Originally posted by glitchplz
I believe COD maps are fairly small. You used meters for your Battlefield 3 kill and 1 mile = 1 609.344 meters. You can use marathon to judge the distance traveled in a map. I don't think I have ever gotten more than 1-2 miles ran in an entire game, so I doubt they are too large. There might be another more accurate way to measure it but this is a possibility.
The best way is the XM-25 grenade launcher, it has a built in distance measurer, catch is that you have to have a direct line of sight in order to measure the correct distance from one side to the other.