Hi everyone,
I have a question regarding GPS receivers that derive their speed measurements from position i.e. not receivers that uses Doppler effect on the carrier frequency.
My problem is.. I have to determine the accuracy of the GPS measured speed. My theory is that I can use the Positional Dilution of Precision to determine the speed accuracy (roughly). I mean, if the positional measurements is of poor accuracy the derived speed most likely will be of poor accuracy as well, true? (It probably depends on the GPS firmware as well, I don't know anything about the receiver more than I mention here)
The speeds I'm talking about could be from 20 km/h up to 200 km/h at ground level. GPS sampling frequency is at 1 Hz. Surrounding terrain could be of any type (buildings, walls, fields, forests).
I can't do anything about the GPS receiver, I have to live with it.
What do you think? I have Googled some without success. A paper or an article would be perfect to reference to.
Best regards, Robin
Replies
I don't yet have experience with this in a UAV environment, but have been working on a ground-vehicle GPS project. You'll likely find the relationship between speed and DOP varies significantly between different modules based on number of satellites tracked, sensitivity, and smoothing algorithms. At low speeds in open country, the absolute positional error will be fairly slow-changing once the visible satellites are locked, so speed and heading will be more accurate than position, except for the occasional jump as satellite selection changes. At higher speeds and with less reliable signal, your error will flop around more, though if you're doing 190km/h does it really matter whether it's 180 or 200 (apart from bragging rights)? I'm guessing 200km/h would be more likely in open terrain where signal is better.