measuring distance

josh_oz

I am trying to measure the distance between two devices. I want to do this because I need to know three distances to determine the position of a moving robot. I thought about using GPS but it is too inaccurate for my application. Instead I want to perform 2-d trilateration. What kind of device could I use that could allow a robot with an onboard javelin stamp know the distance from three points? (it should allow the measurement of distance of upto 30 meters if possible).