2021 AK DGGS Lidar DEM: Tuntutuliak, AK

Lidar-derived elevation data for Tuntutuliak, Southwest Alaska, collected August 18, 2021, Raw Data File 2023-17, provides aerial lidar derived classified point cloud data, a digital surface model (DSM), a digital terrain model (DTM), and an intensity model of Tuntutuliak, Southwest Alaska. Data were collected during leaf-on ground conditions. The survey provides snow-free surface elevation data for assessing coastal erosion and flooding hazards. Ground control data and aerial lidar data were collected on August 18, 2021, and subsequently 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/10.14509/31033).

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) website (https://dggs.alaska.gov/pubs/id/31033). 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 elevation data for assessing coastal erosion and flooding hazards.

>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 compressed LAZ format. Data are classified following ASPRS 2019 guidelines and contain return and intensity information. The average pulse spacing is 55.9 cm, and the average density is 3.21 pts/m2.

>dsm: The DSM represents surface elevations, including heights of vegetation, buildings, boardwalks, powerlines, etc. The DSM is a single-band, 32-bit GeoTIFF file of 50-centimeter resolution. No Data value is set to -3.40282306074e+38 (32-bit, floating-point minimum).

>dtm: The DTM represents bare earth elevations, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file of 50-centimeter resolution. No Data value is set to -3.40282306074e+38.

>lidar_intensity: The lidar intensity image depicts the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is primarily a function of scanned object reflectance in relation to the signal frequency, is dependent on ambient conditions, and is not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit float GeoTIFF file of 1-meter resolution. No Data value is set to -3.40282306074e+38.

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. This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys.

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 48.8 cm between 33 control points and the point cloud. We reduced this offset to 0.1 cm by performing a vertical transformation of the lidar point data. We used ten checkpoints to determine the non-vegetated vertical accuracy (NVA) of the point cloud ground class using a Triangulated Irregular Network (TIN) approach. We calculated the project NVA to have a root mean square error (RMSE) of 3.7 cm. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 6.7 cm RMSE.

This data release is complete.

This is a full-release dataset. There was no over-collect except for aircraft turns that were eliminated from the dataset. The 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 AWS S3.