OPR-O190-FA-16West of Prince of Wales IslandWest of Prince of Wales IslandNOAA Ship FAIRWEATHERH128813Vicinity of McFarland IslandsAlaskaUnited States200002016CDR Mark Van Waes, NOAANavigable Area2016-03-282016-05-092016-06-15Multibeam Echo SounderMultibeam Echo Sounder BackscattermetersUniversal Transverse Mercator (UTM)UTCPacific Hydrographic BranchThe purpose of this survey is to provide contemporary surveys to update National Ocean Service (NOS) nautical charts. All separates are filed with the hydrographic data. Any revisions to the Descriptive Report (DR) generated during office processing are shown in bold, red italic text. The processing branch maintains the DR as a field unit product, therefore, all information and recommendations within the body of the DR are considered preliminary unless otherwise noted. The final disposition of surveyed features is represented in the OCS nautical chart update products. All pertinent records for this survey, including the DR, are archived at the National Centers for Environmental Information (NCEI) and can be retrieved via http://www.ncei.noaa.gov/.NOAAThe survey area is located along the West of Prince of Wales Island, within the sub-locality of the Vicinity of McFarland Islands.55.08665133.00783888955.0315111111132.889072222H12881 Sheet Limits (in blue) overlaid onto Chart 17408SupportFiles\H12881 Sheet Limits.jpgData for survey H12881 was acquired to the survey limits in accordance with the requirements in the Project Instructions and the NOS Hydrographic Surveys Specifications and Deliverables (HSSD) dated March 2016, as shown in Figure 1. In all areas where the 4-meter depth contour or the sheet limits were not met, the Navigable Area Limit Line (NALL) was defined as the inshore limit of bathymetry due to the risks of maneuvering the survey vessel in close proximity to the steep and rocky shoreline. For example, Figure 2 shows an area in the middle of the McFarland Islands and Figure 3 shows a cove on the SW corner of Sukkwan Island. The arrows in Figure 3 indicate where large and shallow rocks make it unsafe for boats to enter the area. The two areas have also been included as proposed new foul areas in the H12881_Final_Feature_File.H12881 Foul area in central McFarland IslandsSupportFiles\Central McFarlands Foul.jpgH12881 Foul area near SW Sukkwan IslandSupportFiles\Strike cove with coverage.jpgThe purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products. The survey area will address 14 SNM of navigationally significant waters in accordance with the National Hydrographic Survey Priorities Edition 2012.The entire survey is adequate to supersede previous data.Data acquired in H12881 meet multibeam echo sounder (MBES) coverage requirements for complete coverage, as required by the HSSD. This includes crosslines (see Section B.2.1), NOAA allowable uncertainty (see Section B.2.10), and density requirements (see Section B.2.11). Additional compliance statistics can be found in the Standards and Compliance Review located in Appendix II of this report.The Standards and Compliance Review is archived at NCEI and is not appended to this report.Inshore limit to 8 meters water depthComplete coverage MB with backscatter (Section 5.2.2.3) or Set Line Spacing at 100 meters (Section 5.2.2.4).Greater than 8 meters water depthComplete Coverage MBES with Backscatter. Refer to HSSD Section 5.2.2.3The entirety of H12881 was acquired with complete coverage MBES with backscatter, meeting the requirements listed above and in the HSSD. See Figure 4 for an overview of coverage. H12881 Survey Coverage (16m) overlaid onto Chart 17408SupportFiles\H12881 Overview.jpgS22008.070000000FA-28050101.05000008.070FA-28060186.050000011.880FA-28070112.510000000FA-2808020.36000002.6700428.530000022.6205.2860140014.752016-05-102016-05-132016-05-142016-05-252016-06-062016-06-072016-06-082016-06-092016-06-102016-06-112016-06-122016-06-132016-06-142016-06-15Refer to the OPR-O190-FA-16 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.S22070.48.6428058.641.1228068.641.1228078.641.1228088.641.12Draft of S220 is reported incorrectly and should be 5.03 meters.Reson7125 SV1MBESKongsbergEM710MBESApplanixPOS/MV V4Positioning and Attitude SystemResonSVP70Sound Speed SystemResonSVP71Sound Speed SystemSeabird19PlusConductivity, Temperature, and Depth SensorRolls RoyceMVP200Conductivity, Temperature, and Depth SensorVelodyneVLP-16Lidar SystemCrosslines were collected, processed and compared in accordance with Section 5.2.4.3 of the HSSD. To evaluate crosslines, a 16-meter CUBE surface using strictly mainscheme lines, and a 16-meter CUBE surface using strictly crosslines were created. From these two surfaces, a difference surface (mainscheme - crosslines = difference surface) was generated at a 16-meter resolution (Figure 5), and is submitted in the Separates II Digital Data folder. Statistics show the mean difference between the depths derived from mainscheme and crosslines was 0.08 meters (with mainscheme being shoaler) with 95% of nodes falling within 4.80 meters (Figure 6). For the respective depths, the difference surface was compared to the allowable NOAA accuracy standards (Figure 7). In total, 94.3% of the depth differences between H12881 mainscheme and crossline data are within allowable NOAA accuracies (Figure 9). The largest differences exhibited are where the density of soundings were degraded in areas where the geologic structure of the seafloor is dynamic, as seen in Figures 5 and 8 and is discussed further in Section B.2.11.H12881 Crossline Difference OverviewSupportFiles\H12881 MS XL Difference.jpgH12881 Crossline Difference StatisticsSupportFiles\H12881_MS_XL_Difference.pngDepth differences between H12881 mainscheme and crossline data as compared to NOAA allowable uncertainty standards for the associated depthsSupportFiles\H12881 XL NOAA Allowable Uncertainty Overview.jpgH12881 Crossline NOAA Allowable Uncertainty Example of Areas of High DifferenceSupportFiles\H12881 NOAAness XL Difference.jpgH12881 Crossline NOAA Allowable Uncertainty StatisticsSupportFiles\H12881 NOAAness XL Difference Stats.jpegThe Separates are archived at NCEI and are not appended to this report.00.02ERS via PMVD00.097Discrete Zoning00TCARIS220N/A10.528052N/A0.528062N/A0.528072N/A0.528082N/A0.5In addition to the usual a priori estimates of uncertainty provided via device models for vessel motion, discrete zoning tides, ERZT, and PMVD, real-time and post-processed uncertainty sources were also incorporated into the depth estimates of survey H12881. Real-time uncertainties were provided via EM710 and Reson 7125 MBES data, Applanix Delayed Heave RMS, and TCARI tides. Following post-processing of vessel motion, real time uncertainties of vessel roll, pitch, gyro and navigation were applied in CARIS HIPS and SIPS via a Smoothed Best Estimate of Trajectory (SBET) RMS file generated in Applanix POSPac.H12881 junctions with two adjacent surveys from this project: H12865 and H12880, as shown in Figure 10. Data overlap between all surveys was achieved. These areas of overlap between surveys were reviewed with CARIS HIPS and SIPS by surface differencing (at equal resolutions) to assess surface agreement. The multibeam data were also examined in CARIS Subset Editor for consistency and agreement. The junctions with H12881 are generally within the NOAA allowable uncertainty in their areas of overlap. For all junctions with H12881, a negative difference indicates H12881 was deeper, and a positive difference indicates H12881 was shoaler.H12881 Junction BoundariesSupportFiles\H12881 Junction Boundaries.jpgH12865200002016NOAA Ship FAIRWEATHERNWSurface differencing in CARIS HIPS and SIPS was used to assess junction agreement between the 16 meter combined surface from H12881 and the 16 meter combined surface from H12865. The statistical analysis of the difference surface shows a mean of -0.26 meters with 95% of all nodes having a maximum deviation of +/- 1.76 meters, as seen in Figure 12. A detailed graphical overview can be seen in Figure 11. In addition, a comparison surface was created between the difference surface and the NOAA allowable uncertainty (See Figure 13). It was found that 99% of nodes are within allowable NOAA uncertainty (Figure 14). The largest differences are located at the edges of the junction where there were no overlapping lines for the individual surveys to provide greater density.H12881 Junction with H12865SupportFiles\H12881_H12865 Junction Difference Surface.jpgH12881 Junction with H12865 StatisticsSupportFiles\H12881_H12865_Difference.pngH12881 Junction with H12865 NOAA Allowable UncertaintySupportFiles\H12881_H12865 Junction NOAA Allowable Uncertainty.jpgH12881 Junction with H12865 NOAA Allowable Uncertainty StatisticsSupportFiles\H12881_H12865 Junction NOAA Allowable Uncertainty Statistics.jpgH12880200002016NOAA Ship FAIRWEATHERNESurface differencing in CARIS HIPS and SIPS was used to assess junction agreement between the 16 meter combined surfaces from H12881 and the 16 meter combined surface from H12880. A detailed graphical overview of the junction boundary can be seen in Figure 15. The statistical analysis of the difference surface shows a mean of 0.11 meters with 95% of all nodes having a maximum deviation of +/- 1.52 meters, as seen in Figure 16. In addition, a comparison surface was created between the difference surface and the allowable NOAA uncertainty (Figure 17). It was found that 99% of nodes are within allowable NOAA uncertainty (Figure 18). The largest differences are located at the edges of the junction where there were no overlapping lines for the individual surveys to provide greater density.H12881 Junction with H12880SupportFiles\H12881_H12880 Junction.jpgH12881 Junction with H12880 StatisticsSupportFiles\H12881_H12880_Difference_Stats.pngH12881 Junction with H12880 NOAA Allowable UncertaintySupportFiles\H12881_H12880 Junction NOAA Allowable Uncertainty.jpgH12881 Junction with H12880 NOAA Allowable Uncertainty StatisticsSupportFiles\H12881_H12880 Junction NOAA Allowable Uncertainty Statistics.jpgSonar system quality control checks were conducted as detailed in the quality control section of the DAPR.None ExistThere were no conditions or deficiencies that affected equipment operational effectiveness.Sea Grass and KelpKelp and sea grass were present throughout the survey area and at times, indistinguishable from the seafloor (Figure 19). In areas where they were distinguishable, the soundings on the vegetation were rejected to enable more accurate representation of the true seafloor. Where vegetation was indistinguishable, all soundings were retained. Furthermore, in some areas, patches of dense kelp prohibited safe navigation of the survey vessels. The limits of these areas were then used to define the NALL (Figure 20). Documentation can be found in the vessel boat sheets, which are located in the Separates II Digital Data folder.H12881 Representative area near Kellogg Point of kelp and sea grass masking the seafloorSupportFiles\Kellog Point Kelp 3.jpgH12881 Kelp resulting in new NALL instead of 4m line or sheet limitSupportFiles\H12881 Kelp and NALL coverage.jpgThe Separates are archived at NCEI and are not appended to this report.Sound SpeedThroughout the survey area of H12881, there are instances of soundings being affected by changes in sound speed. This resulted in the soundings generally being deeper (tracklines are bent down or "frowning") than the surrounding soundings. All casts were conducted as referenced below in Section B.2.7. In order to minimize the impact of the sound speed issues, affected lines were examined with various methods of sound speed profile association applied (Nearest in distance with time at multiple intervals, Nearest in distance and Nearest in time) and the best application of sound speed profiles was left as final. In general, soundings are within the HSSD specifications for sound speed uncertainty for their respective depths, and had a negligible impact on the Finalized CUBE surfaces. Figure 21 shows an example of affected soundings that were most likely caused by a large variation in sound speed through the water column. In this case, the general area is relatively shallow (<20m) and the sound speed changed by approximately 10 m/s within the water column. An over sampling of casts would most likely have been the only way to correct for this artifact.H12881 Sound Speed Issue 2807 Dn162SupportFiles\H12881 SV issues.jpgThe data is adequate for charting despite the presence of sound speed errors.Casts were conducted at a minimum of at least one per every 4 hours during launch acquisition. Casts were conducted more often in areas where the influx of freshwater had an effect on the speed of sound in the water column and when there was a change in surface sound velocity greater than two meters per second. MVP casts on S220 were conducted approximately every 15 minutes as recommend by Pydro CastTime, a software tool that determines optimum cast frequency based on observed sound speed variations. Detailed Sound Speed methods are described in the DAPR.All equipment and survey methods were used as detailed in the DAPR.HolidaysH12881 data were reviewed in CARIS HIPS and SIPS for holidays in accordance with Section 5.2.2.3 of the 2016 HSSD. Seventy eight apparent holidays which meet the 3 by 3 node definition were identified via Pydro QC Tools Holiday Finder function. This tool automatically scans finalized surfaces for holidays as defined in the HSSD. All flagged areas by Holiday Finder were examined and all apparent holidays were determined to be from areas where an adjoining surface covered the gap (e.g., a holiday in the 2m finalized surface was covered by the 1m finalized surface due to the area being shoaler than the depth range for the 2m surface), as seen in Figure 22. The numbers in red indicate the number of nodes identified as data gaps. H12881 Apparent Holidays in Coveragefile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881%20Coverage%20non-Holidays.jpgIn many cases, the holidays are a result of not being able to ensonify the tops of rocks with multibeam. In these cases, the field unit added a rock with an unknown least depth to the final feature file. These approximate features will be forwarded for inclusion in the chart update product.NOAA Allowable UncertaintyTo verify that all data meet the accuracy specifications as stated in the HSSD, a child layer titled “NOAA_Allowable_1” was created for each of the 1-meter, 2-meter, 4-meter, and 8-meter (72-100m) and "NOAA_Allowable_2" for the 8-meter (100-160m) and 16-m finalized surfaces using the equations stated in Section C. 2.1 of the DAPR. These surfaces were then analyzed using the Pydro Finalized CSAR QA tool. Figure 23 shows an overview of the NOAA Allowable Uncertainty layers in each of the surfaces. Figure 24 shows the statistics for each of the individual surfaces. It was found that at least 99% of nodes in the 1-meter, 2-meter, 4-meter, 8-meter, and 16-m grids meet or exceed NOAA Allowable Uncertainty specifications for all depths of survey H12881. For individual graphs per surface of uncertainty requirements, see the Standards Compliance Review in Appendix II. H12881 NOAA Allowable Uncertainty OverviewSupportFiles\H12881 NOAA Allowable Uncertainty Overview.jpgH12881 NOAA Allowable Uncertainty StatisticsSupportFiles\H12881 NOAA Allowable Uncertainty Statistics.jpgThe Standards and Compliance Review is archived at NCEI and is not appended to this report.DensityFinalized surfaces were analyzed using the Pydro Finalized CSAR QA tool and the results are shown in Figure 25 below. Density requirements for H12881 were achieved with at least 99.7% of finalized surface nodes containing five or more soundings. For individual graphs per surface of density requirements, see the Standards Compliance Review in Appendix II. The few nodes that did not meet density requirements are generally due to sparse data in the outer beams, especially near steep slopes and rocky areas where acoustic shadowing occurred, and at the edges of the survey limits. See Figure 26.H12881 Density OverviewSupportFiles\H12881 Density Overview.jpgH12881 Density StatisticsSupportFiles\H12881 Density Statistics.jpgThe Standards and Compliance Review is archived at NCEI and is not appended to this report. Reduced density in the outer beams and in steep and rocky areas is to be expected to a certain extent. The data is adequate for charting despite the reduced density in these instances.All data reduction procedures conform to those detailed in the DAPR.All sounding systems were calibrated as detailed in the DAPR.Raw Backscatter data was logged as .7k file for Reson 7125 data. Kongsberg EM710 stores the backscatter data in the .all file. The data have been sent to the Pacific Hydrographic Branch for processing. One line per vessel per day of acquisition was processed by the field unit for quality control.CarisHIPS and SIPS9.1QPSFledermaus FMGT7.5.3NOAA Extended Attribute Files V5_4H12881_MB_1m_MLLWCUBE1NOAA_1mComplete MBESH12881_MB_2m_MLLWCUBE2NOAA_2mComplete MBESH12881_MB_4m_MLLWCUBE4NOAA_4mComplete MBESH12881_MB_8m_MLLWCUBE8NOAA_8mComplete MBESH12881_MB_16m_MLLWCUBE16NOAA_16mComplete MBESH12881_MB_1m_MLLW_FinalCUBE1026NOAA_1mComplete MBESH12881_MB_2m_MLLW_FinalCUBE21852NOAA_2mComplete MBESH12881_MB_4m_MLLW_FinalCUBE436104NOAA_4mComplete MBESH12881_MB_8m_MLLW_FinalCUBE872208NOAA_8mComplete MBESH12881_MB_16m_MLLW_FinalCUBE16144416NOAA_16mComplete MBESThe NOAA CUBE parameters mandated in the HSSD were used for the creation of all CUBE surfaces in Survey H12881. The surfaces have been reviewed where noisy data, or "fliers," are incorporated into the gridded solutions causing the surface to be shoaler or deeper than the true sea floor. Where these spurious soundings cause the gridded surface to be shoaler or deeper than the reliably measured seabed by greater than the maximum allowable Total Vertical Uncertainty at that depth, the noisy data have been rejected and the surface recomputed. Flier Finder v3, part of the QC Tools package within Pydro, was used to assist the search for spurious soundings following gross cleaning. Flier Finder was run multiple times for each surface, reducing the flier height value for each consecutive run. This allowed Flier Finder to very accurately and quickly identify gross fliers, but as the flier height was reduced the effectiveness of the tool diminished. With smaller heights, Flier Finder began to incorrectly flag dynamic aspects of the seafloor such as steep drop offs and rocky areas as fliers resulting in hundreds of false positives. At this point, the hydrographer ceased using the tool and returned to manual cleaning for these dynamic regions of seafloor In order to prevent visual data gaps between the finalized surfaces, the 1, 2, 4, 8, and 16 meter surface depths were extended for greater overlap between the surfaces. The surfaces and depth ranges are listed in Table 11. All finalized surface depth ranges were extended deeper by 6 times the surface resolution. To determine how much to expand the depth range by, the largest gap in coverage that could be found was measured in CARIS HIPS and SIPS subset editor. The distance of the gap was divided by the resolution of the surface that would cover the gap to determine how many multiples of that resolution it would take to cover that gap. This number was then multiplied by 2 to ensure that all gaps would be covered resulting in the extension of the surfaces by 6 times their resolution. All surfaces still meet the density and NOAA uncertainty requirements for their extended ranges. As a minimal percentage by area of H12881 met the depth threshold for the 32 meter depth range, a waiver to extend the 16 meter surface depth range and not submit a 32 meter surface was granted from the Hydrographic Survey Division Operations Branch, and is located in Appendix II. All data within the extended 16 meter surface meets the coverage requirements as defined by the HSSD. This waiver also covers the extension of all grids per the methods described in the previous paragraph.See attached correspondence regarding the surface resolution waiver.Data LogsData acquisition and processing notes are included in the acquisition and processing logs, and additional processing such as final tide and sound velocity application are noted in the H12881 Data Log spreadsheet. All data logs are submitted digitally in the Separates I folder.The Separates are archived at NCEI and are not appended to this report.CARIS HIPS/SIPS Subset Editor Reference SurfacesWhen viewing data in HIPS and SIPS Subset Editor, a video card incompatibility between the processing computer and CARIS caused visual artifacts to randomly appear as part of the displayed reference surface. Figures 27 and 28 show some of the more egregious errors observed. These issues were purely visual and did not actually correlate to the surfaces, however, they caused difficulties for the Hydrographer when identifying fliers and designating soundings. H12881 Caris Subset editor reference surface errorsSupportFiles\Bad CARIS 1.jpgH12881 Caris Subset editor reference surface errorsSupportFiles\more rocket launcher.jpgDesignated SoundingsSurvey H12881 contains 26 designated soundings. Three designated soundings are used to represent DTONs, which are addressed in Section D.1.6 Dangers to Navigation, and the other 23 designated soundings are used to accurately represent the seafloor. Soundings were designated in accordance with the HSSD Section 5.2.1.2.3 Designated Soundings . The majority of designated soundings are located along the shoreline near Kellogg Point and Dunbar Inlet in areas where the CUBE surface did not accurately depict the true seafloor. Figure 29 shows an overview of the survey area and the location of designated soundings. Figure 30 shows an example of a designated sounding where the feature is >1m proud of the seafloor and exceeds the allowable TVU for the depth, thus satisfying the requirements stated in the HSSD.H12881 Designated Soundingsfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881%20Critical%20Soundings.jpgH12881 Example of Designated Sounding Near Entrance to Dunbar Inletfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881%20Designated%20Sounding%20Example%202.jpgSee attached DTON Report.Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying Horizontal and Vertical Control Report (HVCR).Mean Lower Low WaterPort Alexander, AK9451054Ketchikan, AK9450460Entrance to Windy Cove9450251Dunbar Inlet Tide Buoy945BBBBDiscrete ZoningTCARI9451054.tidFinal ApprovedOPRO190CORP.zdfPreliminaryO190FA2016.tcFinal2016-06-152016-09-07Initial reduction of acquired data to MLLW was accomplished via traditional tidal means using the discrete zoning / Tidal Constituent And Residual Interpolation (TCARI) grid provided by HSD-OPS. Following the successful application of SBETs and computation of an Ellipsoidally Referenced Zone Tide (ERZT) separation model, ERS methods were used for reducing data to MLLW. After final tides were received, the final TCARI grids / discrete zones were applied to the data and used for reducing features to MLLW.See attached Tide Note dated September 6, 2016.ERS via Poor Mans VDATUMO190FA2016CORP_PMVDERZT_UTM-WGS84-8N_WGS84-MLLW_100m.csarERS methods were used as the final means of reducing H12881 to MLLW for submission. Data was initially reduced via traditional tidal means until an ERZT separation model could be calculated. This empirically derived model was then checked for consistency and compared to the Poor Man’s VDatum (PMVD) separation model provided with the Project Instructions. The PMVD separation model was then vertically shifted such that the average difference between these two separation models is zero. This vertical shift de-biases the PMVD separation model, correcting for local offsets that cannot be effectively modeled by the PMVD. In areas where the PMVD model did not have sufficient coverage such as near shore areas, the ERZT separation model was appended to the PMVD model creating the composite ERZT/PMVD separation model listed above and used to reduce H12881 to MLLW. For further information see the ERS Capability Memo, submitted under a separate cover. See attached ERS Approval Memo.Word Geodetic System 1984 (WGS84)UTM Zone 8 NorthSingle Base9677LarsonVessel kinematic data were post-processed using Applanix POSPac processing software and Single Base Positioning methods described in the DAPR. Smoothed Best Estimate of Trajectory (SBET) and associated error (RMS) data were applied to all MBES data in CARIS HIPS. For further details regarding the processing and quality control checks performed, see the H12881 POSPAC Processing Logs spreadsheet located in the Separates folder. See also the OPR-O190-FA-16 Horizontal and Vertical Control Report (HVCR), submitted under a separate cover. Hydrographic Technical Directive (HTD) 2016-3, which revises the horizontal datum requirement to NAD83, was released after acquisition was completed for OPR-O190-FA-16. The field unit conferred with HSD-OPS and determined no waiver was required to maintain WGS84 as the datum for submission. This correspondence has been included in Appendix II.The Separates and HVCR are archived at NCEI and are not appended to this report. See attached correspondence regarding HTD 2016-3.Annette Island, AK (323kHz)Level Island, AK (295kHz)Differential correctors from the US Coast Guard beacon at Annette Island (323kHz) and Level Island (295kHz) were used during real time acquisition when not otherwise noted in the acquisition logs, and were the sole method of positioning of detached positions (DP) and bottom samples.Vertical OffsetsDuring post-acquisition analysis, vertical offsets were discovered in data acquired by launch 2806 on multiple days. These offsets varied depending on time and location, but were were generally 0.20 meters. This offset is only present in the data when reduced to MLLW via ellipsoidal methods (see Section C.1) and not when reduced via traditional tidal methods as shown in Figure 31. All SBETS on the affected days were re-processed and re-applied, however the offset remained in the data. As this offset also varies internally within 2806 data it was determined the offset was not caused by any static biases within the acquisition and processing work flow. Due to the offset being random in nature and within allowable uncertainty, the Hydrographer considers all impacted 2806 data to remain adequate to supersede previous data. H12881 Vertical Offset of Data From FA 2806 DN165 and DN167SupportFiles\2806 Offset Dn165_167_2.jpgA comparison was performed between survey H12881 and charts 17407 and 17408 as well as ENC US5AK4DM, and US5AK4EM using CARIS HIPS and SIPS sounding and contour layers derived from the 16m combined surface. The contours and soundings were overlaid on the charts to assess differences between the surveyed soundings and charted depths. ENCs were compared to a 16m combined grid by extracting all soundings from the chart and creating a TIN which was differenced to the combined surface. All data from H12881 should supersede charted data. In general, surveyed soundings do not agree with the majority of charted depths. A full discussion of the disagreements follows below.17407272640000162014-122016-09-062016-08-20The charted soundings and contours of Chart 17407 are identical to those found on ENC US5AK4DM. As such, all discussions regarding comparisons between surveyed soundings and charted depths are covered under the ENC US5AK4DM discussion below. The field unit did not perform a chart comparison with chart 17408. Chart 17407 does not fully cover the entirety of the survey area. The following is the chart comparison performed by the reviewer. Chart 17408 and survey H12881 show very good agreement with majority of the soundings agreeing within 1-2 fathoms.Boundaries of ENC and RNC Coveragefile:///M:/OPRO190FA16/Surveys/H12881/Compilation/Report/Components/Editable_Docs/Images/DR_Graphic.pngUS5AK4DM4000022016-07-012015-05-12falseWhile individual soundings generally agree within 1-2fm, the overall chart comparison between survey H12881 and ENC US5AK4DM showed large areas of disagreement. A difference surface was created from the H12881 16m combined surface and a 16m TIN created from the combined soundings on both ENC US5AK4DM and US5AK4EM. Figure 33 shows that the majority of the charted depths on the ENC are deeper than the surveyed soundings from H12881. Overall, 95% of nodes have a difference of +\- 40.49m with a mean difference of 2.38m when compared to the charted depths, as seen in Figure 34. Contours from H12881 are in a general agreement with charted contours on ENC US5AK4DM with the exception of the missing 50 fathom and 100 fathom contours as shown in Figure 35. These contours are present in US5AK4EM and simply do not extend north into US5AK4DM. The Hydrographer recommends adding these contours to ENC US5AK4DM as to provide continuity to the mariner. H12881 Surface difference to US5AK4DM and US5AK4EMSupportFiles\H12881_ENC_Difference_Surface_16m.jpgH12881 ENC Difference comparison statisticsSupportFiles\H12881_ENC_Difference_new.pngH12881 Recommended Addition of 50fm ContourSupportFiles\H12881 US5AK4DM 50fm contour addition.jpgUS5AK4EM4000012016-08-152015-05-14falseAs discussed under ENC US5AK4DM and shown in Figure 33 above, while individual soundings match within 1-2fm, the overall chart comparison between survey H12881 and ENC US5AK4EM showed large and varying areas of disagreement. An example of these differences is shown in Figure 35 near Sukkwan Island where differences range from 8 fathoms deeper to 7 fathoms shoaler in the same relative geographic location. This is indicative of the trends throughout the survey area for H12881 and highlights the need for updated charts in the area. Contours from H12881 are in a general agreement with charted contours on ENC US5AK4EM as shown in Figure 36. The largest differences are a lack the 20 fathom contour and lack of detail in the 10 fathom, 5 fathom, and 3 fathom contours as seen in Figures 36, 37, and 38, respectively. The Hydrographer recommends adding these contours to ENC US5AK4EM as to provide additional information to the mariner.H12881 Sounding Discrepancies with ENC US5AK4EMfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881%20US5AK4EM%20sounding%20variations.jpgH12881 Contour Comparison and Recommend Addition of 20fm Contourfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881_ENC_contour%20overview.jpgH12881 Proposed addition of 10fm contour to US5AK4EM in North East McFarland Islandsfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881_ENC_10fm%20contour%20additions.jpgH12881 Proposed addition of 5fm and 3fm contour to US5AK4EM in Dunbar Inletfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881_ENC_5fm%203fm%20contour%20additions.jpgNo Maritime Boundary Points were assigned for this survey. All assigned features were addressed and are included in the H12881_Final_Feature_File. Survey H12881 contains 101 new features that are addressed in the H12881_Final_Feature_File. Of these features, there are 7 new Obstructions; 16 new Seabed Areas; 65 new Underwater Rocks of which, 3 are submitted as DTONs; 8 new Kelp features; 1 new land area and 4 new land elevations.1H12881_DTON2016-08-05Three Dangers to Navigation (DTONs) were found within the limits of survey H12881, and were reported to the Marine Chart Division on August 05, 2016. Two rocks exist in the NE corner of Dunbar Inlet. Their respective depths are 1.5 and 1.25 fathoms. Two DTONs were created as the rocks are approximately 56m apart, which is greater than the NOS HSSD requirement of 2mm at survey scale. The shoaler of the two rocks is used as the least depth for a new rocky foul area submitted in the H12881_Final_Feature_File. See Figures 40 and 41 for visualizations. The third DTON is located on a 4 1/2 fathom charted depth at the Eastern edge of the entrance to Dunbar Inlet. The least depth is 1.5 fathoms. Figures 43 and 44 show chart location and a subset view respectively. Danger to Navigation Reports are included in Appendix II of this report.H12881 Chart 17408 location of DTONs in NE Dunbar InletSupportFiles\H12881 DTONs NE Dunbar Inlet Chart View.jpgH12881 1.5fm and 1.25fm DTONs 3D subset viewSupportFiles\H12881 DTONs NE Dunbar Inlet 3D View.jpgH12881 Chart 17408 location of DTONs at Eastern Entrance to Dunbar InletSupportFiles\H12881 DTONs Entrance to Dunbar Inlet Chart View.jpgH12881 1.5fm DTON 3D subset viewSupportFiles\H12881 DTONs Entrance to Dunbar Inlet 2 point 8 m 3D.jpgSee attached DTON Report.No shoals or potentially hazardous features exist for this survey.No channels exist for this survey. There are no designated anchorages, precautionary areas, safety fairways, traffic separation schemes, pilot boarding areas, or channel and range lines within the survey limits.Six bottom samples were acquired in accordance with the Project Instructions for survey H12881. One bottom sample, located in the middle of the survey area, returned no good sample after three attempts. All bottom samples were entered in the H12881_Final_Feature_File. See Figure 43 for a graphical overview of sample locations.H12881 Bottom Sample Locationsfile:///M:/OPRO190FA16/Surveys/H12881/Report/Office/SupportFiles/H12881%20Bottom%20Sample%20Locations.jpgFairweather personnel conducted limited shoreline verification and reconnaissance, utilizing both traditional shoreline and Lidar methods, at times near predicted negative or low tides within the survey limits. Annotations, information, and diagrams collected on DP forms and boat sheets during field operations are scanned and included in the Separates I Detached Positions folder. Shoreline verification procedures for survey H12881 conform to those detailed in the DAPR. For clarification, the Lidar data noted above were acquired from a surface vessel, not from an aircraft. The Separates are archived at NCEI and are not appended to this report.No prior survey comparisons exist for this survey.No Aids to navigation (ATONs) exist for this survey.No overhead features exist for this survey.No submarine features exist for this survey.No ferry routes or terminals exist for this survey.No platforms exist for this survey.No Significant Features 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 insets 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 meet or exceed requirements as set forth in the NOS Hydrographic Surveys and Specifications Deliverables Manual, 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.CDR Mark Van Waes, NOAAChief of Party2016-09-30LT Bart O. Buessler, NOAAField Operations Officer2016-09-30HCST Douglas A. BravoChief Survey Technician2016-09-30HSST Clinton R. MarcusSheet Manager2016-09-30Data Acquisition and Processing Report2016-09-30Horizontal and Vertical Control Report2016-09-30Tides and Water Levels Package2016-07-15Coast Pilot Report2016-09-30