Bare Earth:  LiDAR points that are filtered to represent the ground, are then triangulated to create a 3D surface.  Also referred to as a Digital Elevation Model (DEM) or Digital Surface Model (DSM).​
There are several different applications for LiDAR systems, such as atmospheric, climate research, bathymetry, and surface terrain.  For this site, we will focus directly on the application of surface terrain modeling.
Full Feature:  All relevant LiDAR points including ground and points above ground, are triangulated and a 3D surface is created.  Also known as a Digital Terrain Model (DTM).  
I.M.U.:  Inertial Measurement Unit - Used to detect the pitch, roll, and yaw of the aircraft.

G.P.S.:  Global Positioning System - Uses satellites to determine the latitude and longitude of the aircraft.

LASER:  Light Amplification by Stimulated Emission of Radiation - An optical device that prduces an intense beam of light.

LiDAR:  Light Detection and Ranging - A measuring system using laser light, some components include: I.M.U., G.P.S., LASER, refractors, collectors, and data storage tools.

Remote Sensing:  Recording information without being in physical contact with the object.​
False Color:  Can be applied to a Bare Earth or Full Feature model.  The change in color represents a change in elevation based on the area of the model.​

What is Light Detection And Ranging?

In the 1950's a system combining a laser range finder and data collector captured point data from the air.  Over the past 60 years, innovation has been playing a big role in the evolution of the modern day Light Detection And Ranging system.  Faster computers, larger data storage capacity,Inertial Measurement Units, and Global Positioning Systems, have made LiDAR a much more viable and accurate technology to adopt in the modern day digital terrain modeling industry. 

    The LiDAR system is attached to the bottom of an aircraft, the LASER emits a pulse of light towards the ground where it is reflected back and collected by the receiver.  The time it took to transmit the light and receive a reflection gives the system a distance to the aircraft.  Different technologies allow the LASER to be projected at angles, and up to 200,000 pulses of light per second sweep across the terrain.  While the LASER is transmitting and the receiver is receiving, GPS receivers, and IMU's are constantly recording the position and attitude of the aircraft.  GPS and IMU data is combined with the laser data and corrections are made to the elevation and position of the laser point.