In order to calculate the distance between two points, we'll need to use some spherical geometry calculations. The problem we will have to overcome is that our charts and maps are flat. But the actual planet is very close to being spherical. While the spherical geometry may be a bit advanced, the programming is pretty simple. It will show us several features of the Python math library.

The distance between two latitude and longitude points on a sphere is defined as follows:

This formula determines the cosine between the two positions; the angle with that cosine is multiplied by the radius of the earth, R, to get the distance along the surface. We can use R = 3,440 NM, R = 3,959 mi, or R = 6,371 km; we get reasonably accurate distances in nautical miles, statute miles, or kilometers.

This formula doesn't work well with small distances. The haversine formula is preferred to compute distances more accurately. Here is some background information http://en.wikipedia.org...