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Apache Jena GeoSPARQL

An implementation of GeoSPARQL 1.0 standard for SPARQL query or API.

Integration with Fuseki is provided either by using the GeoSPARQL assembler or using the self-contained original jena-fuseki-geosparql. In either case, this page describes the GeoSPARQL supported features.

Measurement units

(Source : Apache Jena GeoSPARQL)

Measurement units use the OGC Units of Measure 1.0 vocabulary

The following table gives some examples of units that are supported (additional units can be added to the UnitsRegistry using the javax.measure.Unit API. These URI are all in the namespace http://www.opengis.net/def/uom/OGC/1.0/ and here use the prefix units.

URI Description
units:kilometre or units:kilometer Kilometres
units:metre or units:meter Metres
units:mile or units:statuteMile Miles
units:degree Degrees
units:radian Radians

Full listing of default Units can be found in org.apache.jena.geosparql.implementation.vocabulary.Unit_URI.

Spatial and geometry property functions

Original documentation (before integration into Jena): galbiston / geosparql-jena

Apache Jena Spatial Functions/WGS84 Geo Predicates

The jena-spatial module contains several SPARQL functions for querying datasets using the WGS84 Geo predicates for latitude (http://www.w3.org/2003/01/geo/wgs84_pos#lat) and longitude (http://www.w3.org/2003/01/geo/wgs84_pos#long). These jena-spatial functions are supported for both Geo predicates and Geometry Literals, i.e. a GeoSPARQL dataset. Additional SPARQL filter functions have been provided to convert Geo predicate properties into WKT strings and calculate Great Circle and Euclidean distances.

Supported Features

The Geo predicate form of spatial representation is restricted to only 'Point' shapes in the WGS84 spatial/coordinate reference system. The Geo predicates are properties of the Feature and do not use the properties and structure of the GeoSPARQL standard, including Geometry Literals. Methods are available to convert datasets from Geo predicates to GeoSPARQL structure, see: io.github.galbiston.geosparql_jena.configuration.GeoSPARQLOperations

The spatial relations and query re-writing of GeoSPARQL outlined previously has been implemented for Geo predicates. However, only certain spatial relations are valid for Point to Point relationships. Refer to pages 8-10 of 11-052r4 GeoSPARQL standard for more details.

Geo predicates can be converted to Geometry Literals in query and then used with the GeoSPARQL filter functions.

    ?subj wgs:lat ?lat .
    ?subj wgs:long ?lon .
    BIND(spatialF:convertLatLon(?lat, ?lon) as ?point) .
    BIND("POLYGON((...))"^^<http://www.opengis.net/ont/geosparql#wktLiteral> AS ?box) . #Coordinate order is Lon/Lat without stated SRS URI.
    FILTER(geof:sfContains(?box, ?point))

Alternatively, utilising more shapes, relations and spatial reference systems can be achieved by converting the dataset to the GeoSPARQL structure.

    ?subj geo:hasGeometry ?geom .
    ?geom geo:hasSerialization ?geomLit .
    BIND("POLYGON((...))"^^<http://www.opengis.net/ont/geosparql#wktLiteral> AS ?box) . #Coordinate order is Lon/Lat without stated SRS URI.
    FILTER(geof:sfContains(?box, ?geomLit))

Datasets can contain both Geo predicates and Geometry Literals without interference. However, a dataset containing both types will only examine those Features which have Geometry Literals for spatial relations, i.e. the check for Geo predicates is a fallback when Geometry Literals aren't found. Therefore, it is not recommended to insert new Geo predicate properties after a dataset has been converted to GeoSPARQL structure (unless corresponding Geometry and Geometry Literals are included).

Filter Functions

These filter functions are available in the **http://jena.apache.org/function/spatial# namespace** and here use the prefix spatialF.

Function Name Description
?wktString spatialF:convertLatLon(?lat, ?lon) Converts Lat and Lon double values into WKT string of a Point with WGS84 SRS.
?wktString spatialF:convertLatLonBox(?latMin, ?lonMin, ?latMax, ?lonMax) Converts Lat and Lon double values into WKT string of a Polygon forming a box with WGS84 SRS.
?boolean spatialF:equals(?geomLit1, ?geomLit2) True, if geomLit1 is spatially equal to geomLit2.
?boolean spatialF:nearby(?geomLit1, ?geomLit2, ?distance, ?unitsURI) True, if geomLit1 is within distance of geomLit2 using the distance units.
?boolean spatialF:withinCircle(?geomLit1, ?geomLit2, ?distance, ?unitsURI) True, if geomLit1 is within distance of geomLit2 using the distance units.
?radians spatialF:angle(?x1, ?y1, ?x2, ?y2) Angle clockwise from y-axis from Point(x1,y1) to Point (x2,y2) in 0 to 2π radians.
?degrees spatialF:angleDeg(?x, ?y1, ?x2, ?y2) Angle clockwise from y-axis from Point(x1,y1) to Point (x2,y2) in 0 to 360 degrees.
?distance spatialF:distance(?geomLit1, ?geomLit2, ?unitsURI) Distance between two Geometry Literals in distance units. Chooses distance measure based on SRS type. Great Circle distance for Geographic SRS and Euclidean otherwise.
?radians spatialF:azimuth(?lat1, ?lon1, ?lat2, ?lon2) Forward azimuth clockwise from North between two Lat/Lon Points in 0 to 2π radians.
?degrees spatialF:azimuthDeg(?lat1, ?lon1, ?lat2, ?lon2) Forward azimuth clockwise from North between two Lat/Lon Points in 0 to 360 degrees.
?distance spatialF:greatCircle(?lat1, ?lon1, ?lat2, ?lon2, ?unitsURI) Great Circle distance (Vincenty formula) between two Lat/Lon Points in distance units.
?distance spatialF:greatCircleGeom(?geomLit1, ?geomLit2, ?unitsURI) Great Circle distance (Vincenty formula) between two Geometry Literals in distance units. Use http://www.opengis.net/def/function/geosparql/distance from GeoSPARQL standard for Euclidean distance.
?geomLit2 spatialF:transform(?geomLit1, ?datatypeURI, ?srsURI) Transform Geometry Literal by Datatype and SRS.
?geomLit2 spatialF:transformDatatype(?geomLit1, ?datatypeURI) Transform Geometry Literal by Datatype.
?geomLit2 spatialF:transformSRS(?geomLit1, ?srsURI) Transform Geometry Literal by SRS.

A dataset that follows the GeoSPARQL Feature-Geometry-GeometryLiteral can have simpler SPARQL queries without needing to use these functions by taking advantage of the Query Rewriting functionality. The geof:isValid filter function and geo:isValid property for a Geometry resource are not part of the GeoSPARQL standard but have been included as a minor variation.

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