Airborne Lidar: A Tutorial for 2025 : Part I: Lidar basics

Abstract

Since the beginning of the 21st century, airborne lidar (light detection and ranging) has entirely revolutionized topographic data acquisition. National mapping agencies around the globe have quickly adopted this active remote sensing technology and gradually changed their production workflows for the generation of national and transnational digital terrain models (DTMs). Over the last 25 years, enormous progress has been made in both sensor technology and data processing strategies. The weight and size of sensors has decreased significantly, and this now allows the integration of survey-grade laser scanners on UAVs (uncrewed aerial vehicles). Scan rates, in turn, have increased dramatically, enabling point densities beyond 20 points/m2 (ppsm) and, consequently, derived products with sub-meter resolution. While the precise geometry and the capability to penetrate vegetation are highlights of airborne lidar, the radiometric content is increasingly used, e.g., for improved semantic labeling of the captured 3D point cloud. The aim of this four-part tutorial is to revisit the principles of airborne lidar and to discuss current trends. While Part I covers the basics, Parts II-IV provide details about integrated sensor concepts, laser bathymetry and UAV-lidar.