On Wed, Jun 01, 2005 at 11:38:23PM +0100, Dylan wrote:
> Hi All,
> I'm trying to overlay images of maps onto aerial protographs. Using the 
> photo as a background, I need to scale and rotate the map image so that 
> the two line up. Is this possible with the Gimp? What approach should I 
> use?
> If it's not feasable with Gimp, does anyone know any (Linux) software 
> which would be suitable?

Definitely possible and feasable.  As long as you have a simple perspective
transform in your images.  Once things like WGS'84 and other coordinate
systems rear their head, the best bet is something made for this like GRASS.

Anyway, the main tool you would be looking for is the Rotate, Scale, Shear,
and Perspective tools (Shift-R, Shift-T, Shift-S, Shift-P by default)
Perspective and Rotate will probably be the most useful.

I've done it, and it works as long as your data isn't too distorted.  Don't
try anything like the overlays Google Maps does, though, you would
definitely need something like GRASS then.


Computer Science is as much about computers as astronomy is about telescopes
        -- Edsger Wybe Dijkstra (1930-2002)

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