Personally I have a group without too much fear of math, and we usually have a calculator handy, so we prefer to break out a little pythagorian theorum and find the actual linear distance to the flyer, rounding to the nearest integer value. It just makes more sence and feels more real to us that way.

But yes Joe is correct you use the same method for accounting for the range between the flyer and the ground pounder regardless of which was doing the firing.