AltosMapTransform transform = new AltosMapTransform(px_size, px_size, zoom, new AltosLatLon(lat, lon));
AltosLatLon upper_left = transform.screen_lat_lon(new AltosPointInt(0, 0));
AltosMapTransform transform = new AltosMapTransform(px_size, px_size, zoom, new AltosLatLon(lat, lon));
AltosLatLon upper_left = transform.screen_lat_lon(new AltosPointInt(0, 0));