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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 Illinois

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

County or City SPCS27 Code SPCS83 Code
Adams 11202 1202
Alexander 11202 1202
Bond 11202 1202
Boone 11201 1201
Brown 11202 1202
Bureau 11202 1202
Calhoun 11202 1202
Carroll 11202 1202
Cass 11202 1202
Champaign 11201 1201
Christian 11202 1202
Clark 11201 1201
Clay 11201 1201
Clinton 11202 1202
Coles 11201 1201
Cook 11201 1201
Crawford 11201 1201
Cumberland 11201 1201
DeKalb 11201 1201
De Witt 11201 1201
Douglas 11201 1201
Du Page 11201 1201
Edgar 11201 1201
Edwards 11201 1201
Effingham 11201 1201
Fayette 11201 1201
Ford 11201 1201
Franklin 11201 1201
Fulton 11202 1202
Gallatin 11201 1201
Greene 11202 1202
Grundy 11201 1201
Hamilton 11201 1201
Hancock 11202 1202
Hardin 11201 1201
Henderson 11202 1202
Henry 11202 1202
Iroquois 11201 1201
Jackson 11202 1202
Jasper 11201 1201
Jefferson 11201 1201
Jersey 11202 1202
Jo Daviess 11202 1202
Johnson 11201 1201
Kane 11201 1201
Kankakee 11201 1201
Kendall 11201 1201
Knox 11202 1202
Lake 11201 1201
La Salle 11201 1201
Lawrence 11201 1201
Lee 11202 1202
Livingston 11201 1201
Logan 11202 1202
McDonough 11202 1202
McHenry 11201 1201
McLean 11201 1201
Macon 11201 1201
Macoupin 11202 1202
Madison 11202 1202
Marion 11201 1201
Marshall 11202 1202
Mason 11202 1202
Massac 11201 1201
Menard 11202 1202
Mercer 11202 1202
Monroe 11202 1202
Montgomery 11202 1202
Morgan 11202 1202
Moultrie 11201 1201
Ogle 11202 1202
Peoria 11202 1202
Perry 11202 1202
Piatt 11201 1201
Pike 11202 1202
Pope 11201 1201
Pulaski 11202 1202
Putnam 11202 1202
Randolph 11202 1202
Richland 11201 1201
Rock Island 11202 1202
St. Clair 11202 1202
Saline 11201 1201
Sangamon 11202 1202
Schuyler 11202 1202
Scott 11202 1202
Shelby 11201 1201
Stark 11202 1202
Stephenson 11202 1202
Tazewell 11202 1202
Union 11202 1202
Vermilion 11201 1201
Wabash 11201 1201
Warren 11202 1202
Washington 11202 1202
Wayne 11201 1201
White 11201 1201
Whiteside 11202 1202
Will 11201 1201
Williamson 11201 1201
Winnebago 11202 1202
Woodford 11202 1202

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