ZED-F9P-Integration Manual
UBX-18010802 - R02
4 Receiver description Page 62 of 114
Advance Information
• CFG-TP-LEN_TP1 = 100 000 µs
• CFG-TP-TIMEGRID_TP1 = 1 (GPS)
• CFG-TP-PULSE_LENGTH_DEF = 0 (Period)
• CFG-TP-ALIGN_TO_TOW_TP1 = 1
• CFG-TP-USE_LOCKED_TP1 = 1
• CFG-TP-POL_TP1 = 1
• CFG-TP-PERIOD_LOCK_TP1 = 100 000 µs
• CFG-TP-LEN_LOCK_TP1 = 100 000 µs
The 1 Hz output is maintained whether or not the receiver is locked to GPS time. The alignment to
TOW can only be maintained when GPS time is locked.
Figure 38: Example 1
4.11 Forcing a receiver reset
Typically, in GNSS receivers, one distinguishes between cold, warm, and hot starts, depending on
the type of valid information the receiver has at the time of the restart.
• Cold start: In cold start mode, the receiver has no information from the last position (e.g.
time, velocity, frequency etc.) at startup. Therefore, the receiver must search the full time and
frequency space, and all possible satellite numbers. If a satellite signal is found, it is tracked
to decode the ephemeris (18-36 seconds under strong signal conditions), whereas the other
channels continue to search satellites. Once there is a sufficient number of satellites with
valid ephemeris, the receiver can calculate position and velocity data. Other GNSS receiver
manufacturers call this startup mode Factory Startup.
• Warm start: In warm start mode, the receiver has approximate information for time, position,
and coarse satellite position data (Almanac). In this mode, after power-up, the receiver normally
needs to download ephemeris before it can calculate position and velocity data. As the ephemeris
data usually is outdated after 4 hours, the receiver will typically start with a warm start if it has
been powered down for more than 4 hours. In this scenario, several augmentations are possible.
See the section on Multi-GNSS Assistance.
• Hot start: In hot start mode, the receiver was powered down only for a short time (4 hours or
less), so that its ephemeris is still valid. Since the receiver does not need to download ephemeris
again, this is the fastest startup method.
In the UBX-CFG-RST message, one can force the receiver to reset and clear data, in order to see
the effects of maintaining/losing such data between restarts. For this, the UBX-CFG-RST message
offers the navBbrMask field, where hot, warm and cold starts can be initiated, and also other
combinations thereof.
Data stored in flash memory is not cleared by any of the options provided by UBX-CFG-RST.
So, for example, if valid AssistNow Offline data stored in the flash it is likely to have an impact
on a "cold start".
To Next Page
Loading...
Need help?
General
