GCP transform is not solvable for some BSB charts

[vadp]

gdalwarp and gdaltransform (GDAL 1.7.2) do fail with some KAP files with

Failed to compute GCP transform: Transform is not solvable

The way to reproduce the error:

gdalwarp G0602_3.KAP G0602_3.KAP.tif

[Even Rouault]

The issue is that this image has 6 GCPs, so gdalwarp will select by default a polynomial transform of order 2. But as the image is upside down and due to the values of the selected GCPs, it comes that second order is not solvable. The good news is that it works perfectly if you try adding "-order 1" or "-tps" on gdalwarp command line.

I'm not sure how we can automatically improve the choice of the default transformer.

[vadp]

Actually I have found that G0602_3.KAP and similar are chartlets from a larger chart and many of them are poorly calibrated, hence the error and distortions when manipulating these data.