Error while exporting GeoJSON from PostGIS

Question

$ ogr2ogr -f "GeoJSON" test.geojson -t_srs EPSG:4326 PG:"host=localhost user=postgres dbname=sp_join port=5432" -sql 'select gid, geom from test'

I am using the following code in ogr2ogr to export a table from PostGIS to GeoJSON, but get the following errors:

ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported
ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported
ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported
ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported
ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported
ERROR 1: Reading EWKB with 4-dimensional coordinates (XYZM) is not supported

How can I avoid 4-dimensional coordinates?

Answer 1

You can remove unwanted ordinates with any of:

• ST_Force2D, which drops the Z and M ordinates,
• ST_Force3D, which drops the M ordinate, and
• ST_Force3DM, which drops the Z ordinate.

So you could modify your -sql argument like this:

-sql 'select gid, st_force2d(geom) from test'