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, GEBCO for bathymetry and depth contours, EMODnet for the shoreline, and Marine Regions for maritime boundaries. Everything but the seafloor is refetched hourly.