High-Resolution GNSS-Tracked Drifter for Studying Surface Dispersion in Shallow Water

The use of Global Navigation Satellite System (GNSS)-tracked Lagrangian drifters allows more realistic quantification of fluid motion and dispersion coefficients than Eulerian techniques because such drifters are analogs of particles that are relevant to flow field characterization and pollutant dispersion. Using the fast-growing real-time kinematic (RTK) positioning technique derived from GNSS, drifters are developed for high-frequency (10 Hz) sampling with position estimates with centimeter accuracy. The drifters are designed with small size and less direct wind drag to follow the subsurface flow that characterizes dispersion in shallow waters. An analysis of position error from stationary observation indicates that the drifter can efficiently resolve motion up to 1 Hz. The result of the field deployments of the drifter in conjunction with acoustic Eulerian devices shows a higher estimate of the drifter streamwise velocities. Single particle statistical analysis of field deployments in a shallow estuarine zone yielded estimates of dispersion coefficients comparable to those of dye tracer studies. The drifters capture the tidal elevation during field studies in a tidal estuary.