Novatel OM-20000077 user manual Appendix E, Ttff and Satellite Acquisition, Time-To-First-Fix Ttff

Appendix E

TTFF and Satellite Acquisition

E.1 Time-To-First-Fix (TTFF)

The receiver enters Navigation mode, see Operational States on Page 31, and provides valid outputs in less than 50 seconds after completion of the self-test and the following initialization criteria have been met:

1.Valid time (±10 minutes) and position data (±100 km) from actual position

2.Valid almanac data (less than a year old)

3.At least 4 satellites greater than 5° elevation above the horizon

4.HDOP < 6

The time allowed for self-test and device initialization is less than 5 seconds.

In the case where the following additional conditions are met, the TTFF is reduced to less than 30 seconds:

•Unit has not been off for more than a week before nominal power is re-applied

•Last navigation fix occurred within the last 2 hours

•Valid ephemeris data (less than 4 hours old) for at least 5 satellites

With no initialization, the time from power application to valid navigation output is typically less than 3 minutes.

E.2 Re-Acquisition

Re-acquisition is the resumption of tracking and measurement processing.

There is no disruption of navigation data output when a satellite signal is lost unless there is a power interruption for a period of less than or equal to 200 ms. Also, the receiver re-acquires the satellite signal within 0.3 seconds after satellite visibility has been restored.

When a satellite signal is lost due to signal masking, the signal is typically re-acquired within 2-3 seconds after the satellite signal meets the minimum input levels. The vehicle dynamics during the masking period are assumed to be less than or equal to 0.5 g acceleration and 100 m/s velocity.

When total signal masking occurs, navigation resumes within 3-5 seconds of a Navigation mode criteria being met.

The receiver is capable of acquiring satellite signals with a minimum input carrier-to-noise density ratio (C/N0) to the correlator of 34 dB-Hz. Once a signal has been acquired, the receiver is capable of tracking satellite signals with a minimum input carrier-to-noise density ratio (C/N0) to the correlator of 31 dB-Hz.

SUPERSTAR II User Manual Rev 3 63