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Technical information

OGC

WMS – WFS – CSW



OGC: Open Geospatial Consortium

http://www.opengeospatial.org/

« non-profit, international, voluntary consensus standards organization that is leading the development of standards for geospatial and location based services »

WMS: Web Map Service

WFS: Web Feature Service

Catalogue Service [CSW]



WMS / WFS / CSW

… Are Web Services…

Are requested « over HTTP » (use of a URL http://.... Or a HTTP form)

The parameters in the request HTTP communicate with the Web Service to indicate: Which operation is called With wich parameter

+> Very simple to use.

They response:

A XML file (description of the response) Or an image (Web Map Service, operation getMap)



WMS: Web Map Service

http://www.opengeospatial.org/standards/wms

« Provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases. »

« A WMS request defines the geographic layer(s) and area of interest to be processed. »

« The response to the request is one or more geo-registered map images (returned as JPEG, PNG, etc) that can be displayed in a browser application. »

« The interface also supports the ability to specify whether the returned images should be transparent so that layers from multiple servers can be combined or not. »



WMS: getCapabilities

The first operation supported by a WMS is: getCapabilities. Response is a XML file describing:

+> The information about the server (title, abstract, access constraints,…)

+> The coordinate system, area, scale, …

+> The datasets (layers), with for each: * is queryable * the legend to use * the title, * … WMS: http://serviziogeologico.apat.it/cocoon/Onegeology/wms_enGetCapabilities:http://serviziogeologico.apat.it/cocoon/Onegeology/wms_en?service=wms&request=getCapabilities&version=1.1.1



WMS: getMap

The second operation supported by a WMS is: getMap The query contains: +> The name of the layer(s) called

+> The area (bbox), and the coordinate system used

+> The type of the image (png, gif, …)

+> The size of the image

http://serviziogeologico.apat.it/cocoon/Onegeology/wms_en?VERSION=1.1.1&REQUEST=GetMap&SERVICE=WMS&LAYERS=ITA_APATSGI_EN_500k_Lithology&SRS=EPSG:4326&BBOX=2.342014940440123,35.581577943782676,22.854835453260648,48.197949615272464&WIDTH=1143&HEIGHT=703&FORMAT=image/png&STYLES=Default&TRANSPARENT=TRUE

The response is… the image



WMS: getMap with SLD

A SLD is a Style (Styled Layer Description) describing +> How to draw the Features

http://appgeosciml.brgm.fr/GeoserverGeoSciML_boreholes/wms?SERVICE=WMS&request=GetMap&LAYERS=brgm:fra_nordpdc_bss_brgm&WIDTH=800&HEIGHT=500&VERSION=1.0.0&FORMAT=image/png&SRS=EPSG:27582&BBOX=544892.9,2555869.7,732402.0,2675770.0&STYLES=bss

http://appgeosciml.brgm.fr/GeoserverGeoSciML_boreholes/wms?SERVICE=WMS&request=GetMap&LAYERS=brgm:fra_nordpdc_bss_brgm&WIDTH=800&HEIGHT=500&VERSION=1.0.0&FORMAT=image/png&SRS=EPSG:27582&BBOX=544892.9,2555869.7,732402.0,2675770.0&STYLES=bss_withdepth_greaterThan_200




<?xml version="1.0" encoding="utf-8"?><StyledLayerDescriptor version="1.0.0" > <NamedLayer><Name>bss</Name><UserStyle> <FeatureTypeStyle>

<Rule> <ogc:Filter> <ogc:PropertyIsEqualTo> <ogc:PropertyName>prof_debut</ogc:PropertyName> <ogc:Literal>0</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <PointSymbolizer> <Geometry><ogc:PropertyName>geom_l2e</ogc:PropertyName></Geometry> <Graphic> <Mark><WellKnownName>triangle</WellKnownName> <Fill><CssParameter name="fill">#fffc00</CssParameter></Fill> <Stroke>

<CssParameter name="stroke">#000000</CssParameter> <CssParameter name="stroke-width">1</CssParameter>

</Stroke>

</Mark><Size>10</Size> </Graphic> </PointSymbolizer> </Rule>

</FeatureTypeStyle> </UserStyle> </NamedLayer></StyledLayerDescriptor>




<?xml version="1.0" encoding="utf-8"?><StyledLayerDescriptor version="1.0.0" > <NamedLayer><Name>bss</Name><UserStyle> <FeatureTypeStyle>

<Rule>

<ogc:Filter> <ogc:PropertyIsGreaterThan> <ogc:PropertyName>prof_fin</ogc:PropertyName> <ogc:Literal>200</ogc:Literal> </ogc:PropertyIsGreaterThan> </ogc:Filter> <PointSymbolizer> <Geometry><ogc:PropertyName>geom_l2e</ogc:PropertyName></Geometry> <Graphic> <Mark><WellKnownName>triangle</WellKnownName> <Fill><CssParameter name="fill">#990000</CssParameter></Fill> <Stroke>

<CssParameter name="stroke">#000000</CssParameter> <CssParameter name="stroke-width">1</CssParameter>

</Stroke> </Mark><Size>5</Size> </Graphic> </PointSymbolizer> </Rule>

</FeatureTypeStyle> </UserStyle> </NamedLayer></StyledLayerDescriptor>



WMS: getFeatureInfo

The third (optional) operation supported by a WMS is: getFeatureInfo The query contains: +> The name of the layer(s) called

+> The area (bbox), and the coordinate system used

+> The size of the image

+> The point in the image

http://serviziogeologico.apat.it/cocoon/Onegeology/wms_en?&VERSION=1.1.1&REQUEST=GetFeatureInfo&SERVICE=WMS&LAYERS=ITA_APATSGI_EN_500k_Lithology&SRS=EPSG:4326&BBOX=2.34201494,35.581577944,22.854835453,48.197949615&WIDTH=1143&HEIGHT=703&INFO_FORMAT=text/html&FORMAT=image/png&FEATURE_COUNT=100&QUERY_LAYERS=ITA_APATSGI_EN_500k_Lithology&STYLES=default&X=442&Y=190

The response is… the attributes



WFS: Web Feature Service

http://www.opengeospatial.org/standards/wfs

« Defines an interface specifying requests for retrieving geographic features across the Web using platform-independent calls. »

« Defines interfaces and operations for data access and manipulation on a set of geographic features, including:

Get or Query features based on spatial and non-spatial constraints Create a new feature instance Get a description of the properties of features Delete a feature instance Update a feature instance Lock a feature instance

« The specified feature encoding for input and output is the Geography Markup Language (GML) although other encodings may be used. »



WFS: getFeature

WFS are several operations. The main is « getFeature »

The query contains: +> The name of the layer(s) called

+> The filter to select features:* Area (bbox)

* or other operations http://192.168.6.47/GeoserverGeoSciML/wfs?

service=WFS&request=GetFeature&maxFeatures=3&typeName=fra_nordpdc_50k_fgeol

The response is an XML file displaying the features (GML)



Catalogue Service

http://www.opengeospatial.org/standards/cat

« Supports the ability to publish and search collections of descriptive information (metadata) about geospatial data, services and related resources. »

« Providers of resources use catalogues to register metadata that conform to the provider's choice of an information model; such models include descriptions of spatial references and thematic information. » [WP4]

« Client applications can then search for geospatial data and services in very efficient ways.» [WP6]



CSW getRecords

CSW is the language used to request the catalogue service.

GetRecords: An operation to request for a list of results, according to a constraint (filter)

http://193.56.4.106/geonetwork/srv/en/csw?request=GetRecords&service=CSW&version=2.0.2&CONSTRAINTLANGUAGE=FILTER&resultType=results&maxRecords=3&constraint_language_version=1.1.0&Constraint=<Filter xmlns="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml"><Not><PropertyIsLike><PropertyName>type</PropertyName><Literal>dataset</Literal></PropertyIsLike></Not></Filter>

Response in XML form.

+> Used for the search engine



CSW getRecordById

CSW is the language used to request the catalogue service.

GetRecordById: An operation to request for a record in the metadata catalogue, according to its ID

http://193.56.4.106/geonetwork/srv/en/csw?request=GetRecordById&service=CSW&version=2.0.2&id=2865feee55bcc2f2c55075885d09faaa38e20c4

Response in XML form.



Conclusion

Simple to use

Several softwares (open source or commercial) implementing these standards

But…

Multilingual issues?

Harmonization issues? (GeoSciML for WFS, format of the getFeatureInfo response)

WFS: performance issues?



OneGeology Europe

Services



Geological Survey C

web

web

PortalGeological Survey BGeological Survey A

HarmonizedWeb Services

Harmonization:

Mapping rules (between national data model and 1G data specification)

which database, which attribute, to fill 1GE data spec

Translations (dictionaries) for a given attribute for which a dictionary is defined, for each national database value, which common dictionary concept has to be used.

Datasets

Datasets

WMS

WFS

W*S

Mapping rules

1GE



Data Base

Datasets

Datasets

DictionnariesTransformation

Service (coordinates)

Geological Survey

getCapabilities

getFeatureInfo

getCapabilities

GeoSciML

getFeatures

INSPIRE WMS

INSPIRE WFS

1GE

DATA

MODEL

getMap

1GE SLDs

?1GE

?1GE

Date post:	19-Dec-2015
Category:	Documents
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