Problems in GeoSPARQL geometry examples

[VladimirAlexiev]

@Sveino @ThomasRanvikEriksen @EmilieSkog
(continuing #337)

The current data includes 4 geo:Feature with 3 geo:Geometry in Telemark-120_AO.jsonld. Eg one of them is:

"@id": "urn:uuid:7d8a6fba-409a-4dc0-9b1b-f1d46668366e",
"@type": "geo:Geometry",
"geo:asWKT": {
  "@value": "\"LINESTRING (6502691.542169236 972304.9284766684,6502691.540990914 972304.9204293368)", 
  "@type": "geo:wktLiteral"
},
"geo:asGeoJSON": {
  "@value": "\"{\"type\": \"LineString\", \"coordinates\": [[[8.7007293714585, 58.41467201058505, 20], [8.7007293, 58.414672, 20]]]}", 
  "@type": "geo:geoJSONLiteral"
},
"geo:asGML": {
 "@value": "<gml:LineString xmlns:gml=\"http://www.opengis.net/gml/3.2\" srsName=\"urn:x-ogc:def:crs:EPSG::5972\" srsDimension=\"3\"><gml:posList>6474917.289 482515.352 40.81 6474917.288 482515.348 40.81</gml:posList></gml:LineString>", 
  "@type": "geo:gmlLiteral"
}

I see these problems:

• invalid leading quote \" in WKT and GeoJSON
• WKT lacks the Z coordinates. Use LINESTRING Z and include the Z
• Why are the numbers in WKT different from those in GML? Does WKT use a different CRS? Which one?
• Is the coordinate order in GML correct?
  • This conversion from EPSG:5972 to EPSG:4326 maps 482515.352, 6474917.289 to 8.7007295, 58.414672, which matches the GeoJSON coordinates and falls in Norway
  • But this conversion in the order given in GML maps 6474917.289, 482515.352 to 56.2549442, 2.954377, which is somewhere in Africa
  • Where does https://epsg.io/5972 say that the coordinate order is y,x?
• Why is the Z (height) different between GeoJSON and GML (20 vs 40.81)?
  https://epsg.io/5972 describes it as "ETRS89 / UTM zone 32N + NN2000 height".
  The last part means "Norway Normal Null 2000" and has PARAMETER["latitude_of_origin",0].
  I don't know what is "Null 2000" but is why would it change the height by 20.81m?
• Which spec does urn:x-ogc:def:crs:EPSG::5972 come from?
  According to this example https://opengeospatial.github.io/ogc-geosparql/geosparql11/document.html#_b99084ae-8fbd-c3f4-d43c-afaeb1fe1626 ,
  I would use this URL http://www.opengis.net/def/crs/EPSG/0/5972, which resolves and returns the correct data.
• WKT lacks a coordinate system.
  The default is WGS84 (lat long) so the numbers should be the same as in GeoJSON but are not.
  6502691 is an invalid latitude value (too big).
  According to the same example, you can write
  "<http://www.opengis.net/def/crs/EPSG/0/5972> LINESTRING Z (6474917.289 482515.352 40.81, 6474917.288 482515.348 40.81)"