2021 NOAA NGS Topobathy Lidar DEM: Revillagigedo Channel, Southeast Alaska

NOAA Southeast AK Topobathymetric Lidar data were collected by NV5 Geospatial (NV5) using Leica Hawkeye 4X and Riegl 1560i systems and delivered to NOAA in four blocks. The NOAA Southeast AK Topobathymetric Lidar Block01 was acquired between 20210608 and 20210730 in 13 missions, Block02 was acquired between 20210611 and 20210730 in 14 missions, Block03 was acquired between 20210730 and 20210823 in 6 mission and Block 04 was acquired between 20210625 and 20210823 in 7 missions. The four block dataset includes topobathymetric data in a LAS format 1.4, point data record format 6, with the following classifications in accordance with project specifications and the American Society for Photogrammetry and Remote Sensing (ASPRS) classification standards:
1 - unclassified
2 - ground
7 Withheld -low noise
18 Withheld - high noise
40 - bathymetric bottom or submerged topography
41 - water surface
42 Synthetic- Chiroptera synthetic water surface
43 - submerged feature
45 - water column
64 - Submerged Aquatic Vegetation (SAV)
65 - overlap bathy bottom - temporally different from a separate lift
71 - unclassified associated with areas of overlap bathy bottom/temporal bathymetric differences
72 - ground associated with areas of overlap bathy bottom/temporal bathymetric differences
81 - water surface associated with areas of overlap bathy bottom/temporal bathymetric differences
82 Synthetic - Chiroptera synthetic water surface associated with areas of overlap bathy bottom/temporal bathymetric differences
85 - water column associated with areas of overlap bathy bottom/temporal bathymetric differences
1 Withheld - edge clip
1 Overlap Withheld - unrefracted green data from Chiroptera sensor

        The channel bits are as follows:
        0 - Riegl VQ1560 NIR channel A and Chiroptera green shallow laser
        1 - Riegl VQ1560 NIR channel B and Chiroptera/Hawkeye synthetic water surface
        2 - Hawkeye green deep laser
        3 - Chiroptera NIR

        The user byte is mapped as the following:
        0 - Riegl NIR channel A
        1 - Riegl NIR channel B
        10 - Chiroptera green shallow
        11 - Chiroptera green shallow 4X
        12 - Chiroptera green shallow synthetic
        20 - Hawkeye green deep
        21 - Hawkeye green deep 4X
        22 - Hawkeye green deep synthetic
        30 - Chiroptera NIR

Data in all blocks includes lidar intensity values, number of returns, return number, time, and scan angle. The block01 boundary extent covers 103,002 acres , the Block02 boundary extent covers 76,119 acres, the block03 boundary extent covers 55,929 acres and Block04 boundary extent covers 18,351 acres of the combined topographic and bathymetric project boundaries.

After the initial Southeast AK Topobathymetric Lidar submission, NOAA reviewed the data and provided NV5 Geospatial with a feedback edit review. NV5 Geospatial has corrected these feedback edits and incorporated them into the final block datasets. Additionally, green laser intensity values were normalized for depth for the dataset resulting in a full redelivery of all LAS files. LAS files were compiled in 500 m x 500 m tiles. The final classified lidar data were then transformed from ellipsoid (GRS80) to geoidal height (Geoid12b) and used to create topobathymetric DEMs in GeoTIFF format with 1m pixel resolution.