The State Plane Coordinate System is a set of many different projections organized by Zone. Transverse Mercator projections are the basis for the State Plane Coordinate System in U.S. States having predominately north-south extent. Lambert Conformal Conic projections are also used in many of the U.S. State Plane Coordinate System zones.
The State Plane Coordinate System projections are found under the National Grids heading in Manifold projections dialogs. There are three choices:
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State Plane (NAD27, feet) |
State Plane Coordinate System used within the United States based on NAD27 datum. A mix of different projections and parameters, but mostly UTM-based. In feet. |
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State Plane (NAD83, feet) |
State Plane Coordinate System used within the United States based on NAD83 datum. A mix of different projections and parameters, but mostly UTM-based. In feet. |
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State Plane (NAD83, meters) |
State Plane Coordinate System used within the United States based on NAD83 datum. A mix of different projections and parameters, but mostly UTM-based. In meters. |
Note that the NAD 27 version is provided in feet. Since some State Plane users of the NAD 83 version use either feet or meters the NAD 83 version is provided in both feet and meter based projections.
Limitations
The accuracy of Transverse Mercator projections quickly decreases from the central meridian. Therefore, it is strongly recommended to restrict the longitudinal extent of the projected region to +/- 10 degrees from the central meridian. [The US Army standard allows +/- 24 degrees from the central meridian].
This requirement is met within all State Plane zones that use Transverse Mercator projections. However, given modern computer technology these recommended limits result in ludicrously inaccurate maps. But then again, people seriously interested in exploiting the power of modern computers would not be using the State Plane system in the first place.
Because many state plane zones use Transverse Mercator projections they are subject to the same difficulties and limitations of the Universal Transverse Mercator (UTM) system, which also employs Transverse Mercator projections. It is very important for new users to realize that each State Plane Zone is a separate projection. Due to distortion effects induced by Transverse Mercator projections the State Plane system is highly unsuited for creating maps that combine more than more State Plane zone.
See the Universal Transverse Mercator (UTM) topic for a discussion of this and other problems with Transverse Mercator projections.
Comments
Like UTM or Gauss Kruger, the State Plane Coordinate System is a living fossil. It was created mostly as a reflection of the technological limitations of an earlier era. When used with skill as originally intended it still functions well in expert hands. The problem with the State Plane system (as with UTM and Gauss Kruger) is that it is constantly misused in civil applications by inexpert users who do not realize the limitations built into the system.