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zellige / wkt-geom

Wkt Geometry Parser
Apache License 2.0
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Using hs-geojson objects means trouble #8

Open newmana opened 5 years ago

newmana commented 5 years ago

As we discovered in #7 there are certain things you can express in WKB, WKT or GeoJSON that don't line up. You can express differing geometry types (2D and 3D) within a feature or a geometry types like 2D+M which doesn't exist in GeoJSON. Currently, if you roundtrip a 2D+M in WKB to GeoJSON it will come back as XYZ (the M vs Z is lost).

The solution would be to create types in wkt-geom (WKT, eWKT, WKB, GeoJSON) and show these mappings. Prevent these mappings from occurring, so WKB -> GeoJSON if XYM is an error.

dendrei commented 5 years ago

The other issue is that in hs-geojson objects lines and polygons can contain points of different coordinate schemes e.g. XY, XYZ points in the same line string. WKB has no way of expressing such objects.

E.g. the following is a valid hs-geojson object but cannot be correctly serialized (i.e. you can't round trip it).

Geospatial.GeoLine $ LineString.makeLineString (Geospatial.GeoPointXYZ (Geospatial.PointXYZ 3.0 4.0 5.0)) (Geospatial.GeoPointXY (Geospatial.PointXY 1.0 2.0)) Sequence.empty

This is because the coordinate type (XY, XYM, XYZ, XYZM) is defined for the whole LineString, (or LinearRing) in WKB.