Satellite imagery

Digital imagery can greatly enhance a GIS. Part of the raster data types, imagery is a powerful visual aid and serves as a source of derivative information such as planimetrics and classification schemes to derive such information as land use or vegetation. If your GIS covers a particularly large area, aerial imagery may not be a practical or economical choice. Satellite imagery is often the preferred choice of imagery for larger regions. More and more choices of satellite imagery are becoming available and the cost associated with its purchase is dropping.

Listed here are some of the most prominent sources of currently available satellite imagery and future satellite launches. This guide is meant to be a launching point for searching for and acquiring information about available satellite imagery. Individual choice of imagery will depends on many factors such as resolution, image type and cost.

Many of the imagery can be purchased directly from the associated agencies. In addition, there are online sites that also specialize in satellite imagery sales. Plangraphics is a reseller of Space Imaging’s IKONOS imagery. EOMOnline sells several imagery such as Landsat 5, IRS Imagery and Landsat 7. Terraserver is also a well-known source of satellite imagery.

Here are some basic satellite imagery related terms that are useful:

Hyperspectral imagery

Useful for classifying material types on the Earth’s surface – beneficial in agriculture and forestry management, mineral exploration, environmental monitoring and national security activities.

Interval

Amount of time that passes before the satellite scans the same point of the globe.

Multispectral

Two or more images taken simultaneously, but each image taken in a different part of the electromagnetic spectrum.

Panchromatic

Imagery taken of all wavelengths within the visible spectrum, though not uniformly.

Orbit

The act of circling the earth. The type of orbit describes the path the satellite takes as it circles the earth.

Resolution

The amount of ground covered in one pixel of the image. For example an image with one meter resolution means that each pixel in the image represents one square meter on the ground. Click here for examples of imagery at different resolutions.

Sun-synchronous

An orbit that always passes over the earth at the same local sun time.

Swath

Amount of ground covered lengthwise in the passing of the satellite.

Satellite imagery

*one-meter fused panchromatic and multispectral resolution.