Return True if xllcorner==yllcorner==0 indicating that points
        in question are absolute.

def is_absolute(self):
        """Return True if xllcorner==yllcorner==0 indicating that points
        in question are absolute.
        """

        # FIXME(Ole): It is unfortunate that decision about whether points
        # are absolute or not lies with the georeference object. Ross pointed this out.
        # Moreover, this little function is responsible for a large fraction of the time
        # using in data fitting (something in like 40 - 50%.
        # This was due to the repeated calls to allclose.
        # With the flag method fitting is much faster (18 Mar 2009).

        # FIXME(Ole): HACK to be able to reuse data already cached (18 Mar 2009).
        # Remove at some point
        if not hasattr(self, 'absolute'):
            self.absolute = num.allclose([self.xllcorner, self.yllcorner], 0)

        # Return absolute flag
        return self.absolute