As a bit of a techy I thought I would whip up a simple program to display max speed, distance etc.
I have the specification of the NMEA sentences that are logged but am intrigued to see that my results differ from Realspeed.
I'm using the maximum speed written to the file (RMC and VTG) and not calculating it.
How are the distances calculated ?
Are there any standards for this sort of software with regards to accuracy ??
Any thoughts ?
Distances is usually calculated from the trackpoints Lat. / Long. It is accumulated and takes into account the non spherical nature of the Earth.
In RealSpeed, I believe Mal has included an algorithm to calculate distances from the doppler speeds and the time. (Meters per second).
It is accurate if it agrees very closely with RealSpeed and GPS-Results. 
Hmm this is getting interesting.
What about altitude ? if you're going up and down in ocean swell !
Which is more accurate, GPS calculated speeds (Using altitude and Co-ords) or Realspeed ?
I'm starting to understand why guys like Finian don't value the speeds recorded with GPS's.
