They are textures, I have used Photoshop and many layers. I have tried a new technique with these three airfields but I am not 100% satisfied with them... I must regenerate the main idea when I use the old aerial photos with the airfield textures...
At first I rotate, scale and skew the aerial photo to 1024 x 1024 pixels image using airfield map as reference (I have scaled the map to 1 mile x 1 mile = 1024 x 1024 pixels image). After that the airfield is very near to it's real life dimensions:
Then I took my different textures, the bottom texture should be for ex. my forest texture:
Then I use my dark heather texture:
I create the airfield area with those two textures (forest and heather):
Then I use the sand texture:
I pick all the aerial photo's light areas (with the "Magic Wand" tool) from the sand texture and blur them. Then it looks something like this:
Lastly I mix all the layers together, for ex. the old aerial photo is about 30% transparent, sand is something 20% etc.
Then I create the grayscale BumpH-file, assign all the airfield stuff (hangars, plates etc.) and that's it!
I must use (with the airfields) "stretched" textures (x2) so the resolution is not good (512 pixels / mile). That is because there is coming so many so custom airfields to this map.
And Zoran: Thank you for those airfield photos!