[gdal-dev] geotransform rotation and gdal_merge
Chaitanya kumar CH
chaitanya.ch at gmail.com
Sat Jul 21 07:46:06 PDT 2012
You said that you have lat/lon values for each pixel. Can you explain?
On Fri, Jul 20, 2012 at 8:44 PM, David Hoese <dhoese at gmail.com> wrote:
> I'm attempting to put aircraft scan data into geotiffs (1-3 scanlines
> each) and then use gdal_merge.py to combine them into one large geotiff
> that has the entire aircraft's path. The scan lines are 15 pixels wide and
> taken every 10 seconds, the geotiffs are wgs84 lat/lon, and I have lat/lon
> values for each pixel. To handle the case when the aircraft isn't flying
> straight north I think I have to use the 2 rotation parameters in the
> affine geotransform, is that right? I don't have any test cases, but I
> think if I don't use rotation anything that reads the geotiff will think
> that the image is square(aligned) in lat/lon space.
> Whether or not I need to use this, can someone explain to me how to use
> the rotation coefficients? What are the actual values of the coefficients
> supposed to be? I couldn't find a good example and I couldn't get any
> basic situations to make sense, like a 2x3 array turned 45 degrees. I used
> these equations:
> Xgeo = GT(0) + Xpixel*GT(1) + Yline*GT(2)
> Ygeo = GT(3) + Xpixel*GT(4) + Yline*GT(5)
> And lastly, does gdal_merge.py handle rotation? I checked the source and
> it doesn't ever seem to use elements 2 and 4 in its calculations.
> Thanks for any help.
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
Chaitanya kumar CH.
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