[gdal-dev] Unknown file type

[Greg Ederer]

Hi Frank,

Just FYI, I had to flip the sign on the pixel height parameter:

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

Many thanks!

Greg


On Jan 9, 2009, at 12:21 PM, Frank Warmerdam wrote:

> 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,
> -- 
> --------------------------------------- 
> +--------------------------------------
> 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    | Geospatial Programmer for  
> Rent
>