Warm start is performed whenever the GPS receiver has only access to valid almanac data, and has not significantly moved since the last valid position calculation. This is typically th ecase, if the receiver has been shut off for more than 2 hours, but still has knowledge oflast position, time and almanac. This allows it to predict the current visible SCs. However, since ephemeris data is not available oroutdated, the receiver needs to wait for the ephemeris broadcast to complet.