[FOSS-GPS] Shocks/vibrations on antenna and cycle slips

[Simon Treny]

Hello all,

I'm using RTKLib to perform RTK positioning using UBlox M8T evaluation-kits (EVK). I have great results when the GPS antenna is attached on the rooftop of a car driving on a track (accuracy <10cm).
But as soon as a I attach the EVK and the antenna on a quad bike and drive on a bumpy road, the accuracy becomes really bad (the distance between 2 antennas can be off by >3 meters).
In both cases, I have a clear view of the sky and no tree or building around.

By looking at the recordings with RTKPlot, I've noticed that I get much more losses of lock when the antenna is on the quad-bike/bumpy-road rather than on the car/track. My guess is that the shocks caused by driving on the bumpy-road causes these losses of lock. I've measured with the accelerometer of my phone the acceleration on both the car and the quad-bike: on the car, the vertical acceleration never goes beyond 3g, while the vertical acceleration on the quad-bike can go up to 8g.

I've reproduced this observation by attaching the antenna on a pole, and shaking the pole vertically. As soon as I shake it, many losses of lock occur.
If I do the same by attaching the EVK on the pole and letting the antenna static on the ground, there is no loss of lock (excluding the possibility that it comes from the oscillator).

Is this a known issue with low-cost receivers/antennas? Is there a way to improve the situation? Are there other low-cost receivers that support shocks or vibrations better than the UBlox M8T?

Cheers,
Simon