This instructable describes how to make an ultrasonic radar-style display using an Arduino microcontroller, an ultrasonic sensor, and a small stepping motor.
An optional sensor modification allows multiple objects to be detected with each ping.
Construction is simple … all you need are two drills, a sharp knife, a pair of side-cutters , and a soldering iron.
Photo 1 shows the basic parts. The insert shows a random-dot test pattern. Dots representing primary objects are shown in red … dots representing secondary objects are shown in blue.
Photo 2 shows the assembled unit.
Photo 3 shows an actual screen shot of seven objects.

The azimuth and distance of each primary object are shown in red. Any echo from a secondary object is shown in blue. Without the sensor modification you will only see the red objects.
Since the sonic pulses expand in a cone-like manner, distant objects appear wider. The actual bearing of each object is the midpoint of each continuous (red or red/blue) line.
Continuous lines containing both red and blue dots are a single object, part of which is in shadow.”