Frequently Asked Questions
As RADAR is RAdio Detection and Ranging, LIDAR is LIght Detection and Ranging. Radar sends out sound waves and Lidar sendout light or laser pulses. The lasers used by the police to check your speed on the highway are commonly LIDAR, although you do not often hear it referred to as such. If you have a radar detector that also can detect lasers you have a lidar detector.
That depends on what type of LIDAR system is used and how it is used. A high altitude system can cover more ground for each flying pass but it will not be as accurate as a low altitude system. Part of the accuracy equation is the accuracy of the DGPS used to locate each lidar pulse return point. DGPS is usually accurate to 5 or 7 centimeters. Advanced LIDAR Technology's low altitude ATLAS-SL laser mapping system has an absolute elevation accuracy of about 15 centimeters.
As LIDAR is flown the time it takes for each laser pulse to return is recorded, that is how the elevation is calculated. These pulses are matched with the GPS information, so each pulse gets an x,y and z data point. Along with this information digital photogrpahy is taken so that each pixel can be given an x,y and z data point. Digital movies can also be taken and those pixels can also be given an elevation and an absolute x and y location.
There are many. One is that you fly over the area being mapped so there are no problems with permitting or access. As these problems are minimized you can more easily fly over an area as often as necessary to document what changes have occurred. Coastal beach erosion monitoring is an example of this. One of the big advantages is that the output is in digital form and that you get a digital map of everything that is flown over, the ground surface, buildings and man made objects, and even the foliage. The digital output means you can have anything from simple contour maps to digital elevation models to flyover movies to work with.
LIDAR can be flown by either type of aircraft, but it usually depends on the altitude of the flight. Advanced LIDAR Technology's high resolution system is flown from lower altitudes for higher resolutions, so it would normally be flown from a helicopter.
Before the 2000 Summer Olympics in Sydney, Australia, the Australian Army had LIDAR flown over the olympic site. They used the digital elevation map of the buildings and ground surface to plan their response to various security issues. As an example the Army could use the digital elevation map for picking the best routes for low flying helicopters to take for medical evacuations, etc.