can anybody explain this,
doppler speeds are normally lower than trackpoint speeds, but doppler distance is greater than trackpoint distance.
So in the same time period doppler has you going further at a lower speed, this seems to invoke the use of something exotic like short cuts thru extra dimensions.

I can see that trackpoints underestimates total distance as it's a series of straight lines between the points, and doesn't follow the greater distance of the curve you actually travel, (look at a close up of some alpha tracks).
Think I've worked it out to some extent, the main difference in speeds is the short time max, due to inaccuracies in trackpoints giving a variation in speed, these variations cancel out at longer times, so it's possible that longer time trackpoint speeds are actually less than doppler.

My feeling is that if you use doppler for your speed posts, you can also use doppler for your distance, but if you're using trackpoint derived speeds, you should also use trackpoint distance.

Any thoughts to any of this ramble?

grumplestiltskin said...


surely if the distances are longer but the time is the same then its logical that the speed is slower

Umm, no if you want to go further in the same time, you have to go faster!

So does old age mate!!!!!

Elmo, liked your slant on latest session GPS Challenge. Whats the bit about waves and no speed stuff? no speed mast or something?