrammétrie
Titre 3D building model reconstruction from multi-view aerial imagery and Lidar dataAuteur(s) CHENG (L.), GONG (J.), LI (M.) et LIU (Y.)Source PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, vol 77, n° 2, [01/02/2011], pp 125 - 139Langue AnglaisMots clés CONTOUR, DONNEES LIDAR, DONNEES MULTISOURCES, IMAGE AERIENNE, INTEGRATION
DE DONNEES, PRECISION GEOMETRIQUE (IMAGERIE), RECONSTRUCTION 3D DU BATIN° notice A2011-045Résumé d’auteur A novel approach by integrating multi-view aerial imagery and lidar data is proposed to
reconstruct 3D building models with accurate geometric position and fine details. First, a new algorithm is introduced for determination of principal orientations of a building, thus benefiting to improve the correctness and robustness of boundary segment extraction in aerial imagery. A new dynamic selection strategy based on lidar point density analysis and K-means clustering is then proposed to identify boundary segments from non-boundary segments. Second, 3D boundary segments are determined by incorporating lidar data and the 2D segments extracted from multi-view imagery. Finally, a new strategy for 3D building model reconstruction including automatic recovery of lost boundaries and robust reconstruction of rooftop patches is introduced. The experimental results indicate that the proposed approach can provide high quality 3D models with high-correctness, high-completeness, and good geometric accuracy.
Titre Swedish Lidar Project: New Nationwide Elevation ModelAuteur(s) PETERSEN (Y.) et ROST (H.)Source GIM INTERNATIONAL, vol 25, n° 2, [01/02/2011], pp 20 - 23Langue AnglaisMots clés DONNEES LIDAR, DONNEES LOCALISEES 3D, MODELE NUMERIQUE DE TERRAIN,
SPECIFICATION DE PRODUIT, TELEMETRIE LASER AEROPORTEN° notice A2011-037Résumé d’auteur Airborne Lidar is being used to establish a new national elevation model of the entire
territory of Sweden (450,000km2), one point per two m2. The project, spanning 2009 to 2013, is the responsibility of two internationally operating Scandinavian geospatial product service providers: Blom, headquartered in Oslo, Norway, and Denmark-based COWI. The authors discuss specifications, status and challenges posed by this large-scale, long-term project.
Titre Comparaison de PhotoModeler Scanner et David Laserscanner pour l'obtention de nuages de points denses
PATRIMOINE, PHOTOGRAMMETRIE NUMERIQUEN° notice A2011-098Résumé d’auteur L'étude d'objets lapidaires en archéologie se fait dans un souci de préservation. Il est
courant de pouvoir étudier les objets, en partie, par le biais d'une représentation tridimensionnelle. Si l'on ne considère pas le coût, il existe des outils permettant cette acquisition pour toutes les échelles d'étude. Parmi ceux-ci, on peut citer : bras laser, scanner à main, laser à triangulation et laser terrestre. Cette gamme couvre une grande plage de caractéristiques permettant de produire toutes sortes de données tridimensionnelles. En archéologie, comme dans beaucoup de domaines de recherche, la question des coûts ne peut pas être ignorée. C'est une des raisons pour lesquelles cette technologie est peu développée dans cette communauté. La question inhérente aux méthodes et savoir-faire a aussi toute son importance. Malgré les apparences, une acquisition tridimensionnelle ne se réalise pas sans un minimum de prérequis. C'est dans ce contexte qu'une solution de numérisation bon marché et à l'emploi accessible apparaît pertinente pour promouvoir les outils d'acquisition. Dans notre étude, nous nous intéressons particulièrement à deux outils : David Laserscanner et PhotoModeler Scanner. Les techniques mises en œuvre dans les deux systèmes sont à base de lasergrammétrie et de photogrammétrie. Elles permettent toutes les deux la production de nuages de points de petits objets. Nous avons déterminé plusieurs critères pour mener à bien notre comparaison. Le plus important est indiscutablement la précision ; il est important de pouvoir quantifier la capacité à produire un nuage de points fidèle à l'objet. La comparaison entre deux jeux de données dans de bonnes conditions s'est faite
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par référence à des données beaucoup plus précises obtenues avec un bras laser articulé. Le deuxième critère considère la résolution spatiale que l'on peut obtenir par optimisation des paramètres de mesure. L'acquisition peut se faire sur une grande quantité d'objets et dans des conditions parfois difficiles ; l'ergonomie devient dans ces conditions un critère déterminant. Deux points de vue peuvent être pris en compte pour l'ergonomie : le matériel et le logiciel.
Titre Mise en valeur numérique et reconstruction 3D du théâtre gallo-romain de Mandeure
ARCHITECTURALE, RESTITUTION 3D, SITE ARCHEOLOGIQUE, THEATREN° notice A2011-095Résumé d’auteur Depuis 2007, le groupe PAGE (Photogrammétrie Architecturale et GEomatique) de
l'INSA de Strasbourg intervient sur le site du théâtre antique de Mandeure dans le cadre d'un Projet Collectif de Recherches. L'ensemble des données acquises depuis 3 ans vise à la sauvegarde numérique du site via la construction de modèles tridimensionnels servant de support à l'expertise archéologique. La réalisation de ces modèles nécessite la combinaison de données lasergrammétriques et photogrammétriques. L'utilisation de la technique de Corrélation Epipolaire Dense (CED) nous permet ainsi de générer des nuages de points 3D à partir d'images 2D et ainsi de compléter le nuage lasergrammétrique. En veillant à la cohérence géométrique de l'ensemble, nous construisons ensuite le modèle surfacique maillé représentant le théâtre dans son état actuel. Avec l'appui d'expertises architecturales et archéologiques conjointes, nous pouvons alors proposer une restitution tridimensionnelle du théâtre dans son état antique. Des images de synthèse sont alors créées à des fins de communication, notamment pour le grand public.
Titre Quality analysis on 3D building models reconstructed from airborne laser scanning data
Auteur(s) ELBERINK (S.) et VOSSELMAN (G.)Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 157 -
165Langue AnglaisMots clés DONNEES LASER, HAUTEUR DU BATI, MESURE DE LA QUALITE, MODELISATION 3D,
PRECISION GEOMETRIQUE (imagerie), QUALITE DES DONNEES, RECONSTRUCTION 3D DU BATI
N° notice A2011-070Résumé d’auteur This paper presents a method to assess the geometric quality of 3D building models. The
quality depends on properties of the input data and the processing steps. Insight in the quality of 3D models is important for users to judge whether the models can be used in their specific applications. Without a proper quality description it is likely that the building models are either treated as correct or considered as useless because the quality is unknown. In our research we analyse how the quality parameters of the input data affect the quality of the 3D models. The 3D models have been reconstructed from dense airborne laser scanner data of about 20 pts/m2. A target based graph matching approach has been used to relate specific data features to general building knowledge. The paper presents a theoretical and an empirical approach to identify strong parts and shortcomings in 3D building models reconstructed from airborne laser scanning data without the use of reference measurements. Our method is tested on three different scenes to show that a proper quality description is essential to correctly judge the quality of the models.
Titre Forestry applications for satellite Lidar remote sensingAuteur(s) ROSETTE (J.), SUAREZ (J.), NORTH (P.) et LOS (S.)Source PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, vol 77, n° 3, [01/03/2011], pp 271 - 279Langue AnglaisMots clés ALTIMETRIE, CROISSANCE VEGETALE, DONNEES LIDAR, FORET, GEOSCIENCE LASER
ALTIMETER SYSTEM, RISQUE NATURELN° notice A2011-080Résumé d’auteur This paper presents a method to estimate forest parameter and surface topography from
NASA's Geosciences Laser Altimeter System (GLAS). Their potential use as observational
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inputs to models is demonstrated using a wind-risk model for the UK, ForestGALES. Relative heights above ground were used as biophysical parameter estimators. Top Height was estimated with R2 = 0.73, RMSE = 4.5 m. Diameter at breast height estimates differed for conifer-dominated stands (R2 = 0.72, RMSE = 0.07 m) and for stands containing mostly broadleaves (R2 = 0.41, RMSE = 0.11 m). Ground elevation estimation produced R2 = 0.997, RMSE = 2.2 m. These three parameters were applied to ForestGALES for stand-level assessment of wind-throw risk. Stability is sensitive to small differences in tree dimensions, and therefore vegetation parameters require greater accuracy than those currently retrievable from GLAS to more reliably determine risk of wind-throw. Future satellite lidar mission such as NASA's DESDynl sensor aim to produce improved vegetation parameter estimation plus greater spatial coverage which would offer more appropriate inputs for forestry models.
Titre Etude des couverts forestiers par inversion de formes d'onde Lidar à l'aide du modèle de transfert radiatif DART développé par le CESBIO
Auteur(s) UEBERSCHLAG (A.)Source XYZ, n° 126, [01/03/2011], pp 22 - 26Mots clés COUVERT FORESTIER, FORME D’ONDE, INVERSION, LEAF AREA INDEX, MODELE DE
TRANSFERT RADIATIF, ONDE LIDARN° notice A2011-096Résumé d’auteur Les problématiques environnementales et de gestion des ressources non renouvelables
préoccupent de plus en plus notre société. Pour apporter des solutions, il est devenu primordial d'étudier le fonctionnement des surfaces continentales et leurs interactions avec le climat et l'Homme. Le modèle DART (Discrete Anisotropic Radiative Tranfer), développé au CESBIO, contribue à cet objectif via la simulation de mesures de télédétection et du bilan radiatif de milieux naturels et urbains. Depuis peu, il comprend un module "Lidar", bien adapté à l'étude des couverts végétaux. Ce Projet de Fin d'Etudes a consisté à valider ce module et à proposer des améliorations en termes de fonctionnalité et de robustesse, principalement à travers l'inversion de mesures Lidar pour la détermination de paramètres structuraux des couverts forestiers : hauteur du couvert végétal et profil vertical de densité volumique foliaire. Ce travail a été réalisé en collaboration avec la NASA pour la préparation de la mission DESDynl.
Titre Incremental segmentation of Lidar point clouds with an octree-structured voxel space
D'OBJET, SEGMENTATION, SEMIS DE POINTS, VOXELN° notice A2011-077Résumé d’auteur Lidar (light detection and ranging) data implicitly contains abundant three-dimensional
spatial information. The segmentation of lidar point clouds is the key procedure for transforming implicit spatial information into explicit spatial information. Common criteria used for point cloud segmentation are proximity and coherence of point distribution. An effective segmentation algorithm may apply various steps or combinations of criteria depending on the application. This paper proposes a four-step segmentation method for lidar point clouds to deliver incremental segmentation results. Segmentation results of each step can provide the fundamental data for the next step. In the first step, the input point cloud is organised into an octree-structured voxel space, in which the point neighbourhood is established. In the second step, connected voxels which are not empty are grouped to obtain grouped points based on proximity. The third step is a coplanar point segmentation based on both coherence and proximity, which was performed on each point group obtained in the second step. Finally, neighbouring coplanar point groups are merged into “co-surface” point groups based on the criteria of plane connection and intersection. This scheme enables an incremental retrieval and analysis of a large lidar data-set. Experimental results demonstrate the effectiveness of the segmentation algorithm in handling both airborne and terrestrial lidar data. It is anticipated that the incremental segmentation results will be useful for object modelling using lidar data.
Titre Full waveform-based analysis for forest type information derivation from large footprint spaceborne lidar data
Auteur(s) ZHANG (J.), GIER (A. DE), XING (Y.) et SOHN (G.)_______________________________________________________________________________________
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Source PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, vol 77, n° 3, [01/03/2011], pp 281 - 290Langue AnglaisMots clés CANOPEE, CLASSIFICATION PAR MACHINE A VECTEURS DE SUPPORT, CONIFERE,
COUVERT FORESTIER, DECOMPOSITION DE GAUSS, DONNEES LIDAR, ECHO LASER, FEUILLU, FORME D'ONDE PLEINE
N° notice A2011-081Résumé d’auteur This study developed a new method to derive forest type information from large-footprint
lidar data based on full waveform analysis. For this purpose, the raw waveform was decomposed into Gaussian components, and canopy return and ground return of the waveforms were separated. Two types of metrics hypothesized to have relationship with forest types were derived from the canopy return part of the waveform. The first type of metrics is quantile-based metrics reflecting the vertical distribution of canopy return energy, and the second type is statistical characteristics of the Gaussian components of canopy return part. Support Vector Machine classification was applied to different combinations of the metrics to find their relationship with different forest types. The results showed that the second type of metrics, indicating the canopy stratum characteristics, showed great promise in separating broad-leaved and needle-leaved forests with the accuracy ranging from 88.68 percent to 90.57 percent and Kappa statistic from 0.7406 to 0.7868.
Navigation et positionnement
Titre Dynamic duo: combined GPS/GLONASS receivers in urban environmentsAuteur(s) O'DRISCOLL (C.), LACHAPELLE (G.) et TAMAZIN (M.)Source GPS WORLD, vol 22, n° 1, [01/01/2011], pp 51 - 58Langue AnglaisMots clés ANALYSE COMPARATIVE, CANYON URBAIN, DEGRADATION DU SIGNAL, RECEPTEUR
GLONASS, RECEPTEUR GNSS, RECEPTEUR GPS, RECEPTEUR MIXTE, TRAITEMENT DU SIGNAL
N° notice A2011-053Résumé d’auteur The impact of adding GLONASS to HS-GPS is assessed using a software receiver
operating in an actual urban canyon environment. Results are compared with standard and high sensitivity GNSS receivers and show a significant improvement in the availability of position solutions when GLONASS is added. An assisted high sensitivity receiver architecture is introduced which enables high fidelity signal measurements even in degraded environments.
Titre La navigation saharienne avant le GPS : seconde partie : Le compas solaire Abrams et astronomie de position
Auteur(s) TSCHAEN (L.) et COURBON (P.)Source XYZ, n° 126, [01/03/2011], pp 57 - 63Mots clés ASTRONOMIE DE POSITION, COMPAS SOLAIRE, DECLINAISON, INSTRUMENT DE
NAVIGATION, TEMPS SOLAIREN° notice A2011-100Résumé d’auteur Le GPS a révolutionné le positionnement terrestre. Tout d'abord utilisé en géodésie, puis
en topographie, il a peu à peu conquis les déplacements en voiture, même dans nos pays développés où les routes sont bien balisées, les carrefours renseignés (parfois très mal !) et les rues munies de plaques. En effet, malgré les progrès effectués depuis 30 ans, une étude montrerait que la grande majorité des automobilistes ne sait pas bien lire une carte. Alors, vive un appareil dont la voix synthétique décide pour vous et vous guide sans que vous ayez à réfléchir ou à faire le moindre effort. L'automatisation est reposante, mais est-elle si bénéfique que cela ? Le formatage qu'elle génère peut énerver, même quand le GPS vous averti de la présence d'un radar ! Au Sahara, quand on a quitté les grandes pistes et qu'on se trouve en terra incognito, le GPS est devenu incontournable, mais il n'est pas toujours la panacée pour rejoindre un point dont on connaît les coordonnées. La ligne droite n'est pas forcément le meilleur itinéraire pour joindre deux points connus par leurs coordonnées ; les pièges du sable ou du relief vous obligent souvent à de nombreux détours, les rallyes sahariens ont réservé de nombreuses surprises aux pilotes tous dotés de GPS performants. Les montagnards le savent eux aussi.
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Titre Demands of the road: an assisted-GNSS solution uses the EGNOS data access service
Auteur(s) SHERIDAN (K.), TOMAS (D.) et al.Source GPS WORLD, vol 22, n° 3, [01/03/2011], pp 28 - 35Langue AnglaisMots clés NAVIGATION AUTOMOBILE, POSITIONNEMENT PAR EGNOS, POSITIONNEMENT PAR GPS,
RECEPTEUR GNSSN° notice A2011-093Résumé d’auteur For use in billing drivers in road-user charging schemes, onboard units employing GNSS
must meet stringent reliability and availability requirements, and at the same time, be based on low-cost equipment systems. The SIGNATURE [Simple GNSS Assisted and Trusted Receiver] unit includes an assistance service which provides ephemeris data and corrections from EDAS, optimized for user location.
Titre Sensors in web 2.0Auteur(s) BERMUDEZ (L.)Source GEO:GEOCONNEXION INTERNATIONAL, vol 10, n° 4, [01/04/2011], pp 40 - 44Langue AnglaisMots clés INTEROPERABILITE, SERVICE FONDE SUR LA POSITION, STANDARD OGC, TELEPHONIE
MOBILE, UTILISATEUR, WEB 2.0N° notice A2011-092Résumé d’auteur Web 2.0 to recent trends in the world wide web: social networking, user-focused design,
information sharing, collaboration, and new kinds of interoperability.
Photogrammétrie numérique
Titre Indirect georeferencing of digital SLR [single-lens reflex] imagery using signalised lidar control points
GEOREFERENCEMENT INDIRECT, IMAGE NUMERIQUE, POINT D'APPUI, POSITIONNEMENT PAR GPS
N° notice A2011-078Résumé d’auteur Photogrammetric and lidar data-sets have been used together in mapping procedures
because of their complementary characteristics. However, to perform this integration both data-sets must be within a common reference frame. Although all lidar systems include a direct georeferencing procedure, the majority of low-cost photogrammetric systems do not have a facility for direct georeferencing of images even if the data-sets are captured simultaneously. In recent years, the high accuracy of the lidar data has enabled it to provide a source of photogrammetric control and thus to offer indirect georeferencing. This paper presents a methodology for the indirect georeferencing of digital SLR images using signalised lidar control points, together with the results obtained. The intensity image and raw lidar data-set were used to extract 3D coordinates of signalised control points. Two bundle adjustments of 21 images were performed. In the first case the coordinates of the control points were obtained by using GPS survey. In the second, they were extracted from a lidar data-set. The results obtained from these experiments confirm the feasibility of the proposed methodology.
Systèmes de référence et réseaux
Titre ETRS89 realization: current status, ETRF2005 and future developmentAuteur(s) ALTAMIMI (Z.)Source BOLLETTINO DI GEODESIA E SCIENZE AFFINI, vol 68, n° 3, [01/10/2009], pp 255 - 267Langue AnglaisMots clés EUROPEAN TERRESTRIAL REFERENCE FRAME 2005, EUROPEAN TERRESTRIAL
REFERENCE SYSTEM 1989, INTERNATIONAL TERRESTRIAL REFERENCE SYSTEMN° notice A2009-567
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Résumé d’auteur The European Terrestrial Reference System 1989 (ETRS89) was defined and adopted by EUREF in 1990 and since then is largely used by most of European countries as the basis of their national geodetic system. This paper re-discusses the ETRS89 definition, its mathematical link to the International Terrestrial Reference System (ITRS), focuses on the main ways allowing its realization and raises the awareness of possible misinterpretation of its definition and in particular the misuse of the epoch 1989.0 inherent in its definition. Some numerical examples are provided in order to illustrate the discussion. Particular focus is given to the ETRF2005 and its consequences in terms of frame shifts (origin, scale and orientation) as well as consequent station coordinate changes with respect to ETRF2000. Nonetheless, a mathematically sound alternative of the ETRS89 realization is also proposed, leading to frame definition changes due to the well known estimation process, while perfectly satisfying the ETRS89 definition. Given the fact that the ETRS89 is designed primarily for practical geo-referencing applications where these frame shifts are not desired, it is therefore recommended to adopt the ETRF2000 as the basic frame of the ETRS89 realization for future adoption by the European National Mapping Agencies. Procedure how to access the ETRF2000 frame from any ITRF version is described.
Titre Final results of the Italian "Rete Dinamica Nazionale" (RDN) of Istituto Geografico Militare Italiano (IGMI) and its alignment to ETRF2000
Auteur(s) BARONI (L.), CAULI (F.), FAROLI (G.) et MASEROLI (R.)Source BOLLETTINO DI GEODESIA E SCIENZE AFFINI, vol 68, n° 3, [01/10/2009], pp 289 - 315Langue AnglaisMots clés EUROPEAN TERRESTRIAL REFERENCE SYSTEM 1989, RESEAU GEODESIQUE
PERMANENT, STATION GPSN° notice A2009-568Résumé d’auteur We present the general aspects, the main features and the final results of the Rete
Dinamica Nazionale (RDN), the new geodetic reference frame system for Italy adopted from January 1th 2009. RON which means National Dynamic Network is aligned to the most recent official realization of ETRS89, ETRF2000 at the epoch 2008.0. It will update the previous Italian realisation of ETRS89, materialized with the IGM95 frame. RDN consists of a network of 99 GPS permanent stations aligned to 13 IGS fiducial stations included in the ITRF2005 solution. The other stations were selected taking into account the homogeneous spatial distribution and the quality of location and equipment. The observation campaign lasts 28 days, from 23th December 2007 to 19th January 2008 and the data are daily files in RINEX format with 30 seconds sample rate. The computation was performed by the Data Processing Centre of the Geodetic Service of Istituto Geografico Militare Italiano (IGMI) and the processing strategy followed the standard procedures adopted by EUREF guidelines. The same computation also was performed independently by University of Padova (prof. Caporali) and by the G3 group in Milano (prof. Sanso) in order to test the results. In this article we show all the processing steps until the final results and then all the comparisons with other data centers.
Titre Homogeneous reprocessing of the EUREF permanent network: first experiences and comparisons
Source BOLLETTINO DI GEODESIA E SCIENZE AFFINI, vol 68, n° 3, [01/10/2009], pp 207 - 218Langue AnglaisMots clés CATREF, EUREF EUROPEAN PERMANENT NETWORK, RESEAU GEODESIQUE PERMANENTN° notice A2009-566Résumé d’auteur The GPS analysis strategies, the applied models and software have been considerably
changed since the global (IGS - International GNSS Service) and regional (EPN - EUREF Permanent Network) CORS networks are operational. All changes brought along temporal inhomogeneities in the estimated parameters, most apparently in the coordinate time series. After the introduction of the absolute phase centre variation (PCV) models of the satellite and ground GPS antennae, the complete re-analysis of the historical measurements could not be postponed. Within the IGS the re-analysis is now in progress and it will be followed by a coordinated re-processing of the EPN observations from 1996 on. $In preparation of the EPN reprocessing a pilot re-analysis has been done at the Military University of Technology (MUT) in Poland covering the complete EPN dataset and similar work has been started at the Royal Observatory of Belgium (ROB). The target of this work was to assess the required resources, the status and completeness of the
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database and to quantify the improvement gained by the reprocessing. Using the CATREF software (Altamimi et al. 2004) two cumulative solutions have been created by stacking the standard and the reprocessed weekly EPN SINEX solutions. In this paper the first analysis of the estimated coordinates, velocities and the residual time series is presented. We detected 10-30% improvement in the weekly weighted RMS, we got smoother time series with smaller coordinate repeatability and a more «ITRF2005-conform» velocity field. The results highly support the need for a complete (from global to local level) GPS reprocessing and the establishment of a new ITRS realization in agreement with the GPS absolute PCV models.
Titre Analysis of the DORIS contributions to ITRF2008Auteur(s) ANGERMANN (D.), SEITZ (M.) et DREWES (H.)Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1633 - 1647Langue AnglaisMots clés DONNEES DORIS, INTERNATIONAL TERRESTRIAL REFERENCE FRAME, POSITIONNEMENT
PAR DORIS, SERIE TEMPORELLE, STATION DORISN° notice A2010-567Résumé d’auteur In its function as an ITRS Combination Centre, DGFI is in charge with the computation of
an ITRF2008 solution. The computation methodology of DGFI is based on the combination of datum-free normal equations (weekly or session data sets, respectively) of station positions and Earth orientation parameters (EOP) from the geodetic space techniques DORIS, GPS, SLR and VLBI. In this paper we focus on the DORIS part within the ITRF2008 computations. We present results obtained from the analysis of the DORIS time series for station positions, network translation and scale parameters, as well as for the terrestrial pole coordinates. The submissions to ITRF2008 benefit from improved analysis strategies of the seven contributing IDS analysis centres and from a combination of the weekly solutions of station positions and polar motion. The results show an improvement by a factor of two compared to past DORIS data submitted to ITRF2005, which has been evaluated by investigating the repeatabilities of position time series. The DORIS position time series were analysed w.r.t. discontinuities and other non-linear effects such as seasonal variations. About 40 discontinuities have been identified which have been compared with the results of an earlier study. Within the inter-technique combination we focus on the DORIS contribution to the integration of the different space geodetic observations and on a comparison of the geodetic local ties with the space geodetic solutions. Results are given for the 41 co-location sites between DORIS and GPS.
Titre Global sea-level rise and its relation to the terrestrial reference frame Auteur(s) COLLILIEUX (X.) et WOPPELMANN (G.)Source JOURNAL OF GEODESY, vol 85, n° 1, [01/01/2011], pp 9 - 22Langue AnglaisMots clés INTERNATIONAL TERRESTRIAL REFERENCE FRAME, NIVEAU MOYEN DES MERS,
PROPAGATION D'ERREUR, STATION GPSN° notice A2011-056Résumé d’auteur We examined the sensitivity of estimates of global sea-level rise obtained from GPS-
corrected long term tide gauge records to uncertainties in the International Terrestrial Reference Frame (ITRF) realization. A useful transfer function was established, linking potential errors in the reference frame datum (origin and scale) to resulting errors in the estimate of global sea level rise. Contrary to scale errors that are propagated by a factor of 100%, the impact of errors in the origin depends on the network geometry. The geometry of the network analyzed here resulted in an error propagation factor of 50% for the Z component of the origin, mainly due to the asymmetry in the distribution of the stations between hemispheres. This factor decreased from 50% to less than 10% as the geometry of the network improved using realistic potential stations that did not yet meet the selection criteria (e.g., record length, data availability). Conversely, we explored new constraints on the reference frame by considering forward calculations involving tide gauge records. A reference frame could be found in which the scatter of the regional sea-level rates was limited. The resulting reference frame drifted by 1.36 + 0.22 mm/year from the ITRF2000 origin in the Z component and by -0.44 + 0.22 mm/year from the ITRF2005 origin. A bound on the rate of global sea level rise of 1.2 to 1.6 mm/year was derived for the past century, depending on the origin of the adopted reference frame. The upper bound is slightly lower than previous estimates of 1.8 mm/year discussed in the IPCC fourth report.
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Titre An analytical method to transform geocentric into geodetic coordinatesAuteur(s) VERMEILLE (H.)Source JOURNAL OF GEODESY, vol 85, n° 2, [01/02/2011], pp 105 - 117Langue AnglaisMots clés COORDONNEES CARTESIENNES GEOCENTRIQUES, COORDONNEES GEODESIQUES,
SYSTEME DE COORDONNEES, TRANSFORMATION DE COORDONNEESN° notice A2011-068Résumé d’auteur A closed-form analytical method needing no approximation and deduced from a single
quartic equation is offered to transform geocentric into geodetic coordinates. It is valid at any point inside and outside the Earth including the polar axis, the equatorial plane and the Earth’s center. Comparison with the method of extrema with constraints to obtain this quartic equation is made.
Techniques orbitales
Titre DORIS/Jason-2: Better than 10 cm on-board orbits available for near-real-time altimetry
Auteur(s) JAYLES (C.), CHAUVEAU (J.P.) et ROZO (F.)Source ADVANCES IN SPACE RESEARCH, vol 46, n° 12, [15/12/2010], pp 1497 - 1512Langue AnglaisMots clés ALTIMETRIE, DIODE (DÉTERMINATION D'ORBITE), DONNEES DORIS, JASON,
ORBITOGRAPHIE, PRECISION CENTIMETRIQUE, TEMPS REEL, TRAJECTOGRAPHIE PAR DORIS
N° notice A2010-563Résumé d’auteur DIODE (DORIS Immediate Orbit on-board Determination) is a real-time on-board orbit
determination software, embedded in the DORIS receiver. The purpose of this paper is to focus on DIODE performances. After a description of the recent DORIS evolutions, we detail how compliance with specifications are verified during extensive ground tests before the launch, then during the in-flight commissioning phase just after the launch, and how well they are met in the routine phase and today. Future improvements are also discussed for Jason-2 as well as for the next missions. The complete DORIS ground validation using DORIS simulator and new DORIS test equipments has shown prior to the Jason-2 flight that every functional requirement was fulfilled, and also that better than 10 cm real-time DIODE orbits would be achieved on-board Jason-2. The first year of Jason-2 confirmed this, and after correction of a slowly evolving polar motion error at the end of the commissioning phase, the DIODE on-board orbits are indeed better than the 10 cm specification: in the beginning of the routine phase, the discrepancy was already 7.7 cm Root-Mean-Square (RMS) in the radial component as compared to the final Precise Orbit Ephemerides (POE) orbit. Since the first day of Jason-2 cycle 1, the real-time DIODE orbits have been delivered in the altimetry fast delivery products. Their accuracy and their 100% availability make them a key input to fairly precise Near-Real-Time Altimetry processing. Time-tagging is at the microsecond level. In parallel, a few corrections (quaternion problem) and improvements have been gathered in an enhanced version of DIODE, which is already implemented and validated. With this new version, a 5 cm radial accuracy is achieved during ground validation over more than Jason-2 first year (cycles 1–43, from July 12th, 2008 to September 11th, 2009). The Seattle Ocean Surface Topography Science Team Meeting (OSTST) has recommended an upload of this v4.02 version on-board Jason-2 in order to take benefit from more accurate real-time orbits. For the future, perhaps the most important point of this work is that a 9 mm consistency is observed on-ground between simulated and adjusted orbits, proving that the DORIS measurement is very precisely and properly modelled in the DIODE navigation software. This implies that improvement of DIODE accuracy is still possible and should be driven by enhancement of the physical models: forces and perturbations of the satellite movement, Radio/Frequency phenomena perturbing measurements. A 2-cm accuracy is possible with future versions, if analysis and model improvements continue to progress.
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Traitement d'image
Titre Automatic fuzzy clustering using modified differential evolution for image classification
Auteur(s) MAULIK (U.) et SAHA (I.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 48, n° 9, [01/09/2010], pp 3503 -
3510Langue AnglaisMots clés ALGORITHME GENETIQUE, CLASSIFICATION FLOUE, CLASSIFICATION NON DIRIGEE,
EVOLUTION DIFFERENTIELLE, IDENTIFICATION AUTOMATIQUE, IMAGE SATELLITE, OCCUPATION DU SOL, REGROUPEMENT DE DONNEES
N° notice A2010-571Résumé d’auteur The problem of classifying an image into different homogeneous regions is viewed as the
task of clustering the pixels in the intensity space. In particular, satellite images contain landcover types, some of which cover significantly large areas while some (e.g., bridges and roads) occupy relatively much smaller regions. Automatically detecting regions or clusters of such widely varying sizes is a challenging task. In this paper, a new real-coded modified differential evolution based automatic fuzzy clustering algorithm is proposed which automatically evolves the number of clusters as well as the proper partitioning from a data set. Here, the assignment of points to different clusters is done based on a Xie-Beni index where the Euclidean distance is taken into consideration. The effectiveness of the proposed technique is first demonstrated for two numeric remote sensing data described in terms of feature vectors and then in identifying different landcover regions in remote sensing imagery. The superiority of the new method is demonstrated by comparing it with other existing techniques like automatic clustering using improved differential evolution, classical differential evolution based automatic fuzzy clustering, variable length genetic algorithm based fuzzy clustering, and well known fuzzy C-means algorithm both qualitatively and quantitatively.
Titre Graph-based feature selection for object-oriented classification in VHR airborne imagery
Auteur(s) CHEN (T.), FANG (T.), HUO (H.) et LI (D.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 49, n° 1, [01/01/2011], pp 353 -
CARACTERISTIQUES, GRAPHE, IMAGE A ULTRA HAUTE RESOLUTION, IMAGE AERIENNE, KAPPA DE COHEN, MATRICE, PONDERATION, SIMILITUDE, VOISINAGE
N° notice A2011-051Résumé d’auteur Linearly nonseparability and class imbalance of very high resolution (VHR) imagery make
feature selection for object-oriented classification quite challenging, while such characteristics, especially class imbalance, have usually been ignored in open literature. To cope with the challenges, this paper proposes a new graph-based feature selection method named locally weighted discriminating projection (LWDP). First, the popular graph-based criteria of feature selection are reformulated to present linear or nonlinear mapping in feature space. Second, weight matrices of graphs characterize dissimilarity rather than similarity between pairwise neighbors, to well-preserved local structure when the difference of distance between a sample and its neighbors is large. Finally, LWDP provides a new perspective to alleviate class imbalance at both global and local levels, by restricting the pairwise relationships in the weight matrices. Specifically, neighborhood unions are introduced to employ the local class distribution and class size to constrain pairwise relationships in the weight matrices when classifying unbalanced sample sets. To evaluate the performances of LWDP in low dimensions, a holistic scoring scheme is proposed to stress the performances under low dimensions. In addition, overall accuracy curves and Kappa Index of Agreement (KIA) curves, which exhibit KIA in dimensions, are also used. The experimental results show that LWDP and its kernel extension outperform the other classic or latest methods in processing unbalanced sample set of VHR airborne imagery.
Titre Land cover classification of cloud-contaminated multitemporal high-resolution images
Auteur(s) SALBERG (A.)
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Langue AnglaisMots clés CLASSIFICATEUR NON PARAMETRIQUE, CLASSIFICATION BARYCENTRIQUE,
CLASSIFICATION DIRIGEE, CLASSIFICATION PAR MAXIMUM DE VRAISEMBLANCE, IMAGE LANDSAT-ETM+, IMAGE LANDSAT-TM, IMAGE MULTITEMPORELLE, IMAGE OPTIQUE, OCCUPATION DU SOL
N° notice A2011-052Résumé d’auteur We show how methods proposed in the statistical community dealing with missing data
may be applied for land cover classification, where optical observations are missing due to clouds and snow. The proposed method is divided into two stages: 1) cloud/snow classification and 2) training and land cover classification. The purpose of the cloud/snow classification stage is to determine which pixels are missing due to clouds and snow. All pixels in each optical image are classified into the classes cloud, snow, water, and vegetation using a suitable classifier. The pixels classified as cloud or snow are labeled as missing, and this information is used in the subsequent training and classification stage, which deals with classification of the pixels into various land cover classes. For land cover classification, we apply the maximum-likelihood (assuming normal distributions), -nearest neighbor, and Parzen classifiers, all modified to handle missing features. The classifiers are evaluated on Landsat (both Thematic Mapper and Enhanced Thematic Mapper Plus) images covering a scene at about 900 m a.s.l. in the Hardangervidda mountain plateau in Southern Norway, where 4869 in situ samples of the land cover classes water, ridge, leeside, snowbed, mire, forest, and rock are obtained. The results show that proper modeling of the missing pixels improves the classification rate by 5%-10%, and by using multiple images, we increase the chance of observing the land cover type substantially. The nonparametric classifiers handle nonignorable missing-data mechanisms and are therefore particularly suitable for remote sensing applications where the pixels covered by snow and cloud may depend on the land cover type.
Titre A hybrid classification scheme for mining multisource geospatial dataAuteur(s) VATSAVAI (R.) et BHADURI (B.)Source GEOINFORMATICA, vol 15, n° 1, [01/01/2011], pp 29 - 47Langue AnglaisMots clés APPRENTISSAGE SEMI-DIRIGE, CLASSIFICATION DE DEMPSTER-SHAFER,
CLASSIFICATION HYBRIDE, CLASSIFICATION PAR MAXIMUM DE VRAISEMBLANCE, DONNEES AUXILIAIRES, EXPLORATION DE DONNEES GEOGRAPHIQUES, IMAGE LANDSAT, IMAGE MULTIBANDE, PRECISION DE LA CLASSIFICATION
N° notice A2011-027Résumé d’auteur Supervised learning methods such as Maximum Likelihood (ML) are often used in land
cover (thematic) classification of remote sensing imagery. ML classifier relies exclusively on spectral characteristics of thematic classes whose statistical distributions (class conditional probability densities) are often overlapping. The spectral response distributions of thematic classes are dependent on many factors including elevation, soil types, and ecological zones. A second problem with statistical classifiers is the requirement of the large number of accurate training samples (10 to 30 ˚ |dimensions|), which are often costly and time consuming to acquire over large geographic regions. With the increasing availability of geospatial databases, it is possible to exploit the knowledge derived from these ancillary datasets to improve classification accuracies even when the class distributions are highly overlapping. Likewise newer semi-supervised techniques can be adopted to improve the parameter estimates of the statistical model by utilizing a large number of easily available unlabeled training samples. Unfortunately, there is no convenient multivariate statistical model that can be employed for multisource geospatial databases. In this paper we present a hybrid semi-supervised learning algorithm that effectively exploits freely available unlabeled training samples from multispectral remote sensing images and also incorporates ancillary geospatial databases. We have conducted several experiments on Landsat satellite image datasets, and our new hybrid approach shows over 24% to 36% improvement in overall classification accuracy over conventional classification schemes.
Titre Impervious surface area extraction from IKONOS imagery using an object-based fuzzy method
Auteur(s) HU (X.) et WENG (Q.)Source GÉOCARTO INTERNATIONAL, vol 26, n° 1, [01/02/2011], pp 3 - 20
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Langue AnglaisMots clés CLASSIFICATION FLOUE, DETECTION D'OBJET, EXTRACTION AUTOMATIQUE, IMAGE
IKONOS, IMAGE MULTIBANDE, LOGIQUE FLOUE, MILIEU URBAIN, PANSHARPENING, SURFACE IMPERMEABLE, VILLE
N° notice A2011-034Résumé d’auteur The study of impervious surfaces is crucial to the sustainable development of urban areas
due to its strong impact on urban environments. Remotely sensed high-resolution imagery has the advantage of providing more spatial details; however, digital image processing algorithms have not been well developed to accommodate this advantage and other characteristics of such imagery. In this article, an object-based fuzzy classification approach for impervious surface extraction was developed and applied to two pan-sharpened multi-spectral IKONOS images covering the residential and central business district (CBD) areas of Indianapolis, Indiana, USA. Fuzzy rules based on spectral, spatial and texture attributes, were developed to extract impervious surfaces. An accuracy assessment was performed for the final maps. The results indicated that the spatial patterns of extracted features were in accordance with those in the original images and the boundaries of features were appropriately delineated. Impervious surfaces were extracted with an accuracy of 95% in the residential area and 92% in the CBD area. Road extraction achieved accuracy a bit lower, with 93% and 90% from the residential and CBD area, respectively. Buildings were extracted with an accuracy of 94% from the residential area while 89% from the CBD area. It is suggested that the CBD area had a higher spectral complexity, building displacement and the shadow problem, leading to a more difficult estimation and mapping of impervious surfaces.
Titre A genetic algorithm approach to moving threshold optimization for binary change detection
Auteur(s) IM (J.), LU (Z.) et JENSEN (J.)Source PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, vol 77, n° 2, [01/02/2011], pp 167 - 180Langue AnglaisMots clés ALGORITHME GENETIQUE, DETECTION DE CHANGEMENT, IMAGE QUICKBIRD, SEUILLAGE
D’IMAGEN° notice A2011-047Résumé d’auteur This study investigated the use of a genetic algorithm (GA) approach, a widely used
optimization method, to identify optimum thresholds for remote sensing-based binary change detection. Automated GA-based calibration models using a moving threshold window (MTW) were developed and tested using a case study. Two sets of the bi-temporal QuickBird imagery were used to evaluate the new optimization models. The GA-based models using MTW were free from the assumption of symmetry of thresholds for difference- or ratio-type of change-enhanced images, unlike traditional binary change detection methods, allowing more flexibility and efficiency in selecting optimum thresholds. Exhaustive search techniques using symmetric threshold window (STW) and MTW were evaluated for comparison. The stability of the GA-based models in terms of accuracy variation was also examined. The GA-based calibration models successfully identified optimum thresholds without a significant decrease in accuracy. The GA-based models using MTW outperformed the GA-based model using STW in both calibration and validation, revealing that optimum thresholds tended to be asymmetric. Multiple change-enhanced images generally resulted in better performance than single change-enhanced images based on the GA-based models.
Titre Construction of digital 3D highway model using stereo IKONOS satellite imageryAuteur(s) SHAKER (A.), YAN (W.) et EASA (S.)Source GÉOCARTO INTERNATIONAL, vol 26, n° 1, [01/02/2011], pp 49 - 67Langue AnglaisMots clés AUTOROUTE, EXTRACTION SEMI-AUTOMATIQUE, GEOREFERENCEMENT INDIRECT,
IMAGE IKONOS, MODELE GEOMETRIQUE DE PRISE DE VUE, MODELE NUMERIQUE DE SURFACE, MODELE PAR FONCTIONS RATIONNELLES, PANSHARPENING, POINT D'APPUI
N° notice A2011-036Résumé d’auteur This study aims to assess the accuracy of using stereo high resolution satellite imagery
for extracting the highway profiles and plans and constructing accurate 3D highway visualization model. Two stereo-pair IKONOS satellite images for Hong Kong and Toronto are geo-referenced by using a number of ground control points acquired by global positioning system measurements. A polynomial-based generic pushbroom model and rational function model are used to perform the sensor orientation, respectively. The
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highway alignments are extracted semi-automatically using stereoscopic measurements, and a 3D digital model along the highway is constructed. It is found that the highway alignments retrieved from the stereo IKONOS images result in less than 1-m root mean squared error in most of the cases in the horizontal and vertical directions. Near half-pixel accuracy can be achieved by using pansharpening stereo satellite imagery and under the condition that clear road surface markings can be identified along the highway.
Titre Automatic reasoning for geometric constraints in 3D city models with uncertain observations
Auteur(s) LOCH-DEHBI (S.) et PLUMER (L.)Source ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING, vol 66, n° 2, [01/03/2011], pp 177 -
187Langue AnglaisMots clés BATI 3D, CONTRAINTE GEOMETRIQUE, GEOMETRIE PROJECTIVE, HAUTEUR DU BATI,
MODELISATION 3D, RECONSTRUCTION AUTOMATIQUEN° notice A2011-071Résumé d’auteur This paper presents a novel approach to automated geometric reasoning for 3D building
models. Geometric constraints like orthogonality or parallelity play a prominent role in man-made objects such as buildings. Thus, constraint based modelling, that specifies buildings by their individual components and the constraints between them, is a common approach in 3D city models. Since prototyped building models allow one to incorporate a priori knowledge they support the 3D reconstruction of buildings from point clouds and allow the construction of virtual cities. However, high level building models have a high degree of complexity and consequently are not easily manageable. Interactive tools are needed which facilitate the development of consistent models that, for instance, do not entail internal logical contradictions. Furthermore, there is often an interest in a compact, redundancy-free representation. We propose an approach that uses algebraic methods to prove that a constraint is deducible from a set of premises. While automated reasoning in 2D models is practical, a substantial increase in complexity can be observed in the transition to the three-dimensional space. Apart from that, algebraic theorem provers are restricted to crisp constraints so far. Thus, they are unable to handle quality issues, which are, however, an important aspect of GIS data and models. In this article we present an approach to automatic 3D reasoning which explicitly addresses uncertainty. Hereby, our aim is to support the interactive modelling of 3D city models and the automatic reconstruction of buildings. Geometric constraints are represented by multivariate polynomials whereas algebraic reasoning is based on Wu’s method of pseudodivision and characteristic sets. The reasoning process is further supported by logical inference rules. In order to cope with uncertainty and to address quality issues the reasoner integrates uncertain projective geometry and statistical hypothesis tests. Consequently, it allows one to derive uncertain conclusions from uncertain premises. The quality of such conclusions is quantified in a way which is sound both from a logical and a statistical perspective.
Traitement d'image radar
Titre Edge enhancement algorithm based on the wavelet transform for automatic edge detection InSAR images
Auteur(s) ALONSO (M.), LOPEZ-MARTINEZ (C.), MALLORQUI (J.) et SALEMBIER (P.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 49, n° 1, [01/01/2011], pp 222 -
235Langue AnglaisMots clés ACCENTUATION DE CONTOURS, DETECTION AUTOMATIQUE, DETECTION DE CONTOUR,
IMAGE RADAR MOIREE, INTERFEROMETRIE PAR RADAR A ANTENNE SYNTHETIQUE, TRAIT DE COTE, TRANSFORMATION EN ONDELETTES
N° notice A2011-050Résumé d’auteur This paper presents a novel technique for automatic edge enhancement and detection in
synthetic aperture radar (SAR) images. The characteristics of SAR images justify the importance of an edge enhancement step prior to edge detection. Therefore, this paper presents a robust and unsupervised edge enhancement algorithm based on a combination of wavelet coefficients at different scales. The performance of the method is first tested on simulated images. Then, in order to complete the automatic detection chain, among the different options for the decision stage, the use of geodesic active
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contour is proposed. The second part of this paper suggests the extraction of the coastline in SAR images as a particular case of edge detection. Hence, after highlighting its practical interest, the technique that is theoretically presented in the first part of this paper is applied to real scenarios. Finally, the chances of its operational capability are assessed.
Titre Physical limitations on detecting tunnels using underground-focusing spotlight synthetic aperture radar
Auteur(s) MARTINEZ-LORENZO (J.), RAPPAPORT (C.) et QUIVIRA (F.)Source IEEE TRANSACTIONS ON GEOSCIENCE & REMOTE SENSING, vol 49, n° 1, [01/01/2011], pp 65 - 70Langue AnglaisMots clés CONSTANTE DIELECTRIQUE, DETECTION DE PARTIE CACHEE, FORME D'ONDE, IMAGE
SAR, PROPAGATION DU SIGNAL, REFLECTANCE DU SOL, REFRACTION ATMOSPHERIQUE, RUGOSITE DU SOL, SABLE, SIGNAL RADAR, TUNNEL
N° notice A2011-048Résumé d’auteur This paper examines the feasibility of underground-focusing spotlight synthetic aperture
radar (UF-SL-SAR) systems for tunnel detection applications. A general formulation is reviewed for generating UF-SL-SAR imaging by using multiple frequencies across a wide band and by focusing in space to subsurface points using well-known ray refraction at the nominal ground surface. A full-wave finite-difference frequency-domain model is used to consider wave propagation in realistic soil with loss- and frequency-dependent dielectric constant and a randomly rough ground surface, both of which serve to obscure and distort the returned tunnel target signal. Imaging results are presented for two representative soil scenarios: dry sand and moist clay loam. Considering the ground surface ray refraction for focusing greatly improves the SAR image relative to conventional SAR focusing at the ground surface. Using UF-SL-SAR, a small shallow tunnel is reasonably imaged for the sand case, despite the roughness of the ground interface. However, for higher conductivity moist clay loam, the clutter from the rough surface overwhelms the significantly attenuated target signal, which must propagate through the lossy intervening soil. It is demonstrated that, despite ideal focusing, the tunnel is successfully imaged only for the sand case.
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