Three-Dimensional Mapping of Water Surface Waves Using Air-Coupled Sonar

More than 70 percent of the Earth's surface is covered by the ocean and other bodies of water, making them abundant sources of valuable information. In particular, the water surface can be sensed and mapped to extract key parameters related to water dynamics. These parameters have far-reaching implications spanning industrial, environmental, energy, navigation, and various other applications. Existing approaches for measuring the water surface each have their own respective limitations, thus leaving high-resolution spatial and temporal water surface wave mapping an open challenge in the research community. This work proposes a non-contact, acoustic surface mapping system that uses air-coupled ultrasonic transducers to capture three-dimensional spatial maps of the water surface via active sonar imaging. Within, we provide a holistic overview of the system's design parameters before narrowing in on details related to the hardware, ultrasonic transmit waveforms, and signal processing pipeline. Through verification in simulation, the proposed air-coupled sonar system demonstrates high-fidelity surface mapping with millimeter-scale accuracy and spatial resolution from standoffs up to several meters above the water.