Some ways to measure distance during autonomous

[Alan Anderson]

Going by time alone is known as "dead reckoning" and is the choice of last resort. Many uncertainties will keep you from being very precise or repeatable.

Using a "follower wheel" is a good idea. As long as you can keep it in contact with the ground and avoid problems with sideways travel, it'll tell you exactly how far you've gone without regard for slipping drive wheels.

The other two typical options are encoders or gear tooth sensors in the drivetrain, and optical sensing of reflective stripes on the wheel hubs. Both are relatively easy and effective. Kevin Watson makes available code for using encoders; just drop it in and it works.