NASA's Tips For Interpreting Satellite Images

Example tip: Farmed vegetation often looks brighter green than natural vegetation

Straight Lines Mark Off Land Parcels in a Mixed-Use Forest

NASA Earth Observatory image by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer

Here at Popular Science, we love satellite images. They offer cool views of Earthly phenomena such as plankton blooms and erupting volcanoes. They give important perspective on the impact of natural disasters such as floods and fires. Seeing stuff from space can be a bit disorienting, however. But fear not. The Earth Observatory, NASA's public site for its Earth sciences, has listed some cool patterns to look for while interpreting satellite images. Some highlights:

  • A line of clouds can indicate there are mountains below, as the mountains push warmer air upwards to higher elevations, where it cools and forms clouds. A line of vortices in the ocean, on the other hand, can indicate there are peaks below the surface of the water, perturbing the water's flow.
  • There's an optical illusion called relief inversion that can happen with satellite images. Mountains appear to be canyons, or vice versa. The Earth Observatory explains:

It happens because most of us expect an image to be lit from the top left corner. When the sunlight comes from another angle (especially from the lower edge), the shadows fall in ways we don’t expect and our brains turn valleys into mountains to compensate. The problem is usually resolved by rotating the image so the light appears to come from the top of the image.

    Happy Earth-watching.