Our distances are not driving distances, but are calculated as a 'straight-line' distance starting from Brentwood. A straight line distance ignores obstructions like rivers, canyons, lakes, et cetera - it's truly a line drawn from Point A (ie- Brentwood) to Point B.
Our distance measurements begin at a specific point in Brentwood. The point that we are using is located at these GPS coordinates - Latitude: 33.7773, Longitude: -86.6292 [Map]. In this case, the coordinates for Brentwood have been provided by the Geographic Names Information System (GNIS).