Description of parameters of GDAL SetGeoTransform

gdal
david_p picture david_p · Nov 27, 2014 · Viewed 8.6k times · Source

Can anyone help me with parameters for SetGeoTransform? I'm creating raster layers with GDAL, but I can't find description of 3rd and 5th parameter for SetGeoTransform. It should be definition of x and y axis for cells. I try to find something about it here and here, but nothing.

I need to find description of these two parameters... It's a value in degrees, radians, meters? Or something else?

Answer

Rutger Kassies picture Rutger Kassies · Nov 27, 2014

The geotransform is used to convert from map to pixel coordinates and back using an affine transformation. The 3rd and 5th parameter are used (together with the 2nd and 4th) to define the rotation if your image doesn't have 'north up'.

But most images are north up, and then both the 3rd and 5th parameter are zero.

The affine transform consists of six coefficients returned by GDALDataset::GetGeoTransform() which map pixel/line coordinates into georeferenced space using the following relationship:

Xgeo = GT(0) + Xpixel*GT(1) + Yline*GT(2)
Ygeo = GT(3) + Xpixel*GT(4) + Yline*GT(5)

See the section on affine geotransform at: http://www.gdal.org/gdal_datamodel.html

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