The surface of Mars has been divided into thirty cartographic quadrangles by the United States Geological Survey. Each quadrangle is a region covering a specified range of latitudes and longitudes on the Martian surface. The quadrangles are named after classical albedo features, and they are numbered from one to thirty with the prefix "MC" (for "Mars Chart"),[1] with the numbering running from north to south and from west to east.
The quadrangles appear as rectangles on maps based on a cylindrical map projection,[1] but their actual shapes on the curved surface of Mars are more complicated Saccheri quadrilaterals. The sixteen equatorial quadrangles are the smallest, with surface areas of 4,500,000 square kilometres (1,700,000 sq mi) each, while the twelve mid-latitude quadrangles each cover 4,900,000 square kilometres (1,900,000 sq mi). The two polar quadrangles are the largest, with surface areas of 6,800,000 square kilometres (2,600,000 sq mi) each.[2][3]