[OSRS-PROJ] Older Stateplane Definitions

Craig Bruce csbruce at cubewerx.com
Sat Jul 27 17:56:44 EDT 2002

Frank Warmerdam <warmerdam at pobox.com> wrote:

> The ESRI WKT format has the false easting and northing in the same
> units as the projected coordinate system, which is why they are integral
> (numbers of feet).  Note that the OGC Coordinate Transforms specification
> states that these values are always in meters (unless otherwise indicated
> by a units field), so it is not very easy to have different uses of
> WKT coordinate system interoperate sometimes.

I believe that I have the same problem as well.  I'm pretty sure that
the source is that the EPSG tables define parameter units on a per-
coordinate-system basis, and many derived definitions also have this
problem.  (While EPSG tries to make their tables very "legal", they fail
to make them maximally "usable".)  Also, the OGC WKT format was formerly
(still?) quite ill-defined, which required creative interpretation.

I am using the WKT definitions that were derived from the EPSG tables
a couple of years ago by non other than yourself and another guy, which
use the coordsys units for the parameters instead of metres.

The problem also applies to the angular units used in the parameter
definitions.  I think that there are only a few coordinate systems
that don't use Degrees, but the angular parameters within them may be
in the units of the alternate definition.  I think that this problem
primarily affects NTF-Paris coordinate systems, because they use Gradians
(circle/400) for angular parameter definitions.  (I think other people
were having problems with this.)

What is the location of the definitive modern spec for the OGC WKT
coordsys format?  It'll be a nightmare to deploy different parameter units.

Dr. Craig S. Bruce        | Tel: 819-771-8303 x205 |             CubeWerx Inc.
Senior Software Developer |   Home: 613-565-1344   |  Gatineau, Québec, Canada
csbruce at cubewerx.com      | http://www.csbruce.com |  http://www.cubewerx.com/
    "Everything should be built from the top down, except the first time."

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