Most road map oriented GPS units are not that bad for speed accuracy.
FWIW my GPS datalogger is pretty accurate speed wise:
"With average GPS reception, speed accuracy is about 0.1mph (or 0.1% if greater) when you are just driving along at fairly constant speed, and about 0.2mph (or 0.1% if greater) during fast accelerations or braking. The only exception is at very low speeds (under 10mph) where the error increases to about 1mph. Do not be fooled by exaggerated claims from other manufacturers… this is as good as it gets!"
The unit takes a GPS reading 5 times a second and reconciles that with accelerometer data logged 100 times per second. And yes out speedo reads high!!
Last edited by Stan; 01-03-2005 at 12:02 PM.