Short Citation:
National Geodetic Survey, 2021: 2014 NOAA NGS Topobathy Lidar: Post Sandy, Rhode Island, https://www.fisheries.noaa.gov/inport/item/48214.

Item Identification

Title: 2014 NOAA NGS Topobathy Lidar: Post Sandy, Rhode Island
Short Name: ri2014_ngs_post_sandy_m4976_metadata
Status: Completed
Publication Date: 2015-12-20
Abstract:

These data were collected by the National Oceanic Atmospheric Administration National Geodetic Survey Remote Sensing Division using a Riegl VQ820G system. The data were acquired from 20140717 - 20140809 in twenty two missions. The missions flown on 20140718, 20140719, 20140720, 20140721, 20140722, 20140723, 20140724, 20140725, 20140731, 20140806, and 20140807 represent the Low Water missions and the missions flown on 20140717, 20140718, 20140719, 20140722, 20140723, 20140725, 20140731, 20140801, 20140807, 20140808, and 20140809 represent the High Water (everything outside of MLLW tidal requirements) missions. The data includes topobathy data in an LAS 1.2 format file classified as unclassified (1), ground (2), topo noise (7), refracted High Water data landward of the MLLW land/water interface (18), bathy noise (22), noise as defined by the sensor (23), refracted sensor noise (24), water column (25), bathymetric bottom or submerged topography (26), water surface (27), International Hydrographic Organization (IHO) S-57 objects (30), and temporal bathy bottom (31) in accordance with project specifications. The original project consisted of approximately 100 square miles along the Atlantic Coast of Rhode Island. The full project including buffered area and all flightline coverage is approximately 205 square miles. This dataset represents a contiguous area covering 2104 - 500 m x 500 m lidar tiles.

Original contact information:

Contact Org: National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), National Geodetic Survey (NGS), Remote Sensing Division

Phone: 301-713-2663

Purpose:

This lidar data (and digital camera imagery collected under the same task order) was required by 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.

Notes:

10237

Supplemental Information:

Data include 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 full workflow used for this project is found in the Supplemental Sandy Topobathymetric Processing and QC documentation.

Keywords

Theme Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Science Keywords Earth Science > Land Surface > Topography > Terrain Elevation > Topographical Relief Maps
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
None Bathymetry/Topography
None lidar
None Topography

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords Continent > North America > United States Of America > Rhode Island
None Rhode Island
None United States

Physical Location

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

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: None Planned
Data Presentation Form: las
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: We request that you credit the National Oceanic and Atmospheric Administration (NOAA) when you use these data in a report, publication, or presentation.

Support Roles

Data Steward

CC ID: 625126
Date Effective From: 2015-12-20
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: 625128
Date Effective From: 2015-12-20
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: 625129
Date Effective From: 2015-12-20
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: 625127
Date Effective From: 2015-12-20
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: 1006947
W° Bound: -71.911094
E° Bound: -71.072906
N° Bound: 41.542635
S° Bound: 41.143347

Extent Group 1 / Time Frame 1

CC ID: 1006946
Time Frame Type: Range
Start: 2014-07-17
End: 2014-08-09

Spatial Information

Spatial Representation

Representations Used

Vector: Yes

Access Information

Security Class: Unclassified
Data Access Procedure:

This data can be obtained on-line at the following

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4976;

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: 744014
Download URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4976
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2015-12-20 - Present)
File Name: Customized Download
Description:

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

File Type: Zip

Distribution 2

CC ID: 744015
Download URL: https://coast.noaa.gov/htdata/lidar4_z/geoid18/data/4976
Distributor: NOAA Office for Coastal Management (NOAA/OCM) (2015-12-20 - Present)
File Name: Bulk Download
Description:

Simple download of data files.

File Type: LAZ

URLs

URL 1

CC ID: 744017
URL: https://coast.noaa.gov/dataviewer
Name: Digital Coast Data Access Viewer
URL Type:
Online Resource

URL 2

CC ID: 744018
URL: https://coast.noaa.gov
Name: Office for Coastal Management
URL Type:
Online Resource

Activity Log

Activity Log 1

CC ID: 625144
Activity Date/Time: 2017-03-20
Description:

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 625143
Activity Date/Time: 2017-11-14
Description:

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Activity Log 3

CC ID: 717957
Activity Date/Time: 2018-02-08
Description:

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 744016
Activity Date/Time: 2018-03-13
Description:

Partial upload to move data access links to Distribution Info.

Technical Environment

Description:

OS Independent

Data Quality

Horizontal Positional Accuracy:

Project specifications require horizontal positions to meet 1.0m RMSE. This elevation data is compiled to meet the 1.0 m RMSE horizontal accuracy specification through rigorous processing of airborne GPS and IMU, use of control, and calibration procedures. For the Rhode Island dataset, horizontal accuracy was tested with 4 checkpoints identifiable in the lidar intensity images resulting in and RMSEr of 0.221 m. The horizontal accuracy of the lidar was tested by Dewberry.

Vertical Positional Accuracy:

The vertical accuracy of the lidar was tested independently by Dewberry. The survey checkpoints were evenly distributed, as much as possible, throughout the project area in three land cover categories: bare earth/open terrain, brush and small trees, and submerged topography. Overall 52 survey checkpoints were used to assess vertical accuracy. The vertical accuracy is tested by comparing survey checkpoints to a triangulated irregular network (TIN) that is created from the lidar points. Checkpoints are always compared to interpolated surfaces created from the lidar point cloud because it is unlikely that a survey checkpoint will be located at the location of a discrete lidar point. Checkpoints in bare earth/open terrain were used to compute the Fundamental Vertical Accuracy (FVA). Project specifications require a FVA of 0.245 m at the 95% confidence level based on RMSEz (0.125 m) x 1.9600. All checkpoints located in all land cover categories other than submerged topography were used to compute the Consolidated Vertical Accuracy (CVA). CVA must meet 0.36 m based on the 95th percentile. Submerged topography points were to be tested separately. Project specifications require submerged topography to meet 0.49 m at the 95% confidence level based on RMSEz (0.25 m) x 1.9600. Using NSSDA and FEMA methodology, vertical accuracy at the 95% confidence level (called Accuracyz) was computed by the formula RMSEz x 1.9600. The Rhode Island dataset tested 0.139 m vertical accuracy at 95% confidence level in open terrain using 25 check points, based on RMSEz (0.070 m) x 1.9600. This independent vertical accuracy testing was conducted by Dewberry. Using NSSDA and FEMA methodology, vertical accuracy at the 95% confidence level for submerged topography was computed by the formula RMSEz x 1.9600. The Rhode Island Lidar dataset tested 0.149 m vertical accuracy at 95% confidence level in submerged topography using 6 checkpoints, based on RMSEz (0.076 m) x 1.9600. This independent vertical accuracy testing was conducted by Dewberry. Using NDEP and ASPRS methodology, consolidated vertical accuracy (CVA) was computed using the 95th percentile method. The Rhode Island Lidar dataset tested 0.244 m consolidated vertical accuracy at 95th percentile in all land cover categories excluding submerged topography (46 check points). This independent vertical accuracy testing was conducted by Dewberry. Using NDEP and ASPRS methodology, supplemental vertical accuracy (SVA) was computed using the 95th percentile method. The Rhode Island dataset tested 0.291 m supplemental vertical accuracy at 95th percentile in the brushlands and trees land cover category. This independent vertical accuracy testing was conducted by Dewberry.

Completeness Report:

Original data extents include 2,104 tiles (500m x 500m tiles). 2,096 tiles were kept for distribution through the Digital Coast as they only included classes which were removed (noise classes).

Conceptual Consistency:

Not applicable

Lineage

Sources

Lidar

CC ID: 1006941

Process Steps

Process Step 1

CC ID: 1006942
Description:

Data for the NOAA Post Hurricane Sandy Topobathymetric lidar Mapping for Shoreline Mapping project was acquired by Quantum Spatial (QS) using a Riegl VQ-820G Topobathy lidar system. All delivered lidar data is referenced to:

Horizontal Datum-NAD83 (2011) epoch: 2010

Projection-UTM Zone 19

Horizontal Units-meters

Vertical Datum-NAD83 (2011) epoch: 2010 (ellipsoid heights)

Vertical Units-meters

This dataset encompasses 2104 500m x 500m tiles in Rhode Island. Green lidar data was acquired with the Riegl sensor 9999609 and NIR lidar data (for water surface model creation that is used during refraction of the green bathymetric data) was acquired with the Leica ALS 50-II sensor 94.

QS reviewed all acquired flight lines to ensure complete coverage and positional accuracy of the laser points. To correct the continuous onboard measurements of the aircraft position recorded throughout the missions, QS concurrently conducted multiple static Global Navigation Satellite System (GNSS) ground surveys (1 Hz recording frequency) over each monument. 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. QS then resolved kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data. A 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.3.10, Blue Marble Geographic Calculator 2013, and PosPac MMS 6.2 SP2 are used for these processes.

Next, QS used RiProcess 1.6 to calculate laser point positioning of the Riegl VQ-820G 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. Erroneous points are filtered and then automated line-to-line calibrations are performed for system attitude parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift. Calibrations are calculated on matching surfaces within and between each line and results are applied to all points in a flight line. Every flight line is used for relative accuracy calibration. This same process is performed on the NIR data using IPAS TC 3.1/Inertial Explorer 8.5 to generate the SBET and Leica ALSPP 2.75 to apply the SBET to the raw scan range files.

Green data and NIR data are calibrated together using TerraScan, TerraModeler, and TerraMatch. Accuracy of the calibrated data is assessed using ground RTK survey data. All data are then exported to LAS 1.2 format and are ready for processing and editing.

QS also creates an initial product call Quick Look Coverage Maps. These Quick Looks files are not fully processed data or final products. The collected lidar data is immediately processed in the field by QS 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 is created in POSPAC MMS 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 are inspected for sensor malfunctions and then passed through automated classification routines (TerraScan) to develop an initial topo-bathymetric ground model. The ground models are posted to the Sandy project portal where they are further inspected by NOAA to determine adequate coverage of submerged topography for each flight mission of collected lidar data.

Process Date/Time: 2015-07-02 00:00:00

Process Step 2

CC ID: 1006943
Description:

QS verified complete coverage. Relative accuracy of the green swaths compared to overlapping and adjacent green swaths as well as the relative accuracy of green swaths compared to overlapping and adjacent NIR swaths was verified through the use Delta-Z (DZ) orthos created using QS's DZ Ortho creator.

QS used E-Cognition to create 2D breaklines representing land/water interfaces. These 2D breaklines were manually reviewed and adjusted where necessary to ensure all well-defined hydrographic features (at 1:1200-scale) were represented with breaklines. Using TerraScan, all green lidar data within breaklines are classified as water column and a sub-set of these points meeting specific criteria are classified as green water surface points. Using TerraScan, all NIR lidar data within breaklines are classified as water column and a sub-set of these points meeting specific criteria are classified as NIR water surface points.

QS used the green water surface points and NIR water surface points to create water surface models. These models are used in the refraction tool to determine the depth of bathymetric points and 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.

Using the SBET data and the water surface models, all green lidar data classified as water column (data within the breaklines) is refracted using Dewberry's lidar Processor (DLP). 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 travelled) and horizontal position (change of angle/direction) of the green lidar data. Using statistics and limited manual review, the output data is verified to ensure the refraction tool functioned properly.

Once all green data has been refracted by flight lines, all flight lines covering each tile are combined into a single 500 m x 500 m tile. As the various flight lines may include data collected at Mean Lower Low Water (MLLW) and higher water (HW), which includes everything that is outside the range of MLLW, any HW refracted data points landward of the MLLW land/water interface were classified to class 18 to ensure these HW bathymetric points were not used when MLLW exposed ground points exist in those locations.

QS used algorithms in TerraScan to create the initial ground/submerged topography surface. QS then performed manual editing to review and improve the final topobathy surface. Locations of temporal differences were resolved using the Temporal Difference Decision Tree approved by NOAA. Polygons marking the locations of large temporal differences are provided as part of the deliverables.

All lidar data was peer-reviewed. All necessary edits were applied to the dataset. QS'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 final classification scheme is as follows:

1-Unclassified

2-Ground

7-Topo Noise

18-Refracted High Water data landward of the MLLW land/water interface

22-Bathy Noise

23-Sensor Noise (as defined by the sensor using Riegl's noise classifier)

24-Refracted Sensor Noise

25-Water Column

26-Bathymetric Bottom or Submerged Topography

27-Water Surface

30-International Hydrographic Organization (IHO) S-57 objects

31-Temporal Bathymetric Bottom

QS then produced a final set of DZ orthos using the final ground (2) and submerged topography (26) classes.

All data is then verified by an Independent QC department within QSI. The independent QC is performed by separate analysts who do not perform manual classification or editing. The independent QC involves quantitative and qualitative reviews.

Process Date/Time: 2015-07-02 00:00:00

Process Step 3

CC ID: 1006944
Description:

Lidar data were received from NOAA NGS by NOAA OCM in LAS 1.2 format. Noise classes were dropped from the dataset (classes 7,18,22,23,24). Duplicate points were removed on a tile by tile basis using lasduplicate. Data were transformed from UTM zone 19 to geographic coordinates. Data points below -55 meters (approximately 25 meters below sea level) were considered noise and removed. The files were compressed to LAZ format with laszip and ingested into the Digital Coast Data Access Viewer system for distribution.

Process Date/Time: 2015-12-01 00:00:00
Process Contact: Office for Coastal Management (OCM)

Catalog Details

Catalog Item ID: 48214
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-14 14:20+0000
Metadata Record Last Modified By: Kirk Waters
Metadata Record Last Modified: 2021-01-20 16:32+0000
Metadata Record Published: 2021-01-20
Owner Org: NGS
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Next Review Date: 2022-01-21