Light detection and ranging (lidar) data are collected from aircraft using sensors that detect the reflections of a pulsed laser beam. The reflections are recorded as millions of individual points, collectively called a “point cloud,” that represent the 3D positions of objects on the surface including buildings, vegetation, and the ground.
Digital elevation models (DEMs) are one of many products that can be derived from lidar data, though they can also be derived from other sources. DEMs are digital representations of the earth’s topographic surface. They’re a “bare-earth” product because they do not include surface features like buildings and vegetation.
A high-resolution DEM can be derived from lidar point-cloud data by stripping away the surface features and sampling the ground elevation in uniform increments to produce a bare earth model.