Laser radar or ladar an Acronym for LAser Detection And Ranging, it is a way to measure shapes in 3D based on laser illumination.
A ladar system works by firing photons (lasers) at a given object or area, it then measures the time of flight of photons (time to reflect back), this enables a CCD style setup to encode each photon as a pixel and produce a 3D image of the object or area. This is the same technique used in Lidar systems except instead of determining the speed of the object, ladar creates 3D images with the data, this relies on the assumption that the objects being modelled are stationary or the images produced will not show the object as it appears in real life.
The primary advantage of a ladar system over radar is that the smaller wavelengths of a laser provide higher resolution than convetional radar, this can be up thousands of times the resolution of regular radar systems. The wavelength is so small that ladar is often used for making measurements of smoke and other airborne particles, and in fact the molecules of the air themselves.
--- Adapted from: Wikipedia. LADAR - Wikipedia. http://en.wikipedia.org/wiki/LADAR/. Accessed: 23:10 GMT 26 March 2004.
Ladar can also be used in zero or low light conditions. As well as having the ability to produce images from multiple angles, allowing it to see around obstacles such as trees.
There is more than one use for Laser Radar but a common misconception is that it has one or another specific use only, for example:
LADAR - Laser radar. Developed primarily for use in missiles, LADAR is a solid state system that provides near photographic quality images of potential targets. Precise target range is determined by measuring elapsed time from a laser transmission to the reflected return of the pulse. Unlike thermal imaging, a LADAR produces high resolution three dimensional images of near photographic quality, similar to a black and white photo.
--- From: SPACE & ELECTRONIC WARFARE LEXICON. Glossary L. http://www.sew-lexicon.com/gloss_l.htm. Accessed: 23:14 GMT 26 March 2004.
The system was actually intially invented for the US Department of Defense for use in ballistic missile seekers. The Images produced where used to determine if an object was a valid target or not. However this system is now also used in underwater environments by submarines and boats in addition to regular sonar to give a more accurate images of the sea bed and objects close by.
Other applications include mapping and autonomous vehicle navigation.