On Thursday, August 7, 2014 11:46:30 AM UTC-4, Ramy wrote:
Even with 8m accuracy, It is more than sufficient for accurate collision avoidance, unless someone considers half a wingspan not accurate enough for collision warning with another glider or obstacle.

Prompted to comment here by my Geek Fascination Syndrome (GFS)...

I'd guess that the error on each position fix is not significant. Flarm is computing trajectories from multiple position fixes, so a maximum +/- 8M error for each fix will be smoothed out by the statistical distribution of a large number of position fix errors. Some of the errors are + and some are -. Average 100 GPS position fixes and you will get a pretty accurate position.

I'd expect that the sampling rate is high enough to make the trajectory calculations quite accurate. If the sampling rate was not fast enough they could put a faster processor into the units. Plus as Ramy pointed out, FLARM must be alerting for 'possible near misses' because there will be small deviations in trajectory caused by turbulence and pilot control inputs.

The 8M 'error' of GPS is unlikely to be the critical factor that keeps FLARM from fulfilling its mission. I'd bet that the critical factor is the human pilot, that being the most inherently error prone and undependable part of the system.