Light Detection and Ranging (lidar) is a technology used to create high-resolution models of ground elevation with a vertical accuracy of 10 centimeters (4 inches). Lidar equipment, which includes a laser scanner, a Global Positioning System (GPS), and an Inertial Navigation System (INS), is typically mounted on a small aircraft. The laser scanner transmits brief pulses of light to the ground surface. Those pulses are reflected or scattered back and their travel time is used to calculate the distance between the laser scanner and the ground.
Lidar data is initially collected as a “point cloud” of individual points reflected from everything on the surface, including structures and vegetation. To produce a “bare earth” Digital Elevation Model (DEM), structures and vegetation are stripped away.
The USGS hopes to complete collection of lidar data for all of the U.S. and its territories by 2022 (status map). Due to high cloud cover and remote locations, Interferometric Synthetic Aperture Radar (IfSAR)—rather than lidar—is being used in Alaska.
The National Map is the primary repository for USGS base geospatial data. Access lidar data using:
- 3DEP LidarExplorer – Point cloud data and lidar-derived DEMs
- The National Map Download Client
- The National Map Services