This ultrasonic radar project is from [mircemk] who uses a small ultrasonic distance sensor attached to a rotating platform.

They rebuild one of the most iconic components for an electronics tinkering beginner — an ultrasonic distance sensor, and what’s fun is, it stays fully functional after the rebuild!

A low-cost (~$100), do-it-yourself (DIY) ultrasonic water level sensor/datalogger has been designed, constructed, and tested for use in education, citizen/community science, and research settings. The ...

Now, researchers have channeled that idea to create an ultrasonic sensor array that gives its wearer increased situational awareness, or SpiderSense.