rotating raster maps

[charnotw]

> If anyone could help... I have many air photos that were scanned in as tif 
> files that were imported into GRASS as raster files. The problem is that 
> the north end of the photos were not orientated to the top of the map or 
> in this case, the top of the screen. The plan is to geo-reference these 
> images to UTM coords and to rectify the images. I have not been able to 
> find a program within GRASS that would allow me to rotate these images. 
> Does such a program exist? Or do the photos need to be scanned in with 
> north orientated to the top of the screen?
> 
> Any comments would be appreciated. Thanks. 

i.rectify applies "scaling,translation and rotation" so rectifying
and georeferencing the maps with i.points and i.rectify will
mean that the poles are lined up properly.  (assuming you pick the
points accurately 8-)  I assume that photo.rectify in ortho.photo
does similar things.  I don't think correct allignment is a necessary
prerequisite for rectification and georeferencing, I could be wrong.

cheers  Tom  8-) 

Tom Charnock                       O--O
Dept Civil Engineering            (~~~~)
Aston University                 (  __  )
Birmingham B4 7ET UK             /|\  /|\
charnotw at sun.aston.ac.uk