[gdal-dev] Axis order in the kml driver

Cédric Traizet cedric.traizet at c-s.fr
Wed Jun 5 05:56:30 PDT 2019


I am trying to use the kml ogr driver in gdal 3.0, but there is 
something I find weird with the spatial references:

- When a layer is created (in the constructor), a wgs84 geoCRS is 
created, without setting its "Axis mapping strategy" to 
OAMS_TRADITIONAL_GIS_ORDER, meaning that it uses latitude first and 
longitude second. This spatial reference is then compared to the source 
spatial reference, and if it doesn't match, a 
OGRCoordinateTransformation is created to convert from the source SRS to 
wgs84 (as kml only supports wgs84).

- When opening a kml datasource using the driver, a wgs84 geoCRS is 
created, this time with its axis mapping strategy set to 
OAMS_TRADITIONAL_GIS_ORDER (longitude first and latitude second). A 
layer is then created with this spatial reference and compared with a 
lat/long wgs84 as described above. And as they mismatch, a coordinate 
transformation is created between the two geoCRS.

I think the wgs84 spatial reference of the layer should also have its 

Or maybe I am not understanding correctly of spatial references work in 
this driver ? I am still a bit confused with these axis order issues.


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