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Short Citation:
Office for Coastal Management, 2023: 2014 NOAA Post-Sandy Topobathymetric Lidar: Void DEMs Rhode Island, https://www.fisheries.noaa.gov/inport/item/48366.

Item Identification

Title: 2014 NOAA Post-Sandy Topobathymetric Lidar: Void DEMs Rhode Island
Short Name: 2014_NOAA_Rhode_Island_DEM_m4977_metadata
Status: Completed
Publication Date: 2015-12-20
Abstract:

These lidar 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 with points classified by target type (e.g. ground, water, etc). 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. The final classified lidar data were then used to create topobathymetric DEMs in IMG format with 1m pixel size using ground points. This dataset represents a contiguous area covering 2104 - 500 m x 500 m lidar tiles. This data referenced by the online linkage is the Void DEM data referenced in the processing steps. The void areas have not been interpolated. While Sandy was considered an extra-tropical storm when it struck, the word hurricane is in this sentence for search purposes.

Original contact information:

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

Title: Chief, 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:

11386

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. Classes 2 (ground) and 26 (submerged topography) were used to create the final DEMs. 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 > COASTAL PROCESSES > COASTAL ELEVATION
UNCONTROLLED
ISO 19115 Topic Category elevation
None Bathymetry/Topography
None DEM
None LiDAR
None Topography

Temporal Keywords

Thesaurus Keyword
UNCONTROLLED
None 20140717
None 20140718
None 20140719
None 20140720
None 20140721
None 20140722
None 20140723
None 20140724
None 20140725
None 20140731
None 20140801
None 20140806
None 20140807
None 20140808
None 20140809

Spatial Keywords

Thesaurus Keyword
Global Change Master Directory (GCMD) Location Keywords
CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > RHODE ISLAND
UNCONTROLLED
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: Map (digital)
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: 631880
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: 631882
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: 631883
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: 631881
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: 631886
W° Bound: -71.924765
E° Bound: -71.055575
N° Bound: 41.551073
S° Bound: 41.127647

Extent Group 1 / Time Frame 1

CC ID: 631885
Time Frame Type: Range
Start: 2014-07-17
End: 2014-08-09

Spatial Information

Spatial Representation

Representations Used

Grid: Yes

Access Information

Security Class: Unclassified
Data Access Procedure:

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer;

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: 744387
Download URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=4977
Distributor:
File Name: Customized Download
Description:

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

Distribution 2

CC ID: 744388
Download URL: https://coast.noaa.gov/htdata/raster2/elevation/RhodeIsland_post_Sandy_DEM_2014_4977
Distributor:
File Name: Bulk Download
Description:

Simple download of data files.

URLs

URL 1

CC ID: 744390
URL: https://coast.noaa.gov/dataviewer
URL Type:
Online Resource

Activity Log

Activity Log 1

CC ID: 631913
Activity Date/Time: 2017-03-20
Description:

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 631912
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: 717166
Activity Date/Time: 2018-02-08
Description:

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 744389
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.; Quantitative Value: 0.221 meters, Test that produced the value: The lidar 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 an RMSEr of 0.221 m. The horizontal accuracy of the LiDAR was tested by Dewberry.

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.

Vertical Positional Accuracy:

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.

The vertical accuracy of the DEMs 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 (25), brush and small trees (21), and submerged topography (6). Overall 52 survey checkpoints were used to assess vertical accuracy. The vertical accuracy is tested by comparing survey checkpoints to the final topobathymetric DEM surface. The elevation of the pixel at the xy location of each checkpoint is extracted and compared to the surveyed elevation of each checkpoint.

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 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.; Quantitative Value: 0.133 meters, Test that produced the value: 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 DEM dataset tested 0.133 m vertical accuracy at 95% confidence level in open terrain using 25 check points, based on RMSEz (0.068 m) x 1.9600. This independent vertical accuracy testing was conducted by Dewberry.; Quantitative Value: 0.139 meters, Test that produced the value: 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 DEM dataset tested 0.139 m vertical accuracy at 95% confidence level in submerged topography using 6 checkpoints, based on RMSEz (0.071 m) x 1.9600. This independent vertical accuracy testing was conducted by Dewberry.; Quantitative Value: 0.246 meters, Test that produced the value: Using NDEP and ASPRS methodology, consolidated vertical accuracy (CVA) was computed using the 95th percentile method. The Rhode Island DEM dataset tested 0.246 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.; Quantitative Value: 0.260 meters, Test that produced the value: Using NDEP and ASPRS methodology, supplemental vertical accuracy (SVA) was computed using the 95th percentile method. The Rhode Island DEM dataset tested 0.260 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:

Data covers the 2104 tiles (500m x 500m tiles).

Conceptual Consistency:

Not applicable

Lineage

Process Steps

Process Step 1

CC ID: 631870
Description:

Data for the NOAA Post 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.

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

Process Step 2

CC ID: 631871
Description:

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 called 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 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.

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.

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

Process Step 3

CC ID: 631872
Description:

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 traveled) 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 4

CC ID: 631873
Description:

Dewberry received a copy of the final LiDAR data and transformed the ellipsoid heights into orthometric heights referenced to NAVD88 using Geoid 12A. LiDAR data classified as ground (2) and submerged topography (26) were then converted to ESRI multipoint format. These multipoints were then used to generate a terrain and the terrain was converted to a raster in IMG format with 1 meter pixel resolution. The terrain and output raster was created over the entire project area to reduce edge-matching issues and improve seamlessness. The project raster is clipped to the tile grid and named according to project specifications to result in tiled topobathymetric DEMs.

All DEM deliverables will include tiled interpolated DEMs where no void layer is used and the DEMs represent a continuous surface. All DEM deliverables will also include tiled DEMs that incorporate the use of a void layer.

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.

Void DEM dataset- The void layer was created in Global Mapper where every bathy bottom point was used to create a grid. The distance or threshold that sets how far Global Mapper can interpolate around each bathy bottom point was set as 2. The higher the interpolation threshold, the more bathy bottom points are connected to create a continuous surface in the Global Mapper grid with fewer areas of NoData. The NoData areas in the Global Mapper grids are exported to polygons. Void polygons greater than 9 square meters are imported into Arc 10.1 Geodatabases where they are incorporated into the terrains as erase features. When the terrains are exported to raster, the void polygons used as an erase in the terrain remain as areas of NoData.

A point density layer has been created and provided to NOAA as part of the deliverables. The point density layer is a raster product in IMG format with 1 meter square pixels. The density grid identifies the number of ground and/or bathy bottom points located within each pixel. The pixels in the point density layer align with the pixels in the topobathy DEMs so that the point density layer shows the density of ground/submerged topography points located in each cell that were used to determine elevations for each cell in the topobathy DEMs. Higher density lends itself to higher confidence. The point density layer can be displayed by unique values or classified into desired bins/ranges for analysis over larger areas.

A confidence layer has been created and provided to NOAA as part of the deliverables. The confidence layer is a raster product in IMG format with 1 meter square pixels. The confidence layer provides a standard deviation value for every pixel by calculating the standard deviation of all ground and/or submerged topography LiDAR points that are located within a single pixel. The confidence layer pixels align to the pixels in the topobathy DEMs. The confidence layer can be displayed by unique values or classified into desired bins/ranges for analysis over larger areas.

Process Date/Time: 2015-08-31 00:00:00

Catalog Details

Catalog Item ID: 48366
GUID: gov.noaa.nmfs.inport:48366
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-14 14:43+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2022-08-09 17:11+0000
Metadata Record Published: 2018-03-13
Owner Org: OCM
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2018-03-13
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2019-03-13