Looking at your tracks overlaid on Google satellite view, it seems like the signal tend to "snap" to the nearby roads.
I've never used a Garmin GPS but I've read somewhere that some devices have a "lock on road" feature. I imagine that such feature would make the tracks consistent with some stored navigation data (that's only my assumption). Is it possible that such a feature exists and was enabled on your device? Cheers, Gilles Jim Ley wrote: > There's no loss of signal though during the warm-up laps where it also > happened, the accuracy on the garmin was reported as being good seeing > lots of satelites weel, and this is a completely open course, no > trees, no nothing, it's mounted on the bike with a clear view of the > sky. And the logs going to and from the event, and every other log - > including a cycle race in a different location were fine. > > I also think that the signal returned at the same points in every lap, > and lost at the same points in every lap make that unlikely. > > Cheers, > > Jim. > > 2009/4/30 Eric Fischer <[email protected]>: >> When my Garmin (eTrex Legend HCx) loses signal, it continues logging as if I >> had continued in a straight line for 30 seconds before either regaining >> signal or giving up and stopping logging, and I imagine you are seeing >> something similar. >> >> I see this all the time when going into tunnels and worked around it by >> postprocessing the logs to drop any run of entries with identical or >> near-identical latitude and longitude deltas (to within 0.000002 degrees) >> leading up either to the end of a log or to a sudden change in speed >> (increasing or decreasing by 10mph in a single second). >> >> Eric >> >> >> On Wed, Apr 29, 2009 at 4:39 PM, Jim Ley <[email protected]> wrote: >>> Hi, >>> >>> Last week, and tuesday I did a cycle circuit race, previously (couple >>> of months ago the tracklog has been >>> pretty flawless, but both the last two times it was interestingly and >>> consistently >>> wrong on every lap, the same errors also happened on my girlfriends >>> Garmin. The logs were both recorded on a Garmin 705, you can get a >>> gzipped version of the tcx file here >>> http://jibbering.com/2009/04/screwy.tcx.gz (or screwy.gpx.gz for a gpx >>> version of it) >>> I also uploaded it to http://connect.garmin.com/activity/3973718 From >>> which you can see that the >>> Garmin recorded the distance log right (as the speed graphs are pretty >>> much correct) but the GPS positions were all way off. >>> >>> What happened was essentially that in a number of areas on every lap, >>> the log went crazy, and instead of following where I went, it went in >>> a weird straight line off course. In the map view of it >>> http://jibbering.com/2009/04/screwy.jpg or on the >>> satellite view on the garmin page you can see the circuit clearly, and >>> previously the logs have been accurately following it, but in both the >>> last two weeks races >>> it was just in a couple of parts of the course where it was on course, >>> the other times being peculiarly off course, with weird straight lines >>> - not just the ones where it suddenly jumped. >>> >>> Anyone have any insight into why this might've happened? Particularly >>> to two seperate devices. >>> >>> Also if anyone can think of a relatively simple way to "fix" the log - >>> to a reasonable approximation I would be happy. >>> >>> Cheers, > > _______________________________________________ > Geowanking mailing list > [email protected] > http://geowanking.org/mailman/listinfo/geowanking_geowanking.org _______________________________________________ Geowanking mailing list [email protected] http://geowanking.org/mailman/listinfo/geowanking_geowanking.org
