After a while using RaceChrono Pro + cheap 1 Hz AD-350 GPS with good overall results, we decided to upgrade to a 10 Hz device in order to improve the race line resolution. So, we bought 3 Qstarz 818XT 10 Hz for go-karting race analysis, which has become our nightmare. After a number of runs I realized 10 Hz is unusable due a very strange effect:http://i.cubeupload.com/3T2Pmi.jpghttp://i.cubeupload.com/KX0Qzj.jpg
Or this below:http://i.cubeupload.com/4UhQLw.jpg
I'm aware RaceChrono might experience problems running @ 10 Hz, but I couldn't find a reasonable explanation for the effect presented in the linked pictures above. Lap after lap, the race line was going displaced to northeast in a semi-regular pattern and the correspondence from real race line and the represented race line was being degraded. So, I decided to lower the frequency to 5 Hz and 1 Hz and got some driving around a block trying to keep the car on the middle of the road. But the results are also quite bad:
5 Hz> http://i.cubeupload.com/HLqkLV.jpg
5 Hz> http://i.cubeupload.com/5pLo1p.jpg
1 Hz> http://i.cubeupload.com/h9toUN.jpg
I also noticed there's a zoned effect on overall error:
Zonal Error> http://i.cubeupload.com/XkmX3f.jpg
When travelling through a rough E-W direction the error significantly increases in comparison to N-S directions which make no sense to me if you ask me. The expected difference from real life and registered lines was 1 meter (the informed Qstarz error during the run) but it delivers differences about 10 meters mostly running on the yellow zones of the last linked picture. So, under 1 or 5 Hz there is no more progressive displacing effect of the race line, but the accuracy is still poor, even more if you bare in mind the cheap 1 Hz device has been presenting better results.
When testing under 1 or 5 Hz I made sure Differential GPS was enabled in all tries. 10 Hz forces DGPS off by default. Also tried to play around with NMEA settings, trying to force all information in several rates, but it has no impact on the GPS performance. I tested all 3 devices as well to make sure isn't a fault unity but the results were the same.
Tips and advice are welcome. I ran out of ideas here.