'Returns the aspect ratio of the raw data.
This method is intended to be overridden by new projection
types.'

def get_data_ratio(self):

    (xmin, xmax) = self.get_xbound()
    (ymin, ymax) = self.get_ybound()
    xsize = max(abs((xmax - xmin)), 1e-30)
    ysize = max(abs((ymax - ymin)), 1e-30)
    return (ysize / xsize)
