Radius of multiple latitude/longitude points

Question

I have a program that takes as input an array of lat/long points. I need to perform a check on that array to ensure that all of the points are within a certain radius. So,

Answer 1

Check out the answers to this question. It gives a way to measure the distance between any two (lat,long) points. Then use a smallest enclosing circle algorithm.

I suspect that finding a smallest enclosing circle may be difficult enough on a plane, so to eliminate the subtleties of working with latitude and longitude and spherical geometry, you should probably consider mapping your points to the XY plane. That will introduce some amount of distortion, but if your intended scale is 100 miles you can probably live with that. Once you have a circle and its center on the XY plane, you can always map back to the terrestial sphere and re-check your distances.