LiDAR is an acronym for Light Detection And Ranging. Airborne LiDAR technology being used by ODOT to perform aerial surveying. The airborne LiDAR system is mounted in an airplane looking downward. The sensor oscillates back and forth scanning the terrain to produce millions of 3-D positions per project.
The ability of the LiDAR system to position 3D points on the ground is the result of multiple components intergrated to work together. The GPS provides the position of the sensor in the air during a mission. An IMU(Inertial Measurement Unit) is used to provide the sensor orientation or rotation about each axis, commonly referred to as roll, pitch and bank(heading). The LiDAR sensor records the scan angle relative to the sensor platform in addition to the range/distance to the ground point. The above information allows the determination of the location of the point of the surface.
The LiDAR system contains parameters that allow the point distribution on the ground to be adjusted. Typically, the parameters are set to generate a uniform distribution of points for the most applications. The LiDAR can also distinguish intensities of the return, which can then be used to develop a set of data points that resembles a black and white photo. The intensity data can be laid over the height elevation model. Some triangulating of points are performed by the software to give us a quick view of what the processed data looks like, which is why the trees appear as triangles.
Representations of the LiDAR data using intensity information with the point positions.
Cross-section view of LiDAR data showing structures, trees and ground surface.
Cross-section view of LiDAR data on man made structures.
Only the "ground" classified LiDAR points are used to create ground surfaces known as a Trianulated Irregular Network(TIN) for many applications.
A high resolution TIN generated from LiDAR data.