[gdal-dev] Should AddPoint(x, y) promote geometries to 3D?

[Daniel Evans]

Using the Python bindings on GDAL 3.2.1 / GEOS 3.8.1, adding a point to a 2D LinearRing automatically promotes it to a 3D geometry:

from osgeo import ogr
ring = ogr.Geometry(ogr.wkbLinearRing)
ring.GetGeometryType()  # 2
ring.GetCoordinateDimension()  # 2

ring.AddPoint(0, 0)
ring.GetGeometryType()  # -2147483646
ring.GetCoordinateDimension()  # 3


Given that the `z` argument for AddPoint is optional, I'd assumed that the behaviour was to leave a 2D geometry as 2D if only x and y are specified; the Python documentation doesn't include any notes on the behaviour. Does one have to always use AddPoint_2D when dealing with 2D geometries?


Dr Daniel Evans
Software Developer


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