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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 Washington

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County or City SPCS27 Code SPCS83 Code
Adams 14602 4602
Asotin 14602 4602
Benton 14602 4602
Chelan 14601 4601
Clallam 14601 4601
Clark 14602 4602
Columbia 14602 4602
Cowlitz 14602 4602
Douglas 14601 4601
Ferry 14601 4601
Franklin 14602 4602
Garfield 14602 4602
Grant 14601 4601
Grant 14602 4602
Grays Harbor 14602 4602
Island 14601 4601
Jefferson 14601 4601
King 14601 4601
Kitsap 14601 4601
Kittitas 14602 4602
Klickitat 14602 4602
Lewis 14602 4602
Lincoln 14601 4601
Mason 14602 4602
Okanogan 14601 4601
Pacific 14602 4602
Pend Oreille 14601 4601
Pierce 14602 4602
San Juan 14601 4601
Skagit 14601 4601
Skamania 14602 4602
Snohomish 14601 4601
Spokane 14601 4601
Stevens 14601 4601
Thurston 14602 4602
Wahkiakum 14602 4602
Walla Walla 14602 4602
Whatcom 14601 4601
Whitman 14602 4602
Yakima 14602 4602

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