I was researching using vex inertial sensors to find a robot’s relative location (practically impossible??) and came across optical flow sensors. I’m surprised vex doesn’t include them already. Think of an optical mouse, which can know its precise location relative to its starting position. Same thing but on a robot. Off the shelf ones are not super expensive either: https://www.mouser.com/ProductDetail/Seeed-Studio/101990480?qs=T3oQrply3y9jS8GRt4DFwA%3D%3D&mgh=1
No contact, no GPS, accurate odometry would be possible with this device. They do not need to be within mm of the surface to function, like a mouse might. They are often used on drones.
And while I’m at it, they have got to provide high strength lock bars, shouldn’t have to buy from third parties just for a basic part.