Our distances are not driving distances, but are calculated as a 'point-to-point' distance that starts in Somerville. A straight line distance ignores things like rivers, canyons, lakes, et cetera - it's truly a line drawn from Point A (ie- Somerville) to Point B.
Our distance measurements begin at a specific point in Somerville. The point that we are using is located at these GPS coordinates - Latitude: 34.4693, Longitude: -86.7957 [Map]. In this case, the coordinates for Somerville have been provided by the Geographic Names Information System (GNIS).