The basic content of a map is called map elements, which include mathematical elements, geographical elements and decorative elements (also called auxiliary elements), so it is also called "three elements" of a map.

(l) Mathematical elements refer to the mathematical basis of a map, such as map projection, scale, control points, coordinate network, height system, map framing, etc. These contents are the basis for determining the range and position of the map sheet and controlling other contents. They ensure the accuracy of the map, as a reliable basis for measuring points, elevations, lengths and areas on the map, and ensure the splicing and use of multiple maps in a large range. Mathematical elements, mathematical elements,

(2) Geographical elements refer to natural and social phenomena with geographical location and distribution characteristics. Therefore, they can be divided into natural factors (such as hydrology, landform, soil quality and vegetation) and socio-economic factors (such as residential areas, traffic lines and administrative boundaries).

(3) Finishing elements mainly refer to some contents of the map that are easy to read and use, such as map name, map number, legend and description of map data, and various characters and graphics in the map.