Jetski-Based Nearshore Bathymetric and Current Survey System

Abstract

Nearshore coastal research programs need a methodology for determining the bathymetry and currents in and near the surf, a region notably difficult to survey in the presence of even moderate waves. A reasonably portable system has been designed and constructed that provides survey data on these variables in the nearshore along remote coastlines using either a jetski or amphibious vehicle. The on-board measurements include 3-D positions obtained using real-time kinematic, Global Positioning System, boat orientation measurements obtained from an inertial measurements unit, and water depth estimates obtained from a precision echo sounder. The result is a low noise measurement of the bottom topography directly in the WGS84 geodetic datum, with no requirement for tidal adjustment. The system also includes an acoustic doppler current profiler to provide vertical profiles of the horizontal current. The depth values are accurate to better than 10 cm (2 sigma), tide levels to better than 5 cm (1 sigma), and current values to better than 5 cm/s (1 sigma) in careful comparisons with standard, independent measurements.