LiDar

LiDAR, short for Light Detection and Ranging, is a remote sensing method that measures distances by emitting laser pulses toward a target and recording the time needed for reflections to return, or by analyzing the phase shift of continuous waves. The collected range data are used to construct three-dimensional representations of surface geometry.

LiDAR systems typically include a laser scanner, a detector, and a data-logging unit, along with a navigation package such as a Global Positioning System (GPS) receiver and an inertial measurement unit (IMU) to georeference measurements. The platform may be airborne, terrestrial, or mobile on a vehicle. Some systems also capture waveform data or the intensity of returns.

LiDAR data are often organized as point clouds. There are discrete-return systems, which record individual return pulses, and waveform LiDAR, which records the full reflected energy over time. There are three main deployment classes: airborne LiDAR (mounted on aircraft or drones), terrestrial or ground-based LiDAR (scanners on tripods or fixed mounts), and mobile LiDAR (mounted on cars, boats, or trains).

LiDAR has widespread applications in topography and mapping (digital elevation models, forest inventories), archaeology, construction and civil engineering, environmental monitoring, flood risk assessment, urban planning, and autonomous vehicles and robotics, where it provides obstacle detection and precise localization in 3D space.

Advantages include high spatial resolution, direct 3D measurements, and rapid data collection. Limitations include sensitivity to weather conditions (fog, rain, snow), reduced penetration through dense vegetation or urban clutter, occlusion of hidden surfaces, and higher cost and processing demands.

LiDAR technology emerged in the 1960s and 1970s following the invention of the laser and has since evolved with advances in optics, scanning mechanisms, and sensor fusion with GNSS/IMU. It is now widely used in surveying, geoscience, and autonomous systems.