02/15/2020 1 PBW 201B GEOINFORMATICS GROUND AND AERIAL INFORMATION SYSTEMS Lecture 1 Introduction • Learning objectives • Introduction and overview • Geomatics defined • Geomatics Workflow • Sciences and Technologies involved • Introduction to Photogrammetry • Next Lecture 2 • The objective of the contents of this lecture is to provide an overview of • course contents and scope; and • Geomatics in general and as applied in Civil Engineering • Introduce the concept of photogrammetry • General overview of orientation of photos • Interior orientation • Upon the conclusion of this lecture students should be able to • Comprehend what Geomatics and Geo-informatics are. • Relate geomatics to civil engineering • Comprehend what photogrammetry is and how it is applied • Understand the concept of interior orientation of photos The course Detailed Topics of Lecture • Why Geoinformatics? • Introductory concept of photogrammetry. • Photos, strips, and blocks • Aerial cameras • Definition of photo and ground coordinate systems • Interior orientation. • Introduction to software حظات م• سأقوم بتدريسه حيث س الجزء الذي فقط علي تنطبقحظاتذه الم ه يشارك د. تدريس هذا الكورس مرسي في سالم. • لجيوماتكست ا و تطبيقا موضوع الفوتوجرامتريضراتي تغطي محا فيد لموضوعات أخري و قد تمتيدترمه وحتي المندسه المدني اله• عملي ونيه فصول ويلفصولي في ال عملن الترملثاني مسبوع ا ا ظري• ي البرامج المستخدمهحانات عمليه عل توجد امت. • مطلوبه وت المعلوما ال ان تغطي كللمقصود منهاضرات ليس المحاذه ا هلمحاضر خ يضيفه اظات وشرح و كل ماحب مسئول عن إضافه ملطال ا لضراتلمحا ا• ند بدئها و يفتح بعدلمحاضره ععة ااب قا يغلق ب15 يسمحيقه فقط و دقدخول بعدها بال• ضراتلمحازات في ا ستعقد كويضروره وستقبلن بالشن دون اعلسكا و اكليه فقطعذار الرسميه من ال ا. By D. Kamal M. Ahmed 1 2 3 4 5 6
Transcript
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PBW 201B
GEOINFORMATICS
GROUND AND AERIALINFORMATION SYSTEMS
Lecture 1
Introduction
• Learning objectives
• Introduction and overview
• Geomatics defined
• Geomatics Workflow
• Sciences and Technologies involved
• Introduction to Photogrammetry
• Next Lecture
2
• The objective of the contents of this lecture is to provide an overview of
• course contents and scope; and
• Geomatics in general and as applied in Civil Engineering
• Introduce the concept of photogrammetry
• General overview of orientation of photos
• Interior orientation
• Upon the conclusion of this lecture students should be able to
• Comprehend what Geomatics and Geo-informatics are.
• Relate geomatics to civil engineering
• Comprehend what photogrammetry is and how it is applied
• Understand the concept of interior orientation of photos and how it is performed using a software
The course
Detailed Topics of Lecture
• Why Geoinformatics?
• Introductory concept of photogrammetry.
• Photos, strips, and blocks
• Aerial cameras
• Definition of photo and ground coordinate systems
• Interior orientation.
• Introduction to software
مالحظات يشارك هذه المالحظات تنطبق فقط علي الجزء الذي سأقوم بتدريسه حيث س•
.سالم مرسي في تدريس هذا الكورس. د
في محاضراتي تغطي موضوع الفوتوجرامتري و تطبيقات الجيوماتكس•الهندسه المدنيه وحتي الميدترم و قد تمتد لموضوعات أخري
ظرياالسبوع الثاني من الترم عملي في الفصول ويليه فصول عملي ون•
.توجد امتحانات عمليه علي البرامج المستخدمه•
هذه المحاضرات ليس المقصود منها ان تغطي كل المعلومات المطلوبه و •ل الطالب مسئول عن إضافه مالحظات وشرح و كل ما يضيفه المحاضر خال
المحاضرات
دقيقه فقط و اليسمح 15يغلق باب قاعة المحاضره عند بدئها و يفتح بعد •بالدخول بعدها
و السكاشن دون اعالن بالضروره وستقبل ستعقد كويزات في المحاضرات•.االعذار الرسميه من الكليه فقط
By D. Kamal M. Ahmed
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اخر الفصول العمليه تسجل الدرجه في السكشن فقط و يسجل الغياب•تم االنصراف قبل الغياب يلغي درجة الحضور و العملي وان. السكشن
.العملي و رصد
خص المنتظر من الطلبه الجديه القصوي في الفصول العمليه و علي اال•طالب تم التنبيه علي المعيدين بإنهاء حضور ال. عند استعمال البرامجالخارج علي النظام
ي و من يمكن امداد الطالب بالبرامج الستعمالها علي الكومبيوتر الشخص•وري لكن يظل من الضر. المفضل احضار الكومبيوتر الشخصي للمعمل
عمل التمارين في وقت المعمل
غير مسموح بالحضور في فصل غير الفصل المسجل فية الطالب•
ال تتوقع ترجمه . من الصعب تدريس هزا الجزء بالعربيه: اللغه•و لكن سأرحب بالمساعده في المحاضره و. المحاضرات او االمتخانات
االمتحان
وله ال تستعمل مصطلحات منق, االجابه بالعربيه مقبوله طالما مفهومه•خاطئه
حساباالمتحان غالبا متعدد االختيارات لكن من المطلوب تدوين خطوات ال•
مالحظات Course and Instructor
• D. Kamal Ahmed Background.
• Lecture management methods and breaks.
• The syllabus• Note grade distribution and lab work policy.
• Graded material• Software
• What I expect from you
What you Learnt
• What did you learn so far?
• Traditional surveying: • Measurements of elevations and coordinates
using levels and total stations
• Applications of mapping and setting out.
• Geodesy and GPS
• Geodesy and GPS
• Now you know about the bases of realistic worldcoordinates and distances.
• Why are you taking this course? Will it make a difference?
• There are more ways to collect information about the surface of the earth and do similar things. The other technologies enabled not just similar surveying works but added speed and modern applications.
• For example, • how would self-driven vehicle avoid accidents with just total
stations, levels, and GPS?
• How would you map a large area such as the city of shikh Zaid in a reasonable time?
• How would you manage information related to map features?
• How would you build accurate 3D models of features معالم and topography of large of large areas fast?
• And more
In this course you will compliment your knowledge of sciences of
measurements and modeling by learning:
• How to do surveying from photographs taken from air or on ground
(photogrammetry) :produce maps, collect information, and produce
models
• Use digital images from space (remote sensing)
• Produce accurate 3D models by laser scanning (LIDAR).
• Learn how seabed is mapped by hydrographic techniques.
• How to connect map or image features to their descriptive information
and do analysis(GIS).
• Learn about how all techniques are used in civil engineering projects
What is Missing
Other Technologies• There are other technologies that can be used to
measure coordinates, mange spatial information, and produce surveying products such as:
• Photogrammetry.
• Remote sensing.
• Hydrographic surveys
• Geographic Information Systems (GIS).
• Laser scanning (LIDAR).
That is in addition to necessary background of theory of errors and adjustment.
Why are you taking this course? Will it benefit you??
Geomatics/ GeoinformaticsDefined
Not all the information the coming series of slides is required as is. The instructor will mention in lecture what you should study.Note a remark on a slide when all information is required.
Geomatics and Geoinformatics
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• There are several definitions of Geomatics, Oxford Dictionaries define geomatics as: “the branch of science that deals with the collection, analysis, and interpretation of data relating to the earth's surface.”
• Where did the term “geo” come from?‒ The term “Geo” in general means “the earth” , the word is of a
Greek origin. The shape of the earth, as based on gravity measurements, is called a “geoid”.
• Geomatics consists of products, services, and tools involved in the collection, integration and management of geographic data. Geographic information can be retrieved from various sources, including earth-orbiting satellites, ground-based instruments and airborne and seaborne sensors. These data are transformed into digital maps and other usable forms with state-of-the-art information technology.
“Applied Geomatics Research Laboratory, University of Waterloo”18
• Another definition of Geomatics by B. Dubuisson in 1969 is that the word is formed from the combination of GEODESY and GEOINFORMATICS terms. Where:
• Geodesy: “the branch of mathematics dealing with the shape and area of the earth or large portions of it.”
• GEOINFORMATICS:” Geoinformatics is the science and the technology which develops and uses information science infrastructure to address the problems of geography, cartography, geosciences and related branches of science and engineering.”
Geomatics is also known as geospatial technology, or geomatics engineering
• Air base: the distance between exposure stations, points where photos are taken.
• H: flying height above datum, h is height of point above datum or elevation of a point, H-h: above ground (unless if mentioned otherwise)
• Uppercase letters refer to ground space, while lowercase letters refer to photo space: (A) is a point in “reality” or in ground system, while (a) is a point on a photograph.
• Standard film cameras are of 9X9” frame size and 6” focal length
• I ft = 12 inch, 1 yard = 3 ft, 1 mile = 5280 ft
• I inch = 2.54 cm
• 1 m = 3.2808333 ft cm, 1 km = 0.6213699 mile
D. Kamal M. Ahmed
The basic concept? الفكره االساسيهره و تلتقط صور من االرض او الجو ثم نوجد العالقه الفراغيه بين الصو•
الواقع
ننشئ محاور علي الصوره و نقيس س و ص بدقه عاليه•
وره ثم نطبق معادالت للحصول علي االحداثيات االرضيه من احداثيات الص•المقاسه
خرائط و تستخدم االحداثيات االرضيه لكافة التطبيقات المساحيه مثل انتاج•عمل مقاطع و توليد اسطح و حساب كميات و انشاء نقط تحكم جديده
قد تلتقط الصور من االرض او الجو من طائرات او اقمار صناعيه •
للقياس الدقيق او لتفسير الصور
ما هي العالقه بين الفوتجرامتري و االستشعار من بعد؟؟
By D. Kamal M. Ahmed By D. Kamal M. Ahmed
تؤخذ صور متداخله من
طائرات
عاد و ثم نولد نموذج ثالثي االب
نقيسه
نسبه ننشئ او نعرف محورين علي الصوره و نقيس احداثيات اي نقطه بال
ص علي الصوره و , ثم نحل العالقه بين س (. ص, س)لهما مثال
.االحداثيات علي االرض
ود هنا الحظ ان المقص. قد تكون الصوره مأخوذه بكاميرا رقميه او ذات فيلم
ن حيث ان الصوره العاديه علي ورقه ممك, نوع الكاميرا و ليست الصوره.عمل سكان لها فتصبح رقميه
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x
y
قه للحل و يتم ذلك بقياس االحداثيات علي الصوره ثم ضبطها و إختيار طري
.انتاج المخرجات المطلوبه مثل الخرائط
, مهفي كل االحوال ونظرا الن احداثيات الصوره ستضرب في ارقام ضخ
مأخوذه يلزم في البدايه عمل معايره للكاميرا و عمل توجيه داخلي للصور ال
.بفيلم و ضبط االحداثيات للتخلص من تأثير عوامل متعدده
التسلسل الطبيعي لقياسات الفوتوجرامتريNormal sequence of photogrammetry operations
قياس االحداثيات من الصور و ضبطها
استعمال العديد من الصورUsing several photos
استعمال زوج من الصورUsing a pair of photographs
الحل من صوره واحدهSingle photo computations
Apply simple equations such as scale and relief displacement
التوجيه النسبي
Relative orientation
Interior Orientation (IO)التوجيه الداخلي
(May not be needed for digital cameras)
التوجيه المطلق
Absolute orientation
Exterior orientation (EO)(Space resection)
التوجيه الخارجي
حساب االحداثيات االرضيه و انتاج
الخرائط و المنتجات المساحيه كاالسطح
Triangulation
Bundle Adjustmentضبط حزمه
GPS/IMU Navigation GPS/ IMUتزويد الطائره ب
لعديد من خرائط هيئة المساحه المصريه انتجت من صور اجويه
Definition and Classification of Photogrammetry
تعريف و تصنيف الفوتوجرامتري
• “Photogrammetry is the art, science, and technology of obtaining reliable information about physical objects and the environment through the processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena.” (ASPRS, 1980)
• The term Photogrammetry is composed of three Greek words: Phot (light) gramma (something drawn) and metrien (to measure).
Definition and classification of Photogrammetry
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• Photogrammetry principles are applied, more than 170 years ago, to imagery of various sources and platforms such as: manned airplanes, drones طائرات بدون طيار, satellites , under water vehicles, user cameras, and more.
• Photogrammetry can be classified in many ways:
1. According to purpose: metric or interpretative2. According to camera location: Aerial or terrestrial
3. According to tilt of optical axis: vertical, tilted, or oblique.
Classification of photogrammetryMetric / Interpretative
Metric
Precise
- Precise
- Intended for measurements
Interpretative
- Recognizing objects and forming an opinion
- Based on shape, texture, shadow, size, etc.
Classification of photogrammetryAerial / Terrestrial
• Aerial• Photos taken form aircraft
• Uses for engineers: mapping, cross sections, elevations, areas, etc.
• Cameras/sensors on aircrafts, drones, satellites, …
Classification of photogrammetryAerial / Terrestrial
• Terrestrial• Photos taken from earth-based
cameras
• Uses for engineers:
• Structure deformation monitoring
• Slope stability measurements
• Medical imagery and modeling.
Foxywalk system by Heliceo
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3D building model using modern photogrammetric applications
Classification of photogrammetryVertical/ Tilted/ Oblique
• Photos are:
•True Vertical: if the camera axis is exactly vertical, or near vertical.
• Tilted Photographs: little tilt, more than 4°
• Oblique photographs: high (horizon visible) and low
• Vertical Photos are the most used type for surveying applications
Low oblique digital aerial image
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High Oblique Aerial Photo
• Analog PhotogrammetryUsing optical, mechanical and electronical components, and where the images are hardcopies. Re-creates a 3D model for measurements in 3D space.• Analytical PhotogrammetryThe 3D modelling is mathematical (not re-created) and measurements are made in the 2D images.• Digital PhotogrammetryAnalytical solutions applied in digital images. Can also incorporate computer vision and digital image processing techniques.• Softcopy Photogrammetry”Softcopy” refers to the display of a digital image, as opposed to a ”hardcopy” (a physical, tangible photo).
Classification of photogrammetryAnalog, Digital, Digital, and Softcopy
Softcopy Digital Photogrammetric Workstations
Taking Aerial Photographsالتقاط الصور الجويه
• Strips and Blocks• Aerial Cameras
Aerial Camera in action
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Geometry of Vertical Photographs
• Define: image coordinate system (right handed), principal point, exposure station.
• If a film is used, measurements could be done using negatives or diapositives, same geometry, referred to the fiducials
• In digital images, row and columns of pixels define a coordinate system
Direction of flight
Taking Aerial PhotographsPhotos, strips, and blocks
A strip of 5 photos
A strip of aerial photographsA block of two strips with side lap
Taking Aerial PhotographsPhotos, strips, and blocks
Strips and blocks (4 photos, two per strip)
Taking Aerial PhotographsPhotos, strips, and blocks
By D. Kamal M. Ahmed
Strip
+Strip
Block
=
G
G
B
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- Sidelap (about 30%) to ensure
that no gaps exist between
flight lines
- Endlap (about 60%) to provide
stereo vision and depth
measurements
- Strips and blocks:
• A strip of photographs is a
set of consecutive photos
along a single line
• A block of photographs is
composed of several strips
Side and End Laps Metric Aerial Cameras• Metric aerial cameras must be (details in lectures):
• Geometrically stable• Have fast and efficient shutters• Have high geometric and optical quality lenses
• They can be classified according to type of frame:• Single lens Frame • Multiple frame• Strip Frame• Panoramic
• They can also be either film or digital cameras. Almost all photogrammetric works today employ digital cameras
THIS COURSE WILL DISCUSS ONLY SINGLE FRAME METRIC CAMERAS
Aerial Cameras Aerial camera with viewfinder and electronic control
A traditional film camera
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Digital aerophotogrammetric cameras(DACs)
• simultaneously record panchromatic, red, blue, green and infrared part of electromagnetic spectrum.
• With the help of GPS (Global Positioning System)and IMU (Inertial Measurement Unit) and gyroscopes, it is possible to get oriented images right after airplane landing.
• The images are directly loaded into Digital Photogrammetric Workstation) DPWs for further processing.
A modern digital aerial photogrammetric camera. Note the mosaicking of the panchromatic image using four camera units, and the separate red, green, blue (RGB) and near infrared camera units.
Solid State CCD imaging array of 14,600 X 17,200 (250 million) pixels.
The camera mount is the mechanism used to attach the camera to the aircraft. Its purpose is to constrain the angular alignment of the camera so that the optical axis is vertical and the format is squarely aligned with the direction of travel.
Camera Mounts
Gyro stabilized aerial camera mount
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• Digital Images and resolution
Metric Aerial Cameras• The number of pixels in one image represent the
resolution of the image, the smaller the pixel, the higher (better) the resolution.
• A mega (million) pixel image includes one million pixel• Number of pixels can be as low as 500X500 = 250,000
pixels, or hundreds of millions of pixels for commercial cameras.
• Example: What is the resolution of a camera that includes a CCD frame sensor, that is 1024 X1024 elements, if the size of a pixels is 5? How many megapixels are there?
Answer: 1024 X 0.005 = mm, and 1024X1024= 1 mega pixel
Digital image resolution Concept of image pyramids
Geometry of digital frame cameras (with CCD array)
Aerial CamerasFrame Cameras
Imaging devices can be categorized according to how the image is formed.
1- Frame cameras(or frame sensors): devices that acquire the image simultaneously over the entire format. Frame cameras generally employ shutters which open and allow light from the field of view to illuminate a two- dimensional (usually rectangular) image plane before closing.
Components of a single frame film camera.
Three main parts:1. Magazine2. Body3. Lens cone assembly
Components and notes to be discussed din lecture
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Components of a single frame film camera.
Fiducial Marks
A vertical Photograph
Components of a single frame film camera.
Example of a corner Fiducial Mark under Magnification
Single lens Frame Cameras
• Standard is 9” (23 cm) frame size and 6” (15 cm) focal length( f).
• They can be classified according to the field of view to:
• Normal angle ( up to 75)• Wide angle ( 75 𝑡𝑜 100)• Super-wide angle (greater
than to 100)
Geometry of aerial cameras
L:
Principal Point (P.P)
2- Devices that sense only a linear projection (strip) of the field of view at a given time. A linear CCD scans the ground at a given time. The vehicle advances a distance equals to one array and capture the next line. Will the entire image be scanned at the same time?
What is the effect of wind turbulence.
Aerial Camerasstrip cameras, linear array sensors, or push-
broom scanners
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Raw image from an airborne linear array sensor exhibiting distortion caused by air turbulence.
Rectified image obtained by correcting the raw image using GPS/INS measurements.
3- Devices that build an image by detecting only a small spot at a time, requiring movements in two directions (sweep and scan) in order for the two-dimensional image to be formed. The geometry is such that the after a row is finished being scanned, the vehicle advanced to the beginning of the next row.
Aerial CamerasFlying Spot Scanners
Effect of Crab
Photo Coordinates Measurements
قياس احداثيات الصوره
Interior Orientationالتوجيه الداخلي
Interior Orientation
As mentioned before, the whole idea of modern photogrammetry is that we measure photo coordinates and apply equations to compute ground coordinates.
To measure photo coordinates, we assume two lines on the photo and call them (x) and (y). For any point, we measure the distance to x and y.
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Interior Orientation Photo coordinates are small when compared to ground coordinates, they will be multiplied by large numbers. Therefore, they must be estimated very precisely, within few microns ( 1 micron is 1/1000 mm).
The purpose of the interior orientation is to calculate all the parameters needed to estimate precise photo coordinates. It is a process that is limited to the camera and the photograph.
• There are several distortions تشوهات in the location of a point on a photograph. The image of a point may be shifted on the photograph due to many factors that should be corrected for prior to the actual measurements of photo coordinates, they are:
A. (a) Film distortions due to shrinkage, expansion, انكماشوتمددالفيلم and lack of flatness;
(b) CCD array distortions due to electrical signal timingissues or lack of flatness of the chip surfacefilm shrinkageand expansion
B. (a) Shift of the Principal Point (PP) (xo, yo) from the fiducialcenter.;
ورهالصحدودعليالعالماتبينالواصلهالخطوطتقاطعنقطةمعPPتطابقعدم(b) Failure of principal point to be aligned with center of CCDarray
Which of the corrections inapplicable for digital images??
Calculations of interior orientation parameters
• The following elements are usually determined by a calibration process in a lab:
• Calibrated focal length• Lens distortion coefficients• Shift of center of fiducials from the P.P• Calibrated coordinates of the fiducial marks, in
film cameras. Note that digital photos do not need fiducials
The following two slides show the calibration certificate for the camera that captured the images you will use in lab sections
A calibration certificate of a metric camera. The results show:• The calibrated focal
length• The coordinates of the
principal point• The coefficients of lens
distortion
• Calibrated fiducial mark coordinates
• The photographs used in lab sections are take with this camera
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Interior Orientation Radial Lens Distortion
Rays of light are displaced as they pass through the lens due to distortions of the lens. These distortions, even though being very small, shift image locations and should be corrected for if precise ground coordinates are needed.There are different types of distortions, the most important is the radial lens distortion. This distortion shifts the image of points from the PP, either to towards it or away from it as shown in the figure.
• The equation to correct for radial lens distortion is:
• Where: Δr is the amount of radial lens distortion, r is the radial distance from the principal point, and k1, k2, k3, and k4 are coefficients of the polynomial
• Example:
The calibration certificate of a Carl Zeiss camera was given in the previous slides. Calculate the radial lens distortion for point (a) if the measured photo coordinates of that point are: (73.362, and 63.372) mm.
Answer:
Atmospheric Refraction
Effect of Earth Curvature
Since the earth’s surface is curved and the ground coordinates in (X,Y) assume a flat surface; the position of a point on a photograph is displaced from the theoretical point on the photograph if the earth was flat.This correction may be neglected if a local limited coordinate system is used.
Performing the interior Orientation• Almost all photogrammetric
applications are of a digital nature.
• The images are either digital images captured by a digital camera, or scanned photos that were captured on film.
• After all corrections are input to the software, it is necessary to relate the rows and columns of pixels of the image to the (x, y) photo coordinates.
• This process is done by applying a two-dimensional coordinate transfection between the two systems, but what are they?
(x, y) and (r, c)• In a digital image, we measure rows and
column locations(r, c).• In a digital camera, the relationship
between pixel locations in (r,c) and photo (x,y) at center is defined within the camera, no need for additional transformation
• In a film camera, the relationship is between photo fiducials (x,y) and ground (X, Y).
• When we scan a photo taken by a film camera, it becomes in a digital format, we measure (r,c). In this case, we need to transform (r,c) that we measure to (x,y) photo coordinates to apply the equations.
• A two-dimensional coordinate transformation from (r, c) to (x, y) is needed if the camera is not digital, this completes the process of interior orientation
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Note on digital imagesNowadays the use of digital aerial cameras, obtaining digital imagery
directly, is common. In such cameras, the image sensor, a CCD (charge-
coupled device) array, is an integral part of the camera and rigidly attached to the camera body. For this reason, it is not necessary to perform
interior orientation on digitally obtained imagery. Only camera calibration is needed and serves for all images obtained with that camera.
If, however, one uses images that were originally obtained on film and
then scanned, interior orientation is needed: the film roll moves — is
transported forward — between exposures, and the precise position of the
film in the camera image field will vary a little from exposure to exposure.
This makes it necessary to reconstruct this precise position, using fiducial
marks exposed onto the same image and rigidly attached to the camera
body, the process known as interior orientation.
ملحوظه بخصوص الصور الرقميه
ن يكون الماسح الضوئي جزء م, الفكره انه لو استعمل كاميرا رقميه•لكن .الكاميرا وال يغير وضعه النسبي داخل الكاميرا من صوره ألخري
قد , نظرا الن الفيلم يتحرك من لقطه الخري, في حالة كاميرا بفيلمره بوضعها يتحرك الفيلم بالنسبه لمكونات الكاميرا و ال تحتفظ كل صو
المات لذا يثبت اطار فيه ع. الدقيق بالنسبه للعدسه و باقي الكاميراحاور هذه العالمات تحدد م. الفيدوشال امام الفيلم ليضهر في كل صوره
م تم عمل في عمليه التوجيه الداخلي لصوره من فيل, و بالتالي. القياسوره يلزم قياس موقع الص, سكان او مسح ضوئي لها فأصبحت رقميه
.بالنسبه للعالمات
يه عمل التحويل الي نظام احداثيات الفيدوشالز هو اخر خطوات التوج•مود الي الداخلي و ينتهي بإنشاء العالقه بين نظام احداثيات الصف و الع
(.ص, س )
و ( دعمو, صف )تقاس في , عند قياس اي نقطه علي الصوره, بعد ذلك•( ص, س ) يحولها البرنامج مباشرة الي
• Pixels in a digital image represent coordinates of rows and columns. The transformation from (r, c) to (x, y) of any pixel is defined within the camera and does not need additional measurements
• However, for a scanned photos captured on film with fiducials, the scanned image now need transformation from (r, c) to (x,y).
• This is done by zooming in to each fiducial and click on it, this is called digitizing. Now, the software knows the precise (x, y) fiduicial coordinates from the calibration report, and the (r, c) of that mark.
• A two-dimensional coordinate transformation is performed by the software to establish the relationship between the two systems.
• Afterwards, when a point is digitized (clicked on), the coordinates of this point are immediately computed in the (x, y) photo coordinate system by the software.
Performing the interior Orientation
• The transformation is usually done using a two-dimensional affine coordinate transformation to allow for different scales in the (x) and (y) directions. This is because the film could have been stretched differently in each direction.
• The equation for a two dimensional conformal transformation is shown in the upper figure, while the affine transformation is given in the lower figure.
Performing the interior Orientation
• To transform the coordinates between two systems (conformal), you need four unknowns: two translations in the x and y for the origins to coincide, a rotation of the axes, and a scale to make shapes fit. The equations to transform between (X, Y) and (E,N) for example are:
• Each point known in both systems, such as (A) in the example equations, will add two equations. Since we have four unknowns: a, b, TE and TN, we need at least two points known in both systems for a unique solution
Performing the interior Orientation
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• two more unknown are added for affine transformation to allow for different scales in x and y directions, and non orthogonality of the axis, the following equations include six unknowns. At least three points defined in both systems are required for a unique solution.
• As you visit the fiducials, 4 or 8 of them, you establish a relationship between the two systems. Each point generates two equations.
• The software will perform a two dimensional affietransformation
• Now what??????
Performing the interior Orientation
Measurement of Feature Positions
Zoomed-in view of a manhole with cross-hair at center.
Zoomed-in view of a chevron target with cross-hair at the intersection of centerlines of the stripes
After the interior orientation is performed, to measure photo coordinates in digital photogrammetry, you zoom-in at the point or intersection to be measured, place position the cursor, and click to measure. Photo coordinates are recorded.
The Software
EFOTO
Wolfpack
Photogrammetry Software
• We will use two software: Efoto and Wolphpack
• You can download both of them for educational use with tutorial data
Efoto
• Work flow: see image to the right
• Demo by the instructor
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interior orientation Using a softwareWolfpack
Start the program by clicking on the icon on the desktop or Under “programs”.
Click on : programs -> photogrammetry -> digitize
Select one of the images, say “5-high”, and click “open.
then give a name for the file to save your answer. You file name should be your first and last name followed by your BN, for example: “Magdy Maged_16” and click on ”save”.
The image is now opened and zoomed onto one of the fiduicials
You can change the shape of the cursor if you want.
Input the fiducial number at “Id”. In this example, I would type “F3”
After you carefully place the cursor on the mark and click, the coordinates are displayed.
Move the mouse and position the cursor again on the mark and click, repeat that at least three times. DO NOT CLICK THREE TIMES WITHOUT MOVING THE MOUSE, the standard deviation will be zero and you may get no grade!
Save the point and move to the next one.
Repeat that for the remainder of the 8 points
When done, click on ” close”, the results file will be displayed. Show the file to the TA, then close the file
Go back to wolfpack main menu, programs, photogrammetry, then, “interior orientation”.
Select the file you digitized and perform the interior orientation, Show the results to the TA before your colleague takes over.
