Lidar is a laser-based method of detection, range finding and mapping. Lidar typically uses a low-power, eye-safe pulsing laser working in conjunction with a camera. The laser illuminates a target and associated software calculates the time it takes for the laser to reflect back from the target. In some applications, specifically-tuned lasers may be used to excite and detect elements or compounds. Lidar's best-known application is measuring the speed of a target, for example in police speed guns (one of the few non-eye-safe applications of the technology). Lidar is used in conjunction with GPS to yield three-dimensional (3-D) topographical maps -- even through foliage -- by sweeping from a vantage point such as the underside of an aircraft. Because Lidar can penetrate forest canopy, the technology has been used to find lost cities. In June 2013, an international team of researchers used Lidar to discover Cambodia's Mahendraparvata, a 1200-year-old city that rivals the current capitol in size and complexity. Other applications of Lidar include: (1) Range-finding and map-making in space exploration. In the 1970s, for example, Lidar was used to map the surface of the moon. (2) Obstacle detection and collision avoidance in autonomous vehicles, such as driverless cars. (3) Biological agent detection and autonomous flight for military operations. (4) Determining the most effective use of fertilizers for farming efficiency. (5) Predicting the energy yield for wind power. (6) Surveying and calculating ore volumes for minerals. It is not known where the word Lidar comes from. According to various sources, the word is an acronym for light detection and ranging, laser interferometry detection and ranging orlight/radar