Existence

Existence sensors are binary. Each can tell whether a wall exists or not. You have to use many existence sensors for error correction purposes because you need a sensor to track each potential location that the wall may appear. On the other hand, existence sensors are cheap and easy to interface with. They are also very easy to interpret in software.

Typically, existence sensors can only detect walls that are immediately around the robot. You can use the entire allow dimension of a micromouse to maximize the mapping capability.