How Accurate and Reliable Are Satellite Imagery Maps?

The accuracy and reliability of maps created from satellite imagery depends upon the orbital device producing the images. As an example, the Pleiades-1A satellite, which was launched in December 2011, is capable of an image-location reliability of about 10 feet, and the accuracy can be increased to about 3.25 feet when ground control points, or GCPs, are used in conjunction with the satellite sensor. The Pleiades-1A satellite covers more than 386,000 square miles each day, and is capable of capturing images covering areas up to about 620 square miles.

A satellite imagery accuracy assessment was recently conducted in relation to forest maps used to determine the composition, distribution and fragmentation of European forests. The high-resolution satellite imagery, or HRSI, maps were produced for the years 2000 and 2006. The 2000 forest map was produced from images collected by the Landsat-7 satellite, and the 2006 map was constructed from images taken by the IRS-LISS-3 and SPOT 4/5 satellites. The 2000 and 2006 satellite maps, which represent a composite image of the distribution of forests across the entire European continent, were determined to possess an overall accuracy of between 84 percent and 90.8 percent.

Ground sample distance, or GSD, refers to the smallest possible size unit a high-resolution satellite sensor can capture. The United States government imposes a GSD resolution restriction of 1.64 feet on civilian imaging. Advancements in GSD resolution technology have enabled some HRSI sensors to distinguish between objects on the ground that are about 1.5 feet apart.