2019 - 2020 USGS QL2 Lidar DEM: Glacier Bay, AK

Product: These are QL2 resolution Digital Elevation Models (DEM) data for the Glacier Bay project. Class 2 (ground) Lidar points in conjunction with the hydro breaklines were used to create a 1 meter hydro-flattened raster DEM.

Geographic Extent: The Quality Level 2, Delivery 1 project area encompassed 345,212 acres. The Quality Level 2, Delivery 2 project area encompassed 739,236 acres. The total QL2 area encompassed 1,084,448 acres in southeast Alaska.

Dataset Description: The Glacier Bay 3DEP Lidar project called for the planning, acquisition, and processing of Lidar data collected at an aggregate nominal pulse spacing (ANPS) of 0.71 meters for all QL2 areas. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. RAW flight line swaths were processed to create classified LAS 1.4 files delineated in 1,000 m x 1,000 m tiles. Each LAS file contains Lidar point information, which has been calibrated, controlled, and classified. Additional derived products include hydro-flattened DEMs, Highest Hit DSMs, Intensity Images, DZ Orthos, Flightline Shapes, Swath Coverage Shapes, Ground Survey Shapes and 3D breaklines of rivers and lakes within the study area.

Ground Conditions: Lidar was collected in summer 2019 and the summer of 2020, while the presence of snow on the ground was at a minimum and rivers were at or below normal levels.

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV). For this data set, the DAV is leveraging the GeoTIFF files hosted by USGS on Amazon Web Services.

The purpose of the Lidar data was to produce a high accuracy 3D dataset that meets all necessary standards laid out by the Glacier Bay contract. The raw Lidar point cloud data were used to create classified Lidar LAS files, hydro-flattened DEMs, Highest Hit DSMs, Intensity Images, DZ Orthos, Flightline Shapes, Swath Coverage Shapes and 3D breaklines of rivers and lakes within the study area.

CONTRACTOR: Quantum Spatial, Inc. Ground Control Points were acquired by DOWL for Quantum Spatial Inc. 2019 Data acquisition was coordinated by Quantum Spatial through Eagle Aerial. Quantum Spatial performed the 2020 data acquisition. All Lidar data calibration, and follow-on processing were completed by Quantum Spatial. Raster File Type = GeoTiff Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 1 meter Interpolation or Resampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners.

Data is available online for bulk and custom downloads.

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

Applanix PosPac 7.1, Microstation Version 8.0, TerraScan Version 19, TerraModeler Version 19, TerraMatch Version 19, ESRI ArcGIS 10.5, Windows 10 Operating System

Lidar horizontal accuracy is a function of Global Navigation Satellite System (GNSS) derived positional error, flying altitude, and INS derived attitude error. The obtained RMSEr value is multiplied by a conversion factor of 1.7308 to yield the horizontal component of the National Standards for Spatial Data Accuracy (NSSDA) reporting standard where a theoretical point will fall within the obtained radius 95 percent of the time. Based on a flying altitude of 2,400 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.015 meters, this project was compiled to meet 0.28 m horizontal accuracy at the 95% confidence level.

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

USGS Determined DEM Vertical Accuracy

Non-Vegetated Vertical Accuracy (NVA) = 4.1 cm RMSE

Vegetated Vertical Accuracy (VVA) = 27.10 cm at the 95th Percentile

Refer to the USGS Project Report for further details. The link to this report is provided in the URL section of this metadata record.

A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

DEM files were tested by Quantum Spatial for vertical accuracy. All data is seamless from one tile to the next, no gaps or no data areas.

Data is backed up to tape and to cloud storage.

The NOAA Office for Coastal Management (OCM) ingested references to the USGS GeoTIFF files that are hosted on Amazon Web Services (AWS), into the Digital Coast Data Access Viewer (DAV). The DAV accesses the raster data as it resides on AWS.