Trimble Outdoors Part Number 45005-00-ENG, AcutimeTM2000 Synchronization Kit manual Byte

Trimble Standard Interface Protocol A

•Minimized Projection - This bit controls the time of the position fix relative to the time of the satellite range measurements. The default mode is OFF. In this mode, the time of solution is the time at which the GPS position fix is computed. Thus, all measurements are projected by an interval which is roughly the amount of time it takes to compute the solution. This approach minimizes the latency between the time tag of the computed solution and the solution output. The drawback is that the measurement projection (which is only about 100 ms) may induce some error during high accelerations.

Alternatively, when minimized projection is ON, the time of the solution is the time of the most recent measurements. Thus, if all measurements are taken at exactly the same time, there is no measurement projection. If a selected satellite's measurement time lags the most recent measurement, then it is projected to this time. The difference is that the fix will have more latency than a fix provided with the above timing option. This is the best choice for users performing non real- time error analysis, or non real-time DGPS solution-space corrections. This is also the preferable mode for users integrating GPS with other sensors, where communication lags are the dominant latencies, and thus the time lag between the applicability and availability of the fix is small.

Byte 3

Byte 3, the auxiliary byte, controls the output of additional fix data. It contains two control bits:

•Bit 0 controls the output of raw measurements (Packet 5A).

•Bit 1 controls whether the raw measurements output in packet 5A are doppler smoothed.

A-34 Acutime 2000 Synchronization Kit User Guide