State Plane Coordinate System

Set of geographic coordinate systems for regions of the United States

The State Plane Coordinate System (SPCS) is a set of 125 geographic zones or coordinate systems designed for specific regions of the United States. Each U.S. state contains one or more state plane zones, the boundaries of which usually follow county lines. There are 108 zones in the contiguous United States, with 10 more in Alaska, five in Hawaii, one for Puerto Rico and the United States Virgin Islands, and one for Guam. The system is widely used for geographic data by state and local governments. Its popularity is due to at least two factors. First, it uses a simple Cartesian coordinate system to specify locations rather than a more complex spherical coordinate system. By using the Cartesian coordinate system's simple XY coordinates, "plane surveying" methods can be used, speeding up and simplifying calculations. Second, the system is highly accurate within each zone. Outside a specific state plane zone accuracy rapidly declines, thus the system is not useful for regional or national mapping.

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