Seafloor Relief
The shaded picture of the bottom that sits under every other layer — shelf, canyons, ridges and the deep basin. Always on, with no controls of its own.
Static — does not update
More detail
It is drawn as light and shadow with a tint for depth.
How to see it better. The data layer you have up is drawn on top of it and partly hides it. Data Layers has a row called Seafloor Relief: picking it takes the data layer off. The shading is the same at every date and time.
How to use it. Find the shelf break, the canyons and the ridges at a glance, then tap the Depth button on the bottom bar to put contour lines and depth numbers on them. The depth figure in the readout at the top of the map gives the depth at one spot, and the Waypoints button marks cataloged structure such as rigs, wrecks and reefs.
Limits. Each cell covers about 1.2 nautical miles, so wrecks, small ledges and rock piles do not appear. Deep water offshore is sparsely surveyed and looks smooth. The shading stops at the edge of the water the ocean layers cover, so it can end partway across the screen while the basemap carries on.
Who makes it. The shading comes from NOAA's worldwide seafloor elevation map. The Depth lines come from a different survey, GEBCO with NOAA's coastal survey over the US Gulf shelf. The shading keeps working when the live layers run late.
The numbers
| How often it updates | Never |
| How fresh it usually is | No delay |
| How detailed it is | About 1.2 nautical miles per cell |
| Where it covers | Everywhere the ocean data covers; it stops at that edge |
| Observed or modeled | Observed: NOAA's worldwide seafloor elevation map, drawn as shading |
| What you see on screen | Light-and-shadow relief with a depth color tint. No numbers and no legend |
Source: NOAA NCEI shaded seafloor relief.