There are two State Plane Coordinate Systems defined in the United States, one based on the North American Datum of 1927 and the other based on the North American Datum of 1983.

Each of the State Plane Coordinate Systems divides the United States into over 130 sections, each with its own projection surface and grid network. With the exception of very narrow states, such as Delaware, New Jersey, and New Hampshire, most states divide into two to ten zones.

Zones extending primarily in an east-west direction are based on the Lambert Conformal Projection, while zones extending in a north-south direction are based on the Transverse Mercator Projection. Alaska, Florida and New York use both Transverse Mercator and Lambert Conformal for different areas. The Aleutian panhandle of Alaska uses the Oblique Mercator Projection.

Zone boundaries follow state and county lines and, because each zone is small, distortion is less than 1 in 10,000. Each zone has a centrally located origin and a central meridian that passes through the origin. The United States uses a two-zone numbering system: The United States Geological Survey (USGS) Code System and the National Ocean Service (NOS) Code System. However, other code systems do exist.

The State Plane zone is the only required defining parameter for any of the State Plane Coordinate Systems supported in GeoCalc.

WE STRONGLY RECOMMEND THAT YOU USE THE NGS NADCON GEODETIC DATUM TRANSFORMATION METHOD WHEN CONVERTING STATE PLANE COORDINATES. HOWEVER, YOU MAY USE THE MOLODENSKY METHOD WHEN CONVERTING STATE PLANE COORDINATE SYSTEM OF 1927 COORDINATES AND SELECT ONE OF THE DEFINED SET OF NAD 27 DATUM TRANSFORMATIONS.

A State Plane coordinate is specified in GeoCalc by northing and easting values. The U.S. Survey Foot is the standard unit in the State Plane Coordinate System of 1927. The meter is the standard unit in the State Plane Coordinate System of 1983. Any distance unit defined within GeoCalc may be used to specify State Plane coordinates.

State Plane 1927 and State Plane 1927 Exact