The systems I am referring to does not come complete and are not very accurate. You can use a set of accelerometers that FIRST has provided in the past, I don't recall the make an model, maybe someone else can. They do not however account for drift as I mentioned before. Right now we are working on using two digital compasses that Davantech makes
http://www.acroname.com/robotics/par...7-COMPASS.html
and we can read the data coming from them, the next step is integrating it into the robot controller. It may not be as accurate, but we are not traveling long distances and we have visual feedback from the video cameras as well to make corrections. We will post our findings when we are done working on it. They cost 60 dollars each. The best thing is to use a Doppler Velocity Logger but that is 12 grand. Another compromise is
http://www.cloudcaptech.com/crista_imu.shtm
I think it is about $1500 - $2000 about he price of a IFI control unit
Maybe if FIRST buys lots of these the price might drop?