Spatial Enhancement of UAS Imagery for Surface Current Observation Using a Dual-Camera System

Abstract Measurement of surface currents is critical for analyzing coastal hydrodynamics, sediment transport, and ecosystem dynamics. In this study, we introduce an advanced unmanned aerial system (UAS) imagery technique for surface current measurements that employs a dual-camera system and oblique view angles to expand the spatial coverage of ocean surface observations, enabling the detection of larger-scale circulation phenomena. The resulting videos are rectified using a direct, matrix-based method that relies solely on intrinsic and extrinsic calibration parameters. To validate the technique, a series of field surveys were conducted near Texas City and Freeport, Texas, comparing rectified oblique imagery with nadir imagery over both solid structures and open-water surfaces. We also compared computed near-surface velocity vectors inferred from short-wave Doppler-shift signatures with in situ measurements from an upward-looking acoustic Doppler current profiler. An application at the Freeport north jetty demonstrates the capability of the dual-camera system to generate seamless, large-area current vector maps while avoiding temporal mismatches inherent in sequential waypoint-based surveys. Overall, the methodology provides a reliable and flexible framework for enhancing UAS-based coastal observations.