The number of daily valid GPS fixes transmitted by each buoy. The colour scheme indicates the number of valid fixes received each day from each buoy (buoy number indicated to the right of each colour bar), as follows: green: 24 (100%); yellow: 22–23; cyan: 20–21; blue: 10–19; magenta: 5–9; red: 0–4. Buoys are arranged by cluster, from Cluster 1 in the south to Cluster 4 in the north. DOI: https://doi.org/10.1525/elementa.233.f6