2010 USGS Lidar: Nome Creek, Alaska

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Bulk download of data files in LAZ format, geographic coordinates, orthometric heights. Note that the vertical datum (hence elevations) of the files here are different than described in this document.

Information on the NOAA Office for Coastal Management (OCM)

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

This graphic displays the footprint for this lidar data set.

Link to data set report.

The LiDAR data was captured using AERO-METRIC's twin-engine, fixed wing aircraft equipped with a LiDAR system. The LiDAR system includes a differential GPS unit and inertial measurement system to provide superior accuracy.

Acquisition parameters:

1. Scanner - Optech ALTM Gemini

2. Flight Height - 3800m above mean terrain

3. Scan Angle - 14 degrees

4. Sidelap - 50% for both areas

5. Nominal Post Spacing - 2.095 meters

GPS and IMU processing parameters:

1. Processing Programs and version - Applanix - POSGPS and POSProc, versions 4.4

2. Maximum baseline length - Not greater than 40km.

3. IMU processing monitored for consistency and smoothness - Yes.

Point Cloud Processing:

1. Program and version - Optech LMS

2. Horizontal Datum - NAD83(CORS96)

3. Horizontal Coordinates - Universal Transverse Mercator, Zone 6, in Meters.

4. Vertical Datum - NAVD88

5. Geoid Model used to reduce ellipsoid heights to orthometric elevations - NGS Geoid06.

LIDAR Processing:

1. Processing Programs and versions - TerraSolid TerraScan (version 009.004), TerraModeler (version 009.001 and TerraMatch (version 009.001) and Intergraph MicroStation (version.08.01.02.15).

2. Point Cloud data is imported to TerraScan in a Microstation V8 (V) CAD environment on a specified 5000 foot by 5000 foot tiling scheme.

3. Analyze the data for overall compleness and consistency. This is to ensure that there are no voids in the data collection.

4. Inspect for calibration errors in the dataset using the TerraMatch software. This is accomplished by sampling the data collected accross all flight lines and classifying the idividual lines to ground. The software will use the ground-classified lines to compute corrections (Heading, Pitch, Roll, and Scale).

5. Orientation corrections (i.e. Calibration corrections) are then applied (if needed) to the entire dataset.

6. Automatic ground classification is performed using algorithms with customized parameters to best fit the project area. Several areas of varying relief and planimetric features were inspected to verify the final ground surface.

7. Design Alaska, INC. provided Quality Assurance and Quality Control (QAQC) data for this project. Design Alaska captured QA/QC points in 'open terrian' land cover category that were used to test the accuracy of the LiDAR ground surface. TerraScan's Output Control Report (OCR) was used to compare the QAQC data to the LIDAR data. This routine searches the LIDAR dataset by X and Y coordinate, finds the closest LIDAR point and compares the vertical (Z) values to the known data collected in the field. Based on the QAQC data, a bias adjustment was determined, and the results were applied to the LIDAR data. A final OCR was performed with a resulting RMSE of 0.10m.

8. Once the automatic processing and the testing of LiDAR is complete, AERO-METRIC meticulously reviews the generated bare-earth surface data to insure that proper classification was achieved as part of a Quality Control process.

9. Final deliverables are generated and output to a 1000m by 1000m tiling scheme in accordance with client specifications.

The NOAA Office for Coastal Management (OCM) downloaded 267 laz files from the USGS rockyftp site. The files contained elevation and intensity measurements for the Nome Creek, Alaska project area. The data were in UTM Zone 6 coordinates and NAVD88 (Geoid06) elevations in meters. The data were classified as: 1 -Unclassified, 2 - Ground, 7 - Noise. The NOAA Office for Coastal Management processed all classifications of points to the Digital Coast Data Access Viewer (DAV). Classes available on the DAV are: 1, 2, 7.

OCM performed the following processing on the data for Digital Coast storage and provisioning purposes:

1. The LAStools software scripts lasinfo and lasvalidate were run on the laz files to check for errors.

2. An internal OCM script was run to check the number of points by classification and by flight ID and the gps and intensity ranges.

3. Internal OCM scripts were run on the laz files to convert from orthometric (NAVD88) elevations to ellipsoid elevations using the Geoid06 model, to convert from UTM Zone 6 coordinates to geographic coordinates, to assign the geokeys, to sort the data by gps time and zip the data to database and to http.