[Gdal-dev] Projection issues with OGR/Proj.4.

[Ed McNierney]

Rostic -

It seems that Frank's observation is correct - please see the following
discussion concerning this apparent error in the EPSG database:

http://www.nabble.com/nad27-vs.-epsg-defn-of-CA-State-Plane-zone-VII-t16
6935.html

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com

-----Original Message-----
From: gdal-dev-bounces at lists.maptools.org
[mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of Frank
Warmerdam
Sent: Friday, April 07, 2006 7:03 PM
To: Sheykhet, Rostic
Cc: gdal-dev at lists.maptools.org
Subject: Re: [Gdal-dev] Projection issues with OGR/Proj.4.

Sheykhet, Rostic wrote:
> Hi All,
> 
> I am trying to convert a shape using OGR calls from Lon/Lat to 
> California VII State Plane Projection.  I get Easting and Northing out

> of it, but when I try to use other tools (ArcMap, OSSIM, Corpscon 6) 
> they interpret these easting and northing values to be in a completely

> different place.  Here are the values:
> PROJ.4 coordinate system string:
> 	+proj=lcc +lat_2=34.41666666666666 +lat_1=33.86666666666667
> +lat_0=34.13333333333333 +lon_0=-118.3333333333333
> +x_0=1276106.450596901 +y_0=127079.524511049 +ellps=clrk66
> +datum=NAD27 +to_meter=0.3048006096012192 +no_defs
> 
> Original Lon/Lat:  -117.2038, 32.7161
> 
> OGR/Proj.4 Output: 4534220.33, -96890.84
> 
> Other Tools' idea of what easting/northing for this lon/lat should be:
> 4534487.622, 3647093.557
> 
> Other Tools' idea of where OGR/Proj.4-converted easting/northing 
> values
> are: -117.324683175, 22.495186883.
> 
> Any suggestions are appreciated.

Rostic,

What WKT .prj file does ArcGIS use for the coordinate system?

I checked an old ArcGIS "26747.prj" and I see that it is using a false
northing of 4160926 feet while the OGR definition for
EPSG:26747 has a false northing of 127079 feet.  I'm not sure which is
right but the different might well account for the error.

Best regards,
-- 
---------------------------------------+--------------------------------
---------------------------------------+------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGF,
http://osgeo.org

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