OPR-O190-FA-17West of Prince of Wales IslandSoutheast AlaskaNOAA Ship FAIRWEATHERH128821Baldy BayAlaskaUnited States200002017CDR Mark Van Waes, NOAANavigable Area2017-04-122017-05-292017-06-21Multibeam 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 west of Prince of Wales Island, AK, within the sublocality of Baldy Bay.55.099854133.09827354.969122132.826086H12882 sheet limits (in blue) overlaid onto Chart 17408SupportFiles\H12882_Sheet_Limits.tifData were acquired to the survey limits in accordance with the requirements in the Project Instructions and the March 2017 NOS Hydrographic Surveys Specifications and Deliverables (HSSD) 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. An example of such an area is shown in Figure 2.Area where the NALL was defined by the presence of rocks and kelpSupportFiles\H12882_Nall defined by kelp and rocks.pngThis project will provide contemporary surveys to update National Ocean Service (NOS) nautical charting products in an area where the communities are not accessible by land and the primary means of travel is by sea. Survey vintage in this area dates back to 1912 and 1913 with uncharted dangers littered throughout Tlevak Strait and Cordova Bay. Waterways along the western side of Prince of Wales Island are underlain by pinnacles, rocks, islets, and complex tidal currents. Multiple reported dangerous pinnacles and the local geology give reason to suspect many more such hazards. These waterways are economically significant to the coastal delivery of goods to the towns and villages within this region and provide an alternate route to the standard Inside Passage. Numerous fishing villages are on the west side of Prince of Wales Island. Native groups and recreational boaters often utilize this area for fishing and transportation. Additionally, the Inter-Island Ferry Authority serves as an important marine link for many of the communities in the Prince of Wales Island region of Southeast Alaska. 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.Data acquired in H12882 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.All waters in survey areaComplete coverage multibeam with backscatterThe entirety of H12882 was acquired with complete coverage multibeam, meeting the requirements listed above and in the HSSD. See Figure 3 for an overview of coverage.H12882 survey coverage overlaid onto Chart 17408SupportFiles\H12882_Survey_Coverage_Overview.tif28060111.28000000028080118.690000014.330S220018.8500000000235.490000014.3306.09800019.932017-05-292017-05-302017-05-312017-06-062017-06-072017-06-132017-06-142017-06-192017-06-202017-06-21Refer to the 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.S22070.44.928068.61.128078.71.128088.61.1Kongsberg MaritimeEM 2040MBESKongsberg MaritimeEM 710MBESSea-Bird ScientificSBE 19plus V2Conductivity, Temperature, and Depth SensorODIM Brooke OceanMVP200Conductivity, Temperature, and Depth SensorTeledyne RESONSVP 70Sound Speed SystemTeledyne RESONSVP 71Sound Speed SystemApplanixPOS MV 320 v5Positioning and Attitude SystemVelodyne LiDARVLP-16Lidar SystemThe equipment was installed on the survey platforms as follows: S220 utilized the Kongsberg EM 710 MBES, SVP 70 surface sound speed sensors, and ODIM Brooke Ocean MVP for conductivity, temperature, and depth casts. All launches utilized Kongsberg EM 2040 MBES, Teledyne RESON SVP 71 surface sound speed sensors, and Sea-Bird Scientific 19plus CTDs. Additionally, Launches 2806 and 2808 were equipped with the Velodyne VLP-16 LiDAR for shoreline feature acquisition.Crosslines were collected, processed and compared in accordance with Section 5.2.4.3 of the HSSD. To evaluate crosslines, a surface using strictly mainscheme lines and a surface using strictly crosslines were created. From these two surfaces, a difference surface (mainscheme - crosslines = difference surface) was generated, and is submitted in the Separates II Digital Data folder. See Figure 4 for an overview of the crossline difference surface. Statistics show the mean difference between the depths derived from mainscheme and crosslines is 0.10 meters, with mainscheme being deeper, and 95% of nodes falling within 0.93 meters (Figure 5). For the respective depths, the difference surface was compared to the allowable NOAA uncertainty standards. In total, 99.12% of the depth differences between H12882 mainscheme and crossline data were within allowable NOAA uncertainties. H12882 crosslines overviewSupportFiles\H12882_Crossline_Difference.tifH12882 crossline and mainscheme difference statisticsSupportFiles\H12882 Crossline Difference.png00.03ERS via PMVD0.00.0TCARI280x (all launches)20.5S22010.5In addition to the usual a priori estimates of uncertainty provided via device models for vessel motion, ERZT, and Poor Man's VDatum (PMVD), real-time and post-processed uncertainty sources were also incorporated into the depth estimates of survey H12882. Real-time uncertainties were provided via EM710 and EM2040 MBES data, Applanix Delayed Heave RMS, and TCARI tides. Following post-processing of the real-time vessel motion, recomputed 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.H12882 junctions with two adjacent surveys from this project, H13015 and H13016, and one survey from a prior project, H12881, as shown in Figure 6. Data overlap between H12882 and each adjacent survey 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 H12882 are generally within the NOAA allowable uncertainty in their areas of overlap, with the exception of the junction with survey H12881 (see discussion below). For all junctions with H12882. a negative difference indicates H12882 was shoaler, and a positive difference indicates H12882 was deeper.H12882 junction overviewSupportFiles\H12882_Junction_Overview.tifH12881200002016NOAA Ship FAIRWEATHERNESurface differencing in CARIS HIPS and SIPS, along with Pydro Compare Grids, was used to assess junction agreement between the 8 meter surface from H12882 and the 8 meter surface from H12881. A detailed graphical overview can be seen in Figure 7. The statistical analysis of the difference surface shows a mean of -0.13 meters with 95% of all nodes having a maximum deviation of +/- 6.96 meters, as seen in Figure 8. In addition, a comparison of surface differences was created in Pydro Compare Grids (Figure 9). The Allowable Error Fraction is computed by dividing the observed difference (1st CSAR file – 2nd CSAR file) by the IHO-based HSSD maximum allowable error for soundings (TVUmax) scaled according to the variance sum law, assuming independent, identically distributed observations. It was found that 92.68% of nodes are within NOAA allowable uncertainty (Figure 10). The largest differences are located in areas that are over steep slopes, and in areas where outerbeam data extend beyond 500 meters (Figure 11). Additionally, the H12881 junction surface shows significant spikes along the outer edge that are not indicated in the H12882 surveyed data (Figure 12). Through these analyses, the hydrographer is confident that the uncertainty issues are due to the aforementioned artifacts, and not to systematic biases in the data. Difference surface between H12882 and H12881 SupportFiles\H12882_H12881_Difference_Overview.pngDifference surface statistics between H12882 and H12881 SupportFiles\H12882_H12881_Junction_Difference_Stats.pngH12882 and H12881 Fractional Allowable UncertaintySupportFiles\H12882_H12881_Fractional Allowable Error.pngDifference surface statistics between H12882 and H12881 showing percentage of nodes meeting NOAA allowable uncertaintySupportFiles\H12882_H12881_NOAA_Allowable_Uncertainty.pngExample of outerbeam distance from sonar nadirSupportFiles\Distance of outerbeams.pngH12881 surface spikes not reflected in H12882 dataSupportFiles\H12881 Surface comparison.pngH13015200002017NOAA Ship FAIRWEATHERSWSurface differencing in CARIS HIPS and SIPS was used to assess junction agreement between the surface from H12882 and the surface from H13015. A detailed graphical overview can be seen in Figure 13. The statistical analysis of the difference surface shows a mean of -0.04 meters with 95% of all nodes having a maximum deviation of +/- 0.65 meters, as seen in Figure 14. In addition, a comparison of surface differences was created via Pydro Compare Grids using the same methodology described above. It was found that 99.32% of nodes are within NOAA allowable uncertainty. Difference surface between H12882 and H13015SupportFiles\H12882_Junction Diff_H13015.tifDifference surface statistics between H12882 and H13015SupportFiles\H13015_Junction_Diff_Stats.pngH13016200002017NOAA Ship FAIRWEATHERSESurface differencing in CARIS HIPS and SIPS was used to assess junction agreement between the surface from H12882 and the surface from H13016. A detailed graphical overview can be seen in Figure 15. The statistical analysis of the difference surface shows a mean of -0.61 meters with 95% of all nodes having a maximum deviation of +/- 2.48 meters, as seen in Figure 16. In addition, a comparison of surface differences was created via Pydro Compare Grids using the same methodology as H12881. It was found that 98.63% of nodes are within NOAA allowable uncertainty. Difference surface between H12882 and H13016SupportFiles\H12882_Junction Diff_H13016.tifDifference surface statistics between H12882 and H13016SupportFiles\H13016_Junction_Diff_Stats.pngSonar 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.None ExistThere were no other factors that affected corrections to soundings.Casts were conducted at a minimum of one every 4 hours during launch acquisition. Casts were conducted more frequently in areas where the influx of freshwater had an effect on the speed of sound in the water column, or where there was a change in surface sound speed greater than two meters per second. MVP casts on S220 were conducted at an average interval of 15 minutes based on the observation of surface sound speed. All sound speed methods were used as detailed in the DAPR.All equipment and survey methods were used as detailed in the DAPR.HolidaysH12882 data were reviewed in CARIS HIPS and SIPS for holidays in accordance with Section 5.2.2.3 of the HSSD. Twenty holidays which meet the 3 by 3 node definition were identified via Pydro QC Tools Holiday Finder tool (Figure 17). This tool automatically scans finalized surfaces for holidays as defined in the HSSD and was run in conjunction with a visual inspection of the surface by the hydrographer. The majority of the flagged holidays were either outside of the sheet limits or atop features where the least depth was determined. Gaps in coverage are present at the inshore limits of H12882 and are a result of sparse outerbeam data acquired during the development of the inshore limit of safe navigation. These gaps are most prevalent in the exposed, rocky areas of H12882 as kelp and nearshore topography made it too dangerous to acquire additional bathymetry, as shown in Figures 18 and 19. No holidays exist in areas deemed navigationally significant by the hydrographer.Overview of apparent holidays flagged by QC ToolsSupportFiles\H12882_Holidays_Overview.pngExample of where the top of a rock could not be safely developedSupportFiles\Top of Rock Holiday.pngArea where NALL is defined by dense kelp SupportFiles\NALL is defined by kelp.tifNOAA Allowable UncertaintyThe surface was analyzed via Pydro QC Tools Grid QA feature to determine the percentage of surface nodes that meet specifications. Overall, 99.5% of nodes meet NOAA allowable uncertainty standards for H12882. For a graphical representation of uncertainty compliance, see the Standards and Compliance Review located in Appendix II.DensityThe surface was analyzed via the Pydro QC Tools Grid QA feature to determine the percentage of surface nodes that meet specifications. Overall, 95.4% of surface nodes contain five or more soundings as required by HSSD Section 5.2.2.3. The few nodes that did not meet density requirements are due to sparse data in the outerbeams, especially near steep slopes and in rocky areas where acoustic shadowing occurred, and at the edges of the survey limits. For a graphical representation of density compliance, see the Standards and Compliance Review located in Appendix II.All data reduction procedures conform to those detailed in the DAPR.All sounding systems were calibrated as detailed in the DAPR.Raw Backscatter data were stored in the .all files generated by the Kongsberg MBES systems. The data have been sent to the Pacific Hydrographic Branch for processing.Teledyne CARISHIPS/SIPS10.3.3QPSFledermaus FMGT7.5.3NOAA Profile version 5.6H12882_MB_VR_MLLWCARIS VR Surface (CUBE)1-14-1.9437.5NOAA_VRComplete MBESH12882_MB_VR_MLLW_FinalCARIS VR Surface (CUBE)1-14-1.9437.5NOAA_VRComplete MBESThe NOAA CUBE parameters defined in the HSSD were used for the creation of the CUBE surface for Survey H12882. The surface has been reviewed where noisy data, or "fliers," are incorporated into the gridded solution causing the surface to be shoaler or deeper than the true sea floor. Where these spurious soundings cause the gridded surface vary from the reliably measured seafloor by greater than the maximum allowable Total Vertical Uncertainty at that depth, the noisy data have been rejected by the hydrographer and the surface recomputed. Flier Finder v5, 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 quickly and accurately 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 seafloorData LogsData acquisition and processing notes are included in the acquisition and processing logs, and additional processing such as final tide and sound speed application are noted in the H12882 Data Log spreadsheet. All data logs are submitted digitally in the Separates I folder. Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterKetchikan, AK9450460TCARI9450460.tidFinal ApprovedO190FA2017.tcFinal2017-06-232017-07-05Initial reduction of acquired data to MLLW was accomplished via traditional tidal means using the 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 grid was applied to the data and used for reducing features to MLLW.ERS via Poor Mans VDATUMO190FA2017_PMVD_EPSG3395_NAD83-MLLW_Debiased.csarERS methods were used as the final means of reducing H12882 to MLLW for submission. Data were 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. The de-biased PMVD was used to reduce H12882 to MLLW.North American Datum of 1983 (NAD83)UTM Zone 08 NorthSingle Base9677Willa JaneVessel 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 and SIPS. For further details regarding the processing and quality control checks performed, see the H12882 POSPAC Processing Logs spreadsheet located in the Separates folder. See also the OPR-O190-FA-17 Horizontal and Vertical Control Report (HVCR), submitted under separate cover.Annette Island (323kHz)Differential correctors from the US Coast Guard beacon at Annette Island (323kHz) were used in real-time for acquisition unless otherwise noted in the acquisition logs, and were the sole method utilized for the positioning of bottom samples.A comparison was performed between survey H12882 and ENCs US5AK4EM and US5AK4IM using CARIS HIPS and SIPS sounding and contour layers derived from the H12882 surface. The contours and soundings were overlaid on the charts to assess differences between the surveyed soundings and charted depths. ENCs were compared to the surface by extracting all soundings from the chart and creating an interpolated TIN surface which could be differenced with the surface from H12882. Due to the relatively small portion of H12882 data overlap with ENC US5AK4IM, the TIN surfaces generated for each ENC were combined, and all statistical analyses and comparisons have been incorporated into the comparison with US5AK4EM. All data from H12882 should supersede charted data. In general, surveyed soundings agree with the majority of charted depths. A full discussion of the disagreements follows below.US5AK4EM4000042016-08-152016-08-15falseSoundings from H12882 are in general agreement with charted depths on ENC US5AK4EM, with most depths agreeing within 3 fathoms. Several discrepancies in shoaler areas exist where differences exist on the order of 8 to 10 fathoms (Figure 20). To more accurately visualize trends within these differences, a 16 meter TIN surface was interpolated from the ENC sounding layer. This surface was then differenced with a corresponding 16 meter surface from H12882 and visualized in Figure 21. In this difference surface red colors indicate H12882 was shoaler than ENC US5AK4EM, green colors indicate agreement, and blue colors indicate H12882 was deeper than ENC US5AK4EM. Statistical analysis revealed that the mean difference between surfaces is 2.58 meters, with 95% of nodes falling within 19.63 meters (Figure 22). The majority of discrepancies are due to an insufficient density of soundings from the prior survey to accurately portray dynamic areas of the seafloor. Contours from H12882 are in general agreement with charted contours on ENC US5AK4EM as shown in Figure 23. The largest differences are seen in the 10 fathom contour where surveyed and charted contours differ by over 100 meters, as seen in Figure 24. H12882 area with significant sounding discrepanciesSupportFiles\Areas of discrepancies.pngDifference surface between H12882 and combined interpolated TIN surface from US5AK4EMSupportFiles\H12882 ENC Chart Comparison.tifDifference surface statistics between H12882 and interpolated TIN surface from US5AK4EMSupportFiles\H12882_US5AK4EM_16m_Tin_Diff.tifOverview of H12882 contours overlaid onto ENC US5AK4EMSupportFiles\Overview of survey derived contours_b.tifH12882 contour discrepanciesSupportFiles\Contours Shoaler than charted.tifUS5AK4IM4000072017-11-142016-08-15falseNo Maritime Boundary Points were assigned for this survey.No charted features exist for this survey.Survey H12882 has 97 new features that are addressed in the H12882 Final Feature File. Of these features there are 7 new land areas, 4 new seabed areas, 74 new underwater rocks, and 1 new kelp area.Two potentially hazardous uncharted shoals were discovered during MBES acquisition on H12882. A shoal with a least depth of 1.80 fathoms is present in an area offshore of the 10 fathom contour in the northwestern section Coco Harbor (Figure 25). A second shoal with a least depth of 0.87 fathoms is present in an area offshore of the 10 fathom contour in the southwestern section of Entrance Island (Figure 26). Although neither shoal was determined to be in an area of sufficient navigational significance to warrant the submission of a DTON, attention should be given to these areas when updating the chart.H12882 shoal in the vicinity of Coco HarborSupportFiles\Coco Harbor shoal.tifH12882 shoal in the vicinity of Entrance IslandSupportFiles\Entrance Island shoal.tifNo 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.Eight bottom samples were acquired in accordance with the Project Instructions for survey H12882. Several bottom samples were adjusted for backscatter information that was acquired and processed during survey operations. All bottom samples were entered in the H12882 Final Feature File. See Figure 27 for a graphical overview of sample locations.H12882 bottom sample locationsSupportFiles\H12882_Bottom_Sample_location.tifFairweather personnel conducted limited shoreline verification and reconnaissance at times near predicted negative or low tides within the survey limits. Annotations, information, and diagrams collected DP forms and boat sheets during field operations were scanned and included in the Separates I Detached Positions folder. Shoreline verification procedures for H12882 conform to those detailed in the DAPR.No prior survey comparisons exist for this survey.The daymark located near Reef Point (Figure 28) within H12882 was on station and observed to be serving it's intended purposeH12882 daymarkSupportFiles\DSCN0857.JPGNo 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.Abnormal seafloor and/or environmental conditions were not observed 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 meets or exceeds requirements as set forth in the NOS Hydrographic Surveys and Specifications Deliverables, Field Procedures Manual, Letter Instructions, and all HSD Technical Directives, except as noted in this Descriptive Report. These data are adequate to supersede charted data in their common areas. This survey is complete and no additional work is required unless otherwise noted herein.CDR Mark Van WaesCommanding Officer2017-11-22LT Damian MandaField Operations Officer2017-11-22Sam CandioChief Survey Technician2017-11-22