Altimetry (Sea Surface Height)

Important notes

• Cloud cover doesn't impact this data
• Updates once per day
• Unit is centimeters

What is Sea Surface Height (SSH)

The surface of the ocean isn't flat - there are high spots and low spots. Altimetry is the height of the sea surface compared with mean sea level.

Small changes in sea level can influence the feeding patterns of big game fish.

How is SSH recorded?

Modern satellites orbiting the Earth can accurately measure ocean surface height, to within a few centimeters.

Cloud-cover doesn't affect altimetry measurements in the same way it affects other types of satellite imagery. The altimeter works by sending out a microwave pulse, bouncing it off the ocean's surface and measuring the return signal.

Once a day, we receive data from satellites providing contour lines we can overlay on a map.

How to use SSH to find fish

The best areas to fish are in the intermediate zones between areas of upwelling and areas of convergence. The SSH overlay helps you identify high and low areas of the ocean surface.

Upwellings can be identified by areas on the SSH overlay that are lower than surrounding areas (a little counterintuitive). In low areas, water must rise to the surface to restore equilibrium. Rising water is densely packed with nutrients. When it rises to the surface and is hit by sunlight, microscopic plants (phytoplankton) and animals (zooplankton) are able to grow quickly. Squid and baitfish feed on these microscopic animals, and in-turn attract larger pelagic species. 

Use altimetry data to find areas of upwelling, downwelling and the convergence zones in between that often hold fish. Look for a thicker "0" line! These neutral areas - between the highs and away from the center of the low - is where the food chain will have time to develop.

How SSH can help you predict other conditions

As always, use Altimetry/SSH data in conjunction with other overlays & imagery to identify hotspots.

When cloud cover is blocking other data, this is a key tool.

By identifying areas of upwelling and downwelling you can understand current features and eddies.

Because of the Coriolis effect, currents flow clockwise around high areas in the Northern Hemisphere, (and anti-clockwise around a high in the Southern Hemisphere).