I have an airphoto image and a trail map image, and wish to overlay them so the trails show appropriately on the airphoto. Have set up layer for each, and have to move, rotate, scale, the trail image hoping to line things up. It requires multiple tweaking (each affecting another), and the result is not very satisfactory. Is there a better way? Ideally pick similar locations on each layer image (say road intersections or geographic feature) and the program will scale, rotate, etc the layer as appropriate to get them aligned ?

thanks very much for the reply... that looks like what I want to do, albeit my upper layer is the map (with white made transparent) over an airphoto base layer, but it should work to scale, rotate, and reposition pertinent map details onto the airphoto as I can pick similar geographic locations on each layer. My application example would be to have that roadway route plan (prior to it actually being built) overlaid onto an airphoto and one could see what might become paved over. At this point however my program knowledge fails me and the path help section still leaves me puzzled. Can you advise how I set up this path abcd and particularly how do I use plug-ins or these scripts? Presumably they need to be imported into the main program somehow. Sorry for being kinda dumb with this, gimp is way more complicated than the photo editing software I usually use just to crop, rotate and adjust levels.

There are Gimp plugins that will align two layers but only between two points.

There is a plugin here: http://sourceforge.net/projects/gimp-tools/files/scripts/ ofn-layer-aligner about 30 down the list ofn-

In the very-much simplified example: A four point path A-B-C-D defining the start and finish of intended and actual, scales and rotates to suit. Very much depends on the images, different map projection and camera angle and it might be easier to draw in by hand.

A non-gimp solution might be Hugin which has a stack alignment option. Not easy to use and I have not had much success unless the images are very similar.

thank you very much for this... and if you made that video for me (possibly as I think I was the first viewer) I am very indebted for your help - far beyond any anticipation of assistance. It worked perfectly as a (very much needed) guide to deal with the plugins, and subsequently align some map details onto an aerial google earth image. The overall quality is now limited by the map image resolution rather than my crude alignment techniques. Once again thank you for the time and assistance to help me out. With any luck you have aided a bit of forest not to be cut down.