Why does the rover's position jump when RTK fix is lost
If the rover loses RTK corrections and falls back from RTK Fixed to DGNSS or standalone GNSS, it is normal to see the reported position shift by about a meter or more.
This happens because RTK Fixed depends on continuous correction data to maintain centimeter-level accuracy. If corrections are interrupted, delayed, or become too old, the receiver must switch to a lower accuracy solution, which can cause a sudden jump in the reported position.
When RTK Fix is active, the position is aligned to ITRF2020. When the receiver falls back to DGNSS or standalone GNSS, the position is reported in WGS 84. However, the difference between ITRF2020 and the current WGS 84 realization is only about 1 to 2 cm worldwide, so it is not the cause of the meter-level jump. The main cause is the loss of the high-accuracy RTK solution, often due to an unstable or interrupted internet connection, preventing fresh corrections from arriving.
How to delay fallback to DGNSS on F9P, F9R, F9K, F20P & X20P
For F9, F20 & X20 receivers, the time before fallback to DGNSS can be adjusted using the CFG-NAVSPG-CONSTR_DGNSSTO setting.
This parameter defines how long the receiver waits after correction data stops arriving before dropping from RTK to DGNSS.
The supported range is 1 to 255 seconds. The default value is 60 seconds.
Increasing this timeout can delay fallback, but it does not preserve full RTK accuracy indefinitely.
What happens as correction data gets older, and when corrections return
As correction data gets older, the position solution gradually becomes less accurate because the receiver is relying on outdated corrections that no longer match current error conditions. In practice, position error may increase by a few centimeters per minute until fresh corrections are received again.
When corrections start arriving again, the receiver can usually recover accuracy within a few seconds, as long as RTK conditions are still good.