[GRASS-user] Defining a State Plane Coordinate Location

Glynn Clements glynn at gclements.plus.com
Sun Jul 24 10:43:26 EDT 2011


Rich Shepard wrote:

>    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.

PROJ's EPSG file says:

	# NAD83(HARN) / Nevada East (ft US)
	<3429>
	+proj=tmerc
	+lat_0=34.75
	+lon_0=-115.5833333333333
	+k=0.9999
	+x_0=200000.00001016
	+y_0=8000000.000010163
	+ellps=GRS80
	+units=us-ft

Which is identical except for lat_0 (34.75 vs 43.75), which might be a
transcription error.

According to:

	http://www.ngs.noaa.gov/PUBS_LIB/ManualNOSNGS5.pdf

	"NOAA Manual NOS NGS 5 - State Plane Coordinate System of 1983"

34.75° (34°45') is correct for SPCS 2701 (Nevada East); page 68 (PDF
page 78) says:

                                                                                Grid Origin
                                                Central Meridian        Longitude       Easting
          State/Zone/Code       Projection      and Scale Factor        Latitude        Northing

        Nevada  NV
          East  E       2701    T.M.             115 35                 115 35             20,000.
                                                1:10,000                 34 45          8,000,000.

-- 
Glynn Clements <glynn at gclements.plus.com>


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