While a well-known use of this is sonar, ultrasonic sensors can also be ... A motor rotates it around a 180-degree field-of-view and an Arduino takes and records measurements during its trip.

Sonar is a great sensor to add to any small-scale robot project. And for a couple bucks, the ubiquitous HC-SR04 modules make it easy to do. If you’ve ever used these simple sonar units, ...