What is Airborne Laser Scanning (LiDAR)?
Airborne Laser Scanning is remote sensing technique that allows the collection of topographic (ground height data) over large areas of landscape using a sensor mounted on a plane or helicopter. The basic principle of laser scanning as a survey tool relies on the ability to calculate the time taken by a beam of light to travel from the sensor to the reflecting surface and back.
The sensor scans in a direction perpendicular to the direction of flight, creating a swath of point measurements. The cloud of data points collected can then be used to create high-accuracy surface models of the landscape. These data, usually collected for environmental or hydrological purposes, have also proven to be exceptionally useful for identifying archaeological features.
Unlike aerial photography or digital spectral imaging, ALS is an active remote sensing technique, (meaning that measurements are taken using light emitted from the sensor unit rather than the reflection of natural light) which enables night-time data collection.
Point heights recorded can be filtered to remove vegetation from the terrain model (as shown below) giving a distinct advantage over photographic survey for forested areas.
The terrain data can be processed in a number of ways to accentuate the microtopographic features that represent past human interaction with the landscape.