A typical airborne LIDAR system is coupled with a Global Positioning System (GPS) to determine aircraft position and an Inertial Navigation System (INS) to determine the aircraft attitude. This allows the user to produce geo-referenced “points” on the ground. The performance of this technology enables users to have the benefit of highly accurate Digital Elevation Models (DEMs) that can be collected day or night and in a variety of weather conditions.
A LIDAR system comprises a laser source that projects a laser beam onto a spinning or scanning mirror that sends a brief pulse of light onto the earth’s surface. The mirror rotates or scans at an extremely fast rate, enabling the LIDAR system to project thousands of laser pulses per second, thus creating a dense swath of laser points on the ground. The reflected laser pulse is detected by the system which then, based on the time of travel and the aircraft position and attitude, computes the x, y and z position of each reflection point, i.e. the ground or other intermediate object.
Modern Laser scanning systems are capable of emitting up to 100,000 pulses per second, providing a dense grid of points covering the ground surface and capable of penetrating vegetation. It is then possible to model not only the ground surface below trees but also the tops of trees and buildings.
The LIDAR system acquires data in a swath that can be up to
600 metres wide.
Airborne LIDAR systems can broadly be classified into three main types: Wide Area Mapping systems flown from fixed wing aircraft; Corridor Mapping systems flown from helicopters and Bathymetric mapping systems flown from either platform.
LIDAR systems are often used in conjunction with other remote sensing instruments, including spectral and thermal imaging systems and high resolution video and digital cameras. |
