This HTML5 document contains 105 embedded RDF statements represented using HTML+Microdata notation.

The embedded RDF content will be recognized by any processor of HTML5 Microdata.

Namespace Prefixes

PrefixIRI
n4http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#
dctermshttp://purl.org/dc/terms/
n6http://vos.openlinksw.com/dataspace/owiki/wiki/VOS/VirtGeoSPARQLEnhancementDocs/
atomhttp://atomowl.org/ontologies/atomrdf#
foafhttp://xmlns.com/foaf/0.1/
n24http://spatialreference.org/ref/epsg/4326/
n16http://vos.openlinksw.com/dataspace/services/wiki/
oplhttp://www.openlinksw.com/schema/attribution#
n2http://vos.openlinksw.com/dataspace/owiki/wiki/VOS/
n7https://github.com/openlink/
n8http://vos.openlinksw.com/dataspace/person/dba#
dchttp://purl.org/dc/elements/1.1/
n21http://svn.aksw.org/projects/GeoKnow/Public/
n10http://docs.openlinksw.com/virtuoso/
rdfshttp://www.w3.org/2000/01/rdf-schema#
n20http://trac.osgeo.org/proj/
n17http://rdfs.org/sioc/services#
siocthttp://rdfs.org/sioc/types#
n29http://vos.openlinksw.com/wiki/main/VOS/VirtGeoSPARQLEnhancementDocs/
n18http://trac.osgeo.org/proj/wiki/WikiStart#
n15http://vos.openlinksw.com/dataspace/owiki/wiki/
lodhttp://lod.openlinksw.com/
n19http://
n22https://bit.ly/
rdfhttp://www.w3.org/1999/02/22-rdf-syntax-ns#
n13http://vos.openlinksw.com/dataspace/owiki#
xsdhhttp://www.w3.org/2001/XMLSchema#
n23http://vos.openlinksw.com/dataspace/%28NULL%29/wiki/VOS/
n11http://vos.openlinksw.com/dataspace/person/owiki#
siochttp://rdfs.org/sioc/ns#

Statements

Subject Item
n8:this
foaf:made
n2:VirtGeoSPARQLEnhancementDocs
Subject Item
n16:item
n17:services_of
n2:VirtGeoSPARQLEnhancementDocs
Subject Item
n13:this
sioc:creator_of
n2:VirtGeoSPARQLEnhancementDocs
Subject Item
n15:VOS
sioc:container_of
n2:VirtGeoSPARQLEnhancementDocs
atom:entry
n2:VirtGeoSPARQLEnhancementDocs
atom:contains
n2:VirtGeoSPARQLEnhancementDocs
Subject Item
n2:VOSIndex
sioc:links_to
n2:VirtGeoSPARQLEnhancementDocs
Subject Item
n2:VirtGeoSPARQLEnhancementDocs
rdf:type
atom:Entry sioct:Comment
dcterms:created
2017-06-13T05:47:59.787196
dcterms:modified
2024-10-24T10:18:59.427649
rdfs:label
VirtGeoSPARQLEnhancementDocs
foaf:maker
n11:this n8:this
dc:title
VirtGeoSPARQLEnhancementDocs
opl:isDescribedUsing
n6:sioc.rdf
sioc:has_creator
n13:this
sioc:attachment
n29:GeoApiSparql.log n29:VirtWktGeomerticObjects.png
sioc:content
%META:TOPICPARENT{name="VOS"}% ---+ Virtuoso Geospatial Enhancements %TOC% ---++ Introduction As of Virtuoso 7.1, in both Open Source and Commercial/Enterprise Editions, a number of major enhancements have been made to Geospatial support, improving the Geometry data types and functions supported, and increasing compliance with the emerging [[http://www.geosparql.org][GeoSPARQL]] and [[http://www.opengeospatial.org][OGC]] standards. ---++ Virtuoso Geospatial Geometry data types and sample queries The table below outlines the common WKT (Well Known Text) representations for several types of geometric objects used in RDF: %BR%%BR% <img src="%ATTACHURLPATH%/VirtWktGeomerticObjects.png" alt="graphic table of WKT representations" style="wikiautogen" /> %BR%%BR% The following queries "count the number of items of each type, whose coordinates fall within a bounded box shape" for the various RDF geometry data types now supported by Virtuoso. The links are to live examples of the query running against the OpenLink [[http://lod.openlinksw.com/sparql][LOD Cloud Cache]] instance. ---+++ BOX <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM &lt;http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "BOX(0.3412 43.5141, 9.3412 48.0141)" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2P7mk9C][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2w5TOwl][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ POLYGON <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "POLYGON((1 2, 6 1, 9 3, 8 5, 3 6, 1 2))" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2w6GnfS][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2KReyxl][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ POLYGON WITH HOLE <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "POLYGON((1 2, 6 1, 9 3, 8 5, 3 6, 1 2), (3 3, 5 5, 6 2, 3 3))" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2Ox1G1I][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2B9JXLJ][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ MULTIPOLYGON <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "MULTIPOLYGON(((1 2, 6 1, 9 3, 3 6, 1 2)), ((4 9, 7 6, 9 8, 4 9)))" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2BaoL8p][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2KRPshK][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ GEOMETRY COLLECTION <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "GEOMETRYCOLLECTION( POINT(4 5), POINT(7 4), POINT(6 2), LINESTRING(4 5, 6 7, 7 4, 6 2), POLYGON((1 2, 6 1, 9 3, 8 5, 3 6, 1 2)) )" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2vEUsSc][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2P8nmSH][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ MULTI POINT <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "MULTIPOINT(3 7, 4 2, 8 6)" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2nDC1sU][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2w9O84w][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ LINE STRING <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "LINESTRING(1 2, 3 6, 9 4)" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2MployU][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2KNAiu4][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ MULTI LINE STRING <verbatim> SELECT ?f AS ?facet COUNT(?s) AS ?cnt FROM <http://linkedgeodata.org/> WHERE { ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?f . ?s <http://www.w3.org/2003/01/geo/wgs84_pos#geometry> ?p . FILTER ( bif:st_intersects ( bif:st_geomfromtext ( "MULTILINESTRING((1 8, 4 4), (4 9, 8 5, 6 2, 1 4))" ) , ?p ) ) } GROUP BY ?f ORDER BY DESC(?cnt) LIMIT 10 </verbatim> * [[https://bit.ly/2Me8rZI][View the SPARQL Query Definition via SPARQL Protocol URL]]; * [[https://bit.ly/2MoEN2R][View the SPARQL Query Results via SPARQL Protocol URL]] ---+++ Supported shape types <verbatim> BOX, BOX2D, BOX3D, BOXM, BOXZ, BOXZM CIRCULARSTRING COMPOUNDCURVE CURVEPOLYGON EMPTY GEOMETRYCOLLECTION, GEOMETRYCOLLECTIONM, GEOMETRYCOLLECTIONZ, GEOMETRYCOLLECTIONZM LINESTRING, LINESTRINGM, LINESTRINGZ, LINESTRINGZM MULTICURVE MULTILINESTRING, MULTILINESTRINGM, MULTILINESTRINGZ, MULTILINESTRINGZM MULTIPOINT, MULTIPOINTM, MULTIPOINTZ, MULTIPOINTZM MULTIPOLYGON, MULTIPOLYGONM, MULTIPOLYGONZ, MULTIPOLYGONZM POINT, POINTM, POINTZ, POINTZM POLYGON, POLYGONM, POLYGONZ, POLYGONZM POLYLINE, POLYLINEZ RING, RINGM, RINGZ, RINGZM </verbatim> ---+++ Not yet supported shape types <verbatim> CIRCULARSTRINGM, CIRCULARSTRINGZ, CIRCULARSTRINGZM COMPOUNDCURVEM, COMPOUNDCURVEZ, COMPOUNDCURVEZM CURVE, CURVEM, CURVEZ, CURVEZM CURVEPOLYGONM, CURVEPOLYGONZ, CURVEPOLYGONZM GEOMETRY, GEOMETRYZ, GEOMETRYZM MULTICURVEM, MULTICURVEZ, MULTICURVEZM MULTIPATCH MULTISURFACE, MULTISURFACEM, MULTISURFACEZ, MULTISURFACEZM POLYHEDRALSURFACE, POLYHEDRALSURFACEM, POLYHEDRALSURFACEZ, POLYHEDRALSURFACEZM POLYLINEM SURFACE, SURFACEM, SURFACEZ, SURFACEZM TIN, TINM, TINZ, TINZM </verbatim> ---++ Virtuoso Geospatial geometry functions The following Virtuoso Geospatial geometry functions are available for use in both SQL & RDF Geospatial queries. The listed functions are built-in SQL functions. As all built-in functions of Virtuoso, geo-specific functions can be called from SPARQL with prefix <code>bif:</code> (e.g., <code><nowiki>bif:earth_radius()</nowiki></code> or <code><nowiki>&lt;bif:earth_radius&gt;()</nowiki></code>). * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_earth_radius.html][earth_radius()]]</code></b> %BR% returns <code>geom.mean</code> of radius of Earth in kilometers, <code>6367.43568</code> %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_haversine_deg_km.html][haversine_deg_km (lat1, long1, lat2, long2)]]</code></b> %BR% returns distance between two points on the Earth sphere, adjusting radius of sphere to latitudes. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_dist_from_point_to_line_segment.html][dist_from_point_to_line_segment (Xpoint, Ypoint, Xsegment1, Ysegment1, Xsegment2, Ysegment2)]]</code></b> %BR% return the distance between a point and a segment on a plane. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_point.html][st_point (x,y, {z, {m}})]]</code></b> %BR% returns a point with given coordinates in default SRID. <code>z</code> and/or <code>m</code> may be missing or equal to <code>NULL</code>, indicating the absence of coordinate. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_linestring.html][st_linestring (item1, item2,..., itemN)]]</code></b> %BR% returns a linestring in default SRID. The coordinates of vertices are specified by arguments that are points; 2-, 3-, or 4-item vectors of coordinates; linestrings; arcstrings; or vectors of the above mentioned values. Repeating vertices are automatically removed, except in the case of repeating vertices in the middle of a linestring/arcstring argument. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_x.html][st_x (point)]]</code></b> %BR% returns <code>X</code> or longitude of a point. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_y.html][st_y (point)]]</code></b> %BR% returns <code>Y</code> or longitude of a point. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Z.html][st_z (point)]]</code></b> %BR% returns <code>Z</code> coordinate of geometry. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_XMin.html][ST_XMin (shape), ST_YMin (shape), ST_XMax (shape), ST_YMax (shape)]]</code></b> %BR% return boundaries of a bounding box around a shape. Bounding boxes around arcs are calculated in assumption that no one arc is longer than a half of full circle. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_intersects.html][st_intersects (shape1, shape2 {, proximity})]]</code></b> %BR% checks whether two shapes intersect or some of their points are within the specified <code>proximity</code>. Current version is not complete and does not support arcs of all sorts and rings of polygons; this will be fixed in the next release. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_may_intersect.html][st_may_intersect (shape1, shape2 {, proximity})]]</code></b> %BR% checks whether bounding boxes of two shapes intersect or some of their points are within the specified <code>proximity</code>. This is much faster than the full <code>[[http://docs.openlinksw.com/virtuoso/fn_st_intersects.html][st_intersects()]]</code> check (in fact, this is the initial part of <code>[[http://docs.openlinksw.com/virtuoso/fn_st_intersects.html][st_intersects()]]</code> execution) %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_contains.html][st_contains (haystack_shape, needle_shape {, proximity})]]</code></b> %BR% checks whether <code><nowiki>haystack_shape</nowiki></code> contains the <code><nowiki>needle_shape</nowiki></code>. If <code>proximity</code> is specified, it is treated as an extra wide border around <code><nowiki>haystack_shape</nowiki></code>. In current version, only a combination of bounding box and a point is supported; this functionality will be extended in the next release. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_within.html][st_within (needle_shape, haystack_shape {, proximity})]]</code></b> %BR% returns true if all points of <code><nowiki>haystack_shape</nowiki></code> are in the <code><nowiki>needle_shape</nowiki></code>. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_distance.html][st_distance (shape1, shape2)]]</code></b> %BR% returns the distance in units of plane or in kilometers on sphere. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_isgeometry.html][isgeometry (v)]]</code></b> %BR% returns whether the given <code>v</code> is a spatial object. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_astext.html][st_astext (shape)]]</code></b> %BR% return EWKT representation of a shape. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_SRID.html][ST_SRID (shape)]]</code></b> %BR% returns SRID of shape's spatial reference system or <code>0</code> for shape on plane. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_SetSRID.html][ST_SetSRID (shape, new_srid)]]</code></b> %BR% replaces the SRID of a shape but does not transform the shape or its coordinates from old SRID to a new one. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_geomfromtext.html][st_geomfromtext (ewkt_text)]]</code></b> %BR% Parses the string and returns the corresponding geometry. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_ewkt_read.html][st_ewkt_read (ewkt_text)]]</code></b> %BR% Parses the given text as an EWKT and returns the parsed shape. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_http_st_ewkt.html][http_st_ewkt (shape, ses)]]</code></b> %BR% Writes an EWKT representation of a shape to the given session, a fast replacement for <code><nowiki>http (st_astext (shape), ses)</nowiki></code>. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_http_st_dxf_entity.html][http_st_dxf_entity (shape, attrs, ses)]]</code></b> %BR% writes a DXF (Data Exchange Format) representation of shape into the given output session. <code>Attrs</code> is a vector of arbitrary DXF properties in form <code>(tag1, value1, tag2, value2, ...)</code> where tags are integer codes according to DXF specification; related values are not validated and are printed to the session as-is. Current version does not support <code>ARCSTRINGs</code>, <code>CURVEs</code>, nor <code>CURVEPOLYGONs</code>. If <code>shape</code> is <code>NULL</code>, the function returns without writing anything to the shape. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_get_bounding_box.html][st_get_bounding_box (shape)]]</code></b> %BR% returns <code>BOX2D</code> that is a bounding box of a shape. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_GeometryType.html][GeometryType (shape)]]</code></b> %BR% returns EWKT type name of a shape. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_NumGeometries.html][ST_NumGeometries (shape)]]</code></b> %BR% returns number of members of a <code>MULTI...</code> or <code>...COLLECTION</code> shape; returns <code>1</code> for other sorts of shapes. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_GeometryN.html][ST_GeometryN (shape, idx)]]</code></b> %BR% Given a 1-based index of a member of a <code>MULTI...</code> or <code>...COLLECTION</code> shape, returns the member. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_ExteriorRing.html][ST_ExteriorRing (polygon_shape)]]</code></b> %BR% Returns an external (the very first) ring of a polygon. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_NumInteriorRings.html][ST_NumInteriorRings (polygon_shape)]]</code></b> %BR% returns number of interior rings of the given polygon; returns <code>NULL</code> if shape is not a polygon. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_InteriorRingN.html][ST_InteriorRingN (polygon_shape, idx)]]</code></b> %BR% Given a 1-based index of an interior ring of a polygon, returns the ring. Wrong index is not reported as an error, and <code>NULL</code> is returned. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_get_bounding_box_n.html][st_get_bounding_box_n (shape, idx)]]</code></b> %BR% Given a 1-based index of a member of a <code>MULTI...</code> or <code>...COLLECTION</code> shape, returns the bounding box of a member. This is a fast equivalent of <code>[[http://docs.openlinksw.com/virtuoso/fn_st_get_bounding_box.html][st_get_bounding_box (ST_GeometryN (shape,idx))]]</code>. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Translate.html][ST_Translate (shape, dX, dY {, dZ})]]</code></b> %BR% returns a copy of a shape with all coordinates shifted by the provided <code>dX</code>, <code>dY</code>, and <code>dZ</code>. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_TransScale.html][ST_TransScale (shape, dX, dY, Xfactor, Yfactor)]]</code></b> %BR% returns a copy of a shape with all coordinates shifted by the provided <code>dX</code> and <code>dY</code>, and then multiplied by <code>Xfactor</code> and <code>Yfactor</code>. In the current version, different values for <code>Xfactor</code> and <code>Yfactor</code> will result in distorted arcs. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_st_transform_by_custom_projection.html][st_transform_by_custom_projection (shape, algorithm_id, ...)]]</code></b> %BR% Performs a custom projection of <code>shape</code>, using the specified algorithm and algorithm-specific arguments. Current version supports only one algorithm, <code>[[http://docs.openlinksw.com/virtuoso/fn_st_transform_by_custom_projection.html][st_transform_by_custom_projection (shape, 'OLAEAPS', long_of_center, lat_of_center)]]</code> for Oblique Lampert Azimuthal Equal-Area Projection System with the specified center point. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform (shape, dest_srid, {orig_proj4_string, dest_proj4_string})]]</code></b> %BR% Transforms the given shape from its current spatial reference system to one specified by <code><nowiki>dest_srid</nowiki></code>. Two optional arguments are for "cheating": the SRID of the resulting shape is set to <code><nowiki>dest_srid</nowiki></code>, but the conversion is done by <code>proj4</code> using <code><nowiki>origin_proj4_string</nowiki></code> for projection of original shape and <code><nowiki>dest_proj4_string</nowiki></code> for the result. If <code><nowiki>orig_proj4_string</nowiki></code> or <code><nowiki>dest_proj4_string</nowiki></code> argument is passed but is <code>NULL</code> instead of <code>string</code>, the projection corresponding to original or destination SRID is used. <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code> is provided by a separate plugin named <code>proj4</code>, as described below. When the plugin is loaded, functions like <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Intersects.html][ST_Intersects()]]</code> support pairs of arguments with different SRIDs by converting coords of second argument into the system of the first one, as required by OGC and <nowiki>GeoSPARQL</nowiki>. %BR%%BR% * <b><code>[[http://docs.openlinksw.com/virtuoso/fn_postgis_proj_version.html][postgis_proj_version()]]</code></b> %BR% Returns the version of <code>proj4</code> in use as a <code>string</code>, for compatibility with <nowiki>PostGIS</nowiki>. ---++ Open Source proj4 Plug-in The Virtuoso <code>proj4</code> Hosted Plugin Module is required for performing transformation between different coordinates systems using the <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code> function. The plugin is based on [[http://trac.osgeo.org/proj/][Frank Warmerdam's <code>proj4</code>]] library and it is practical to have the <code>proj4</code> package installed on every box of a Virtuoso cluster, even if the build is performed on single machine including one outside the cluster. The reason is that the plugin should load data about coordinate systems to work, and the simplest way to get the right data from a high-quality source is to use the package. ---+++ Compiling proj4 Plug-in The <code>proj4</code> is currently available in the default <code>develop/7</code> branch of the <code>[[https://github.com/openlink/virtuoso-opensource][Virtuoso Open Source]]</code> git repository, and can be built with the following command sequence. <i><b>Note:</b> The <code>proj.4</code> library (may come from the [[http://trac.osgeo.org/proj/wiki/WikiStart#Download][proj.4 download]] area) must first be installed on the system, which the configure script will detect, enabling the <code>proj4</code> plugin library to be built in <code>~/libsrc/plugin/.libs</code>.</i> <verbatim> git clone https://github.com/openlink/virtuoso-opensource.git cd virtuoso-opensource ./autogen.sh export CFLAGS="-msse4.2 -DSSE42" ./configure make -j 24 make install </verbatim> <verbatim> bash-3.2$ ls libsrc/plugin/.libs/proj4* libsrc/plugin/.libs/proj4.a libsrc/plugin/.libs/proj4.la libsrc/plugin/.libs/proj4.lai libsrc/plugin/.libs/proj4_la-import_gate_virtuoso.o libsrc/plugin/.libs/proj4_la-sql_proj4.o libsrc/plugin/.libs/proj4_la-proj4_plugin.o libsrc/plugin/.libs/proj4.so libsrc/plugin/.libs/proj4.ver </verbatim> ---+++ Installation and Configuration of proj4 Plug-in After the plugin (<code>proj4.so</code>) is built, it must be added to the <code>[Plugins]</code> section of the Virtuoso configuration file (<code>virtuoso.ini</code> or the like). This must be done on every node, if running in a cluster. <verbatim> [Plugins] LoadPath = ./plugins Load2 = plain, proj4 </verbatim> If everything is fine, the <code>virtuoso.log</code> file will contain something like the following lines after the next startup: <verbatim> 21:30:10 { Loading plugin 1: Type `plain', file `shapefileio' in `.' 21:30:10 ShapefileIO version 0.1virt71 from OpenLink Software 21:30:10 Shapefile support based on Frank Warmerdam's Shapelib 21:30:10 SUCCESS plugin 1: loaded from ./plugins/shapefileio.so } 21:30:10 { Loading plugin 2: Type `plain', file `proj4' in `.' 21:30:11 plain version 3208 from OpenLink Software 21:30:11 Cartographic Projections support based on Frank Warmerdam's proj4 library 21:30:11 SUCCESS plugin 2: loaded from ./plugins/proj4.so } 21:30:11 OpenLink Virtuoso Universal Server 21:30:11 Version 07.10.3208-pthreads for Linux as of Mar 31 2014 ... 21:30:28 PL LOG: Initial setup of DB.DBA.SYS_PROJ4_SRIDS data from files in "/usr/share/proj" 21:30:30 PL LOG: DB.DBA.SYS_PROJ4_SRIDS now contains 6930 spatial reference systems ... 21:30:32 Server online at 1720 (pid 9654) </verbatim> To store descriptions of coordinate systems, the plugin creates a table: <verbatim> CREATE TABLE DB.DBA.SYS_PROJ4_SRIDS ( SR_ID INTEGER, SR_FAMILY VARCHAR NOT NULL, SR_TAG VARCHAR, SR_ORIGIN VARCHAR NOT NULL, SR_IRI IRI_ID_8, SR_PROJ4_STRING VARCHAR NOT NULL, SR_WKT VARCHAR, SR_COMMENT VARCHAR, SR_PROJ4_XML ANY, PRIMARY KEY (SR_ID, SR_FAMILY) ); </verbatim> This is filled with data from files <code>epsg</code>, <code>esri</code>, <code>esri.extra</code>, <code>nad83</code>, and <code>nad27</code> of directory <code><nowiki>/usr/share/proj</nowiki></code>. Note these files must exist in the <code><nowiki>/usr/share/proj</nowiki></code> directory; otherwise, a message will be reported in the log file, indicating the file could not be found. Every row of the table is identified with the name of the "family" of coordinate systems and an integer SRID. Different sources may assign the same SRID to different reference systems; however, descriptions of well-known systems will match exactly or with differences that are not noticeable for any practical application. The loading process uses family names '<code>EPSG</code>', '<code>ESRI</code>', '<code>NAD83</code>' and '<code>NAD27</code>'. When the <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code> searches for a coordinate system that corresponds to a given SRID, it returns the first record found while checking the families in the following order: '<code>PG</code>', '<code>EPSG</code>', '<code>ESRI</code>','<code>NAD83</code>', '<code>NAD27</code>'. It is therefore generally practical to put all custom definitions in '<code>PG</code>' family, giving them the highest priority. A sample [[http://www.epsg.org][EPSG]] file containing the mapping for the <code>proj.4</code> <b><code>[[http://spatialreference.org/ref/epsg/4326/][EPSG:4326]]</code></b> coordinate system is: <verbatim> $ cat /usr/share/proj/epsg &lt;4326>+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs&lt;> $ </verbatim> <verbatim> SQL> SELECT * FROM DB.DBA.SYS_PROJ4_SRIDS; SR_ID SR_FAMILY SR_TAG SR_ORIGIN SR_IRI SR_PROJ4_STRING SR_WKT SR_COMMENT SR_PROJ4_XML INTEGER NOT NULL VARCHAR NOT NULL VARCHAR VARCHAR NOT NULL VARCHAR VARCHAR NOT NULL VARCHAR VARCHAR VARCHAR ________________ ________________ _______ ____________________ _______ ________________________________________________ _______ __________ ____________ 4326 EPSG 4326 /usr/share/proj/epsg NULL +datum=WGS84 +ellps=WGS84 +no_defs +proj=longlat NULL NULL 1 Rows. -- 0 msec. SQL> </verbatim> There are two procedures available for loading more coordinate systems: * <code><nowiki>DB.DBA.PROJ4_LOAD_SYS_SRIDS</nowiki></code> is called at server startup, if the <code>proj4</code> plugin is loaded: <verbatim> DB.DBA.PROJ4_LOAD_SYS_SRIDS ( IN projdir VARCHAR := '/usr/share/proj', IN only_if_empty_table INTEGER := 0 ) </verbatim> * <code><nowiki>DB.DBA.PROJ4_LOAD_INIT_FILE</nowiki></code> is a lower-level procedure: <verbatim> DB.DBA.PROJ4_LOAD_INIT_FILE ( IN path VARCHAR, IN _sr_family VARCHAR ) </verbatim> The main part of <code><nowiki>DB.DBA.PROJ4_LOAD_SYS_SRIDS()</nowiki></code> is a sequence of: <verbatim> DB.DBA.PROJ4_LOAD_INIT_FILE (projdir || '/epsg', 'EPSG'); DB.DBA.PROJ4_LOAD_INIT_FILE (projdir || '/esri', 'ESRI'); DB.DBA.PROJ4_LOAD_INIT_FILE (projdir || '/esri.extra', 'ESRI'); DB.DBA.PROJ4_LOAD_INIT_FILE (projdir || '/nad83', 'NAD83'); DB.DBA.PROJ4_LOAD_INIT_FILE (projdir || '/nad27', 'NAD27'); </verbatim> Rows with the same SRID but different <code><nowiki>SR_FAMILY</nowiki></code> values may exist in the table; however, only one projection per SRID is used, and <code><nowiki>SR_FAMILY</nowiki></code> defines the priority. The internal search query for projection by SRID is: <verbatim> SELECT COALESCE ( ( SELECT SR_PROJ4_STRING FROM DB.DBA.SYS_PROJ4_SRIDS WHERE SR_ID= :0 AND SR_FAMILY='PG' ), ( SELECT SR_PROJ4_STRING FROM DB.DBA.SYS_PROJ4_SRIDS WHERE SR_ID= :0 AND SR_FAMILY='EPSG' ), ( SELECT SR_PROJ4_STRING FROM DB.DBA.SYS_PROJ4_SRIDS WHERE SR_ID= :0 AND SR_FAMILY='ESRI' ), ( SELECT SR_PROJ4_STRING FROM DB.DBA.SYS_PROJ4_SRIDS WHERE SR_ID= :0 AND SR_FAMILY='NAD83' ), ( SELECT SR_PROJ4_STRING FROM DB.DBA.SYS_PROJ4_SRIDS WHERE SR_ID= :0 AND SR_FAMILY='NAD27' ) ); </verbatim> This means that for <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code>, function '<code>PG</code>' overrides everything else; <code>EPSG</code> is the next highest priority; then <code>ESRI</code>, <code>NAD83</code>, and <code>NAD27</code>. However, custom queries and procedures may select whatever they please (including <code>SR_FAMILY</code> values not listed here, strings from other tables, etc.), and may feed projection strings directly to <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code>. The coordinate systems can also be updated by directly manipulating the <code><nowiki>DB.DBA.SYS_PROJ4_SRIDS</nowiki></code> table. (This table is readable by public, and writable only by DBA.) After editing the table, the "<code><nowiki>Proj4 cache_reset()</nowiki></code>" function should be called to prevent the SQL runtime from using previously-prepared projections that might now be obsolete. Note that <code>proj4</code> projections are for normalized data in radians, while Virtuoso stores shapes using numbers that come from WKT; i.e., they're latitudes and longitudes in degrees, for almost all cases. The <code>proj4</code> plugin automatically applies the <code><nowiki>RAD_TO_DEG</nowiki></code> multiplier before conversion and/or the <code><nowiki>RAD_TO_DEG</nowiki></code> multiplier after conversion, when source and/or destination coordinate systems are latitude-longitude or geocentric. Even if this conversion is done automatically, you should remember that it happens, because many "how-to" instructions for spatial data sets contain paragraphs like "how to convert these data to WGS-84," and much sample C/C++ code contains transformations like <code><nowiki>{ x *= RAD_TO_DEG; y *= RAD_TO_DEG; }</nowiki></code>. These transformations will probably be redundant in the corresponding Virtuoso/PL code, while <code>proj4</code> strings can be used unchanged and simply passed as the 3rd and 4th arguments of the <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code> function. If degrees-to-radians conversion is made twice, the data may be calculated as if the shape is located in a totally different place of ellipsoid. If the post-transformation radians-to-degrees conversion is also made twice, the resulting shape may <i>look</i> like the real one, but coordinates may be tens of kilometers away from the correct values. ---+++ Example usage of ST_Transform() Below are some example uses of the <code>[[http://docs.openlinksw.com/virtuoso/fn_ST_Transform.html][ST_Transform()]]</code> function to transform some of the sample coordinate systems loaded into Virtuoso: <verbatim> SQL> SELECT * FROM DB.DBA.SYS_PROJ4_SRIDS; SR_ID SR_FAMILY SR_TAG SR_ORIGIN SR_IRI SR_PROJ4_STRING SR_WKT SR_COMMENT SR_PROJ4_XML INTEGER NOT NULL VARCHAR NOT NULL VARCHAR VARCHAR NOT NULL VARCHAR VARCHAR NOT NULL VARCHAR VARCHAR VARCHAR ________________ ________________ _______ ____________________ _______ _____________________________________________________________________________________________________________________________________________________________________________________ _______ __________ ____________ 2005 EPSG 2005 /usr/share/proj/epsg NULL +ellps=clrk80 +k=0.9995000000000001 +lat_0=0 +lon_0=-62 +no_defs +proj=tmerc +units=m +x_0=400000 +y_0=0 NULL NULL 2249 EPSG 2249 /usr/share/proj/epsg NULL +datum=NAD83 +ellps=GRS80 +lat_0=41 +lat_1=42.68333333333333 +lat_2=41.71666666666667 +lon_0=-71.5 +no_defs +proj=lcc +to_meter=0.3048006096012192 +x_0=200000.0001016002 +y_0=750000 NULL NULL 4326 EPSG 4326 /usr/share/proj/epsg NULL +datum=WGS84 +ellps=WGS84 +no_defs +proj=longlat NULL NULL 3 Rows. -- 1 msec. SQL> SELECT st_transform (st_geomfromtext ('POLYGON((-16 20.25,-16.1 20.35,-15.9 20.35,-16 20.25))'), 1, '+proj=latlong +ellps=clrk66', '+proj=merc +ellps=clrk66 +lat_ts=33'); unnamed VARCHAR NOT NULL _____________________________________________________________________________________________________________________________________________ SRID=1;POLYGON((-1495284.211473 1920596.789917,-1504629.737795 1930501.842961,-1485938.685152 1930501.842961,-1495284.211473 1920596.789917)) 1 Rows. -- 0 msec. SQL> SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450, 743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) AS wgs_geom; wgs_geom VARCHAR NOT NULL ___________________________________________________________________________________________________________________ POLYGON((-71.177685 42.390290,-71.177684 42.390383,-71.177584 42.390383,-71.177583 42.390289,-71.177685 42.390290)) 1 Rows. -- 1 msec. SQL> </verbatim> * <a href="%ATTACHURLPATH%/GeoApiSparql.log" style="wikiautogen"><code>GeoApiSparql.log</code></a> ---++ Future Plans * Full support for all DE9-IM based operations. * Full support for <nowiki>GeoSPARQL</nowiki>. * Additional functions for splitting compound geometries into parts and for constructing geometries (except operations that get shapes as arguments and returns other shapes). ---++ Related * [[http://geoknow.eu][GeoKnow]] -- Making the Web an Exploratory for Geospatial Knowledge * [[http://svn.aksw.org/projects/GeoKnow/Public/D1.3.2_Continuous_Report_on_Performance_Evaluation.pdf][Continuous Report on Performance Evaluation]] * [[http://svn.aksw.org/projects/GeoKnow/Public/D2.1.1_Market_and_Research_Overview.pdf][Market and Research Overview]] * [[http://svn.aksw.org/projects/GeoKnow/Public/D2.2.1_Integration_of_Geospatial_Databases.pdf][Integration of Geospatial Databases]] * [[http://svn.aksw.org/projects/GeoKnow/Public/D2.3.1_Prototype_of_Built-in_Geospatial_Capabilities.pdf][Prototype of Built in Geospatial Capabilities]] * Virtuoso GeoSPARQL Geometry Tutorials * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2830%29][BOX]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2831%29][POLYGON ]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2832%29][POLYGON WITH HOLE]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2833%29][MULTIPOLYGON]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2834%29][GEOMETRY COLLECTION]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2835%29][MULTIPOINT]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2836%29][LINESTRING]] * [[http://virtuoso.openlinksw.com/tutorials/sparql/SPARQL_Tutorials_Part_10/SPARQL_Tutorials_Part_10.html#%2837%29][MULTILINESTRING]]
sioc:id
48be1149bdcd3118b462b6f1d29d9f85
sioc:link
n2:VirtGeoSPARQLEnhancementDocs
sioc:has_container
n15:VOS
n17:has_services
n16:item
atom:title
VirtGeoSPARQLEnhancementDocs
sioc:links_to
n4:%2835%29 n4:%2832%29 n4:%2833%29 n7:virtuoso-opensource n10:fn_st_get_bounding_box.html n10:fn_GeometryType.html n10:fn_http_st_ewkt.html lod:sparql n10:fn_http_st_dxf_entity.html n10:fn_st_geomfromtext.html n10:fn_st_ewkt_read.html n10:fn_ST_SRID.html n10:fn_ST_SetSRID.html n10:fn_ST_Translate.html n10:fn_ST_TransScale.html n10:fn_ST_InteriorRingN.html n10:fn_st_get_bounding_box_n.html n10:fn_ST_ExteriorRing.html n10:fn_ST_NumInteriorRings.html n10:fn_ST_NumGeometries.html n10:fn_ST_GeometryN.html n18:Download n19:www.epsg.org n20: n10:fn_ST_Intersects.html n10:fn_postgis_proj_version.html n10:fn_st_transform_by_custom_projection.html n10:fn_ST_Transform.html n4:%2830%29 n4:%2831%29 n21:D2.2.1_Integration_of_Geospatial_Databases.pdf n21:D2.3.1_Prototype_of_Built-in_Geospatial_Capabilities.pdf n21:D1.3.2_Continuous_Report_on_Performance_Evaluation.pdf n22:2w9O84w n21:D2.1.1_Market_and_Research_Overview.pdf n23:GeoSPARQL n22:2MployU n2:OpenLink n24: n22:2P8nmSH n19:geoknow.eu n22:2nDC1sU n22:2KRPshK n22:2vEUsSc n22:2B9JXLJ n22:2BaoL8p n10:fn_st_y.html n10:fn_ST_Z.html n22:2MoEN2R n10:fn_st_linestring.html n10:fn_st_x.html n22:2KNAiu4 n10:fn_dist_from_point_to_line_segment.html n22:2Me8rZI n10:fn_st_point.html n10:fn_earth_radius.html n10:fn_haversine_deg_km.html n10:fn_isgeometry.html n10:fn_st_astext.html n10:fn_st_within.html n10:fn_st_distance.html n10:fn_st_may_intersect.html n10:fn_st_contains.html n10:fn_ST_XMin.html n10:fn_st_intersects.html n19:www.geosparql.org n19:www.opengeospatial.org n22:2KReyxl n22:2Ox1G1I n22:2w5TOwl n22:2w6GnfS n22:2P7mk9C n4:%2836%29 n4:%2837%29 n4:%2834%29
atom:source
n15:VOS
atom:author
n8:this
atom:published
2017-06-13T05:47:59Z
atom:updated
2024-10-24T10:18:59Z
sioc:topic
n15:VOS