[Gdal-dev] Re: OGR/GDAL and datum transformations

[Dylan Beaudette]

On Friday 09 March 2007 02:12, Jose Gomez-Dans wrote:
> Hi Dylan,
> A few months ago, you mentioned a number of tests on the accuracy of
> GDAL/OGR coordinate transforms on the GRASS mailing list, and you
> blogged about it
> <http://casoilresource.lawr.ucdavis.edu/drupal/node/259>.
>
> In the past, I have written a small GUI app that reprojects shapefiles
> in the three or four geographic references we use at work here, and
> while so far no one has complained, I am aware that there are
> significant changes due to different datums (we shift from European
> Datum 1950 to WGS84 and viceversa). My program just uses "EPSG:XXXX"
> and gdal_translate/ogr2ogr, but I am now a thinking that I need to
> provide the parameters for the transfomration. For example, GRASS
> offers me different options for EPSG:23030, but I don't know how to
> add these to the GDAL command line or WKT. Do you know  how to specify
> which datum transform to use in GDAL/OGR?
>
> Many thanks!
> Jose

Hi Jose. Please note that I am not an expert in specifying datum 
transformation parameters to GDAL. I think that it has to be done with the 
7-parameter transform used in the 'to_wgs80'  (?) option. Perhaps someone 
else on the list can help.

cheers,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341