1Centroid - polygonM (problem case - GEOS throws away the M coordinates) 2:memory: #use in-memory database 3SELECT astext(centroid(geomFromText('POLYGONM((0 0 1, 0 2 1, 2 2 1, 2 0 1, 0 0 1))'))) 41 # rows (not including the header row) 51 # columns 6astext(centroid(geomFromText('POLYGONM((0 0 1, 0 2 1, 2 2 1, 2 0 1, 0 0 1))'))) 7POINT(1 1) 8 9