LIDAR

http://earthobservatory.nasa.gov/Features/Lidar/lidar3.php

LIDAR or light detection and ranging is a type of remote sensing that uses light to measure features of an object or location. To do this a laser is used to shine light on the object and the scattered light is measured to create an image. This image recorded by NASA in 2003 is of Johnson’s Reef in the Virgin Islands. Each square represents 100 square meters of reef and the color represents the height is the reef in meters.