LiDAR (Light Detection and Ranging) is an active remote-sensing technique that emits laser pulses and measures their return time to compute distance. Mounted on aircraft, drones, or ground tripods, it produces dense 3D point clouds with x, y, z coordinates, from which high-resolution elevation models are built.
How it works
Each pulse can produce multiple returns as it interacts with successive surfaces — for example treetop, mid-canopy, and finally bare ground. By classifying returns into ground and non-ground points, analysts can generate both a DTM (bare earth) and a DSM (top surface) from the same survey. Airborne LiDAR commonly achieves point densities of several to tens of points per square metre and vertical accuracy at the decimetre level.
Why it matters
LiDAR's ability to penetrate vegetation gaps makes it uniquely valuable for terrain work in forested or rugged areas, where photogrammetry and satellite stereo cannot see the ground. LiDAR-derived 1 m DEMs reveal subtle features — fault scarps, landslide head scarps, old channels, archaeological earthworks — that coarser data simply cannot resolve.
Common pitfall
Confusing LiDAR with photogrammetry or radar. LiDAR uses laser light and directly measures range; photogrammetry infers elevation from overlapping optical images; SAR uses microwave radar. Also note that standard topographic LiDAR does not penetrate water or dense solid canopy — bathymetric LiDAR uses a different (green) wavelength for shallow water. The common exchange format is LAS / compressed LAZ.