Real velocity Measurement Sensor

[Gdeaver]

A camera and 2d optic flow algorithms will give you x and y. A optic mouse is an example of a sensor that uses optic flow to give this. The problem with mice sensors are the optics and the maximum velocity they can work at. Recently, some drone hobbyist have taken a good camera and interfaced it to a Cortex M4 Arm microcontroller. They also added a ST Micro gyro. There is not allot of feed back as to ground based applications and I believe it is best at greater than 12" off the floor. Different optics and some Lighting experimentation may yield a very good solution. Our team has been looking at auton navigation this summer. OpenCV has optic flow algorithms that could be used if these solutions are not fast and accurate enough. Goggle optic flow and check Wikipedia. A gyro and an accelerometer like the Invensense MPU-6050 will give a very good tilt compensated Yaw.
The other possibility is to use astral navigation. Every event has lights in the ceiling that are fixed like stars. Point a camera up at the ceiling. Using some filters a pixel matrix of dark and light (0 and 1) can be produced. Then run 2 d optic flow on that matrix. The lights are far enough away that some triangulation can also be done. Every event has different lights and it would have to be calibrated at each event. This stuff is hard else every one would be doing it.