Spatial Filter/OGC Service Type Matrix
In addition to the spatial filters listed above, we intend to eventually support Intersect by Line and Intersect by Point. For the time being, "Intersect by Point" can be faked by using "Entirely within Distance from a Point", where the distance is set to zero. See the example farther below. For any GetFeature request, one or more input spatial filters are supported. For a GetMap request, a single bounding box spatial filter is required. For additional information about Open Geospatial Consortium (OGC) compliant spatial filters, please visit OGC compliant spatial filters For these web services, spatial filters must be expressed using the version 1.0 filter encoding. Spatial Filter Extent LimitThe total extent defined by any spatial filter cannot exceed 10,100,000,000 square meters (approximately 3,900 square miles or 2,500,000 acres).Spatial Filter Descriptions and ExamplesIntersect by Bounding BoxAll features that share any coincidence with the bounding box are returned.Bounding Box - BBOX Shorthand example:BBOX=-114.006,32.1823,-113.806,32.2823Bounding Box - Intersect by Rectangle example:Filter=<Filter><BBOX><PropertyName>Geometry</PropertyName><Box srsName='EPSG:4326'><coordinates>-86.46878,40.56448 -86.45282,40.57646</coordinates></Box></BBOX></Filter> Intersect by Bounding PolygonAll features that share any coincidence with the bounding polygon are returned.Intersect by Bounding Polygon example:Filter=<Filter><Intersect><PropertyName>Geometry</PropertyName><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>-88.0865046533,37.5555143852 -88.0860204771,37.5600435404 -88.0782858287,37.5595392364 -88.0787704736,37.5550101113 -88.0865046533,37.5555143852</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs> </gml:Polygon></Intersect></Filter> Within Distance from a PointAll features that lie within a distance from a point are returned.Within Distance of a Point example:Filter=<Filter><DWithin><PropertyName>Geometry</PropertyName><gml:Point><gml:coordinates>-91.22,38.46</gml:coordinates></gml:Point><Distance%20units='m'>600</Distance> </DWithin></Filter> Workaround to achieve Intersect by Point (set distance to 0) example:Filter=<Filter><DWithin><PropertyName>Geometry</PropertyName><gml:Point><gml:coordinates>-91.22,38.46</gml:coordinates></gml:Point><Distance%20units='m'>0</Distance> </DWithin></Filter> Spatial Filter Spatial Reference SystemWeb Feature ServicesAn output spatial reference system is inherent to each web feature service. In other words, each web feature service corresponds to one and only one output spatial reference system. For a web feature service there is no explicit parameter for the output spatial reference system.An EPSG value may be specified within the Filter, for example the point for a "DWithin" may defined with <gml:point srsName='EPSG:4326'>. The coordinate pair for the point must therefore be specified in terms of the WGS84 coordinate system. Any of the EPSG codes listed in the Spatial Reference Help page may be used. Similarly the EPSG code may be specified for a Filter's BOX or Polygon nodes as needed. Note that the attribute name "srsName" is case-sensitive and, if employed, must be used as shown here. Web Map ServiceFor the web map service, an explicit output spatial reference system is required, and the spatial filter must be expressed using the BBOX tag. The bounding box coordinates must be in the same spatial reference system as the output spatial reference system. |