GPS Speed Measurement Using Doppler Shift

"Any guidance as to how one can go about this?"

."Any idead how i should go about it ?"

Go about what? What's the question?

sorry ...should not have left the question open ended....the question is how is one supposed to go about measuring the speed using doppler shift of the carrier wave..

The carrier wave is electromagnetic radiation...which will go at the speed of light.
Ok it will slow down in some media.
Light doesn't go so fast in water or brick for that matter.
Hmmm, still not sure what you are after...
Or am I missing something? Help me out some one quick.
Del

Sounds a bit unlikely to me unless speeds are high.
Position and time are probably more accurate.
You don't say what you want to measure the speed of...a man shambling along to buy his newspaper isn't going to give much doppler shift.

So my guidance would be 'don't do it that way'
Del
(I reserve the right to be completely wrong...)

You are not going to get much better info from this forum than you can get from a good google search result like this...

http://nujournal.net/HighAccuracySpeed.pdf

Good luck with your project.

As I said to you via PM and on your previous thread....

You don't have to worry about the mixing requirement of the transmitted wave and the received wave to get the doppler frequency...

This is all done for you in the microwave module... there is a transmitter section at 10.7 GHz and next to it is a receiving section with a gunn diode demodulator, built in and tuned to the same frequency.

Because the transmitted frequency leaks into the receiving section you automatically have a mixed signal picked up by the gunn diode....

This IS the doppler frequency....

John.

As I understand GPS, the satellite(s) are moving at high (orbital) velocity. How do you distinguish your speed (using doppler effect) without knowing your relationship to the transmitted GPS signal? Sounds a bit to difficult to get reasonable accuracy. Try using delta between (2) samples of the same signal and calculate speed that way.

MRH

GPS Velocity calculation.

This can be done fairly easily if you have access to some of the underlying GPS data. The calculation involves knowing the satellites measured doppler shift. Your position, the position of all satellites in view, the satellite position and doppler can be calculated using the ephemeris data and the current gps time. Your position and velocity can then be derived from a couple of least squares fits to two matrix equations, one for position and one for velocity. The position one has to be repeated to find the minimum error but once that is done the velocity eqn only needs to be solved once. I used the eqns in the article mentioned earlier and get accuracies of 0.05m/s or better. This also gives you the reciever clock drift as an extra bonus.The position eqns are well described in plenty of articles.

Mark