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How is the State Plane Coordinate system set up? Can GPS provide coordinates in these values? What about Public Land Survey System (PLSS) readouts?

The State Plane Coordinate System (SPCS) is a plane coordinate system (N-S and E-W lines are perpendicular) in which each individual state has from one to six zones, depending on the state's size and shape. The grid system in some states is based on the Lambert Conformal Conic Projection, while the system for other states is based on the Transverse Mercator Projection. As a general rule-of-thumb, states that are longer E-W than N-S use Lambert, while states that are longer N-S use Transverse Mercator. The most notable exception to this is California, which is based on Lambert.

For NAD27, all coordinates were based on U. S. Survey Feet. USGS 7.5' maps show 10,000 foot black grid ticks along the perimeter of the map. The appropriate zone is listed in the margin data at the lower left-hand corner of the map.

For NAD83, coordinates may be in meters, U. S. Survey Feet, or International Feet depending on the State. Each State was allowed to choose which unit of measure they wanted for surveys within their boundaries. Some states changed origins for their State Plane Coordinate System when switching from NAD27 to NAD83. For these reasons, using this grid system has become less popular than in the past.

Some Trimble professional grade GPS receivers are capable of providing positions in the State Plane Coordinate System. Of course, latitude/longitude or UTM positions recorded in the field or post processed in a computer, can be transformed to SPCS through computer software.

GPS cannot provide readouts in the Public Land Survey System (PLSS). Points can be plotted onto a map in lat/long or UTM. From that position a user can determine the Section that encompasses the point.


Tags: Map Coordinate Systems, National Atlas, Coordinates, Latitude and Longitude