# GNSS signal tracking options

To use observations from a GNSS constellation in a real-time or postprocessed survey, you must enable tracking for each signal type you want to use in both the Rover options and the Base options screens. In a real-time survey the tracked signals are sent in the RTK data stream. In a postprocessed survey the tracked signals are saved in the logged data.

- GNSS signals tracked by the rover receiver must also be tracked by the base receiver.
- If you enable tracking of satellite signals that are not being tracked by the base or contained in the RTK messages coming from the base, then those signals will not be used in RTK at the rover.
- To save receiver battery power, enable only those signals available in the base data you are going to use.
- GNSS surveys with firmware earlier than version 6.00 must contain either GPS or BeiDou observations, and signal tracking for both GNSS constellations is enabled in new survey styles. If you disable one, then tracking the other constellation is automatically enabled.
- The GNSS signal tracking options are not shown with the Trimble DA2 receiver

GPS

To disable the use of GPS, clear the GPS check box. If GPS signal tracking is disabled, BeiDou signal tracking is automatically enabled because surveys must contain either GPS or BeiDou data.

If you disable GPS at the rover for RTK you can use either the CMRx or RTCM v3.2 MSM broadcast format. Disabling GPS at the base can only be done for the RTCM v3.2 MSM broadcast format. For CMRx transmission from the base, GPS must remain enabled even though GPS can be disabled at the rovers that are using that CMRx base.

For real‑time surveys where the base data contains L2C observations, select the GPS L2C check box. The Use L2e setting is read‑only.

The L5 check box is available only when the Broadcast format is set to CMRx, RTCM RTK 3.2 (MSM), RTX (SV), or RTX (internet).

GLONASS

The GLONASS check box is always available.

In a real-time survey, you can enable GLONASS satellite tracking at the rover even if the base receiver is not tracking GLONASS. However, the satellites will not be used in the RTK processing.

Galileo

If you enable Galileo tracking, the satellites will be used in the solution when they are healthy.

QZSS

To fall back to QZSS SBAS positioning if your RTK radio link goes down, select SBAS in the Satellite differential field, and select the QZSS option. In this case, the QZSS option is only available if the Broadcast format is set to CMRx.

BeiDou

When BeiDou signal tracking is enabled in an SBAS differential survey, the BeiDou SVs are used to augment the solution if their corrections are available.

NavIC

In a real‑time kinematic survey where the base and rover receivers can track and use IRNSS/NavIC signals for RTK, select the NavIC check box.

In a FastStatic survey where the base and rover receivers and track and log IRNSS/NavIC signals, select the NavIC check box.

NavIC data logging is available only during a FastStatic survey when logging to the receiver. As NavIC satellites are tracked on L5 only they are not included in the point timers which rely on dual-frequency data.

xFill

Select the xFill check box in the Rover options screen to continue surveying during base data outages for up to 5 minutes. To use this option, your GNSS receiver must support xFill. xFill is not available if you have selected OmniSTAR as the fallback option in the Satellite differential field. See Bridging data outages using xFill.