OPR-F324-FH-24 Approaches to Wilmington North Carolina H13752 28 NM Southeast of Carolina Beach Inlet -0400 2024-05-27 2024-06-25 DOC/NOAA/NOS/OCS -- Office of Coast Survey HSD.Chief@noaa.gov NOAA Ship Ferdinand Hassler (S250) CC0-1.0 (NOAA Field Units) CC0-1.0 https://creativecommons.org/publicdomain/zero/1.0/ https://creativecommons.org/publicdomain/zero/1.0/legalcode These data were produced by NOAA and are in the public domain within the United States. NOAA waives any potential copyright and related rights in these data worldwide through the Creative Commons Zero 1.0 Universal Public Domain Dedication (CC0). H13752_MB_1m_MLLW_1of1 Projected UTM 18 North American Datum 1983 (2011) Mean Lower Low Water found by multi beam Yes Yes 2.0m (General 1) 10% (General 1) Yes Yes No 1m (Exceptional) N/A 0.15m (Exceptional) 0.75% (Exceptional/Critical) S250 NOAA Ship Ferdinand R. Hassler Positioning and Attitude System Applanix POS MV 320 v5 POS MV V5 5807 2024-03-21 Multibeam Kongsberg Maritime EM 2040 Dual-Dual 40144 200-400kHz 2024-03-21 2024-03-25 Sound Speed System Teledyne RESON SVP 70 N/A 0217026 N/A 2023-06-19 2023-06-19 Sound Speed System Teledyne RESON SVP 70 N/A 3722084 N/A 2023-08-15 2023-08-15 Conductivity, Temperature, and Depth Sensor AML Oceanographic MVP200 MVP-X2 9196 N/A 2023-06-29 2024-03-13 Crosslines were collected, processed, and compared to mainscheme in accordance with Section 5.9 of the 2024 HSSD. To evaluate the crosslines, a 1m Single Resolution (SR) Combined Uncertainty and Bathymetry Estimator (CUBE) surface using strictly mainscheme data and a 1m SR CUBE surface of strictly crossline data were created. From these two surfaces, a 1m difference surface (mainscheme - crosslines = difference surface) was generated using the Compare Grids tool in Pydro. Pydro is a suite of software maintained by NOAA's Hydrographic Systems and Technology Branch(HSTB), which contains various tools that aid in the analysis and quality control of hydrographic data. The results of this comparison indicate that 99.99% of grid-node comparisons between the two surfaces are within the Fraction of Allowable Error for depth/height, exceeding the specification of 95% stipulated by NOAA's 2024 Hydrographic Surveys Specifications and Deliverables (HSSD). The mean difference between these surfaces is -0.03m , with a standard deviation of 0.10m, verifying the consistency of the data. H13752 Crossline Comparison Statistics file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_MLLW-1m_MS-H13752_MB_MLLW-1m_XL_depth_delta_2024.png H13752 Crossline Node Depth vs Allowable Error file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_MLLW-1m_MS-H13752_MB_MLLW-1m_XL_fracAllowErr_vsDepth_General_1.png Ferdinand R. Hassler's primary bathymetric data review and quality control tool is the CARIS CUBE surface. The CUBE algorithm generates a surface consisting of multiple hypotheses that represent the possible depths at any given position. The CUBE surface is a grid of estimation nodes where depth values are computed based on the horizontal and vertical uncertainty of each contributing sounding. Any individual sounding’s Total Propagated Uncertainty (TPU) is derived from the assumed uncertainty in the echosounder measurement itself, as well as the contributing correctors from sound speed, water levels, position, and attitude. Uncertainty values for tide and sound speed must be entered for each vessel during TPU computation. Ferdinand R. Hassler is currently using the following uncertainty values: -GPS tide uncertainty is unique to the separation model in use and is supplied by the project manager. -Measured sound speed uncertainty was set to a value of 2 m/s as recommended by the NOAA Field Procedures Manual when a minimum of 1 cast is taken every 4 hours. -Surface sound speed value is dependent on the manufacturer specifications of the unit utilized to measure surface SV values for refraction corrections to flat-faced transducers. A value of 0.5 m/s is used for surface sound speed uncertainty. All other error estimates are read from the Hydrographic Vessel File (HVF). The HVF contains all offsets and system biases for the survey vessel and its systems, as well as error estimates for latency, sensor offset measurements, attitude and navigation measurements, and draft measurements. The HVF also specifies which type of sonar system the vessel is using. In addition to the usual a priori estimates of uncertainty, some real-time and post-processed uncertainty sources were incorporated into the depth estimates. Real-time uncertainties from the Kongsberg EM2040 dual-dual were recorded and applied in post-processing. Applanix TrueHeave files are recorded, which include an estimate of the heave uncertainty, and are applied during post processing. Uncertainties associated with vessel roll, pitch, gyro, and navigation are applied in CARIS HIPS and SIPS via a Smoothed Best Estimate of Trajectory (SBET) and RMS files generated in Applanix POSPac. Statistical analysis of grid layers was conducted to assess the quality of the bathymetry. The "GridQA" program contained within Pydro's QC Tools 4 was used to assess grid density, resolution, and uncertainty against allowable standards specified in the 2024 HSSD. This survey was assigned quality metrics of General 1 and the delivered grids exceed the specified standards. The uncertainty metrics reported in the Metadata section of this report reflect the highest Quality Metric that was achieved for the survey (Exceptional). The CUBE surface child layers: uncertainty, standard deviation, hypothesis count, and node standard deviation were used to help focus directed editing to soundings that were negatively affecting the BASE surface. Another method to check the quality of sounding data prior to submission is the Pydro QC Tools 4 “Flier Finder.” This software scans the CUBE surface for potential anomalous grid data. Lowering the flier height value increases the sensitivity of Flier Finder, resulting in more nodes being flagged. Fliers are then exported as .000 S-57 files that can be imported into CARIS HIPS and SIPS to aid in further cleaning. If desired, the user can set a new tolerance (“Flier Height”) and rerun Flier Finder. 8 fliers remain on H13752, which are false fliers located along true seafloor features. On occasion, the resolution of the CUBE surface may not be sufficient to capture the shoalest point of a feature. In less than 20m of water, a feature is considered inadequately captured by the CUBE surface when the most probable accurate sounding is shoaler than the CUBE surface by greater than one half the allowable OCS Quality Metrics for Uncertainty. In greater than 20m of water, this allowable error is expanded to the full OCS Quality Metric at that depth. Although missed shoal points may occur on irregular shoals or rock pinnacles, man-made features such as piles and wrecks are of particular concern. These features have very slender high points that extend far above the surrounding seafloor as well as the CUBE surface. To ensure that these features are properly represented, the shoalest point is flagged “designated” in CARIS. During the “finalization” process, the CUBE surface is forced to honor all soundings which have been flagged “designated.” In the case of a survey where the high points of many features (i.e. a boulder field) are not being captured by the CUBE surface, the hydrographer may decide to produce higher resolution CUBE surfaces to ensure that these features are being honored. 0 designated soundings exist in H13752. Most holidays are identified and addressed while in the field collecting mainscheme. During night processing, Pydro QC Tools' "Holiday Finder" is used to detect holidays not addressed in the field. This tool scans the grid, and any empty nodes surrounded by populated nodes are identified. In the event any holidays are found, small polygons are made in HIPS to direct data acquisition to fill them in. The ship then returns to the sheet an acquires these identified holidays. 0 holidays remain in H13752. There are no factors that affect the survey's adequacy and accuracy. This entire survey is adequate to supersede previous data in the area. N/A N/A To evaluate the junction between H13752 and the adjacent survey, the H13752 1m SR finalized CUBE surface was compared to the finest resolution grid from the adjacent survey using the Pydro Compare Grids tool. This generates a difference surface (H13752 - Junction Surface = Difference Surface) and associated statistics. Survey H13752 junctions with prior survey H13751. A comparison between the final 1m SR CUBE surface of survey H13752 and the final 1m SR surface of survey H13751 was completed. The mean difference between the surfaces was -0.03m, with a standard deviation of 0.09m. The results indicate that 100% of grid-nodes are within the Fraction of Allowable Error standards for depth/height, exceeding the specification of 95% stipulated by the 2024 HSSD. H13752 to H13751 Junction Comparison Statistics file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_1m_MLLW_1of1_Final-H13751_MB_1m_MLLW_Final_depth_delta_2024.png H13752 to H13751 Junction Fraction of Allowable Error Statistics file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_1m_MLLW_1of1_Final-H13751_MB_1m_MLLW_Final_fracAllowErr_vsDepth_General_1.png Relative The EM2040 Dual-Dual system was cross calibrated between heads (essentially a vessel-to-vessel comparison) using QPS' FMGT program to assess intensity differences at each depth mode for 200 and 300 kHz. The resulting values are placed in the backscatter projects during processing to remove any sonar head dependent biases. The EM2040s have the dynamic range to accommodate the relatively homogeneous survey area. On H13752, the frequency was held constant at 300 kHz while the system automatically controlled pulse type. No special techniques were used outside of normal considerations for quality data acquisition for a bathymetric survey. Sound speed profiles were acquired at a minimum of once every 4 hours in order to apply appropriate absorption coefficients during acquisition. Backscatter data was paired with cleaned HDCS data in QPS' FMGT program further reducing any potential environmental effects. Please refer to Section 4.3.2.1.2 Acoustic Backscatter Imagery of the Field Procedures Manual for the backscatter post processing workflow. Backscatter data was processed daily as a part of night processing allowing the quality to be evaluated and potential bottom sample locations to be evaluated. The data was paired to HDCS data after the bathymetric data was cleaned. Total Propagated Uncertainty (TPU) values for H13752 were derived from a combination of fixed values for equipment and vessel characteristics, as well as field assigned values for sound speed uncertainties. The uncertainty for the VDatum model was provided to the field by the project manager. In addition to the usual a priori estimates of uncertainty, some real time and post processed uncertainty sources were also incorporated into the depth estimates of the survey. Real-time uncertainties from the Kongsberg MBES sonars were incorporated and applied during post processing. Uncertainties associated with vessel roll, pitch, gyro, navigation, and heave were applied during post-processing. All of the aforementioned uncertainties were applied in CARIS HIPS/ SIPS. H13752 is an ellipsoidally referenced survey (ERS) and the tidal component was accomplished with a VDATUM separation model. There are two places in CARIS where the user directly defines uncertainty values to calculate TPU values, in the HVF and during the application of SV and GPS model values during the TPU computation portion of the georeferencing process. TPU values for all motion, navigation position and timing values are taken directly from Appendix IV (Uncertainty values for use in CARIS with vessels equipped WITH an attitude sensor) of the FPM. All timing values were set to 0.001 seconds as outlined for setups with Ethernet connections and precise timing. All offset values were chosen to be 0.02 meters based on the accuracy provided by professional surveys. Reference the vessel HVF for specific uncertainty values used for data processing for H13752. The bathymetric surface of survey H13752 exceeds uncertainty standards stipulated in the 2024 HSSD. The Uncertainty Standards plots depicted here were generated using the "Grid QA" tool in the Pydro QC Tools 4 suite. The results illustrate that over 99.5% of nodes in the H13752 MBES surface comply with NOAA General 1, Critical, and Exceptional quality metrics for uncertainty. H13752 Uncertainty Statistics, General 1 file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_1m_MLLW_1of1_Final.QAv7.tvu_qc.gn1.png H13752 Uncertainty Statistics, Critical file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_1m_MLLW_1of1_Final.QAv7.tvu_qc.cri.png H13752 Uncertainty Statistics, Exceptional file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/H13752_MB_1m_MLLW_1of1_Final.QAv7.tvu_qc.exc.png Bathymetric grids are evaluated for systematic and random errors using the child layers in CARIS including uncertainty, node standard deviation, and hypothesis count, among others. These layers highlight areas of potentially erroneous data for the hydrographer to evaluate. In addition, Flier Finder and Grid QA in Pydro's QC Tools 4 aid in the direct editing of the grids. A data log is used to ensure that all correctors were properly applied to the multibeam lines. Any errors encountered were investigated and corrected if possible. Anomalous soundings that could not be corrected were rejected from the data set and any data gaps were reacquired. Sound Velocity Issues: Some multibeam data on H13752 contains some evident outer beam spreading visible primarily as "smilies/ frowns" in the data subset. This is likely caused by sound speed variations in the area that were not evident in the SIS surface sound speed comparison and not captured by a Moving Vessel Profiler (MVP) cast. The most probable cause is dynamic currents in the area. In areas where the beam spreading was obvious, rather than a true seafloor feature, the spurious soundings were rejected and surfaces recomputed. After cleaning, these areas meet or exceed the uncertainty requirements for a Exceptional survey. Outer Beam Spreading Line 0041 file:///T:/AHB_Archive/H13752/Metadata/Reports/Images/Outer%20Beam%20Spreading%20H13752.PNG Clusters of ancient paleochannels had been found in previous sheets assigned for this project, and were also found on the Southeast region of H13752. No modifications were made to the project instructions for H13752. Final Survey Outline 2024-07-05 NCEI Sound Speed Data 2024-07-05 Trained Marine Mammal Observers list 2024-07-05 Coast Pilot Report 2024-07-03 As Chief of Party, field operations for this hydrographic survey were conducted under my direct supervision, with frequent personal checks of progress and adequacy. I have reviewed and approved all data and metadata.The survey meets or exceeds requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives. The survey is complete and no additional work is required with the exception of any deficiencies noted in the Report of Survey. CDR William G. Winner, NOAA Chief of Party