OPR-Y393-KR-24 Southern Lake Michigan Offshore Chicago and Michigan City Geodynamics H13943 4 3.8 NM East of Wilmette Illinois United States 5000 2024 Nicholas Damm, CH Navigable Area 2024-06-12 2024-08-10 2024-10-18 Multibeam Echo Sounder Multibeam Echo Sounder Backscatter meters UTC Atlantic Hydrographic Branch Any revisions to the Descriptive Report (DR) applied during office processing are shown in red italic text. The DR is maintained as a field unit product, therefore all information and recommendations within this report are considered preliminary unless otherwise noted. The final disposition of survey data is represented in the NOAA nautical chart products. All pertinent records for this survey are archived at the National Centers for Environmental Information (NCEI) and can be retrieved via https://www.ncei.noaa.gov/. Products created during office processing were generated in NAD83 UTM 16N, LWD. All references to other horizontal or vertical datums in this report are applicable to the processed hydrographic data provided by the field unit. CC0-1.0 (NOAA Contractors) CC0-1.0 https://creativecommons.org/publicdomain/zero/1.0/ https://creativecommons.org/publicdomain/zero/1.0/legalcode These data were produced under contract with NOAA and any potential copyright was assigned to NOAA. NOAA waives any potential copyright and related rights in these data worldwide through the Creative Commons Zero 1.0 Universal Public Domain Dedication (CC0). Contractor Geodynamics conducted a hydrographic survey in the assigned area of H13943 located within the sublocality of 3.8 NM East of Wilmette, Southern Lake Michigan. Within H13943, all survey operations were conducted in accordance with the provided Statement of Work (SOW), Hydrographic Survey Project Instructions (PI), and the March 2022 National Ocean Service (NOS) Hydrographic Survey Specifications and Deliverables (HSSD). Any deviations from the aforementioned guidelines have been approved by the National Oceanographic and Atmospheric Administration (NOAA) Hydrographic Survey Division (HSD) Operations (OPS) branch and are documented in the survey correspondences. 42.24391466666667 87.68665366666667 42.04622341666666 87.51464263888889 Data were acquired to the survey limits in accordance with the requirements listed in the PI and the HSSD. It should be noted that as a part of CLIN2 for this project, an additional 51 LNMs were added to the planned project area. This area was selected by Geodynamics and approved by NOAA HSD OPS. The additional LNMs were developed offshore of H13943 (Figure 3). As directed by NOAA HSD OPS, the additional LNMs were added to the overall deliverable package and report for H13943. See DR Appendix II Supplemental records for related correspondence with NOAA HSD OPS. Overview of project survey limits (H13943 shown in blue), overlaid onto Chart US2MI01M file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Survey_Limits.png H13943 survey limits overlaid onto Charts US4IL1YX, US4IL1YY, and US5CHILL file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Survey_Limit.png H13943 extents of additional coverage past survey limits as part of CLIN2 for this project, overlaid onto Charts US4IL1YX, US4IL1YY, and US5CHILL file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Survey_Limit_2.png This project is located in Southern Lake Michigan, northeast of Chicago, Illinois extending to Michigan City, Indiana. The Chicago harbor is the northern entrance to the Mississippi River and has a tremendous amount of local barge traffic moving commodities throughout the year. Much of this 481 SNM survey area has not been surveyed since the late 1940's, forcing many throughout the Lake Michigan community to predict the hazards and depths associated with the area near shore, including tug and barge operators as well as recreational boaters. Conducting a modern bathymetric survey in this area will provide critical data for the updating of NOS nautical charting products and services to increase maritime safety near the Michigan, Indiana, and Illinois shoreline. Survey data from this project is intended to supersede all prior survey data in the common area. The entire survey is adequate to supersede previous data. Survey quality in H13943 meets or exceeds requirements set forth in the HSSD. Survey quality was assessed through visual inspection, the analysis of crosslines, and utilizing QC Tools to assess uncertainty and density. Additionally, junction analyses were conducted between overlapping data collected on this project and existing bathymetric data. For more information on methods and results of the data quality assessments for this survey, refer to section B.2 of this report. All waters in survey area Complete Coverage (HSSD 5.2.2.3) The entirety of H13943 was acquired with complete coverage within the planned survey extents as described in the PI, in accordance with section 5.2.2.3 of the HSSD. As previously mentioned, the additional 51 LNMs added to this project as part of CLIN2 extended the survey coverage of H13943. These additional LNMs were acquired to complete coverage specifications (HSSD 5.2.2.3) and are reported on and included in the final deliverable package for H13943. See DR Appendix II Supplemental records for related correspondence with NOAA HSD OPS. H13943 survey coverage overlaid onto Charts US4IL1YX, US4IL1YY, and US5CHILL file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Survey_Coverage.png R/V Benthos 0.0 348.28 0.0 0.0 0.0 0.0 0.0 69.8 0.0 R/V Substantial 0.0 923.22 0.0 0.0 0.0 0.0 0.0 3.1 0.0 0.0 1271.5 0.0 0.0 0.0 0.0 0.0 72.89 0.0 5.73 10 0 0 0 46.2 2024-08-10 2024-08-11 2024-08-12 2024-08-13 2024-08-14 2024-08-17 2024-09-16 2024-09-17 2024-09-18 2024-09-21 2024-09-25 2024-09-26 2024-09-30 2024-10-02 2024-10-03 2024-10-06 2024-10-08 2024-10-09 2024-10-10 2024-10-13 2024-10-17 2024-10-18 Bottom samples were collected on 10/13/2024, 10/17/2024, and 10/18/2024. It should be noted that several bottom samples were collected after the last day of MBES collection. Therefore, the last day of survey and SORDAT reflects a bottom sample acquisition day and does not have accompanying MBES data for that specific date. See Project Correspondence for more information. Refer to the OPR-Y393-KR-24 Data Acquisition and Processing Report (DAPR) for a complete description of data acquisition and processing systems, survey vessels, quality control procedures and data processing methods. Additional information to supplement sounding and survey data, and any deviations from the DAPR are discussed in the following sections. R/V Benthos 9.14 0.61 R/V Substantial 18.0 2.22 MBES Kongsberg Maritime EM 2040C Positioning and Attitude System Applanix POS MV OceanMaster Sound Speed System AML Oceanographic 3-RT Velocity Probe Sound Speed System AML Oceanographic AML-3 LGR Sound Speed System AML Oceanographic MVP30-350 R/V Benthos and the R/V Substantial utilized a dual-head Kongsberg EM 2040C multibeam system, a POS M/V OceanMaster positioning and attitude system, and AML Oceanographic AML-1 RT surface sound speed units. The R/V Benthos utilized an AML-3 LGR sound speed system for sound speed profiles. The R/V Substantial utilized an AML MVP30-350 sound speed profiling system, with usage of the AML-3 LGR only when MVP equipment issues occurred. Further details on equipment and software used can be found in the DAPR. Multibeam crosslines acquired for H13943 totaled 5.73% of mainscheme acquisition. H13943 crosslines were collected and analyzed in accordance with section 5.2.4.2 of the HSSD. Crosslines were evaluated in CARIS HIPS with a detailed visual inspection followed by a thorough statistical analysis. To conduct the statistical analysis, a 2 m CUBE surface was generated with strictly mainscheme data and another, separate 2 m CUBE surface was generated with only crossline data. The mainscheme and crossline surfaces were analyzed using the Compare Grids tool in Pydro Explorer, which generated a difference surface and associated statistics. In addition to the direct statistics from the surface differencing, the tool assessed the difference surface statistics and computed the proportion of NOS total allowable vertical uncertainty (TVU) consumed by the mainscheme to crossline differences per surface node. The statistical results of the difference comparison show 95% of nodes falling within +/- 0.11 m, with a mean difference of -0.01 m (Figure 5). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. H13943 crossline to mainscheme difference statistics file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MS_2m-H13943_XL_2m_depth_delta.png ERS via VDATUM 0.0 0.045 R/V Benthos 2.00 N/A N/A 0.05 R/V Substantial 2.00 2.00 N/A 0.05 The finalized CUBE surfaces were analyzed using the HydrOffice QC Tools Grid QA tool to assure at least 95% of the surface nodes met TVU specifications. The results of the Grid QA tool determined that all finalized CUBE surfaces meet or exceed the TVU specifications, as shown in Figures 6-8. The multibeam surfaces were finalized with the computed uncertainty, derived from a mix of a priori and real-time uncertainty estimates, assigned as the uncertainty value. It should be noted that the uncertainty associated with the SEP model was applied in CARIS as the GPS Sounding Datum uncertainty, and not as Tide Zoning uncertainty. Additional details related to uncertainty methods may be found in the DAPR. Finalized 1 m CUBE surface TVU statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_1m_LWD_Final.GQv6.tvu_qc.png Finalized 2 m CUBE surface TVU statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD_Final.GQv6.tvu_qc.png Finalized 4 m CUBE surface TVU statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_4m_LWD_Final.GQv6.tvu_qc.png H13943 junctions with H13942 and H13944. H13943 also junctions with previously existing 2020 Geodynamics MBES data, registry numbers H13364 and H13368, as well as the provided 2023 Ocean Surveys Inc MBES data, registry numbers H13814 and H13815. (Figure 9). Please refer to PI and Project Correspondence for further information. Data overlap between H13943 and the adjacent surveys were attained. To conduct junction analyses, similar to section B.2.1 of this report, the Pydro Compare Grids tool was utilized. The inputs for this tool were the surfaces for each individual survey at matching resolutions. In addition to the statistical results of the junction analyses, the resultant difference surfaces were visually inspected and CARIS HIPS Subset Editor was used to examine overlapping data for consistency, agreement between surveys, and confirming data met TVU specifications. Details regarding the results of the comparisons can be found below. Overview of H13943 junction surveys file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Junctions.png H13944 20000 2024 Geodynamics E Please refer to the H13944 Descriptive Report for the junction analysis between H13943 and H13944. H13942 20000 2024 Geodynamics N The statistical results of the difference comparison with the H13942 Finalized 1 m MBES CUBE surface show 95% of nodes falling within +/- 0.04 m, with a mean difference of 0.02 m (Figure 10). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. The statistical results of the difference comparison with the H13942 Finalized 2 m MBES CUBE surface show 95% of nodes falling within +/- 0.11 m, with a mean difference of - 0.00 m (Figure 11). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. The statistical results of the difference comparison with the H13942 Finalized 4 m MBES CUBE surface show 95% of nodes failing within +/- 0.11 m, with a mean difference of 0.01 m (Figure 12). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13943 and H13942 Finalized 1 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_1m_LWD_Final-H13942_MB_1m_LWD_Final_depth_delta.png Junction analysis between H13943 and H13942 Finalized 2 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD_Final-H13942_MB_2m_LWD_Final_depth_delta.png Junction analysis between H13943 and H13942 Finalized 4 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_4m_LWD_Final-H13942_MB_4m_LWD_Final_depth_delta.png H13364 5000 2020 Geodynamics SW The statistical results of the difference comparison with the H13364 Finalized 1 m MBES CUBE surface show 95% of nodes falling within +/- 0.16 m, with a mean difference of 0.05 m (Figure 13). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13943 and H13364 Finalized 1 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_1m_LWD_Final-H13364_MB_1m_LWD_6of6_Final_depth_delta.png H13368 20000 2020 Geodynamics S The statistical results of the difference comparison with the H13368 Finalized 1 m MBES CUBE surface show 95% of nodes falling within +/- 0.17 m, with a mean difference of 0.09 m (Figure 14). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. The statistical results of the difference comparison with the H13368 Finalized 2 m MBES CUBE surface show 95% of nodes falling within +/- 0.20 m, with a mean difference of 0.11 m (Figure 15). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13943 and H13368 Finalized 1 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_1m_LWD_Final-H13368_1m_CUBE_depth_delta.png Junction analysis between H13943 and H13368 Finalized 2 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD_Final-H13368_MB_2m_LWD_depth_delta.png H13814 5000 2023 Ocean Surveys Inc NW The statistical results of the difference comparison with the H13814 Finalized 2 m MBES CUBE surface show 95% of nodes falling within +/- 0.10 m, with a mean difference of 0.03 m (Figure 16). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13943 and H13814 Finalized 2 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD_Final-H13814_MB_2m_LWD_Combined_depth_delta.png H13815 5000 2023 Ocean Surveys Inc W The statistical results of the difference comparison with the H13815 2 m MBES CUBE surface show 95% of nodes falling within +/- 0.10 m, with a mean difference of - 0.03 m (Figure 17). Additionally, greater than 95% of the difference surface nodes meet or exceed TVU specifications, as described in section 5.1.3 of the HSSD. Junction analysis between H13943 and H13815 2 m MBES CUBE surface file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD-H13815_MB_2m_LWD_Combined_depth_delta.png Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR. Multibeam Echosounder Ping Drops On rare occasions, it was observed that the R/V Benthos multibeam echosounder would experience a "ping drop" issue which resulted in unexpectedly missing ping records, which were not observed by survey personnel at the time of acquisition. These ping drops were observed in the multibeam data from R/V Benthos on 10/08/2024 and 10/10/2024. An example of these ping drops is shown below in Figure 18. Ping drops resulting in data gaps were recovered and no holidays resulting from these intermittent issues remain in the final delivered surfaces. Additionally, in the final delivered surfaces, density requirements were achieved for the finalized CUBE surfaces (see Section B.2.10 below). For further information on echo sounding equipment, please reference the DAPR. Example of MBES ping drops observed from R/V Benthos on 10/10/2024 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Ping_Drop_BE_DN284.png Sound Speed The spatio-temporal variability in temperature of the water column created complex sound speed conditions throughout the survey. These complexities often created challenges for the field team and resulted in occasional refraction artifacts in the survey data and resultant surfaces, as shown in Figures 19 and 20. The hydrographer made considerable efforts to reduce the impact of sound speed issues during acquisition. These efforts included increasing frequency of casts, closely monitoring real-time swath "smiling" or "frowning", utilizing alerts for surface-to-profile sound speed deviation, observing the real-time standard deviation map display, and increasing the percentage of swath overlap. Additional efforts in post-processing to minimize refraction artifacts included outer beam filtering, manual outer beam editing, and assessing the application of sound speed profiles. In addition to the outer beam noise associated with refraction, the convex or concave trend in the across-track sonar data is most prevalent in the outer beams and is noticeable in the surface as a striped line to line artifact. Remaining artifacts in the final delivered surfaces are all within the allowable TVU limit. H13943 surface artifacts as a result of refraction causing the soundings to trend concave / convex file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_SV.png H13943 surface artifacts as a result of refraction causing outer beam noise file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_SV2.png Sound speed casts were acquired at least once every four hours. Casts were often conducted more frequently than this time interval because of the dynamic water properties in the survey area. Additionally, the R/V Substantial utilized an MVP onboard which allowed for a higher frequency of casts. Surface sound speed was compared in real-time to the sound speed profile. When the comparison differed by more than 2 m/s, a new sound speed profile was acquired. Additionally, QPS Qinsy and Kongsberg SIS provided a real-time visual assessment of data quality (standard deviation grids, bathymetric grids, swath views) aiding the hydrographer in determining when a new cast was required. For more detailed information on sound speed methods, please refer to the DAPR. All equipment and survey methods were used as detailed in the DAPR. All equipment and survey methods were used as detailed in the DAPR. Holidays All CUBE surfaces were analyzed using HydrOffice QC Tools Holiday Finder to determine if the surfaces contained holidays, as described in section 5.2.2.3 of the HSSD. The tool scanned the CUBE surfaces, identifying any holidays, and generated an S-57 file to illustrate the locations of holidays. Another method of holiday evaluation was to visually pan the CUBE surfaces to identify holidays. The hydrographer would often alter the surface display (color ranges, symbology, shading) to help aid the hydrographer in identifying coverage gaps. The results reflected the same outcome as the tool and no holidays were identified within the survey area. Density All finalized CUBE surfaces were analyzed using HydrOffice QC Tools Grid QA tool to assure data met the required density specifications. Density requirements were achieved for the finalized surfaces in H13943 with greater than 95% of the surface nodes containing at least five or more soundings, exceeding the specifications required by section 5.2.2.3 of the HSSD (Figures 21 - 23). Finalized 1 m CUBE surface density statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_1m_LWD_Final.GQv6.density.png Finalized 2 m CUBE surface density statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_2m_LWD_Final.GQv6.density.png Finalized 4 m CUBE surface density statistics for H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_MB_4m_LWD_Final.GQv6.density.png Flier Finder In addition to a visual inspection, all CUBE surfaces were analyzed using HydrOffice QC Tools Flier Finder tool to assure data does not contain fliers. While the Flier Finder tool flags surface fliers meeting a set criteria, it will also flag real surface features that meet the same criteria. Spurious soundings flagged by Flier Finder were cleaned until either no fliers remained or the remaining flagged fliers were deemed valid aspects of the surface. All data reduction procedures conform to those detailed in the DAPR. All data reduction procedures conform to those detailed in the DAPR. All sounding systems were calibrated as detailed in the DAPR. All sounding systems were calibrated as detailed in the DAPR. Raw backscatter data were collected and stored within the .ALL files. Backscatter data were processed and reviewed for quality assurance in QPS FMGT. In accordance with the HSSD, GSFs and backscatter mosaics were exported from FMGT. Hydrographers in the field monitored backscatter intensities in real-time and made efforts to collect quality backscatter without hindering bathymetric data quality. Refer to the DAPR for more information on backscatter data acquisition and processing procedures. H13943 combined backscatter coverage file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Backscatter.png CARIS HIPS and SIPS 11.4.20 CARIS HIPS and SIPS 11.4.26 QPS FMGT 7.11.1 NOAA Profile Version 2023 H13943_MB_1m_LWD_Final CARIS Raster Surface (CUBE) 1 7.8 20.0 NOAA_1m Complete MBES H13943_MB_2m_LWD_Final CARIS Raster Surface (CUBE) 2 18.0 40.0 NOAA_2m Complete MBES H13943_MB_4m_LWD_Final CARIS Raster Surface (CUBE) 4 36.0 40.98 NOAA_4m Complete MBES H13943_MB_1m_LWD CARIS Raster Surface (CUBE) 1 8.04 41.04 NOAA_1m Complete MBES H13943_MB_2m_LWD CARIS Raster Surface (CUBE) 2 8.06 41.03 NOAA_2m Complete MBES H13943_MB_4m_LWD CARIS Raster Surface (CUBE) 4 8.15 40.98 NOAA_4m Complete MBES H13943_MBAB_2m_Substantial_300kHz_1of2 MB Backscatter Mosaic 2 N/A Complete MBES H13943_MBAB_2m_Benthos_300kHz_2of2 MB Backscatter Mosaic 2 N/A Complete MBES All surfaces submitted are in compliance with the complete coverage MBES requirements per section 5.2.2.3 of the HSSD. See Figure 25 below for an overview of the submitted finalized surface resolutions. Image representing 1 m, 2 m, and 4 m finalized CUBE surface resolutions in H13943 file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_Surface_Resolution.png Designated Soundings H13943 contains six designated soundings in accordance with section 5.2.1.2.3 and 7.4 of the HSSD. These designated soundings were created to facilitate feature management and best represent the least depths over features in the Final Feature File (FFF). In the finalized CUBE surfaces, the CARIS HIPS Apply Designated Soundings function ensured designated soundings depths are retained in the finalized surfaces. Additional information discussing the vertical and horizontal control for this survey can be found in the accompanying DAPR. Low Water Datum IGLD-1985 ERS via VDATUM OPR-Y393-KR-24_100m_NAD83_2011-LWD_IGLD85_geoid18.csar Real-time positional and GPS Height data were corrected with G2+ Global Navigation Satellite System (GNSS) satellite corrections provided by the Fugro Marinestar Satellite-Based Augmentation System (SBAS). To improve the accuracy of the real-time data, real-time position and GPS Height data were post-processed using Applanix POSPac Mobile Mapping Solution (MMS) software. Trimble CenterPoint RTX correction methods were used to create Smoothed Best Estimate of Trajectory (SBET) files, which were applied to the survey data in CARIS HIPS. The provided separation model was then utilized to bring the data from ellipsoid heights to chart datum. For further information regarding processing and application of SBET and SEP files, please reference the DAPR. North American Datum 1983 (2011) Projected UTM 16 Real-time positional and GPS Height data were corrected with G2+ GNSS satellite corrections provided by the Fugro Marinestar SBAS. A comparison was performed in CARIS HIPS between H13943 and the ENCs listed in Table 14 of section D.1.1. Sounding layers were generated from the CUBE surface and overlaid onto the ENCs to visually assess differences between the surveyed and charted depths. In addition to a detailed visual inspection in CARIS HIPS, all soundings from the chart were downloaded as a shapefile from NOAA's ENC Direct to GIS application and differenced with the nearest surveyed depth from the 2 m surface in ESRI ArcPro. A statistical analysis of the difference comparison is shown in Figure 26. The surveyed depths from H13943 generally agree with the charted soundings from the largest scale ENCs within the survey area, with a mean difference of 0.88 m. Areas with large discrepancies between the charted soundings and surveyed depths were assessed and two shoal soundings as well as one obstruction, were determined to pose an imminent danger to navigation and were subsequently reported as Dangers to Navigation (DTONs). Refer to Section D.1.2 of this report for further information. H13943 statistical analysis of surveyed depths to charted soundings file:///B:/OPR-Y393-KR-24/Surveys/H13943/01_HDR/Reports/Descriptive_Report/SupportFiles/H13943_ChartComparison_Histogram.png US4IL1YX 90000 1 2024-08-27 2024-08-27 US4IL1YY 80000 1 2023-06-02 2023-06-02 US5CHILL 12000 1 2024-12-31 2024-12-31 Two shoals were identified as hazardous in H13943 and were reported and forwarded to MCD as Dangers to Navigation (DtoNs) and are included in the FFF with Special Feature Type as "DTON". It should be noted that the grids accurately represent the least depths of the two shoals, therefore, they were submitted as two sounding features and were selected as sounding features based off of the shoal sounding layers created from the bathymetric CUBE surface. These sounding features do not have accompanying designated soundings. Additionally, one dangerous obstruction was reported and forwarded to MCD as a Danger to Navigation (DtoN) and is included in the FFF with Special Feature Type as "DTON'. It should be noted that the least depth, position, or feature geometry may have changed slightly during post-processing for reported DTONs. Refer to the FFF for the remarks and recommendations for each feature. See DR Appendix II Supplemental Records for DTON related correspondence. No assigned charted features existed for this survey; however, one charted feature was detected outside of the sheet limits, within junctioning sheet H13815 (Ocean Surveys Inc, 2023). This charted feature (Unique ID: 4_005_1) was investigated and is addressed as a Delete/New in the FFF with New Feature Unique ID: 4_005_2 in accordance with section 7.3 of the HSSD. This charted feature (Unique ID: 4_005_1) was imported into the FFF from ENC US4IL1YX. All new features found within H13943 are detailed in the FFF in accordance with section 7.3 of the HSSD. No channels exist for this survey. All ATONs located within the survey area were observed to be on station and serving their intended purpose. No Maritime Boundary Points were assigned for this survey. Ten bottom samples were acquired in accordance with section 7.2.3 of the HSSD and are described in the FFF. Predetermined bottom sample locations were not provided for this project. Instead, ten bottom sample locations within each sheet were identified by the team of hydrographers based off of multiple factors including but not limited to, backscatter data, bathymetric data, geologic and/or navigation areas of interest. See Project Instructions for more information. Bottom samples were collected on 10/13/2024, 10/17/2024, and 10/18/2024. It should be noted that several bottom samples were collected after the last day of MBES collection. Therefore, the last day of survey and SORDAT reflects a bottom sample acquisition day and does not have accompanying MBES data for that specific date. See Project Correspondence for more information. No overhead features exist for this survey. No submarine features exist for this survey. No platforms exist for this survey. No ferry routes or terminals exist for this survey. No abnormal seafloor or environmental conditions exist for this survey. No present or planned construction or dredging exist within the survey limits. No new surveys or further investigations are recommended for this area. No new ENC scales are recommended for this area. 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 the attached survey data and reports. All field sheets, this Descriptive Report, and all accompanying records and data are approved. All records are forwarded for final review and processing to the Processing Branch. The survey data 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. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required with the exception of deficiencies noted in the Descriptive Report. Nicholas Damm, CH Chief of Party 2025-02-21 Data Acquisition and Processing Report 2025-01-20 Coast Pilot Report 2024-11-27