2019 - 2020 USGS QL1 Lidar DEM: Glacier Bay, AK

Timeframe of the lidar collections, performed over two seasons in 2019 and 2020. See Survey Report for detailed collection dates.

Create custom data files by choosing data area, map projection, file format, etc. A new metadata will be produced to reflect your request using this record as a base.

Bulk download of data files in GeoTIFF format, UTM Zone 8N NAD83(2011), meters coordinates and elevations in NAVD88(Geoid 12B) meters.

Bulk download of data files in GeoTIFF format, UTM Zone 8N NAD83(2011), meters coordinates and elevations in NAVD88(Geoid 12B) meters.

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.

Link to the USGS work package report that provides project information, vertical accuracy results, classifications used, sensors used, and work unit information.

Link to the additional information available for this data set from the USGS. This information includes reports, tile index shapefiles, and hydro breaklines.

Link to the Quantum Geospatial, Inc. lidar report for AK_GlacierBay_B3

Link to the Quantum Geospatial, Inc. lidar report for AK_GlacierBay_5

Lidar Pre-Processing:

1. Review flight lines and data to ensure complete coverage of the study area and positional accuracy of the laser points.

2. Resolve kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data.

3. Develop a smoothed best estimate of trajectory (SBET) file that blends post-processed aircraft position with sensor head position and attitude recorded throughout the survey.

4. Calculate laser point position by associating SBET position to each laser point return time, scan angle, intensity, etc. Create raw laser point cloud data for the entire survey in *.las format. Convert data to orthometric elevations by applying a geoid correction.

5. Import raw laser points into manageable blocks to perform manual relative accuracy calibration and filter erroneous points. Classify ground points for individual flight lines.

6. Using ground classified points per each flight line, test the relative accuracy. Perform automated line-to-line calibrations for system attitude parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift. Calculate calibrations on ground classified points from paired flight lines and apply results to all points in a flight line. Use every flight line for relative accuracy calibration.

7. Adjust the point cloud by comparing ground classified points to supplemental ground control points.

Lidar Post-Processing:

1. Classify data to ground and other client designated classifications using proprietary classification algorithms.

2. Manually QC data classification

3. After completion of classification and final QC approval, calculate NVA and VVA, and density information for the project using ground control quality check points. For Ql1 areas single swath nominal pulse spacing (NPS) was designed to be 0.50 at nadir and the aggregate Nominal Pulse Spacing (ANPS) was calculated to be 0.31 using all valid first return points.

Hydro-flattening Breaklines and Hydro-flattened DEM creation: Water boundary polygons were developed using an algorithm which weights Lidar-derived slopes, intensities, and return densities to detect the water's edge. The water's edge was then manually reviewed and edited as necessary. Elevations were assigned to the water’s edge through neighborhood statistics identifying the lowest Lidar return from the water surface. Lakes were assigned a consistent elevation for an entire polygon while rivers were assigned consistent elevations on opposing banks and smoothed to ensure downstream flow through the entire river channel. These breaklines were incorporated into the hydro-flattened DEM by enforcing triangle edges (adjacent to the breakline) to the elevation values derived from the breakline. This implementation corrected interpolation along the hard edge. Breaklines were also used to classify all ground points within the identified water bodies to class 9 (water).

The NOAA Office for Coastal Management (OCM) created references to the USGS GeoTIFF files that were ingested into the NOAA Digital Coast Data Access Viewer (DAV). No changes were made to the data. The DAV will access the raster data as it resides on Amazon Web Services (AWS).

These are the GeoTIFF files that are being accessed:

https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Elevation/OPR/Projects/AK_GlacierBay_2019_B19/AK_GlacierBay_B3_2019/TIFF/

https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Elevation/OPR/Projects/AK_GlacierBay_2019_B19/AK_GlacierBay_5_2019/TIFF/