In another thread from a few days ago I posted a comparison of all the big ofp, cwa, arma maps I could find. I could not use ingame screenshots of every overview map since I only have the current alpha installed so I had to use what I could find online. I tried to use official looking images and was kinda lucky to find most of them even with scale bars. How accurate those scales are, I cannot say.
Also I'm not entirely sure, if the grids that are used have a common scale. Is one sqaure always 1km² in every game? Some maps suggest so others don't. So I used an official looking mock travel map of Chernarus that has a grid. The image is cropped at the top a little bit I guess, but 5 squares line up to the 5km scale bars of the other images. And that's what I did, I resized the different images so that they use one identical 5km scale bar.
The Post/Thread:
http://forums.bistudio.com/showthread.php?147121-Putting-Stratis-into-perspective-on-size&p=2342702&viewfull=1#post2342702
The Image:
http://s7.directupload.net/images/130317/b333uo3s.jpg
And the Takistan map is only a very rough guess based on some pictures showing the borders and cities of Chernarus and Takistan next to each other.