Geospatial Nearby

Support
1

Not sure if there is a bug ... But I have a list of ports and their lats/longs. I ran the following query:

prefix geof: <http://www.opengis.net/def/function/geosparql/>
prefix geo: <http://www.opengis.net/ont/geosparql#>
prefix unit: <http://qudt.org/vocab/unit#>
prefix wgs: <http://www.w3.org/2003/01/geo/wgs84_pos#> 
SELECT ?name ?lat ?long  {
  ?port a geo:Geometry ; 
        # geof:nearby ("Point(9.933333, 53.550000)"^^geo:wktLiteral 1000 unit:Kilometer) ;
        rdfs:label ?name ;
        wgs:lat ?lat ;
        wgs:long ?long }

And get lots of results. All of the prefixes are defined. The datatype of the ?lat and ?long variables is xsd:decimal.

However, if I remove the comment in front of geof:nearby, then I get an error:

WARN  2020-06-08 13:20:49,765 [stardog-user-8] com.complexible.stardog.protocols.http.server.StardogUndertowErrorHandler:accept(64): Unexpected exception was handled by the server
java.text.ParseException: Expected a number
	at org.locationtech.spatial4j.io.WKTReader$State.nextDouble(WKTReader.java:507) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.io.WKTReader.point(WKTReader.java:401) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.io.WKTReader.parsePointShape(WKTReader.java:213) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.io.WKTReader.parseShapeByType(WKTReader.java:156) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.io.WKTReader.parseIfSupported(WKTReader.java:110) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.io.WKTReader.parse(WKTReader.java:81) ~[spatial4j-0.7.jar:?]
	at org.locationtech.spatial4j.context.SpatialContext.readShapeFromWkt(SpatialContext.java:258) ~[spatial4j-0.7.jar:?]
	at com.complexible.stardog.spatial.db.query.NearbyPropertyFunction$NearbyOperator.getLocation(NearbyPropertyFunction.java:366) ~[stardog-spatial-core-7.3.1-SNAPSHOT-20200527.jar:?]
...

What is "not a number"?

Andrea

2

Hi Andrea,

geof:nearby is expecting either a Geometry or a latitude as the first argument. So in this case it's finding a Literal and therefore expecting a number.

To get the results you're looking for, try geof:nearby (9.933333 53.550000 1000 unit:Kilometer) ;

3

I tried geof:nearby (53.550000 9.933333 1000 unit:Kilometer) ; (lat comes first)

but get no results, which is why I tried using the wktLiteral approach.

If I comment out the geof:nearby, I get all the details back.

Andrea

4

And, yes, geospatial is enabled on the db.

Andrea

5

You read my mind!

WKT is fun to deal with, because Point actually accepts (LONG LAT) instead of the way we generally think about it. If you switch the 2 numbers do you see results then?

6

No. I just updated my reply to indicate that.

Andrea

7

Can you share a toy dataset that should be producing results?

8

Trying to create one.

Andrea

9

I have attached a small file that is a subset of data from NGA's World Port Index.

testNGA.ttl (11.2 KB)

Here is the query that works if geof:nearby is commented out:

prefix geo: <http://www.opengis.net/ont/geosparql#>
prefix unit: <http://qudt.org/vocab/unit#>
prefix wgs: <http://www.w3.org/2003/01/geo/wgs84_pos#> 
prefix : <urn:example:ontology:> 

SELECT ?name ?lat ?long where {
  ?port 
        geof:nearby (53.550000 9.933333 1000 unit:Kilometer) ;
        :label ?name ;
        wgs:lat ?lat ;
        wgs:long ?long .
}

I am running 7.3.1.

Andrea

10

Hang on ... The query is wrong for the test data. It should have been geof:nearby (64.15 -21.93 1000 unit:Kilometer) ;

I got it to work with the test data. But the difference is that I had reasoning on to get the wgs:lat/long in the first case (from :lat ?lat and :long ?long), but hard-coded it into my data in the sample.

Would that have changed the results?
Andrea

11

You very well might need wgs:lat and wgs:long explicitly in the database in order to get the Geometry into the spatial index. In fact, I think you do...

12

I do. Reasoning did not work.

Next question .... How can I get distance to work ... If I do:

prefix geosparql: <http://www.opengis.net/ont/geosparql#>
prefix unit: <http://qudt.org/vocab/unit#>
prefix wgs: <http://www.w3.org/2003/01/geo/wgs84_pos#> 
prefix : <urn:example:ontology:> 

SELECT ?name ?lat ?long ?distance where {
  ?port a geosparql:Geometry ;
        geof:nearby (53.550000 9.933333 50 unit:Kilometer) ;
        :label ?name ;
        wgs:lat ?lat ;
        wgs:long ?long .
  BIND(geof:distance(?port, (53.550000 9.933333), unit:Kilometer) as ?distance)
}

I get the error:

com.complexible.stardog.plan.eval.ExecutionException: Encountered " <DECIMAL> "9.933333 "" at line 13, column 40.
Was expecting one of:
    ")" ...
    "=" ...
    "!=" ...
...

Thanks.
Andrea

13

Never mind ... I got this to work ...

BIND(geof:distance(?port, ("Point(9.933333 53.55)"^^geosparql:wktLiteral), unit:Kilometer) as ?distance)

14

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