The drifters used in this study were designed and constructed by Jessie Lacy (Stanford University) and are shown in Figure 1. In order to minimize the effect of wind pushing the drifters off course, Jessie maximized the underwater surface area (the sail) and minimized the surface area projected above the water surface (small flag).
To achieve the maximum tidal excursion for a given tide, the drifters were placed in groups of two at their starting locations just after slack water. Using two drifters at each location allowed us to measure the "uniqueness" of each drifter track and to estimate tidal dispersion. In most cases the drifters remained in close proximity to each other, and a single track is indicated in the Figures of each drifter location. In situations where the drifters separated by a distance greater than 50 yards, two paths are shown beginning at the point of separation (Figures 6b and 7).
The drifters were tracked and their positions periodically (roughly every 15 minutes depending on conditions) recorded using the research vessel Holly Day Barnett (Figure 2). This R/V is equipped with Maptech navigation software and a differential GPS receiver (+/- 2 yards horizontal accuracy).