[gdal-dev] GCPsToGeoTransform returns wrong values

[Bar Ori]

Hi,
I noticed something that for me looks weird and I would like to know maybe I am doing something wrong.
If not, how should I overcome this behavior.

I set 4 GCPs as follows:

var gcps = new[]
{
new GCP(LeftUp.X, LeftUp.Y, LeftUp.Z, 0.5, 0.5, null, "1"),
new GCP(RightUp.X, RightUp.Y, RightUp.Z, Width - 0.5, 0.5, null, "2"),
new GCP(RightDown.X, RightDown.Y, RightDown.Z, Width - 0.5, Height - 0.5, null, "3"),
new GCP(LeftDown.X, LeftDown.Y, LeftDown.Z, Height - 0.5, null, "4")
};

And when I am doing as follows:

var geotransform = new double[6];
Gdal.GCPsToGeoTransform(gcps, geotransform, 0)

Or (after using dataSet.SetGCPs(gcps, projection) :

var geotransform = new double[6];
dataSet.GetGeoTransform(geotransform);

So the values returned, are wrong.
For example, if the LeftUp.X was 35.01050 so the value of geotransform[0], which supposed to be the same value, can be 35.0082.
The same with all the geotransform values.
If I am getting from the dataset and setting again, every time it is changing more and more.
Is there any connection to the use of the "0.5"?

Thanks.


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Ori Bar | Software Developer
Applications Development
Elbit Systems Land and C4I
T  +972-9-8898900  |   M  +972-504-734296




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