GPS speedometer replacement (update)
After a lot of crawling around and investigation I have had it with trying to get my VDO speedometer working right. I am going to go to a Speedhut Legacy 0-100 mph gps speedometer. A simple install a...
Forum Discussion
mrkoje wrote:
There shouldn't be any delay since the GPS device only receives information from the GPS satellites and it does so at the speed of light!
No, a GPS uses a radio signals from GPS satellites which does not travel at the speed of light. Sorry, I do not know the frequency. A timestamp is in the signal. With 3 GPS satellites you can caculate your position and since the GPS knows where the sattelites are supposed to be, it can calculate the delays. The differences of the timestamps gives your position.
The difference between a speedometer and GPS is that the GPS calculates speed by calculating the time it took to travel between 2 points. So it is an average since the last reading. This depends on how often the GPS calculates your position. A speedometer calculates speed by counting rotations of something on the vehicle, like transmission shaft or axle.
Also, epecially on older GPS's you can get speed inaccuracies if the altitude is incorrect when traveling up and down hills because the distance calculation will no be correct.
David
