Working out coordinates for a bounding box with 3 mile radius from original lat/long I have a latitude/longitude. I need to get lat/long coordinates that create a bounding box covering roughly a 3 mile radius around the original location. Ideally I'd like to have 4 sets of lat long creating the bounding box - with the center being the original location. I know how to measure the distance between two different longitude/latitudes but in this instance I obviously only have the initial point to work from.

Let's suppose your original point is $(\theta,\phi)$ in radians.

Let $s$ be arc length, in your case, $s=3$, $r$ be the radius of sphere. If you are talking about earth, then $r$ is the radius of earth in miles.

The new latitude will be $\theta\pm \frac{s}{r}$. The new longitude will be $\phi \pm \frac{s}{r}$.

$\pm$ means $+$ or $-$. So the new points are: $(\theta+\frac{s}{r}, \phi +\frac{s}{r}), (\theta+\frac{s}{r}, \phi -\frac{s}{r}), (\theta-\frac{s}{r}, \phi +\frac{s}{r}), (\theta-\frac{s}{r}, \phi -\frac{s}{r})$, in the order of upper right, lower right, upper left, lower left.