Advice wanted: rectifying of aerial photographs

[Philip Verhagen]

Dear all,

I need some expert advice on the (im)possibilities of rectifying
aerial photographs with GRASS or other software. The problem: I
received a set of hand-drawn maps that are based on a photo-interpretation
of an area of approx. 10x15 km. The maps have been combined, by sticking
colour copies together, to a map that is roughly on 1:20,000. However, the set
of photos on which this map is based consists of two runs that are not
exactly on the same scale. Needless to say that the number of reference
points that I can find on the photographs is rather limited, and that
the area is far from flat. The author of the map wants me to have it
digitized and rectified in the UTM system.

Is there any chance of doing this with a reasonable accuracy (e.g.
with i.rectify), and if so, what are the conditions that should be 
met? Any advice will be greatly appreciated!

Philip Verhagen

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