Airborne Lidar: A Tutorial for 2025 : Part II: Integrated Systems

Abstract

The first part of the tutorial (lidar basics) reviewed the fundamentals of airborne lidar, also referred to as airborne laser scanning (ALS). We concluded that ALS is a multi-sensor system consisting of a navigation component and a scanning lidar device. The Global Navigation Satellite System (GNSS) antenna/receiver and the Inertial Measurement Unit (IMU) provide precise position and attitude information of the carrier platform. The laser scanner itself is again a multi-sensor system consisting of the scanning and the ranging unit. All these components together comprise the complete ALS system, which delivers dense 3D point clouds of the topography, vegetation, buildings, water bodies, and infrastructure, such as power lines and the like. The outstanding features of ALS are (i) high point density of typically 5-30 points/m2 (ppsm), (ii) good height accuracy in the range of 5-10 cm, (iii) planimetric resolution of around 20 cm, and (iv) the capability of penetrating vegetation. The last of these has made airborne lidar the prime technique for capturing countrywide digital elevation data as the basis for national and transnational digital terrain models (DTMs). Next to precise geometry, ALS also provides radiometric information for each laser point, as either signal intensity or even calibrated reflectance. The latter is a measure which reflects properties of the illuminated object only, while the former also depends on mission parameters such as measurement range and incidence angle, as well as system and atmospheric parameters.