Photogrammetry (rotating)

[Andrea Giacomelli]

> Another problem I have is rotating the base map to magnetic north. I
> can't seem to find a grass routine that will rotate a raster or a vector
> layer. Just rotating the grid would be enough for the base map.
>

...I'm not using GRASS like one year ago...I'll give it a try...

For rasters: 

1- create an imagery  group containing the image you need to rotate
2- set the target (i.target) to the location of your source image
3- compute the values for the rotated coordinates externally
4- instead of providing tie points via i.points, go under the
directory of the "group" you created, and create a file called POINTS
in the following format:

#                   image                          target           status
#            east           north            east           north   (1=ok)
#
         9.648879       43.596939        8.445536       44.476532    1
        13.302691       40.549549        9.231250       44.414099    1
         9.648879       39.513436        9.186607       44.663829    1
        13.607175       37.624054        9.552679       44.351667    1
....
5- i.rectify

...hope this helps (or in the meantime Marcus stuffed in an r.rotate...?)

Cheers,


                =========================================
                Andrea Giacomelli
                Centre for Advanced Studies, Research and
                Development in Sardinia
                Environment Division

                http://www.crs4.it/~andreag
                =========================================