2019 AK DGGS Lidar DEM: Mt. Juneau, AK

The Alaska Division of Geological & Geophysical Surveys (DGGS) used aerial lidar to produce a classified point cloud, digital surface model (DSM), digital terrain model (DTM), and intensity model of Mount Juneau, Southeast Alaska, during near snow-free ground conditions on September 6, 2019. The survey provides snow-free surface elevations for deriving snow depth distribution models with repeat surveys during snow-covered conditions. Ground control data were collected on September 5, 2019, and aerial lidar were collected on September 6, 2019, and subsequently processed in a suite of geospatial processing software. These products are released as a Raw Data File with an open end-user license. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/30731).

The NOAA Office for Coastal Management (OCM) downloaded this data set from this AK DGGS site:

https://elevation.alaska.gov/

This file was processed to make the data available for custom and bulk download from the NOAA Digital Coast Data Access Viewer (DAV) . The total number of files downloaded and processed was 1.

The survey provides snow-free surface elevations for deriving snow depth distribution models with repeat surveys during snow-covered conditions. The goal of this project and related works is to improve understanding of the complex interaction between the changing cryosphere, snow avalanches, natural resources, and people in their natural and built environments.

>classified point cloud data: Classified point cloud data are provided in compressed LAZ format. Data are classified in accordance with ASPRS 2014 guidelines and contain return and intensity information. The average pulse spacing is 7.5 cm and the average density is 15.58 pts/m2.

>digital surface model: The DSM represents surface elevations including heights of vegetation, buildings, 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).

>digital terrain model: 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 image: The lidar intensity image describes the relative amplitude of reflected signals contributing to the point cloud. Lidar intensity is largely 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

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 -19.5 cm between 22 control points and the point cloud. We reduced this offset to +4.4 cm by performing a vertical transformation of the lidar point data. We used six check points 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 10.8 cm. We evaluated the relative accuracy for this dataset as the interswath overlap consistency and measured it at 8.4 cm RMSE. See the accompanying report for tables of checkpoint comparisons.

This data release is complete.

There is lower ground point density in some heavily forested areas than in areas with thinner forest canopy; however, the interpolated areas were deemed sufficient given the resolution of the products and intended scope of the work.

Data were collected by the Alaska Division of Geological and Geophysical Surveys (AK DGGS). OCM downloaded the data from the Alaska DGGS Elevation Portal and processed the data to be available for custom and bulk download from the NOAA Digital Coast Data Access Viewer (DAV).