QUOTE(onesky @ Mar 22 2012, 05:38 PM)
GPS device speed is not accurate because it is based on gps coordinate which has a tolerance of +/- 5m~10m depends on the device you used.
I believe insight speedometer calculate directly just like other car which is definitely accurate.
QUOTE(onesky @ Mar 23 2012, 11:58 AM)
I heard this saying some time back, but is there a solid proof for that?
Gps is totally out as it is not precise. Speedcam I'm not sure, coincident there was no Speedcam that time when you are speeding?
This is totally wrong. GPS speed is the most accurate because they use real time readings to calculate your speed.
The tolerance you are talking about is the absolute positional accuracy. That means that you are standing at one spot and the gps might show an inaccurate reading of 5m-15m from your real location. That depends on the gps signal strength during that time.
Speed is calculated by updating 2 or more points in real time. When you go from one spot to another spot. say first spot is 0m then next spot is 10m, gps will calculate the difference in distance with time to get your speed. So its more accurate than a speedometer thats for sure.