2023 AK DGGS Lidar DEM: Wrangell Island, AK

Lidar-derived elevation data for Wrangell Island, Southeast Alaska, collected July 2023, Raw Data File 2023-28, provides lidar-derived classified point cloud, a digital surface model (DSM), a digital terrain model (DTM), and an intensity model of Wrangell Island, Southeast Alaska, during leaf-on ground conditions. The survey provides snow-free surface elevations for use in shoreline development, resource quantification, hydrographic mapping, and slope stability modeling. Ground control data were collected June 26-30, 2023, and aerial lidar data were collected July 7-11, 2023, and subsequently merged and processed using a suite of geospatial processing software. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31098).

This metadata record supports the data entry in the NOAA Digital Coast Data Access Viewer (DAV).

The NOAA Office for Coastal Management (OCM) downloaded 1 GeoTiff data file from the AK DGGS (Alaska Division of Geological and Geophysical Surveys) from https://dggs.alaska.gov/webpubs/data/rdf2023_028_lidar-wrangell-2023-dtm-merged-only.zip . The data were processed to the NOAA Digital Coast Data Access Viewer (DAV) to make the data available for bulk and custom downloads.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from are also available from the NOAA Digital Coast. A link to these data is provided in the URL section of this metadata record.

The survey provides snow-free surface elevations for use in shoreline development, resource quantification, hydrographic mapping, and slope stability modeling.

>boundaries: A boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data.

>classified_points: Classified point cloud data are provided in LASer (LAS) format. Data are classified following ASPRS 2019 guidelines (table 2) and contain return and intensity information. For all ground points, the average point spacing is 54.6 cm, and the average density is 3.35 pts/m2.

>dsm: The DSM represents surface elevations, including heights of vegetation, buildings, powerlines, bridge decks, etc. The DSM is a single-band, 32-bit GeoTIFF file of 50-cm resolution. No Data value is set to -9999.

>dtm: The DTM represents bare earth elevations, excluding vegetation, bridge decks, buildings, etc. The DTM is a single-band, 32-bit GeoTIFF file of 50-cm resolution. No Data value is set to -9999.

>lidar_intensity: The lidar intensity image describes the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is (1) primarily a function of scanned object reflectance in relation to the signal frequency, (2) dependent on ambient conditions, and (3) not necessarily consistent between separate scans. The intensity image is a single-band, 16-bit unsigned GeoTIFF file of 50-cm resolution. No Data value is set to 0.

The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

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

Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product. 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.

We did not measure horizontal accuracy for this collection.

We measured a mean offset of +94.3 cm between 43 control points and the point cloud. This offset was reduced to +0.9 cm in non-vegetated areas and +10.5 cm in vegetated areas by applying a rubber-sheet vertical correction to the lidar point data. We used 214 checkpoints to determine the vertical accuracy of the point cloud ground class using a Triangulated Irregular Network (TIN) approach. The project vertical accuracy has a root mean square error (RMSE) of 5.3 cm in non-vegetated areas and 17.4 cm RMSE in vegetated areas. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 6.4 cm RMSE.

This data relaease is complete.

This is a full-release dataset. There was no over-collect. Data quality is consistent throughout the survey.

Data is backed up to cloud storage.

Data were collected by the Alaska Division of Geological and Geophysical Surveys (AK DGGS). The data were downloaded by the NOAA Office for Coastal Management (OCM) and processed to make it available for custom download from the NOAA Digital Coast Data Access Viewer (DAV) and for bulk download from S3 AWS.