2022 - 2023 USGS Lidar DEM: Southeast Alaska Landslides

Original Product: These are Digital Elevation Model (DEM) data for Alaska as part of the required deliverables for the SE_AK_Landslides project. Class 2 (ground) LiDAR points in conjunction with the hydro breaklines were used to create a 0.5 hydro-flattened Raster DEM.

Original Dataset Geographic Extent:

AK_SELandslides_1 (Work Unit 300221) - 2 boroughs in Alaska (Ketchikan Gateway, Wrangell), covering approximately 247 total square miles.

AK_SELandslides_2 (Work Unit 300477) - 5 boroughs in Alaska (Juneau, Petersburg, Prince of Wales, Sitka, Yakutat), covering approximately 1300 total square miles.

Original Dataset Description: The SE_AK_Landslides project called for the planning, acquisition, processing, and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LiDAR Specification, 2022 revision A. LiDAR data were delivered as processed Classified LAS 1.4 files formatted to individual 1000 m x 1000 m tiles and as tiled bare earth DEMs; all tiled to the same 1000 m x 1000 m schema. Continuous breaklines were produced in Esri file geodatabase format.

Ground Conditions: LiDAR was collected in fall 2022, while minimal snow was on the ground 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.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create breaklines and raster DEMs. The purpose of these LiDAR data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 0.5 cell size. These raw LiDAR point cloud data were used to create classified LiDAR LAS files, 3D breaklines, and hydro-flattened DEMs as necessary.

Raster File Type = GeoTIFF; Bit Depth/Pixel Type = 32-bit float; Raster Cell Size = 0.5; Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary; Required Vertical Accuracy = 0.196

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

AK_SELandslides_1 (Work Unit 300221)

AK_SELandslides_2 (Work Unit 300477)

To the extent possible under law, the U.S. Government has waived all copyright and related or neighboring rights to this dataset.

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.

AK_SELandslides_1

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% of the time. Based on a flying altitude of 2085 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.019 meters, this project was compiled to meet 0.23 meter horizontal accuracy at the 95% confidence level.

AK_SELandslides_2

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% of the time. Based on a flying altitude of 2478 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.015 meters, this project was compiled to meet 0.27 meter 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 DEM Determined Vertical Accuracy:

Non-Vegetated Vertical Accuracy (NVA) = 3.58 cm RMSE

Vegetated Vertical Accuracy (VVA) = 28.95 cm at the 95th Percentile

Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The raw point cloud is of good quality and data pass Non-Vegetated Vertical Accuracy specifications.

Data cover the entire area specified for this project.

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.