Satellite Image Library

Background Information


Satellite Image Library

This Image Library contains satellite images from 2003 onwards. They were taken with the Moderate Imaging Spectoradiometer (MODIS) on the NASA satellites, Terra and Aqua with minimal post-processing before posting on the website.

Image Interpretation

Water bodies, such as Lake Winnipeg, contain particles (silt and clay), dissolved substances and living organisms(algae). These constituents, as well as the water itself, absorb and scatter light. This affects both the transparency (how clear the water is) and colour of the water. In these images, clear water (with few particles) will appear dark blue-black since most of the light is absorbed and a small amount of light (of the visible colour) is reflected. For example, very dark brown water is due to high concentrations of dissolved organic carbon, much like a cup of strong, black tea. Increasing inorganic particle concentration will cause a range of colours from blue to green to tan. The south basin of Lake Winnipeg often appears tan in colour due to high turbidity caused by particles carried in from the Red River, as well as high winds which stir up the sediment from the bottom of the lake. Highly turbid water due to an algal bloom will appear bright green in colour due to the algal cells at the surface of the lake. The edges of a bloom will appear crisp in the image when the bloom is at the surface of the lake, and less defined when it is below the surface of the lake. 


We acknowledge the use of Rapid Response imagery from the Land Atmosphere Near-real time Capability for EOS (LANCE) system operated by the NASA/GSFC/Earth Science Data and Information System (ESDIS).