why wen i use Ka72 my dopler readings are lower than wen i use GPSarpro ?
should this not be the same in any program u use ?

they all vary abit i use gpsresults v6 and that gives a slightly different reading compared to ka72 as well, Tom's fourier prgram gives the same result as gpsresults though.

lelos,
Have you got "Trapeze" ticked???
I bet you haven't.
Trapeze checks 3 data points as does ka72.
If "Trapeze" is unticked, GPSarpro only uses 2 data points, this is not a 2sec average! (even though it says it is)
As the doppler measurement is almost instantaneous, 2 data points is really only 1sec average, that will obviously give you a higher number.

The guys who really value accuracy are over at www.gps-speedsurfing.com/default.aspx -- they haven't ratified KA72 yet (to the best of my knowledge).

However KA72 gives very similar results to Realspeed, which is ratified. Dylan has worked very hard to get the algorithms working right, and I'm confident that the results that KA72 gives are correct.

The difference between the programs is normally a lot less than 5%, so I wouldn't worry about it too much.

The important thing is to always use the same program for your calculations. If that's one that always gives you higher numbers, then that's fine. I like to draw the analogy of using a set of bathroom scales -- do you choose a set that always reads low, or always reads correctly?

Nebs, I get the same results as realspeed & ka72, from GPSRpro, providing I have "Trapeze" ticked.

Select to expand quote

decrepit said...

Nebs, I get the same results as realspeed & ka72, from GPSRpro, providing I have "Trapeze" ticked.

Sorry Decrep, we posted at the same time, and I hadn't read your message.

I probably should change that sentence to:
The important thing is to always use the same method for your calculations.

THANKS GUYS I'LL GIVE THAT A GO
TRAPEZE WILL BE THE ANSWER I'M SURE.
THANKS AGAIN