def _calculate_max_distance(zoom_level, square_image_length):
global_mercator = GlobalMercator()
resolution = global_mercator.Resolution(zoom_level)
return resolution * (square_image_length / 2)
def _calculate_step_distance(self, zoom_level):
global_mercator = GlobalMercator()
resolution = global_mercator.Resolution(zoom_level)
return resolution * (self._square_image_length / 1.5)