You can access various GMT specific metadata about your grid as follows:
>>> frompygmt.datasetsimportload_earth_relief>>> # Use the global Earth relief grid with 1 degree spacing>>> grid=load_earth_relief(resolution="01d")
>>> # See if grid uses Gridline (0) or Pixel (1) registration>>> grid.gmt.registration1>>> # See if grid uses Cartesian (0) or Geographic (1) coordinate system>>> grid.gmt.gtype1