[gdal-dev] Unknown file type

[Frank Warmerdam]

Greg Ederer wrote:
...
> Note that the pixel/line coordinates in the above are from (0.0,0.0) at 
> the top left corner of the top left pixel to 
> (width_in_pixels,height_in_pixels) at the bottom right corner of the 
> bottom right pixel. The pixel/line location of the center of the top 
> left pixel would therefore be (0.5,0.5).
> </end docs>
> 
> But, I'm still unsure how to compute the required values.  The docs 
> don't give units for GT(1) and GT(5), and for GT(0) and GT(3).  My data 
> have a resolution of 0.1 deg lat X 0.1 deg lon, and the upper left 
> lat/lon is 40N,20W.  Could you give me some pointers on how to compute 
> the transform values?

Greg,

The geotransform coordinate system is whatever is defined by the <SRS>
tag.  So in your case I believe long/lat WGS84.

I imagine your GeoTransform would be:

   -20.05, 0.1, 0.0, 40.05, 0, 0.1

This is assuming that the upper left corner really reflects the center
of the top left pixel in which case a half pixel offset is needed.  I'm
also assuming north up image orientation.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent