Airborne light detection and ranging (lidar) can provide high-quality topographic information over large areas. Lidar is an active remote sensing technology that employs laser ranging in near-infrared and green spectral wavelengths to provide three-dimensional (3D) point information for objects, including Earth’s surface, vegetation, and infrastructure. The U.S. Geological Survey (USGS) National Geospatial Program (NGP) 3D Elevation Program (3DEP) seeks to systematically acquire airborne topographic lidar for the conterminous U.S. (conus), Hawaii, and the U.S. territories. A series of field accuracy assessment surveys, using conventional surveying methods (i.e. total station and Global Navigation Satellite System (GNSS)) along with ground based lidar (GBL), were conducted at test sites in Northeastern Illinois (NEIL) to evaluate the 3D absolute and relative accuracy of airborne lidar acquired for 3DEP.