[gdal-dev] How can I found gcp error in gdalwarp?

[Even Rouault]

Le mardi 15 décembre 2015 11:16:41, OHTSUKA Ko-hei a écrit :
> Hello,
> 
> I use gdalwarp for georeferencing.
> 
> I run gdalwarp with many gcps, then warning says:
> "There is a problem to invert the interpolation matrix"
> 
> I think some errors may exist in gcps, but I don't know how to find where
> it is.
> 
> Are there any simple way to find errors in gcps?

Ko-hei,

I'm afraid there isn't an easy method. There might be "obvious" errors like 
fully duplicated GCP records, or 2 GCPs that would have same pixel,line 
coordinates but different X,Y georeferenced coordinates (or the reverse). But 
there might be far less obvious errors leading to this mathematic anomaly.

I've just added in GDAL trunk an improvement regarding reporting of the 
"obvious" errors: 
https://trac.osgeo.org/gdal/changeset/32187

Even

> 
> Ko-hei

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