i.rectify2

[Bob Courtney]

> 
> I suspect that your second  supposition is the problem---i.rectify2 .
> To check v.proj you are better to compare it to proj of PROJ.4 or
> GCTP but not against i.rectify.
> 
> The clue also seems buried in the "transformation matrix" but since
> I have no experience with i.rectify I can't be of much help other
> than to note that it must be *much* more than a simple scale-rotate-
> shift operation.  That is, i.rectify2 must know all about lcc
> to be able to create a complex non-linear transformation.
> 
> Any i.rectify2 gurus out there?
> 
> Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
> voice: (508)563-6766          Postal: P.O. Box 1027
>   fax: (508)457-2310                  N.Falmouth, MA 02556-1027
> 

Your supposition is right on the mark. i.rectify2 only applies a best
fit second order polynomial transformation to the source image,
whereas the ll to lcc transformation, over the area of interest, is
most likely much more complex.  The problem can be solved using
your PROJ routines to calculate the exact tranformation details
for each pixel in the source image. In practice, one should define an
image in the target coordinate system and calculate the inverse
transformation to ll to find pixel values. A lot of calculations,
but what are computers for.

Bob Courtney
Atlantic Geoscience Centre