Listened to sailquick and bought myself a GT31.
Thought I'd try out GPSResults off the CD.
Big surprise, my 2sec results are bigger than realspeed or GPSARPro! (34.717 against 34.664)
As I suspected looks like gpsresults, unlike realspeed, (by default) and gpsarpro, (selectable) is only averaging 2 readings not 3, can't see anyway to change this either.

Going back to the old subject of apples and oranges, any thoughts anybody????
Or am I missing something?

Trapezoidal integration, averaging three values, it all sounds a bit too complicated for this tired little brain...

Never quite understood why you can't just take the average of two values and call that your 2 sec peak. But I'm sure Mal and others have thought long and hard about it all

Think it's because the doppler reading is virtually instantaneous.
So 2 readings only spans 1sec, you need 3 readings to span 2 seconds.

In GPS-Results, go to EXTRAS menu, then FILTERS and you will see a drop down menu that allows you to select Rectangular, Trapeziodal or Cubic Spline (the last required for 10 sec. records on GPS-SS). Don't know why Quadratic Spline is included? The maths is beyond me.

In my version of RealSpeed (v1.929b - which may differ from yours as it was a special compilation Mal did for me for some testing we were doing) go to TOOLS - OPTIONS and there is a box to select Trapezoidal or Rectangular. In versions without this option, I am pretty sure it is set to Trapezoidal by default.

Opps! Just testing this to see if I get identical results with the same settings and I think I found a bug in GPS-Results. When I set to Trapezoidal it gave me 45 knots for 2 sec. But it also says I only did 36 knots for 1 sec!

I will inform Manfred.......

They may have put an old version on the CD, it's V5.37, 25/2/2008.
Doesn't have any filters anywhere that I can see.

Select to expand quote

decrepit said...

They may have put an old version on the CD, it's V5.37, 25/2/2008.
Doesn't have any filters anywhere that I can see.

OK. Download the latest: v6.70 for Windows. here: www.gps-speed.com/

I have not tried the Mac version v5.27 or a while and all the household Macs are away at the moment. Will try it soon to see if it has the filters.

Just tried some older versions of GPS-Results. No bug in v6.02 and trapeziodal gives identical results as the same setting in RealSpeed.
I also checked GPSAR-Pro v4.16 and it gives exactly the same results (to one decimal place less).

Also tried GPS-Results v5.49 and it has no optional filter settings and appears to use Rectangular as standard so I would assume V5.37 does as well.

Thanks Andrew, that sorts that.

great results on your gps system