GPS Accuracy

Posted in How does it work?

Velocity

The use of GPS in automotive testing is now well established, and Racelogic has been a market leader and innovator for over a decade. GPS systems have revolutionised the accuracy and convenience of testing, development, and validation within the industry. Why and how is it so effective?

There is a common misconception that speed measured via GPS is done so as a function of position against time. If this were the case, GPS velocity would be just about unusable, because GPS position relies on precise measurements of the distance from the receiver to the satellite, and therefore suffers from numerous effects - such as atmospheric interference - which delays the signal.

Fortunately, velocity isn't measured like this: instead, the Doppler shift in the signals coming from the satellites is captured and this leads to an incredibly accurate measurement of speed.

If you are tracking seven satellites, then this is like having seven police radar guns aimed at you: the measurement is made by taking them all into account.

Doppler-Effect

Other crucial factors involved in producing useful velocity measurements for vehicle testing are sample rate, frequency response, latency and noise. See 'GPS Factors' for further explanation.

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