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Item Identification
Keywords
Physical Location
Data Set Info
Support Roles
Extents
Spatial Info
Access Info
Distribution Info
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Data Quality
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Catalog Details

Summary

Short Citation
Office for Coastal Management, 2024: 2018 NOAA National Geodetic Survey Topobathy Lidar DEM (interpolated): Potomac River, Chesapeake Bay, https://www.fisheries.noaa.gov/inport/item/56273.
Full Citation Examples

Abstract

These data were collected by Quantum Spatial, Inc. (QSI) for the National Oceanic and Atmospheric Administration (NOAA), National Geodetic Survey (NGS), Remote Sensing Division (RSD), Coastal Mapping Program (CMP) using a Riegl VQ880G system. The Initial Award lidar data were acquired from 20180215 - 20180417 in eighteen missions. The dataset includes topobathy data in a LAS 1.2 format file with the following classification: unclassified (1), ground (2), noise (7), overlap default (19), overlap ground (20), overlap water column (21), water column (25), bathymetric bottom or submerged topography (26), submerged feature (29), submerged aquatic vegetation (30), temporal bathy bottom (31), and unclassified withheld/edge clip (129) in accordance with project specifications. The contracted project consists of approximately 309.125 square miles (197,840 acres) of the states of Virginia and Maryland covering the confluence of the Potomac River and the Chesapeake Bay. To ensure complete coverage and adequate point densities around survey area boundaries, the Area of Interest (AOI) was buffered by 100m. The full Initial Award project area including buffered area is approximately 478.151 square miles (306,017 acres). LAS files were compiled by 500 m x 500 m tiles. The final classified LiDAR data were then transformed to orthometric heights and used to create topobathymetric DEMs in IMG format with 1m pixel resolution.

Distribution Information

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be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions.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

BATHYMETRY, COASTAL ELEVATION, elevation, SEAFLOOR TOPOGRAPHY

Child Items

No Child Items for this record.

Contact Information

Point of Contact
NOAA Office for Coastal Management (NOAA/OCM)
coastal.info@noaa.gov
(843) 740-1202
https://coast.noaa.gov

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

Extents

Geographic Area 1

-76.791568° W, -76.176395° E, 38.332869° N, 37.715495° S

Time Frame 1
2018-02-15 - 2018-04-17

Item Identification

Title: 2018 NOAA National Geodetic Survey Topobathy Lidar DEM (interpolated): Potomac River, Chesapeake Bay
Short Name: VA1803 M8732
Status: Completed
Publication Date: 2019-05
Abstract:

These data were collected by Quantum Spatial, Inc. (QSI) for the National Oceanic and Atmospheric Administration (NOAA), National Geodetic Survey (NGS), Remote Sensing Division (RSD), Coastal Mapping Program (CMP) using a Riegl VQ880G system. The Initial Award lidar data were acquired from 20180215 - 20180417 in eighteen missions. The dataset includes topobathy data in a LAS 1.2 format file with the following classification: unclassified (1), ground (2), noise (7), overlap default (19), overlap ground (20), overlap water column (21), water column (25), bathymetric bottom or submerged topography (26), submerged feature (29), submerged aquatic vegetation (30), temporal bathy bottom (31), and unclassified withheld/edge clip (129) in accordance with project specifications. The contracted project consists of approximately 309.125 square miles (197,840 acres) of the states of Virginia and Maryland covering the confluence of the Potomac River and the Chesapeake Bay. To ensure complete coverage and adequate point densities around survey area boundaries, the Area of Interest (AOI) was buffered by 100m. The full Initial Award project area including buffered area is approximately 478.151 square miles (306,017 acres). LAS files were compiled by 500 m x 500 m tiles. The final classified LiDAR data were then transformed to orthometric heights and used to create topobathymetric DEMs in IMG format with 1m pixel resolution.

Purpose:

This lidar data (and digital camera imagery collected under the same task order) 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 NOAA Chesapeake Bay Initial Award 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. Classes 2 (ground), 26 (submerged topography), and 29 (submerged features) were used to create the final DEMs.

Keywords

Theme Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > OCEANS > BATHYMETRY/SEAFLOOR TOPOGRAPHY > BATHYMETRY
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > OCEANS > BATHYMETRY/SEAFLOOR TOPOGRAPHY > SEAFLOOR TOPOGRAPHY
Global Change Master Directory (GCMD) Science Keywords
EARTH SCIENCE > OCEANS > COASTAL PROCESSES > COASTAL ELEVATION
ISO 19115 Topic Category
elevation

Temporal Keywords

Thesaurus Keyword
UNCONTROLLED
None 20180215
None 20180417

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords
CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > MARYLAND
Global Change Master Directory (GCMD) Location Keywords
CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > VIRGINIA
UNCONTROLLED
Global Change Master Directory (GCMD) Location Keywords Continent > North America > United States of America > Chesapeake Bay

Physical Location

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

Data Set Information

Data Set Scope Code: Data Set
Data Set Type: Elevation
Maintenance Frequency: None Planned
Distribution Liability:

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

Data Set Credit: NOAA National Geodetic Survey (NGS).

Support Roles

Data Steward

CC ID: 839737
Date Effective From: 2019-05
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: 839738
Date Effective From: 2019-05
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: 839739
Date Effective From: 2019-05
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

Point of Contact

CC ID: 839740
Date Effective From: 2019-05
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

Extents

Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1292051
W° Bound: -76.791568
E° Bound: -76.176395
N° Bound: 38.332869
S° Bound: 37.715495

Extent Group 1 / Time Frame 1

CC ID: 1292050
Time Frame Type: Range
Start: 2018-02-15
End: 2018-04-17

Spatial Information

Reference Systems

Reference System 1

CC ID: 1292048

Coordinate Reference System

CRS Type: Projected
EPSG Code: EPSG:6347
EPSG Name: NAD83(2011) / UTM zone 18N
See Full Coordinate Reference System Information

Access Information

Security Class: Unclassified
Data Access Procedure:

Users may access the data from either a custom download or bulk download link.

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: 839741
Start Date: 2019-05
End Date: Present
Download URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=8732
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2019-05 - Present)
Description:

Link to custom download

File Type (Deprecated): ZIP
Compression: Zip

Distribution 2

CC ID: 839743
Start Date: 2019-05
End Date: Present
Download URL: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid12b/8727/supplemental/2018_ngs_topobathy_potomac_river_m8727.kmz
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2019-05 - Present)
Description:

KMZ displays the footprint for this lidar data set.

File Type (Deprecated): KMZ
Distribution Format: KML/KMZ - Keyhole Markup Language
Compression: Zip

Distribution 3

CC ID: 839742
Start Date: 2019-05
End Date: Present
Download URL: https://noaa-nos-coastal-lidar-pds.s3.us-east-1.amazonaws.com/dem/NGS_PotomacRiver_DEM_Interpolated_2018_8732/
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2019-05 - Present)
Description:

Link to bulk LAZ files

File Type (Deprecated): LAZ
Distribution Format: LAS/LAZ - LASer
Compression: Zip

URLs

URL 1

CC ID: 839744
URL: https://coast.noaa.gov/dataregistry
URL Type:
Online Resource
File Resource Format: HTML
Description:

Web page to the Digital Coast for finding coastal data

URL 2

CC ID: 839745
URL: https://coast.noaa.gov
URL Type:
Online Resource
File Resource Format: HTML
Description:

Web page for the NOAA Office for Coastal Management

URL 3

CC ID: 839746
URL: https://coast.noaa.gov/dataviewer
URL Type:
Online Resource
File Resource Format: HTML
Description:

Data Access Viewer for discovering coastal imagery, land cover, and elevation data

Data Quality

Vertical Positional Accuracy:

Using NSSDA and FEMA methodology, the derived DEM non-vegetated vertical accuracy (NVA) at the 95% confidence level (called Accuracyz) was computed by the formula RMSEz x 1.9600. The NOAA Chesapeake Bay Initial Award West 02 and West 03 dataset tested 0.046 m vertical accuracy at 95% confidence level against the derived bare earth DEM in open terrain using 27 ground check points, based on RMSEz (0.024 m) x 1.9600.

Using NDEP and ASPRS methodology, vegetated vertical accuracy (VVA) was computed using the 95th percentile method against the derived bare earth DEM. The NOAA Chesapeake Bay Initial Award West 02 and West 03 dataset tested 0.155 m vegetated vertical accuracy at 95th percentile against the derived bare earth DEM using 17 mixed landclass points.

Using NSSDA and FEMA methodology, bathymetric vertical accuracy at the 95% confidence level for submerged topography was computed by the formula RMSEz x 1.9600. The NOAA Chesapeake Bay Initial Award West 02 and West 03 dataset tested 0.070 m vertical accuracy at 95% confidence level against the classified points cloud using 727 submerged check points, based on RMSEz (0.036 m) x 1.9600. Submerged topography checkpoints usually occur in depths up to 1m.

Quantitation Limits:

The DEMs are derived from the source LiDAR and inherit the accuracy of the source data. The DEMs are created using controlled and tested methods to limit the amount of error introduced during DEM production so that any differences identified between the source LiDAR and final DEMs can be attributed to interpolation differences. DEMs are created by averaging several LiDAR points within each pixel which may result in slightly different elevation values at a given location when compared to the source LAS, which does not average several LiDAR points together but may interpolate (linearly) between two or three points to derive an elevation value.

Absolute accuracy was assessed using both Non-Vegetated Vertical Accuracy (NVA) and Vegetated Vertical Accuracy (VVA) survey methods. Survey checkpoints were evenly distributed throughout the project area as feasible. NVA compares known ground check point data that were withheld from the calibration and post-processing of the LiDAR point cloud to the triangulated surface generated by the unclassified LiDAR point cloud as well as 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). In the Initial Award West 02 and West 03 areas, 27 survey checkpoints were used to assess the non-vegetated vertical accuracy. 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, urban, or submerged topography were used to compute the Vegetated Vertical Accuracy (VVA). QSI assessed four land cover categories: deciduous forest, mixed forest, and tall grass, and shrubland. In the Initial Award West 02 and West 03 areas, 17 survey checkpoints were used to assess the vegetated vertical accuracy. Project specifications require VVA meet 0.36 m based on the 95th percentile tested against the derived bare earth DEM. Submerged topography points were tested separately. In the Initial Award West 02 and West 03 areas, 727 survey checkpoints were used to assess the submerged topography accuracy. Submerged topography checkpoints usually occur in depths up to 1m. Project specifications require submerged topography to meet 0.490 m at the 95% confidence level based on RMSEz x 1.9600.

Lineage

Sources

Lidar

CC ID: 1292044

Process Steps

Process Step 1

CC ID: 1292045
Description:

Data was acquired by Quantum Spatial (QSI) using a Riegl VQ-880G Topobathy LiDAR system. All delivered LiDAR data is referenced to:

Horizontal Datum-NAD83 (2011) epoch: 2010

Projection-UTM Zone 18N

Horizontal Units-meters

Vertical Datum-GRS 80 Ellipsoid

Vertical Units-meters

The dataset encompasses 5,974 500m x 500m tiles covering the states of Virginia and Maryland at the confluence of the Potomac River and the Chesapeake Bay. Green and NIR (for water surface model creation that is used during refraction of the green bathymetric data) LiDAR data were acquired with the Riegl sensor VQ-880G.

QSI reviewed all acquired flight lines to ensure complete coverage and positional accuracy of the laser points. QSI creates an initial product call Quick Look Coverage Maps. These Quick Look files are not fully processed data or final products. The collected LiDAR data is immediately processed in the field by QSI 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 in POSPAC MMS 8.1 and used in RiProcess which applies pre-calibrated angular misalignment corrections of scanner position to extract the raw point cloud into geo-referenced LAS files. These files were inspected for sensor malfunctions and then passed through automated classification routines (TerraScan) to develop a rough topobathymetric ground model for an initial assessment of bathymetric coverage.

To correct the continuous onboard measurements of the aircraft position recorded throughout the missions, QSI concurrently conducted multiple static Global Navigation Satellite System (GNSS) ground surveys (1 Hz recording frequency) over established monuments located in or around the project area. After the airborne survey, the 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 monument were processed to confirm antenna height measurements and to refine position accuracy. QSI then resolved kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data. A final smoothed best estimate trajectory (SBET) was developed that blends post-processed aircraft position with attitude data. Sensor head position and attitude are calculated throughout the survey. The SBET data are used extensively for laser point processing. The software Trimble Business Center v.3.90, Blue Marble Geographic Calculator 2017, and PosPac MMS 8.1 SP3 are used for these processes.

Process Date/Time: 2018-08-31 00:00:00
Process Contact: National Geodetic Survey (NGS)

Process Step 2

CC ID: 1292046
Description:

Next, QSI used RiProcess 1.8.5 to calculate laser point positioning of the Riegl VQ-880G data by associating SBET positions to each laser point return time, scan angle, intensity, etc. A raw laser point cloud is created in Riegl data format and erroneous points are filtered. Within RiProcess the RiHydro tool was used to classify water surface and create a water surface model. QSI used the green water surface points and as needed NIR water surface points to create water surface models. These models are used in the RiHydro refraction tool to determine angle of incidence and ranging time under water. They are created for a single swaths to ensure temporal differences and wave or water surface height variations between flight lines do not impact the refraction correction of the bathymetric data. All lidar data below water surface models were classified as water column and corrected for refraction. The green laser light travels at slower speed in water than air and its direction of travel is changed when entering water. The refraction tool corrects positioning of under water points by adjusting the ranging distance in water and horizontal position change due to the angle of refraction. Using raster-based QC methods, the output data is verified to ensure the refraction tool functioned properly. QSI used their proprietary LASMonkey refraction tool to correct some refraction in back bay/inland pond areas where RiHydro refraction was found to be inadequate.

Once all green data had been refracted by flight line all data was exported to LAS 1.2 format and are combined into 500 m x 500 m tiles. Data was then further calibrated using TerraScan, TerraModeler, and TerraMatch. QSI used custom algorithms in TerraScan to create the initial ground/submerged topography surface. Relative accuracy of the green swaths was compared to overlapping and adjacent swaths and verified through the use Delta-Z (DZ) orthos created using QSI's DZ Ortho creator. Absolute vertical accuracy of the calibrated data was assessed using ground RTK survey data and complete coverage was again verified.

QSI then performed manual editing to review all classification and improve the final topobathy surface. QSI'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 1.2 and point data record format 3.

Once all green data had been refracted by flight line all data was exported to LAS 1.2 format and are combined into 500 m x 500 m tiles. Data was then further calibrated using TerraScan, TerraModeler, and TerraMatch. QSI used custom algorithms in TerraScan to create the initial ground/submerged topography surface. Relative accuracy of the green swaths was compared to overlapping and adjacent swaths and verified through the use Delta-Z (DZ) orthos created using QSI's DZ Ortho creator. Absolute vertical accuracy of the calibrated data was assessed using ground RTK survey data and complete coverage was again verified.

QSI then performed manual editing to review all classification and improve the final topobathy surface. QSI'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 1.2 and point data record format 3.

The classification scheme is as follows:

1-Unclassified

2-Ground

7-Noise

19-Overlap Default

20-Overlap Ground

21-Overlap Water Column

25-Water Column

26-Bathymetric Bottom or Submerged Topography

29-Submerged feature

30-Submerged Aquatic Vegetation*

31-Temporal Bathymetric Bottom

*Class 30 was submerged aquatic vegetation QSI identified within the bathymetric void shapes that precluded bathymetric bottom returns.

Process Date/Time: 2018-08-31 00:00:00

Process Step 3

CC ID: 1292047
Description:

QSI then transformed the ellipsoid heights of the final LiDAR data to into orthometric heights referenced to NAVD88 using Geoid 12B to create the DEMs. The topobathymetric DEM was output at 1 meter resolution in IMG format into 5000 m x 5000 m tiles.

Interpolated DEM dataset-These DEMs represent a continuous surface with all void areas interpolated. No void layer was incorporated into this DEM and there are no areas of No Data, regardless of whether the LiDAR data fully penetrated to the submerged topography.

Process Date/Time: 2018-08-31 00:00:00
Process Contact: National Geodetic Survey (NGS)

Catalog Details

Catalog Item ID: 56273
GUID: gov.noaa.nmfs.inport:56273
Metadata Record Created By: Maryellen Sault
Metadata Record Created: 2019-05-13 13:00+0000
Metadata Record Last Modified By: Kirk Waters
Metadata Record Last Modified: 2024-01-10 19:05+0000
Metadata Record Published: 2024-01-10
Owner Org: OCM
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2022-03-16
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2023-03-16