LiDar: a giant laser ranging device sending out millions of pulses per second. You can get the distance or the range to the target from LiDar.
GPS(Global Positioning Syestem):To give the location of the LiDAR sensor.
IMU(Inertial measurement unit):used to measure the pitch,roll and heading of an (airborne) platform.
Pulse:a burst of light energy that is admitted by the LiDAR system.
Return:the first reflected light energy that has been recorded by the LiDAR sensor.
NADIR/Off-NADIR
原文：http://www.cnblogs.com/mactep/p/6862749.html