Ocean data visualization

• The layer list, top right, holds the basemaps and every overlay. Only one scalar field and one current depth can show at a time — two of either over the same water cannot be told apart.
• Right-click, or press and hold on a touchscreen, to read the position, the seafloor depth and the current wherever you point. With a temperature or salinity layer on, that too; with maritime boundaries on, whose waters they are.
• The 📏 button measures distance and bearing along as many legs as you click. Escape clears it.
• Under the map: the colour scale, its range, how strongly the depth contours show through, and the forecast hour. Reset puts everything back.
• Your own overlay. Load a KMZ or KML — a survey plan, a station grid, an operating area, a georeferenced chart — and it is drawn over the top and kept in this browser for next time. It stays on your machine; nothing is uploaded anywhere.

The same feeds as the hurricane page, which describes each one: NHC storm forecasts, gliders from four national data centres, NOAA saildrones, the Argo array, the US Navy ESPC-D-V02 forecast for currents, temperature and salinity, NOAA OISST for observed temperature, ECMWF IFS open data for 10 m wind, GEBCO for bathymetry and depth contours, EMODnet for the shoreline, and Marine Regions for maritime boundaries. Everything but the seafloor is refetched hourly.