ROV driven in a mixed trajectory around the receiver.
Each dot is one 0.1 s chirp (every 0.2 s). Its direction (azimuth, elevation) comes from matching the received signal against the single-hydrophone metastructure dictionary, and its distance from the loopback range R. The line is the smoothed track. The receiver (RX) sits at the origin; z is up. Doppler v is the radial velocity estimated jointly with direction (positive = approaching the receiver). The grey shadow is the track projected onto the floor plane to help judge depth.