def resolution(self):
        """
        Get the tile resolution at the current position.

        The scale in WG84 depends on
            * the zoom level (obviously)
            * the latitude
            * the tile size

        References:
            * http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Resolution_and_Scale
            * http://gis.stackexchange.com/questions/7430/what-ratio-scales-do-google-maps-zoom-levels-correspond-to

        Returns:
            float: meters per pixel
        """
        geo_coords = self.to_geographic()
        resolution = abs(_initialresolution * math.cos(geo_coords.lat * _pi_180) / (2**self.zoom))
        return resolution
Get the tile resolution at the current position.

        The scale in WG84 depends on
            * the zoom level (obviously)
            * the latitude
            * the tile size

        References:
            * http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Resolution_and_Scale
            * http://gis.stackexchange.com/questions/7430/what-ratio-scales-do-google-maps-zoom-levels-correspond-to

        Returns:
            float: meters per pixel