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Acutime 2000 Synchronization Kit User Guide F-5
F Theory of Operation
F.2.3 "Garage Search" Strategy
During a warm start search, the smart antenna knows which satellites
to search for, based on the system almanac, the initial position and the
current time. In some cases, the receiver may not be able to acquire
the expected satellite signals (for example, if the Acutime 2000 is in a
jamming environment). Trimble's patented garage search strategy,
also known as a split search, is designed for such situations.
If the receiver does not acquire the expected set of satellites within
five minutes of a warm start, one of the channels is directed in a cold
start search. This strategy minimizes the time to first fix in cases
where the stored almanac, position and time are invalid. If the cold
start search proves effective and the garage search fails, the stored
information is flushed from memory.
F.2.4 Hot Start
A hot start strategy applies when the almanac, position, time and
ephemeris in memory are valid. The hot start search strategy is
similar to a warm start, but since the ephemeris data in memory is
considered current and valid, the acquisition time is typically less
than 30 seconds. This may occur if the GPS signals are temporarily
obscured or jammed.