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The State Plane Coordinate System

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. There are 110 zones in the continental US, with 10 more in Alaska, 5 in Hawaii, and one for Puerto Rico and US Virgin Islands. 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 (the geographic coordinate system of latitude and longitude). By thus ignoring the curvature of the Earth, "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.

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 also long east-west. These zones use the Lambert conformal conic projection, because it is good at maintaining accuracy along an east-west axis. Zones that are long in the north-south direction use the Transverse Mercator projection because it is better at maintaining accuracy along a north-south axis. The panhandle of Alaska, whose maximum dimension is on a diagonal, uses an Oblique Mercator projection, which minimizes the combined error in the X and Y directions.

All State Plane zones in Alaska

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County or City SPCS27 Code SPCS83 Code
Aleutians East 15010 5010
Aleutians West 15010 5010
Anchorage 15004 5004
Bethel 15007 5007
Bristol Bay 15006 5006
Dillingham 15006 5006
Fairbanks North Star 15003 5003
Haines 15001 5001
Juneau 15001 5001
Kenai Peninsula 15004 5004
Ketchikan Gateway 15001 5001
Kodiak Island 15005 5005
Lake and Peninsula 15006 5006
Matanuska-Susitna 15004 5004
Nome 15008 5008
North Slope 15005 5005
Northwest Arctic 15006 5006
Prince of Wales-Outer Ketchikan 15001 5001
Sitka 15001 5001
Skagway-Hoonan-Angoon 15001 5001
Southeast Fairbanks 15002 5002
Valdez-Cordova 15003 5003
Wade Hampton 15007 5007
Wrangell-Petersburg 15001 5001
Yakutat 15001 5001
Yukon-Koyukuk 15004 5004

Click here to go back to the list off all State Plane grids