On non-lidar equipped rovers, how is the width of an obstacle detected such that it can be avoided? If the ultrasonic sensors are used for obstacle detection, these sensors usually don't give data about the width. How is the width derived?
You may use a rotating mechanism such as a servo with the ultrasonic sensor mounted on. The ultrasonic measurements can be fused with the servo arm angle to calculate the width. Usually ultrasonic sensors have a higher field of view. This degrades the accuracy if you assume the ultrasonic wave is focused to a point. If you need more accurate measurements, you may use a mathematical sensor model to fuse the measurements.
ToF sensors have a low field of view compared to ultrasonic sensors