Hi, > Distances are selected by the user using a dropdownlist in the range of .25 > to 4 miles.
A 4 miles square section of the earth is going to be fairly close to flat. A pythagorean distance formula is very likely to give errors of < 20 feet over that range. A quick google search suggests 8 inches curvature/mile which is going to be less than real life topological features. Justin