2011 NGA 133 Cities Lidar: Chicago

Chicago, IL

Dates of data collection.

Custom download for dataset allowing subsets, projection/datum changes, and derived product generation.

LAZ files in geographic coordinates and NAVD88 geoid18 heights in meters.

KMZ extent of data.

Data report by Woolpert describing the collection and processing of data delivered to SAIC.

Water surface points, including Lake Michigan, are coded as ground in the data.

The data report did not specify the NAD83 realization this was collected under and the data was collected the same year as new realization. The data received did not have any georeferencing tags within the data files. NAD83(2011) has been assumed, but it could be NAD83(NSRS2007).

Link to the USGS site with the data in UTM 16N.

The LiDAR data was acquired with a Leica ALS50-II 150 kHz Multiple Pulses in Air (MPiA) LiDAR sensor system, on board a Cessna 404. The ALS50-II LiDAR system, developed by Leica Geosystems of Heerbrugg, Switzerland, includes the simultaneous first, intermediate and last pulse data capture module, the extended altitude range module, and the target signal intensity capture module. The system software is operated on an OC50 Operation Controller aboard the aircraft.

1. Resolved kinematic corrections for three subsystems: inertial measurement unit (IMU), sensor orientation information and airborne GPS data. Developed a blending post-processed aircraft position with attitude data using Kalman filtering technology or the smoothed best estimate trajectory (SBET).

Software: POSPac Software v. 5.3, IPAS Pro v.1.3.

2. Calculated laser point position by associating the SBET position to each laser point return time, scan angle, intensity, etc. Created raw laser point cloud data for the entire survey in .LAS format. Automated line-to-line calibrations were then performed for system attitude

parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift.

Software: ALS Post Processing Software v.2.70, Proprietary Software, TerraMatch v. 10.04.

3. Imported processed .LAS point cloud data into project tiles. Resulting data were classified as ground and non-ground points with additional filters created to meet the project classification specifications. Statistical absolute accuracy was assessed via direct comparisons of ground classified points to ground RTK survey data. Based on the statistical analysis, the LiDAR data was then adjusted in relation to the survey ground control.

Software: TerraScan v.10.018.

4. The .LAS files were evaluated through a series of QA/QC steps to eliminate remaining artifacts and small undulations from the ground class.

Software: TerraScan v.10.018.

Data was retrieved from USGS on August 2, 2023. Data were converted to geographic NAD83(2011) coordinates and ellipsoid heights in meters for ingestion into the Digital Coast Data Access Viewer. Data were also reformatted into the cloud optimized point cloud version of LAZ format, including using LAS 1.4.