The spectrum of sunlight reflected by the Earth's surface contains information about the composition of the surface, and it may reveal traces of past human activities, such as agriculture. Differences in soil texture are revealed by fractional temperature variations. So it is possible to identify loose soil that had been prehistoric agricultural fields, or was covering buried remains. The Maya causeway was detected through emissions of infrared radiation at a different wavelength from surrounding vegetation. The ground above a buried stone wall, for instance, may be a touch hotter than the surrounding terrain because the stone absorbs more heat.
Radar can penetrate darkness, cloud cover, thick jungle canopies, and even the ground.
Such characteristics as elevation, distance from water, distance between sites or cities, corridors, and transportation routes can help to predict the location of potential archeological sites. Computational techniques used to analyze data. 1. sun-angle correction 2. Many features which are difficult or impossible to see standing on the ground become very clear when seen from the air. But, black and white photography only records about twenty-two perceptible shades of gray in the visible spectrum.