While the simplest maps simply distinguish between land and water, satellites collect data that can be used to create a wide variety of more complex maps. By measuring different frequencies of radiation, satellites can distinguish between types of land use – forests, marshes, fields, urban areas and transportation networks. The resulting maps help in planning and monitoring land use, development and environmental initiatives. Topographic maps showing the elevation of each point can be created using special techniques that involve comparing multiple images of the same location. The sensitivity of these techniques is so high that they can detect if the ground subsides by just a few centimetres after an earthquake or following the emptying of an aquifer.
Resource mapping is another important application. Geological features such as fault lines and rock composition are often easily visible from space. Low-frequency radar signals can even penetrate beneath the surface, giving some hint of what lies underground. These tools assist in exploration for mineral deposits, groundwater and oil and gas.
This slideshow contains two images and two animations that show how satellites have influenced mapping and environmental monitoring. The images depict the 1976 discovery of a new island off the coast of Labrador, and oil spills off the coast of the Maritimes in 1996. The animations show clear cutting and reforestation in British Columbia from 1992 and 2003, and a map of monthly green vegetation density around the world between 2000 and 2009.