I don't know if this is a bug or not as what you are doing is very unclear.
The image already is geocoded, to NAD27, NUTM11 and you seem to be trying to
un-geocode it while warping it.
I did what you said and it does not calculate an appropriate transformation.
It is not specific to triangulation. The warp you are trying to do is better
performed using a polynomial warp, with a linear polynomial order. I tried
deleting the existing projection information, and using RAW and local as
output projections, but neither works. I does seem strange that even when
you enter 4 gcp's that where the to and from coordinates are the same, it
cannot define the warp properly.
In the end, I got it to work in the following, unorthodox, manner. I defined
the output projection as RAW, with a coordinate type as Eastings/Northings.
I then entered the gcp's using negative values for the output northings
(since they increase in value northwards). I when I tried to display the
output file, I got the following error: Image Histogram calculation failed:
Image top left coordinate > bottom right coordinate. I edited the header and
changed the coordinate type to RAW and was able to display the image.
While most people usually use geocoding to actually add coordinate
information, I can see where it may be useful to simply warp an image
without a coordinate system. Perhaps this needs to be looked into.
John
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Norges geologiske unders�kelse
Geological Survey of Norway
Email: [EMAIL PROTECTED]
http://www.ngu.no
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