Now we can conclude beyond reasonable doubt "10 seconds" is an inferior measurement for speed claims. 
The unlearned speed peasant me dares to mention 500 meters is the perfect speed filter! 
Now we can conclude beyond reasonable doubt "10 seconds" is an inferior measurement for speed claims. The unlearned speed peasant me dares to mention 500 meters is the perfect speed filter!
/
One of the rationales for the existence of the KA72 website is that it allows you guys to do exactly this kind of analysis. No automatic system is capable of replicating the kind of indepth analysis you've done on a track with such a marginal result in it. We try our best, but at the end of the day there is no substitute for eyeballing the data.
I hope it was useful for the exercise.
Reached 160,000 uploaded kilometres today.
Cheers,
Dylan.
The site is fantastic Dylan, but individual tracks are hard to find, there's just so many there now.
A search function of some sort would help
I tell you, the peer review system works well for GPS tracks
Thanks for all the help that was available from the web community analysing that one, it was a doozy!!! Think I might get myself one of those fancy GT31's soon 
I shudder to think what the community would have thought of a trackpoint-only file 
And it wouldn't be possible without Dylan's wonderful KA72 program 
Top job mate 
I shudder to think what the community would have thought of a trackpoint-only file
The GPS has filters that "smooth" the data before it is recorded. You can see this when you have a crash- it still takes a couple of seconds for the speed to reduce to zero on the gps log, even though you actually stopped in a splitsecond. When analysing transient GPS data you have to consider that these filters are smoothing the data before its recorded. Sudden changes and spikes are spread out in time.
So, to get that result after the filter, the real accelleration/decelleration and max speed would have to have been higher, but over a shorter period.
The decelleration on the tracklog is similar to braking from 100km/hr to a stop in ~6.2 seconds. If we consider the filter, then the actual accelleration/decelleration would have been even more aggressive than that.
I cant say it didnt happen but given that the decelleration appears similar to a crash that must have been one hell of an awesome recovery. Also to accellerate at that rate for so many seconds is quite extraordinary given that such accelleration is usually afforded by body inertia for a fraction of a second before you are yanked off your feet.
From time to time the sirf-based GPSs give an "out-there" reading. I have seen this plenty of times. Every now and then that "out there" data is going to land somewhere in the grey area. Using two GPSs helps to highlight where one of the GPSs might have lost its brain temporarily, so you can treat that data as suspect (from both units). Not perfect but a lot better than running a single GPS, for confidence in the validity of data.
When using one GPS, we have to trust ourselves to be objective. If it seems highly unlikely it probably is.
After reading all the facts & informative and expert responses (here and elsewhere), I think I'll stop sitting on the fence. Time to call this particular myth track busted I suppose.
