Definition

(LIght Detection And Ranging) An instrument that measures distance to a reflecting object by emitting timed pulses of LASER light and measuring the time between emission and reception of reflected pulses.  The measured time interval is converted to distance.  In survey use, the lidar system usually scans the light PULSEs across the TRACK of the SURVEY platform (usually an aircraft) so that successive PULSEs cover a SWATH(E) either side of the platform's track.  Infra-red LASERS will reflect off land and water, and are normally used for TOPOGRAPHIC lidar SURVEYs.  Blue-green LASERS will penetrate water and are used in HYDROGRAPHIC lidar SURVEYs.