Sun glint near Cape Town

Credit: Jeff Schmaltz; MODIS team; NASA, Posted on: Friday, 30 December 2005, 07:47 CST Download full size image

The silver-gray appearance of water in the lower right corner of this image is caused by sun glint.

Sun glint occurs when the sunlight is reflected from the ocean's surface back to the satellite. Normally, water looks dark blue or black. However, under certain conditions (sun-target-sensor geometries), water can act as a specular reflector, much like a mirror.

The surface of the water is influenced by wind, which is why sun glint is often associated with coastlines, where air from the land surface interacts with air over water. The "roughness" of the sea surface and the orientation of waves can also create bands in the sun glint portion of an image.

Because sun glint obscures targets on the Earth's surface and renders them invisible, it is often removed from satellite images. This can be accomplished by examining the overlapping portions of a series of images. If one can isolate and remove all other image artifacts or anomalies, differences between the images will be the result of sun glint. Because the portions of the image that are influenced by sun glint are much brighter than neighboring, unaffected portions, the "extra" brightness of the former can be estimated and adjusted to more closely match the latter.

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