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Physical Location
Data Set Info
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Spatial Info
Access Info
Distribution Info
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Tech Environment
Data Quality
Data Management
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Summary

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Short Citation
National Geodetic Survey, 2024: 2021 NOAA NGS Topobathy Lidar DEM: Revillagigedo Channel, Southeast Alaska, https://www.fisheries.noaa.gov/inport/item/69901.
Full Citation Examples

Abstract

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.

Distribution Information

  • GeoTIFF

    Bulk download of data files in the original coordinate system.

  • Create custom data files by choosing data area, product type, map projection, file format, datum, etc. A new metadata will be produced to reflect your request using this record as a base. Change to an orthometric vertical datum is one of the many options.

Access Constraints:

None

Use Constraints:

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.

Controlled Theme Keywords

COASTAL BATHYMETRY, COASTAL ELEVATION, elevation, Elevation Theme, TERRAIN ELEVATION

Child Items

No Child Items for this record.

Contact Information

Metadata Contact
NOAA Office for Coastal Management (NOAA/OCM)
coastal.info@noaa.gov
(843) 740-1202

Extents

Geographic Area 1

-131.683084° W, -131.14722° E, 55.153375° N, 54.797478° S

Time Frame 1
2021-06-08 - 2021-07-30

Item Identification

Title: 2021 NOAA NGS Topobathy Lidar DEM: Revillagigedo Channel, Southeast Alaska
Status: Completed
Publication Date: 2023
Abstract:

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.

Purpose:

This lidar data was required by National Oceanic and Atmospheric Administration (NOAA), the National Geodetic Survey (NGS), Remote Sensing Division Coastal Mapping Program (CMP) to enable accurate and consistent measurement of the national shoreline. The CMP works to provide a regularly updated and consistent national shoreline to define America's marine territorial limits and manage coastal resources.

Supplemental Information:

The topobathymetric lidar data includes all lidar returns. An automated grounding classification algorithm was used to determine bare earth and submerged topography point classification. The automated grounding was followed with manual editing. The automated grounding was followed with manual editing. Classes 2 (ground), 40 (submerged topography), 43 (submerged object), and 64 (Submerged aquatic vegetation) were used to create the final DEMs. The full workflow used for this project is documented in the NOAA Finger Lakes Topobathymetric Lidar final report and is available upon request.

Keywords

Theme Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > LAND SURFACE > TOPOGRAPHY > TERRAIN ELEVATION
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > OCEANS > BATHYMETRY/SEAFLOOR TOPOGRAPHY > BATHYMETRY > COASTAL BATHYMETRY
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > OCEANS > COASTAL PROCESSES > COASTAL ELEVATION
ISO 19115 Topic Category
elevation
NGDA Portfolio Themes
Elevation Theme

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords
CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > ALASKA
Global Change Master Directory (GCMD) Location Keywords
VERTICAL LOCATION > LAND SURFACE
Global Change Master Directory (GCMD) Location Keywords
VERTICAL LOCATION > SEA FLOOR

Instrument Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Instrument Keywords
LIDAR > Light Detection and Ranging

Platform Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Platform Keywords
Airplane > Airplane

Physical Location

Organization: Office for Coastal Management
City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Data Set Type: Elevation
Maintenance Frequency: None Planned
Data Presentation Form: Model (digital)
Distribution Liability:

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

Data Set Credit: National Oceanic and Atmospheric Administration (NOAA), National Geodetic Survey (NGS), Remote Sensing Division (RSD), Coastal Mapping Program (CMP)

Support Roles

Data Steward

CC ID: 1232907
Date Effective From: 2023
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Distributor

CC ID: 1232905
Date Effective From: 2023
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Metadata Contact

CC ID: 1232906
Date Effective From: 2023
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Originator

CC ID: 1232908
Date Effective From: 2023
Date Effective To:
Contact (Organization): National Geodetic Survey (NGS)
Address: 1315 East-West Hwy
Silver Spring, MD 20910
URL: https://geodesy.noaa.gov/

Extents

Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1299309
W° Bound: -131.683084
E° Bound: -131.14722
N° Bound: 55.153375
S° Bound: 54.797478

Extent Group 1 / Time Frame 1

CC ID: 1299308
Time Frame Type: Range
Start: 2021-06-08
End: 2021-07-30

Extent Group 2

Extent Description:

Work in progress

Extent Group 2 / Geographic Area 1

CC ID: 1299312
W° Bound: -131.817401
E° Bound: -131.114438
N° Bound: 55.392168
S° Bound: 55.059655

Extent Group 2 / Time Frame 1

CC ID: 1299311
Time Frame Type: Range
Start: 2021-06-11
End: 2021-07-30

Extent Group 3

Extent Group 3 / Geographic Area 1

CC ID: 1299315
W° Bound: -131.122052
E° Bound: -130.70137
N° Bound: 55.223374
S° Bound: 54.745594

Extent Group 3 / Time Frame 1

CC ID: 1299314
Time Frame Type: Range
Start: 2021-07-30
End: 2021-08-23

Extent Group 4

Extent Group 4 / Geographic Area 1

CC ID: 1299318
W° Bound: -131.132875
E° Bound: -130.713203
N° Bound: 55.425577
S° Bound: 55.208082

Extent Group 4 / Time Frame 1

CC ID: 1299317
Time Frame Type: Range
Start: 2021-06-25
End: 2021-08-23

Spatial Information

Spatial Representation

Representations Used

Grid: Yes
Vector: No
Text / Table: No
TIN: No
Stereo Model: No
Video: No

Reference Systems

Reference System 1

CC ID: 1299306

Coordinate Reference System

CRS Type: Projected
EPSG Code: EPSG:26909
EPSG Name: NAD83 / UTM zone 9N
See Full Coordinate Reference System Information

Access Information

Security Class: Unclassified
Data Access Procedure:

Data is available online for bulk or custom downloads

Data Access Constraints:

None

Data Use Constraints:

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.

Distribution Information

Distribution 1

CC ID: 1232910
Start Date: 2023-06
End Date: Present
Download URL: https://noaa-nos-coastal-lidar-pds.s3.us-east-1.amazonaws.com/dem/NGS_Revillagigedo_AK_Topobathy_DEM_2021_9834/
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2023 - Present)
File Name: Bulk Download
Description:

Bulk download of data files in the original coordinate system.

File Type (Deprecated): GeoTIFF
Distribution Format: GeoTIFF

Distribution 2

CC ID: 1232909
Start Date: 2021-05
End Date: Present
Download URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=9834
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2023 - Present)
File Name: Customized Download
Description:

Create custom data files by choosing data area, product type, map projection, file format, datum, etc. A new metadata will be produced to reflect your request using this record as a base. Change to an orthometric vertical datum is one of the many options.

File Type (Deprecated): Zip
Compression: Zip

URLs

URL 1

CC ID: 1232911
URL: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/9833/supplemental/extent_ngs_SE_ak__2021_m9833.kmz
Name: Browse graphic
URL Type:
Browse Graphic
File Resource Format: KML
Description:

This graphic displays the footprint for this lidar data set.

URL 2

CC ID: 1232912
URL: https://coast.noaa.gov/dataviewer/
Name: NOAA's Office for Coastal Management (OCM) Data Access Viewer (DAV)
URL Type:
Online Resource
File Resource Format: HTML
Description:

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

Technical Environment

Description:

OS Independent

Data Quality

Horizontal Positional Accuracy:

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 percent of the time (ACCr). The project specification requires horizontal positions to be accurate to 1.0m(RMSE).

Based on a flying altitude of 500 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.008 meters, the RMSEr value for the Leica Chiroptera shallow green and NIR sensor data in all block areas is 0.032 meters, with a ACCr of 0.06 meters at the 95% confidence level.

Block01:The RMSEr value for the Leica Hawkeye deep green sensor data in the block01 area is 0.032 meters, with a ACCr of 0.06 meters at the 95% confidence level based on a flying altitude of 500 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.008 meters. Additionally, based on a flying altitude of 1995 meters, an IMU error of 0.001 decimal degrees, and a GNSS positional error of 0.019 meters, the RMSEr value for the Riegl 1560i NIR sensor data in the block01 area is 0.065 meters, with a ACCr of 0.06 meters at the 95% confidence level.

Block02: The RMSEr value for the Leica Hawkeye deep green sensor data in the block02 area is 0.032 meters, with a ACCr of 0.06 meters at the 95% confidence level based on a flying altitude of 500 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.008 meters. Additionally, based on a flying altitude of 1995 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.019 meters, the RMSEr value for the Riegl 1560i NIR sensor data in the block02 area is 0.126 meters, with a ACCr of 0.06 meters at the 95% confidence level.

Block03: The RMSEr value for the Leica Hawkeye deep green sensor data in the block03 area is 0.032 meters, with a ACCr of 0.06 meters at the 95% confidence level based on a flying altitude of 500 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.008 meters. Additionally, based on a flying altitude of 1995 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.019 meters, the RMSEr value for the Riegl 1560i NIR sensor data in the block03 area is 0.126 meters, with a ACCr of 0.22 meters at the 95% confidence level.

Block04: The RMSEr value for the Leica Hawkeye deep green sensor data in the block4 area is 0.032 meters, with a ACCr of 0.06 meters at the 95% confidence level based on a flying altitude of 500 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.008 meters. Additionally, based on a flying altitude of 1995 meters, an IMU error of 0.002 decimal degrees, and a GNSS positional error of 0.019 meters, the RMSEr value for the Riegl 1560i NIR sensor data in the block04 area is 0.126 meters, with a ACCr of 0.22 meters at the 95% confidence level.

Vertical Positional Accuracy:

Absolute accuracy was assessed using both Non-Vegetated Vertical Accuracy (NVA) and Vegetated Vertical Accuracy (VVA) survey methods. Survey checkpoints were evenly distributed as feasible throughout the project area. NVA compares known ground check point data that were withheld from the calibration and post-processing of the lidar point cloud to the derived gridded bare earth DEM. NVA is a measure of the accuracy of lidar point data in open areas with level slope (less than 20 degrees) where the lidar system has a high probability of measuring the ground surface and is evaluated at the 95% confidence interval (1.96*RMSE). Project specifications require NVA meet 0.196 m accuracy at the 95% confidence interval. Ground check points located in land cover categories other than bare earth or urban were used to compute the Vegetated Vertical Accuracy (VVA). Please refer to the NOAA Southeast AK Topobathymetric Lidar final data report for final accuracies, available upon request.

The block01 area dataset Non-Vegetated Vertical Accuracy tested 0.053 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 9 ground check points, based on RMSEz (0.027 m) x 1.9600. The block01 dataset Vegetated Vertical Accuracy tested 0.200 m vertical accuracy at the 95th percentile against the derived bare earth DEM using 3 landclass points.

The Block02 area dataset Non-Vegetated Vertical Accuracy tested 0.045 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 16 ground check points, based on RMSEz (0.023 m) x 1.9600. The block02 dataset Vegetated Vertical Accuracy tested 0.160 m vertical accuracy at the 95th percentile against the derived bare earth DEM using 12 landclass points.

The Block03 area dataset Non-Vegetated Vertical Accuracy tested 0.106 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 19 ground check points, based on RMSEz (0.054 m) x 1.9600. The block03 dataset Vegetated Vertical Accuracy tested 0.327 m vertical accuracy at the 95th percentile against the derived bare earth DEM using 11 landclass points.

The Block04 area dataset Non-Vegetated Vertical Accuracy tested 0.140 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 9 ground check points, based on RMSEz (0.072 m) x 1.9600. The block04 dataset Vegetated Vertical Accuracy tested 0.509 m vertical accuracy at the 95th percentile against the derived bare earth DEM using 4 landclass points.

Completeness Report:

Data covers the project boundary.

Conceptual Consistency:

Not applicable

Data Management

Have Resources for Management of these Data Been Identified?: Yes
Approximate Percentage of Budget for these Data Devoted to Data Management: Unknown
Do these Data Comply with the Data Access Directive?: Yes
Actual or Planned Long-Term Data Archive Location: NCEI-CO
How Will the Data Be Protected from Accidental or Malicious Modification or Deletion Prior to Receipt by the Archive?:

Data is backed up to tape and to cloud storage.

Lineage

Sources

Acquisition and Processing

CC ID: 1299301
Contact Role Type: Originator
Contact Type: Organization
Contact Name: NV5

Process Steps

Process Step 1

CC ID: 1299302
Description:

Data for the block areas were acquired by NV5 Geospatial (NV5) using Leica Hawkeye 4X and Riegl VQ-1560i topobathymetric lidar systems. All derived LAS data is referenced to:

Horizontal Datum-NAD83(2011) epoch: 2010.00

Projection-UTM Zone 9N

Horizontal Units-meters

Vertical Datum-GRS80 Ellipsoid

Vertical Units-meters

NOAA provided NV5 Geospatial with a bathymetric boundary and a topographic boundary for the NOAA Southeast AK Topobathymetric Lidar project. Two separate acquisition plans were made; one for the bathymetric boundary and one for the topographic lidar boundary. The bathymetric areas for Block01 and Block02 were acquired using a Leica Hawkeye 4X topobathymetric sensor while Block03 and Block04 were acquired using a Leica Chiroptera Hawkeye 4X topobathymetric sensor. The topographic area in Block01 and Block02 was acquired using a Riegl 1560i NIR sensor while Block03 and Block04 was acquired using a Riegl VQ-1560ii NIR sensor. The data were integrated and calibrated together into a singular dataset after the initial extractions. A cutline was drawn through the project area to prioritize the bathymetric data and to produce the smoothest and most cohesive integrated dataset. A more detailed description of data processing is outlined below.

The collected lidar data were immediately processed in the field by NV5 to a level that will allow QA\QC measures to determine if the sensor is functioning properly and assess the coverage of submerged topography. An initial SBET was created using Waypoint Inertial Explorer 8.90, and the raw data were extracted into geo-referenced LAS files using Lidar Survey Studio 3.0 with pre-calculated scanner misalignment angles determined through a boresight protocol. These files were inspected for errors and then passed through an automated workflow, producing rasters to develop an initial assessment of bathymetric coverage. NV5 reviewed all acquired flight lines to ensure complete coverage and positional accuracy of the laser points. These rasters were also used to create an initial product in Quick Look Coverage Maps. These Quick Look files are not fully processed data or final products but provide rapid assessment of approximate coverage and depth penetration.

Process Date/Time: 2022-06-23 00:00:00
Process Contact: NGS Communications and Outreach Branch
Phone (Voice): (301) 713-3242
Email Address: ngs.infocenter@noaa.gov

Process Step 2

CC ID: 1299303
Description:

NV5 resolved kinematic corrections for aircraft position data using aircraft GNSS and Applanix's proprietary PP-RTX solution. When PP-RTX was not used NV5 conducted static Global Navigation Satellite System (GNSS) ground surveys (1 Hz recording frequency) using base stations over known monument locations during flights. After the airborne survey, static GPS data were triangulated with nearby Continuously Operating Reference Stations (CORS) using the Online Positioning User Service (OPUS) for precise positioning. Multiple independent sessions over the same base station were performed to confirm antenna height measurements and to refine position accuracy.

This data was used to correct the continuous on board measurements of the aircraft position recorded throughout the flight. A final smoothed best estimate trajectory (SBET) was developed that blends post-processed aircraft position with attitude data. Using the SBETs, sensor head position and attitude were then calculated throughout the survey. Trimble Business Center v.3.90, Blue Marble Geographic Calculator 2019, and PosPac MMS 8.3 SP3 were used for these processes.

Following final SBET creation for the Leica Chiroptera 4X and Hawkeye systems, NV5 used Leica Lidar Survey Studio (LSS) to calculate laser point positioning by associating SBET positions to each laser point return time, scan angle, and intensity. Leica LSS was used to derive a synthetic water surface to create a water surface model. Light travels at different speeds in air versus water and its direction of travel or angle is changed or refracted when entering the water column. The refraction tool corrects for this difference by adjusting the depth (distance traveled) and horizontal positioning (change of angle/direction) of the lidar data. All lidar data below water surface models were classified as water column to correct for refraction. Using raster-based QC methods, the output data is verified to ensure the refraction tool functioned properly.

In addition, following final SBET creation for the Reigl VQ1560i sensor data, NV5 used RiProcess 1.8.5 to calculate laser point positioning by associating SBET positions to each laser point return time, scan angle, and intensity. Terra 19 and LasTools were used to classify water surface and create a water surface model. They are created for single swaths to ensure temporal differences and wave or water surface height variations between flight lines do not impact the refraction of the bathymetric data. These models are used in NV5's LasMonkey refraction tool to determine the accurate positioning of bathymetric points. Using raster-based QC methods, the output data is verified to ensure the refraction tool functioned properly.

Once all data was refracted by flight line data was exported to LAS 1.4 format and combined into 500 m x 500 m tiles. Data were then further calibrated using TerraMatch. NV5 used custom algorithms in TerraScan to classify the initial ground/submerged topography surface points. Relative accuracy of overlapping swaths was compared and verified through the use Delta-Z (DZ) orthos created using NV5's Las Product Creator. Absolute vertical accuracy of the calibrated data was assessed using ground survey data and complete coverage was again verified.

Process Date/Time: 2022-06-23 00:00:00
Process Contact: National Geodetic Survey (NGS)

Process Step 3

CC ID: 1299304
Description:

Post automated classification NV5 then performed manual editing to review all classification and improve the final topobathymetric surface. NV5's LasMonkey was used to update LAS header information, including all projection and coordinate reference system information. The final lidar data are in LAS format 1.4 and point data record format 6.

The final classification scheme is as follows:

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

Process Date/Time: 2022-06-23 00:00:00

Process Step 4

CC ID: 1299305
Description:

NV5 transformed the final lidar data from ellipsoid heights to orthometric heights referenced to NAVD88, Geoid 12b to create the final topobathymetric void clipped DEMs. The topobathymetric bare earth DEMs were output at 1 meter resolution in GeoTIFF format into 5000 m x 5000 m tiles. The NOAA Southeast AK Option 1 Award Topobathymetric Lidar rasters are clipped to the combinded topographic and bathymetric extents of the project boundary and named according to project specifications.

A bathymetric void shapefile was created to indicate areas where there was a lack of bathymetric returns. This shape was created by triangulating bathymetric bottom points with an edge length maximum of 4.56m to identify all areas greater then 9 square meters without bathymetric returns. This shapefile was used to clip and exclude interpolated elevation data from these areas in the bathymetric void clipped topobathymetric bare earth model.

Process Date/Time: 2022-06-23 00:00:00
Process Contact: National Geodetic Survey (NGS)

Catalog Details

Catalog Item ID: 69901
GUID: gov.noaa.nmfs.inport:69901
Metadata Record Created By: Maryellen Sault
Metadata Record Created: 2023-05-12 14:49+0000
Metadata Record Last Modified By: Kirk Waters
Metadata Record Last Modified: 2024-01-10 19:30+0000
Metadata Record Published: 2024-01-10
Owner Org: NGS
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2022-03-16
Metadata Review Frequency: 3 Years
Metadata Next Review Date: 2025-03-16