The State Plane Coordinate System

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The State Plane Coordinate System (SPS or SPCS) is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. Each state contains one or more state plane zones, the boundaries of which usually follow county lines. Multiple state zones are used to limit distortion errors due to map projections. 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 like the geographic coordinate system of latitude and longitude. 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 (error less than 1:10,000). Outside a specific state plane zone accuracy rapidly declines, thus the system is not useful for regional or national mapping. The State Plane system provides a common coordinate reference for horizontal coordinates over county and multi-county areas while limiting distortion error to specified maximum values. Most state plane zones are based on either a transverse Mercator projection or a Lambert conformal conic projection. The choice between the two map projections is based on the shape of the state and its zones. States that are long in the east-west direction are typically divided into zones that are
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