[GRASS-user] Defining a State Plane Coordinate Location

[Rich Shepard]

On Sun, 24 Jul 2011, Markus Neteler wrote:

> Better use
> - the wxGUI location manager from the startup screen

Markus,

   This is what I've tried. When I select STP as the projection I'm told that
I need to manually enter the definition.

> - or create the location from a GIS file (shape, geotiff, ..) with correct
>  metadata

   This, of course, would be too easy ... if such a map was available. None
of the data I've collected is in SPCS, unfortunately.

> - or create from the EPSG code
>  (is it this one?http://spatialreference.org/ref/epsg/3429/ )

   I'm not sure.

   Searching the Web with Google lead me to a site that has the projection,
datum, and ellipsoid parameters for all SPCS zones. The above reference
uses US Feet as the measurement units while the current standard uses
Metres. (Snyder's book has conversion factors to adjust for NAD83 from
NAD27.)

   Since SPCS is a derivative of the Transverse Mercator projection, the site
I found (which provides the data for free while selling projection
conversion software for Microsoft systems) tells me:

False northing:		8000000
False easting:		200000
Origin Latitude:	43.75
Origin Longitude:	-115.583333333333
Parallel North:		0
Parallel South:		0
Scale Factor:		0.9999

   It also has 0 as the parameters for NAD83 (apparently already adjusted)
and those for GRS89. I intend to use the above to define the location unless
I'm way off.

Thanks,

Rich