Abstract:
This study developed a novel approach to unmanned aerial system (UAS) current mapping based on optical video data of the sea surface. Three-dimensional fast Fourier transform and least-squares fitting were used to measure surface waves’ phase velocities and thereby derive currents via the linear dispersion relationship. The UAS used was a low-cost consumer-grade quadcopter whose camera position and attitude measurements may cause spurious currents as large as the signal. A novel wave-based UAS heading and position correction technique was developed, improving the image rectification accuracy by a factor of ~3.5 and the current measurements’ temporal repeatability by a factor of 1.8 to 4.8. This technique was validated using the data included herein. The UAS mapped the currents across the ~700 m wide tidally dominated Bear Cut channel in Miami, Florida over several days in February 2018. The UAS currents were validated by flotsam tracks, obtained through automated UAS video object detection and tracking, drifter tracks, and Acoustic Doppler Current Profiler (ADCP) measurements. All of these data sources are included here in this dataset, and the video files used are also available in GRIIDC under Unique Dataset Identifier (UDI) R6.x806.000:0012 (DOI: 10.7266/n7-11te-m018). This dataset supports the publication: Lund, B., Carrasco, R., Dai, H., Graber, H. C., Guigand, C. M., Haus, B. K., Horstmann, J., Lodise, J. A., Novelli G, Özgökmen T., Rebozo M. A., Ryab E. H. and Streßer, M. (2021). UAS current mapping: A wave-based heading and position correction. Journal of Atmospheric and Oceanic Technology. doi:10.1175/jtech-d-20-0123.1.
Suggested Citation:
Lund, Bjoern. 2021. Unmanned aerial system (UAS) current mapping in Bear Cut, Florida from 2018-02-19 to 2018-02-23. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/XYFYQHAX
Data Parameters and Units:
The dataset contains flight log data, drifter measurements, Acoustic Doppler Current Profiler (ADCP) measurements, current vectors derived from flotsam tracks within the video data using optical flow techniques, and current maps derived from wave signatures within the video data in NetCDF format.
The main parameters included are: u [increasing to east (m/s)]; v [increasing to north (m/s)]; depth [increasing to surface (m)]; yday [days since 2018-01-01 00:00:00 EDT)]; x [cross-channel (m)]; y [along-channel (m)]; ux [cross-channel current (m/s)]; uy [along-channel current (m/s)]; time [flight time (seconds)]; longitude [decimal degrees]; latitude [decimal degrees]; spd [velocity (m/s)]; direction [degrees (clockwise from north)]; x_cam [pix]; y_cam[pix]; start_time [seconds]; mean_k [rad/m]; lower_lim_k [rad/m]; upper_lim_k [rad/m]; altitude [m]; roll [degrees (positive change rightward)]; pitch [degrees (positive change backward)]; yaw [degrees (clockwise from top)].
Methods:
The Bear Cut unmanned aerial system (UAS) experiment was conducted by the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) in collaboration with the Center for Southeastern Tropical Advanced Remote Sensing (CSTARS) and Helmholtz Zentrum Geesthacht (HZG) from 19 to 23 February of 2018. For detailed methods on the experiment, please refer to the "data overview" and "methodology" sections in the associated publication, Lund et al., 2021.
Instruments:
Unmanned aerial system (UAS) - DJI Phantom 4 Pro (P4); Drifter consisting of a torus float with an integrated GPS and battery, two interlocking drogue panels of 0.4 m × 0.4 m, and a 0.2 m chain link; Acoustic Doppler Current Profiler (ADCP) - Nortek Aquadopp 2 MHz with an internal sampling rate of 23 Hz.
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