Jason Sherlock > Let's say I do have access to phase shift information. Am I only able to > derive speed (directionless magnitude) from these measurements or can I > actually calculate a velocity vector? You could compute a velocity vector. The Doppler/phase information gives you a set of velocity components along lines between the receiver and each satellite. Since these are never orthogonal, you need to solve a system of equations to find the overall velocity of the receiver relative to the whole system (the center of the Earth). -- Dave Tweed -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu