LIDAR, (Light Detection and Ranging), is a remote sensing method that uses light in the form of a pulsed laser to measure variable distances to the Earth. LIDAR uses ultraviolet, visible, or near infrared light to image objects. It can target a wide range of materials, including non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules. A narrow laser beam can map physical features with very high resolutions. For example, an aircraft can map terrain at 30-centimetre (12 in) resolution or better.
Airborne LIDAR is when a laser scanner, while attached to an aircraft during flight, creates a 3-D point cloud model of the landscape. This is currently the most detailed and accurate method of creating digital elevation models, replacing photogrammetry. One of airborne LIDAR’s advantages in the remote sensing field is it can collect larger areas as a plane can acquire 3–4 km wide swaths in a single flyover. Another major advantage in comparison with photogrammetry is the ability to filter out reflections from vegetation from the point cloud model to create a digital surface model which represents ground surfaces such as rivers, paths, and cultural heritage sites, which are concealed by trees.
The LIDAR operational methodology consists on laser light pulses towards a surface and the measurement of the time it takes to return to each emission towards the point of origin. Considering constant and knowing the speed of light, the LiDAR system can calculate the distance that exists between itself and the return surface with a very high precision, so when performing it successively and in motion, the instrument is capable of build a model of the shape of the terrain you are measuring. It is possible to integrate a high resolution and precision photography system, in which each lidar point will have a value in the RGB system.