Compute the Hausdorff distance thanks to the corresponding GEOS function hausdorffdistance - SELECT st_hausdorffdistance( 'POLYGON((0 0, 0 2, 1 2, 2 2, 2 0, 0 0))'::geometry, 'POLYGON((0.5 0.5, 0.5 2.5, 1.5 2.5, 2.5 2.5, 2.5 0.5, 0.5 0.5))'::geometry);