Earth from Space
Home Online Exhibition National Tour Lesson Plans Media & News Resources Credits
divider
Living Planet Water & Air Structure of the Land The Human Presence Satellite Technology

How remote sensing works
Data from remote sensing satellites are recorded from radio transmissions, stored in computer systems, and then transformed into images.

  • Each number sent by the satellite represents one pixel (picture element), visible as "boxes" or squares.
  • Most remote sensing satellites can detect many wavelengths simultaneously. When every pixel is assigned a brightness value, the results are many grayscale images, one for each wavelength.
  • Colors are assigned to each wavelength and then digitally combined to create a full-color picture. The selection of colors is arbitrary, but they are usually chosen to enhance specific details. Red, for example, can be assigned to wavelengths that are reflected by plant life.

Landsat data are used to produce an image centered on the U.S. Capitol. Each pixel here covers about 30 x 30 meters of ground.
Courtesy National Air and Space Museum
See Enlargement
This simulated view of Guadalajara, Mexico, was created by combining Landsat 7 satellite images with elevation data. Topographic data shows the altitude of every pixel within the image. Using computer programs, it is possible to create virtual views that simulate the appearance of the landscape. When an altitude and point of view are chosen, image data are "draped" over the topography.
Courtesy Jesse Allen and Laura Rocchio/Landsat Project Science Office