State Plane Coordinate System for the United States

Earth Point now supports the State Plane coordinate system. The coordinate system was developed in the 1930's, before the advent of computers or GPS, and is used by mapping professionals in all 50 states. Each state is divided into one or more zones based upon Transverse Mercator, Lambert Conformal, or Oblique Mercator projections. These flat-plane projections allow measurements to be made using simple Cartesian coordinates, thus avoiding complex spherical or ellipsoidal calculations of distance, angle, and area.

Earth Point Features:
The ExcelToKml utility maps a list of State Plane coordinates onto Google Earth, where they can be viewed easily and shared without the need to load them into a larger mapping system. An example spreadsheet is available: StatePlaneExample.xls

The StatePlane page converts State Plane coordinates to Latitude/Longitude and back again. Other coordinate systems, such as UTM and MGRS, are also included. Individual coordinates can be mapped onto Google Earth.

The ConvertCoordinates page accepts State Plane coordinates for conversion to Latitude/Longitude, UTM, and MGRS.

Please help validate the results.
I have tested points in all 124 zones (plus three additional zones for Maine 2000). Please try a few yourself, compare the results to a known system, such as CORPSCON, and add a comment to let everyone know the result.

Also, please post any suggestions you might have about the state plane utilities.