2018 USFS Lidar DEM: National Forest Locations (WA, OR)

Sycan Marsh

Acquisition dates based on tile filenames.

East Zone

Methow Twisp

North Aldrich

Rattlesnake

Thomas Creek

Upper Bear Lake

Bulk download of tiles. This will be in an orthometric vertical datum, contrary to this metadata.

Custom download of data allowing subsetting, change of projection, and generation of derived products.

Data report from the lidar acquisition contractor.

KMZ showing the area covered by the data.

Atlantic operated a PACDV (N750DV) outfitted with an Optech Galaxy Prime LiDAR system during the collection of the project area. The data was collected with a nominal pulse spacing of 8 pls/m^2 at a nominal flight height of 1500-1800 meters and a nominal flight speed of 130 kts. Scanner pulse rate was 500 kHz. Atlantic acquired 1588 passes of the AOI as a series of perpendicular and/or adjacent flight-lines executed in 44 flight missions conducted between June 29, 2018 and January 24, 2019. Onboard differential Global Navigation Satellite System (GNSS) unit(s) recorded sample aircraft positions at 2 hertz (Hz) or more frequency. LiDAR data was only acquired when a minimum of six (6) satellites were in view.

Ground Control:

A total of 545 ground survey points were collected in support of this project.

Point cloud data accuracy was tested against a Triangulated Irregular Network (TIN) constructed from LiDAR points in clear and open areas. A clear and open area can be characterized with respect to topographic and ground cover variation such that a minimum of five (5) times the Nominal Pulse Spacing (NPS) exists with less than 1/3 of the RMSEZ deviation from a low-slope plane. Slopes that exceed ten (10) percent were avoided.

Each land cover type representing ten (10) percent or more of the total project area were tested and reported with a GCP. In land cover categories other than dense urban areas, the tested points did not have obstructions forty-five (45) degrees above the horizon to ensure a satisfactory TIN surface. The GCP value is provided as a target. It is understood that in areas of dense vegetation, swamps, or extremely difficult terrain, this value may be exceeded.

Atlantic used Leica software products to download the IPAS ABGNSS/IMU data and raw laser scan files from the airborne system. Waypoint Inertial Explorer is used to extract the raw IPAS ABGNSS/IMU data, which is further processed in combination with controlled base stations to provide the final Smoothed Best Estimate Trajectory (SBET) for each mission. The SBETs are combined with the raw laser scan files to export the LiDAR ASCII Standard (*.las) formatted swath point clouds.

Using a combination of GeoCue, TerraScan and TerraMatch; overlapping swath point clouds are corrected for any orientation or linear deviations to obtain the best fit swath-to-swath calibration. Relative calibration was evaluated using advanced plane-matching analysis and parameter corrections derived. This process was repeated interactively until residual errors between overlapping swaths, across all project missions, was reduced to ≤2cm. A final analysis of the calibrated lidar is preformed using a TerraMatch tie line report for an overall statistical model of the project area.

Multiple automated filtering routines are applied to the calibrated LiDAR point cloud identifying and extracting bare-earth and above ground features. GeoCue, TerraScan, and TerraModeler software was used for the initial batch processing, visual inspection and any manual editing of the LiDAR point clouds. Classified point clouds were cut to match the tile index and its corresponding tile names and delivered in .laz format.

The classification scheme was 1=unclassified; 2=ground; 7=low point (noise), 18=high noise.

U.S. Forest services remove high and low noise from 2 LAZ files the vendor missed. Points with Source ID's less than 200 (189, 193, 194) were removed from -

FRESY4_503588_978808_20181105.laz

FRESY4_505088_978808_20181105.laz

Data were received by NOAA Office for Coastal Management from the U.S. Forest Service with USFS region 6 Albers coordinates in ERDAS Imagine format. Data were converted to cloud optimized GeoTiff format.