NGRC_001

calculated the distance to the nearest park from one point

Use at

• https://qlever.dev/osm-planet/NVqOUP

PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
PREFIX osmkey: <https://www.openstreetmap.org/wiki/Key:>

PREFIX unit: <http://qudt.org/vocab/unit/>
SELECT ?way ?name ?distance ?geom_for_distance
WHERE {
    BIND("POINT (4.895168 52.370216)"^^geo:wktLiteral AS ?origin)

    ?way osmkey:leisure "park" .
    ?way osmkey:name ?name .
    ?way geo:hasGeometry/geo:asWKT ?geom .

    # 判断 geometry 类型，如果是 Point 用自身，否则用 centroid
    BIND(
        IF( STRSTARTS(STR(?geom), "POINT"),
            ?geom,
            geof:centroid(?geom)
        ) AS ?geom_for_distance
    )

    BIND( geof:distance(?origin, ?geom_for_distance) AS ?distance )
}
ORDER BY ASC(?distance) 
LIMIT 5

graph TD
classDef projected fill:lightgreen;
classDef literal fill:orange;
classDef iri fill:yellow;
  v7("?distance"):::projected 
  v5("?geom")
  v6("?geom_for_distance"):::projected 
  v4("?name"):::projected 
  v2("?origin")
  v3("?way"):::projected 
  a1((" "))
  c2(["park"]):::literal 
  bind0[/"sPOINT (4.895168 52.370216)^^<http://www.opengis.net/ont/geosparql#wktLiteral>'"/]
  bind0 --as--o v2
  v3 --https://www.openstreetmap.org/wiki/Key:leisure-->  c2
  v3 --https://www.openstreetmap.org/wiki/Key:name-->  v4
  v3 --http://www.opengis.net/ont/geosparql#hasGeometry-->  a1
  a1 --http://www.opengis.net/ont/geosparql#asWKT-->  v5
  bind1[/"if(starts-with(str(?geom),'POINT'),?geom,http://www.opengis.net/def/function/geosparql/centroid(?geom))"/]
  v5 --o bind1
  bind1 --as--o v6
  bind2[/"http://www.opengis.net/def/function/geosparql/distance(?origin,?geom_for_distance)"/]
  v2 --o bind2
  v6 --o bind2
  bind2 --as--o v7