[Gdal-dev] gdalwarp custom reprojections

[Frank Warmerdam]

kgrootendorst at baird.com wrote:
> 
> Listers,
> First, I'm new to the list - is there anyway to search the list 
> postings?  I don't want to be 'that guy' who posts a question that's 
> been posted a million times before...
> 
> Second, I'm trying to reproject a tif image using gdalwarp.  Specially, 
> from UTM Zone 21N WGS 84 (epsg:32621) to Barbados National Grid 
> (epsg:21292).  I used the following code in  FWTools1.0.0a5:    gdalwarp 
> -s_srs epsg:32621 -t_srs epsg:21292 -co "TFW=YES" 
> d:\Barbados\QB2005w.tif d:\Barbados\QB2005w_BNG.tif
> 
>  I suspect that I may need to do a custom transformation using x, y, z 
> shift values (I have these values).  Is there any way to include these 
> parameters in my gdalwarp code above?

Kevin,

It looks like my current definition for EPSG:21292 is:

   +proj=tmerc +lat_0=13.17638888888889 +lon_0=-59.55972222222222
           +k=0.999999 +x_0=30000 +y_0=75000 +ellps=clrk80
           +towgs84=31.95,300.99,419.19,0,0,0,0 +units=m +no_defs

If the provided towgs84 values seem inappropriate you can given the
explicit PROJ.4 string you would like on the commandline.

eg.

gdalwarp -s_srs epsg:32621 -t_srs '+proj=tmerc ... +towgs84=yourvalues ...' ...

Just make sure you use the whole definition from above, replacing the
+towgs84= section with your values.

Best regards,
-- 
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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