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How to Tell Water Depth From Aerial Pictures

Aerial photography gives the observer an advantage most people don't have on a daily basis. From several hundred or thousands of feet off the ground, objects and water take on a different perspective. Since water molecules absorb light, knowing what colors are absorbed at what depth can indicate a general idea of the depth of the water.

Things You'll Need

Aerial photographs
Magnifying glass
Nautical map showing water depths

Instructions

- 1
  Look at the colors of the water on the picture.
- 2
  Determine if the water is calm or choppy because flat, calm water scatters more light than choppy water.
- 3
  Decide what time of day or night the photo was taken. Bright, noontime sunlight is the most accurate way to determine the water depth, since the light is entering the water at about a 90-degree angle.
- 4
  Look for seaweed or plankton that is near the surface of the water. These objects reflect or absorb light and color first, giving a false indication of depth.
- 5
  If the water is light in color, it is shallow. If the water is dark blue or black, it is deep.
- 6
  Water absorbs the main colors of the spectrum at these depths:
  
  Blue is absorbed at 120 feet.
  
  Green is absorbed at 80 feet.
  
  Yellow is absorbed at 50 feet.
  
  Orange is absorbed at 40 feet.
  
  Red is absorbed at 20 feet.

Nature