Description and Performance of Finescale Drifters for Coastal and Estuarine Studies

The authors have designed and built a differential Global Positioning System (DGPS)-positioned Lagrangian drifter system to study complex nearshore, estuarine, and inner shelf flows with strong gradients and small scales. Various measures of the accuracy of the positioning system were assessed experimentally, as were the windage effects of antennas and floats. The DGPS-indicated position of a fixed drifter has a standard deviation of less than 1 m (over 600 samples) at a distance from the base station of up to 20 km. Windage effects are linear with a slope of about 0.002 drift-to-wind velocity ratio, which is about half the theoretical value.