RE [gdal-dev] Translating between UTM and Geographic

[Steve.Toutant at inspq.qc.ca]

hi,
slight shift in the points (to the east) and an extremely slight shift up 
(to the north).

That seems to be a datum error. Make sure you set the good parameters for 
datum when using nad83 or nad27.
Steve
 




"Henneke, Amanda M" <amanda.m.henneke at boeing.com>@lists.osgeo.org 
Envoyé par : gdal-dev-bounces at lists.osgeo.org
23/09/2009 11:16 AM

A
"gdal-dev at lists.osgeo.org" <gdal-dev at lists.osgeo.org>
cc

Objet
[gdal-dev] Translating between UTM and Geographic








Hello all-

I'm trying to figure out how to reproject some points from a UTM 
projection to Geographic (WGS84) projection.  This works fine when I'm 
working in UTM Zone 12 with NAD83.  When I try the same code for Zone 11 
NAD27, I get a slight shift in the points (to the east) and an extremely 
slight shift up (to the north).

I've included the following code as it stands now, I've tried all sorts of 
things thinking that I need to somehow include more information for the 
new spatial reference (the destination SR), and so far I'm coming up 
empty...

Anyone have any ideas what I'm missing?

Where sSpRefParams is a string that contains the WKT projection 
information from a valid layer...

srOld = new OSGeo.OSR.SpatialReference(sSpRefParams);

srNew.SetGeogCS("Geographic Coordinate System", 
OSGeo.OSR.Osr.SRS_DN_WGS84, OSGeo.OSR.Osr.SRS_DN_WGS84, 
OSGeo.OSR.Osr.SRS_WGS84_SEMIMAJOR, OSGeo.OSR.Osr.SRS_WGS84_INVFLATTENING, 
"Greenwich", 0.0, "degree", 0.0174532925199433);

ctTransform = new OSGeo.OSR.CoordinateTransformation(srOld, srNew);



Amanda M. Henneke
IG/DB Tools - TSS Capability Center
Boeing - St. Louis
314-777-6856



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