LIDAR

http://grass.osgeo.org/screenshots/

LIDAR is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. The word LIDAR is not a acronym, it's a portmanteau of (li) from "light" and (dar) from "radar". LIDAR is used to make high-resolution maps of the surface of the earth. LIDAR provides three dimensional information that allow scientists and mapping professionals to examine both natural and manmade environments with accuracy, precision, and flexibility. There are two types of LIDAR, topographic and bathymetric. Topographic LIDAR uses a near-infrared laser to map the land, while bathymetric LIDAR uses water-penetrating green light to measure seafloor and riverbed elevations.The lidar image above shows a dune migration at Jockey's Ridge State Park, North Carolina where you distinguish different types of land features by the color they emit.