Carrier phase initialization

The receiver can automatically initialize the carrier phase ambiguities as long as at least five common satellites are being tracked at base and rover sites. Automatic initialization is sometimes termed On-The-Fly (OTF) or On-The-Move (OTM), to reflect that no restriction is placed on the motion of the rover receiver throughout the initialization process.

The receiver uses L1 (or for dual-frequency receivers L1 and L2) carrier-phase measurements plus precise code-phase measurements to the satellites to automatically initialize the ambiguities. The initialization process generally takes a few seconds.

As long as at least four common satellites are continuously tracked after a successful initialization, the ambiguity initialization process does not have to be repeated.