Document Type : Research Paper

Author

• Mahdi Modiri

Associate Professor of Urban planning, Malek-Ashtar University of Technolog

Abstract

The earth is spherical, or in a better estimation, spheroid (pseudo-sphere) or elliptical. A map should represent the 3D land on a two-dimensional surface as accurate as possible.
In producing maps, it is important that we achieve a clear and distinguished relationship between realities on the Earth and corresponding points on the map. Therefore, making any map must start with a map projection system. There are dozens of map projection systems that one can choose from among.
The systematic and orderly process of transferring points from spherical surface of the earth to a flat surface (map) in a way that spatial relationships are preserved is called a map projection system. The process of map projection system is implemented through application of geometry and mathematical relations. In terms of geometric concepts, the earth is a spheroid (pseudo-spheroid) which is slightly compressed.
According to another definition, the mapping of the meridian and the earth's orbits as a network called the Geographic Coordinate Network on a flat surface is called the map projection system.