University of Wyoming's Balloon Trajectory program - Assumes about a 270m/sec ascent rate and 4.9m/sec (low altitude) descent rate.

Near Space Ventures Flight Track - Online version of Bill Browns original BASIC Balloon Track (appears to just use US Weather Stations) Try WATTISHAM RAF(03590), COLTISHALL (03495), HEMSBY (03496) as nearest WMO stations to Cambridge.