[Ovmsdev] GPS flatbed alerts from military jamming/spoofing?

[Craig Leres]

On 3/30/22 23:15, Michael Balzer wrote:
> I've had no GPS false alerts since Craig added the NMEA checksum 
> validation and I fixed the VW e-Up state detection.
> 
> That is, until war on Ukraine began. Since then, I've had multiple 
> alerts, mostly late night. I wouldn't have thought military GPS jamming 
> or spoofing would have an effect with that range, the next war region is 
> ~ 1.200 km from here.
> 
> I've added some more logging to see if we can detect and filter this.
> 
> Reduced log from the latest event below. HDOP jumps from 1.8 (good) to 
> 5.6 (bad), but only after the alert has been triggered.
> 
> Should we generally scale the alarm threshold by HDOP (if available)?

If we did scaling based on HDOP I think we could also lower alarm 
distance from 500m (250m was my first guess). Here's a quick spreadsheet:

 
https://docs.google.com/spreadsheets/d/1C9mvMw3PSl58qmg-lRHdzMXzB2S4glE4vitdgb4TiJ0/edit?usp=sharing

It's unfortunate that HDOP lags the increase in distance, maybe you 
could adjust the smoothed calculation to damp that?

		Craig