I have been told that, your standard, run of the mill, high street Sat Nav speed indicator reads 10% lower than your actual/realtime speed. Is this true? Or is it 100% correct to the acutal car speed?

On my Navman, it reads approx 10% lower in my 300, my "dirt bag" Citreon, and the wife's Golf.

 

Al.

Hey Alan, there is no to-ing and fro-ing between your satnav unit and the satellite.

 

Basically all of the satellites emit a signal that the sat-nav units pick up. They then use the different signals to calculate their position, and by analyzing the rate of change in position, can calculate your speed (and direction).

 

So as someone said before, there is no delay other than the processing of the various signals and displaying on the screen. Hard acceleration or deceleration will be slightly less accurate but at a steady speed it should be spot on.

 

Hope that helps.

 

Cheers

Rich

Hey Alan, there is no to-ing and fro-ing between your satnav unit and the satellite.

 

Basically all of the satellites emit a signal that the sat-nav units pick up. They then use the different signals to calculate their position, and by analyzing the rate of change in position, can calculate your speed (and direction).

 

So as someone said before, there is no delay other than the processing of the various signals and displaying on the screen. Hard acceleration or deceleration will be slightly less accurate but at a steady speed it should be spot on.

 

Hope that helps.

 

Cheers

Rich

Spot on. The velocity is calculated using the Doppler shift, so there is no signal sending back and forth to calculate speed.

 

Sorry matey, 0.1 MPH accuracy for GPS speed indicators!?!?

 

If you have a link that backs this up then i will eat humble pie!!

 

Al.

 

Oh BTW.............

 

THIS MY 1000th POST WWHHOOOO!!!!!

Velocity accuracy is listed on the specs of most GPS Units.

Edited July 29, 200916 yr by Yowser

Anyone got any humble pie....... :x: :o

 

Al