OPR-P377-KR-18Southwest Alaska PeninsulaSouthwestern Alaskan PeninsulaTerrasond, Ltd.H131121Unimak Bight ChannelAlaskaUnited States400002018Andrew OrthmannNavigable Area2018-04-242018-06-112018-07-21Multibeam Echo SoundermetersUniversal Transverse Mercator (UTM)UTCPacific Hydrographic BranchContractorThe survey area is located in the Aleutian Island region of southwest Alaska. The closest community is False Pass, population 35 (2010), located approximately 20 NM to the NE on Unimak Island from the center of the survey area. The closest major hub is Dutch Harbor, population 4,376 (2010), located approximately 105 NM to the WSW. Field work was carried out in June and July of 2018 under project OPR-P377-KR-18, with final processing and reporting carried out from August through December, 2018. Four additional survey areas located to the east were surveyed concurrently during this project. Work was done in accordance with the Hydrographic Survey Project Instructions (dated April 24th, 2018) and the NOS Hydrographic Surveys Specifications and Deliverables (HSSD), April 2017 edition.54.6526349444164.26908069454.3915556389163.300755778Survey extents and overviewSupportFiles\H13112 Extents.jpgSurvey limits were acquired in accordance with the requirements in the Project Instructions and the HSSD.The purpose of this project is to provide contemporary surveys to update National Ocean Service nautical charting products to support an increase in vessel traffic in Unimak Passage. Unimak Passage is the gateway to the Bering Strait utilized by cargo, fishing, and trans-Pacific vessels delivering goods to the Aleutian Islands, western Alaska, and the Arctic. This passage and area is specifically utilized by the fishing fleet in Bristol Bay and the Bering Sea and this area was specifically requested by the Alaska Marine Pilots, Alaska Fisheries Development Foundation, the 17th District of the United States Coast Guard, and the Alaska Marine Highway. This project was last surveyed using partial bottom coverage techniques in the 1930's. 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.All waters in survey areaComplete Coverage (Refer to HSSD Section 5.2.2.3) Acquire backscatter data during all multibeam data acquisition (Refer to HSSD Section 6.2)All waters in survey areaLNM no less than 5715 LNM. Report significant shoaling via weekly progress report. COR may adjust survey prioritization based on observed shoaling.Total project-wide LNM acquired for project OPR-P377-KR-18 totaled 5,738, which exceeded the required 5,715.Survey coverage graphicSupportFiles\H13112 Coverage.jpgASV-CW506250000017.70Qualifier 1050657.50000058.9001282.50000076.606.050001472018-06-112018-06-122018-06-132018-06-212018-06-222018-06-232018-06-242018-06-302018-07-012018-07-072018-07-152018-07-162018-07-172018-07-182018-07-202018-07-21Only bottom samples were acquired on 7/21.Refer 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.ASV-CW55.50.5Qualifier 105321.8Survey vessels used on this project - ASV-CW5 (foreground), Q105 (background)SupportFiles\Vessels.jpgThe Qualifier 105 (Q105) is a 32 m aluminum-hull vessel owned and operated by Support Vessels of Alaska. The Q105 acquired multibeam data and provided housing and facilities for on-site data processing. The vessel was also used to collect bottom samples, deploy/recover BMPG tide gauges, conduct sound speed casts, and deploy/recover the ASV-CW5 vessel. The ASV-CW5 (C-Worker 5) is a 5.5 m aluminum-hull Autonomous Surface Vessel (ASV) owned and operated by ASV Global. The ASV was operated in an unmanned but monitored mode, collecting multibeam data in close proximity to the Q105.Sea-Bird ScientificSBE 26 plusTide Guage, SubmergedTrimble5700Base StationTeledyne OceanscienceRapidcastSound Speed Deployment SystemValeportRapidSVSound Speed SystemApplanixPOS MV 320 v5Positioning and Attitude SystemApplanixPOS MV 320 v4Positioning and Attitude SystemTeledyne RESONSeabat T50MBESEffort was made to ensure crosslines had good temporal and geographic distribution, were angled to enable nadir-to-nadir comparisons, and that the required percent of mainscheme LNM was achieved. Crosslines were conducted with both vessels to ensure there was ample overlap for inter-vessel comparisons, with each vessel crossing the other's mainscheme lines. Since the two vessels worked in close proximity and normally ran parallel lines, crosslines were usually collected in sets when both vessels were in simultaneous operation. These lines were often collected when transiting across the survey area to reach a different survey priority. The crossline analysis was conducted using CARIS HIPS “Line QC Report” process. Each crossline was selected individually and run through the process, which calculated the depth difference between each accepted crossline sounding and a "QC" BASE (CUBE-type, 8 m resolution) surface’s depth layer created from the mainscheme data. QC surfaces were created with the same parameters used for 8 m surfaces as the final surfaces, with the important distinction that the QC surfaces did not include crosslines so as to not bias the results. Differences in depth were grouped by beam number and statistics were computed, including the percentage of soundings with differences from the QC surface falling within IHO Order 1a. Note for simplicity IHO Order 1a was used for all comparisons even though the looser IHO Order 2 standard was allowable for depths greater than 100 m. When at least 95% of the sounding differences exceed IHO Order 1a, the crossline was considered to “pass,” but when less than 95% of the soundings compare within IHO Order 1, the crossline was considered to “fail.” A 5% (or less) failure rate was considered acceptable since this approach compares soundings to a surface (instead of a surface to a surface), allowing for the possibility that noisy crossline soundings that don't adversely affect the final surface(s) could be counted as a QC failure in this process. Lines used as crosslines and their % of soundings passing IHO Order 1a, sorted from highest passing to lowest, are listed below. 0118-163-Q105-A1_XL -- 100.0% pass 0899-201-Q105-SheetA_XL_7 -- 100.0% pass 2062-196-ASV-CW5-A1-XL2 -- 100.0% pass 0100-162-Q105-A3-XL0001 -- 100.0% pass 0826-196-Q105-A1_XL_1 -- 100.0% pass 0898-201-Q105-SheetA_XL_6 -- 100.0% pass 0895-201-Q105-SheetA_XL_3 -- 100.0% pass 0889-201-Q105-SheetA_XL_1 -- 100.0% pass 0896-201-Q105-SheetA_XL_4 -- 100.0% pass 0123-164-Q105-A3-XL -- 100.0% pass 0897-201-Q105-SheetA_XL_5 -- 99.9% pass 0827-197-Q105-A1-XL3 -- 99.9% pass 0198-164-ASV-CW5-A2-360-XL -- 99.9% pass 0893-201-Q205-SheetA_XL_2 -- 99.7% pass 0184-163-ASV-CW5-B4_Nearshore-X -- 99.6% pass 0110-163-Q105-A3-A3-B3_XL -- 99.4% pass 0275-172-Q105-A3_XL1 -- 99.0% pass 0409-172-ASV-CW5-A3_XL2 -- 98.2% pass 0145-162-ASV-CW5-A3-A3-B3-XL2 -- 98.1% pass 0108-162-Q105-A3-A3-B3_XL1 -- 97.3% pass Results: Agreement between the mainscheme surface and crosslines soundings is excellent. At least 95% of crossline soundings compare to the mainscheme surface within IHO Order 1a. Refer to Separate II: Digital Data for the detailed Crossline QC Reports.0.0980ERS via PMVDASV-CW5020.025Qualifier 105020.025Real-time (dynamic) error estimates were computed and loaded for the majority of the survey data. This replaced the static error estimates for attitude and navigation during final TPU computation. Exceptions, if they exist, are listed in Section B.3 of this report. Refer to the DAPR for more information on derivation of the values used for TPU estimates. The BASE surfaces were finalized in CARIS HIPS so that the uncertainty value for each grid cell is the greater of either standard deviation or uncertainty. The uncertainty layer of each final surface was then examined for areas of uncertainty that exceeded allowable TVU for the depth (Order 1a for depths less than 100 m, and Order 2 for depths 100 m and deeper). Uncertainty for the surfaces ranges from 0.25 to 1.83 m. Greater than 99.5% of grid cells have uncertainty values within allowable TVU. Highest uncertainties were found in areas of varying bottom topography such as slopes and near bottom features where high standard deviations are caused by the wide depth ranges of soundings contributing to each grid cell, outer edges of multibeam swathes without adjacent line overlap, and areas with unrejected noisy soundings. Despite elevated TPU values for these grid cells, the data is within specifications.This survey junctions with three Current and one Prior survey. NOAA's "Gridded Surface Comparison V18.4" utility was used to complete the junction comparisons. The utility differences the surfaces from the junctioning surveys and generates statistics, including the percentage of grid cells that compare to within allowable TVU.Image showing junctions with this surveySupportFiles\H13112 Survey Junctions.jpgH12065400002009Terrasond, Ltd.WThe 8 m BAG surface "H12065_MB_8m_MLLW_combined.bag" was downloaded from NGDC to use for the comparison (from https://www.ngdc.noaa.gov/nos/H12001-H14000/H12065.html.) It was compared to an 8 m CUBE surface from this survey. During the analysis it was discovered that there was relatively little overlap achieved between the two surveys, despite effort made in the field to ensure sufficient coverage along the survey boundary. This was because the Junction boundary provided in the PRF was used to plan overlap during field operations, but it appears to have been overly generalized based on the 2009 survey resulting in the 2009 data not fully extending to its own boundary in the PRF. Despite this, there was sufficient overlap to compare the two surveys: This survey compares relatively well with H12065 despite the 9 year difference in survey dates. The mean difference between the two surveys in their overlapping area is 0.35 m (Prior survey H12065 is shoaler), with a standard deviation of 0.34 m. Over 99.5% of grid cells compare to within the allowable TVU.H13113400002018Terrasond, Ltd.NE4m CUBE surfaces from each survey was used for this comparison. Agreement is excellent. The mean difference between the two surveys in their overlapping area is 0.00 m, with a standard deviation of 0.14 m. Over 99.5% of grid cells compare to within the allowable TVU.H13114400002018Terrasond, Ltd.E4m CUBE surfaces from each survey was used for this comparison. Agreement is excellent. The mean difference between the two surveys in their overlapping area is 0.03 m, with a standard deviation of 0.22 m. Over 99.5% of grid cells compare to within the allowable TVU.H13115400002018Terrasond, Ltd.SE4m CUBE surfaces from each survey was used for this comparison. Agreement is excellent. The mean difference between the two surveys in their overlapping area is 0.05 m, with a standard deviation of 0.19 m. Over 99.5% of grid cells compare to within the allowable TVU.Sonar system quality control checks were conducted as detailed in the quality control section of the DAPR.Q105 Roll AlignmentIt became evident during operations that a roll bias was periodically present in data collected on the Q105 vessel. This was determined to correlate to deployment and retrieval of the hydraulic multibeam arm, which was not on the same physical mount as the motion sensor IMU on this vessel. Exact cause is unknown but small fluctuations in hydraulic pressure in the arm actuator are suspected. Effect on pitch and yaw, if any, was not discernible. The issue was addressed in processing by systematically examining lines exhibiting trouble and determining new roll alignment values--which was possible due to significant overlap with adjacent survey lines--and applying them via the HVF. There may be remnants of this error remaining periodically in the Q105 data set but the effect on final surfaces is minor and well within specifications. Additional discussion is available in the DAPR.Sound Speed ErrorMild to moderate sound speed error is evident periodically throughout the data set. This is observed as a general downward or upward cupping ("frowning" or "smiling") of the seafloor profiles. The issue was addressed in the field through a relatively high cast frequency and tightening of line spacing. In processing filters were used to remove outer beam soundings most subject to the error, and areas showing excessive "frowning" or "smiling" received additional manual data editing to reject soundings that adversely affected the final surfaces. The effect on final surfaces is relatively minor, generally less than 0.30 m, and within specifications.2Sound speed profiles or casts were acquired aboard the Q105 while underway with an Teledyne Oceanscience RapidCAST system, which utilized a Valeport RapidSV sound speed profiler. The interval between subsequent casts was approximately 2 hours. Casts were taken as deep as possible. On survey lines with significant differences in depth, the deeper portion of the line was favored to ensure changes across the full water column were measured. The cast data was used to correct the sounding data for both vessels, using the "nearest in distance within 4 hours" option within CARIS HIPS.All equipment and survey methods were used as detailed in the DAPR.* All ASV lines used real time attitude data (gyro, pitch, roll) as well as real-time TPU instead of the standard application of post-processed versions. This was due to roll alignment issues on some groups of lines when using the post-processed versions of the attitude data. Note that post-processed navigation and GPS height data was still applied per standard practice. * Applanix SmartBase was used instead of PP-RTX for the post-processing method on ASV lines with prefix 187 and 188 (from JD163) to address minor vertical busts in the PPRTX versionAll sounding systems were calibrated as detailed in the DAPR.All equipment and survey methods were used as detailed in the DAPR.NOAA Profile V_5_7H13112_MB_4m_MLLW_FinalCARIS Raster Surface (CUBE)43680NOAA_4mComplete MBESH13112_MB_8m_MLLW_FinalCARIS Raster Surface (CUBE)872160NOAA_8mComplete MBESThe final depth information for this survey was submitted as CARIS BASE surfaces (CSAR format) which best represented the seafloor at the time of the 2018 survey. The surfaces were created from fully processed data with all final corrections applied. Surfaces were created using NOAA CUBE parameters and resolutions by depth range in conformance with the 2017 HSSD. Surfaces were finalized, and designated soundings were applied where applicable. Horizontal projection was selected as UTM Zone 3 North, NAD83. Non-finalized versions of the CSAR surfaces are also included which do not have a depth cutoff applied. These do not have the "_Final" designation in the filename. An S-57 (.000) file was submitted with the survey deliverables as well. The final feature file (FFF) contains meta-data and other data not readily represented by the final surfaces, including bottom samples and shoreline verification results, if applicable. Each object is encoded with mandatory S-57 attributes and NOAA Extended Attributes (V#5.7). A georeferenced multibeam backscatter mosaic (Geotif format in NAD83 UTM Zone 3N, 1 m resolution) was also produced and is provided with the survey deliverables. Note that backscatter processing and mosaic generation was not a requirement of this survey and the mosaic is provided for interest only. The mosaic may have flaws or holidays which could be addressed through further processing. However, it is of sufficient quality to show the relative changes in seafloor type across the survey area.Additional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterERS via Poor Mans VDATUMOPR-P377-KR-18_NSPMVD_EPSG6332_NAD83-MLLW_Revised.csarAll soundings were reduced to MLLW using the NSPMVD grid provided by NOAA using ERS methodology. Discrete tide zones were provided but used only for preliminary corrections in the field, as well as comparisons. See HVCR for additional information.North American Datum 1983Projected UTM 3Smart BaseAB06False PassCORS station geometry allowed for Applanix SmartBase (ASB) processing on this project, with AB06 (False Pass) used as the the primary control station. However, ASB was only used on lines that experienced issues with PP-RTX. Lines using ASB are itemized in the Data Acquisition and Processing section of this report.The Trimble PP-RTX subscription-based correction service within POSPac was used for final positioning for the majority of lines. Results were good overall, usually at 0.10 m or better vertically.WAAS was used for real-time positioning only.The chart comparison was performed by examining the best-scale Electronic Navigational Charts (ENCs) that intersect the survey area. The latest edition(s) available at the time of the review were used. The chart comparison was accomplished by overlaying the finalized BASE surfaces with shoal-biased soundings, and final feature file on the charts in CARIS HIPS. The general agreement between charted soundings and survey soundings was then examined and a more detailed comparison was undertaken for any shoals or other dangerous features. In areas where a large scale chart overlapped with a small scale chart, only the larger scale chart was examined. When comparing to survey data, chart scale was taken into account so that 1 mm at chart scale was considered to be the valid radius for charted soundings and features. Results are shown in the following sections. It is recommended that in all cases of disagreement this survey should supersede charted data. USCG Notice to Mariners (NM) and USCG Local Notice to Mariners (LNM) were checked for updates affecting the area. No updates affecting the survey area issued subsequent to the date of the Hydrographic Survey Project Instructions and before the end of the survey were found.US3AK61M300000232018-08-132018-08-13falseAgreement is poor overall. Agreement is good in just a few cases. Best agreement is in areas that are relatively flat, likely due to the observation noted below. There appears to be a shift to the west or northwest for many charted soundings (and contours) as relative to the actual seafloor they appear to describe. In other words, moving the position of the charted soundings (and contours where applicable) to the east or southeast by 350-400 m would create a better match with survey data in many (but not all) cases. A common example of this is included in the list of figures below. Discrepancies of particular note are: Charted 96.9 m sounding at 54-28-11.688 N, 163-56-12.787 W was not confirmed by this survey. Despite the area around the sounding being relatively flat, no sounding approaching this depth was observed. The area in the vicinity of the sounding was found to be approximately 86 to 87m. A few other charted soundings nearby also show substantial discrepancy that can't be explained by a horizontal shift in soundings. The seafloor appears to be sand or other mobile materials; it is possible the area has significantly changed in this area by up to 10 m in places since the prior survey. A figure below shows shows the area of change. In a number of other cases it is evident the prior survey technology did not fully capture all seafloor features or depths. For example, a charted 96.9 m sounding at 54-31-34.367 N, 163-29-35.412 W was the shoalest depth in the area of a 50 m seafloor rock pile found approximately 840 m to the ENE. A figure below shows this example.West side of survey area: Soundings from this survey (red) shown on chart US3AK61M (yellow). Soundings in meters.SupportFiles\Chart_West.jpgCenter portion of survey area: Soundings from this survey (red) shown on chart US3AK61M (yellow). Soundings in meters.SupportFiles\Chart_Center.jpgEast side of survey area: Soundings from this survey (red) shown on chart US3AK61M (yellow). Soundings in meters.SupportFiles\Chart_East.jpgFar east side of survey area: Soundings from this survey (red) shown on chart US3AK61M (yellow). Soundings in meters.SupportFiles\Chart_FarEast.jpgExample -- 56 m charted sounding (yellow), appears displaced to the west of the actual seafloor it would be valid for by about 450 m. Charted soundings from this survey are red.SupportFiles\Offset_Sounding_Example.jpgDiscrepancy area -- charted soundings (yellow) from US3AK61M overlaid with soundings from this survey (red). The area appears to have deepened on the west side of the red-dashed area slightly while shoaling significantly on the east side.SupportFiles\Chart_Discrepancy.jpgCharted 97 m sounding (yellow) and other nearby charted soundings show no indication of the 50 m sounding from this survey (red) to the ENE.SupportFiles\Chart_SoundingTechnology.jpgUS4AK5CM8066072018-07-062018-07-06falseAgreement is poor to fair between this chart and the survey. Many soundings agree well while just as many show poor agreement. Greatest discrepancies are usually on slopes and areas of rugged seafloor where it is likely the survey technology used to produce the charted soundings did not fully capture the least depths of the area. An example is shown in a figure below. Soundings from this survey (red) shown on chart US4AK5CM (yellow). Soundings in meters.SupportFiles\Chart5CM_Overview.jpgSoundings from this survey (red) shown on chart US4AK5CM (yellow) in the NE part of the survey. Soundings in meters. Charted soundings miss least depths on seafloor structure in this area.SupportFiles\Chart_NE.jpgNo Maritime Boundary Points were assigned for this survey.No charted features exist for this survey.No uncharted features exist for this survey.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. The survey intersects a charted restricted area with the note "All ships 400 gross tonnage and upwards solely in transit should avoid the Area. This Area is IMO-Adopted (MSC IMO SN.1/Circ.331)."Six bottom samples locations were assigned that fell within the extents of this sheet. Samples were successfully obtained at all locations except one: A bottom sample was not obtained at the assigned location 54-30-35.541 N, 163-44-45.505 W, despite three attempts on site. It is included with NATSUR set to "Unknown" in the accompanying FFF. Black sand was a common constituent in the majority of samples. Broken white shells were a common secondary constituent in most samples as well. Courser materials such as gravel and pebbles were only found in the eastern samples; the western samples were primarily sand or mud. The assigned samples did not correspond to charted samples. Bottom samples are included in the FFF. Photos of the sample, if available, are included in the accompanying "multimedia" folder.Shoreline was not assigned in the Hydrographic Survey Project Instructions or Statement of Work. The survey area does not intersect shoreline.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 platforms exist for this survey.Ferry routes and/or terminals exist for this survey, but were not investigated. During this survey the Alaska Marine Highway System (AMHS) ferry MV Tustumena was observed transiting the area. AMHS provides ferry service approximately every two weeks during the summer months between Homer, Kodiak, and Dutch Harbor as well as various ports between.No abnormal seafloor and/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 insets are recommended for this area.Field operations contributing to the completion of this survey were conducted under my direct supervision with frequent personal checks of progress, integrity, and adequacy.This report, digital data, and all other accompanying records are approved. All records are respectfully submitted for final review and acceptance.The survey data meets or exceeds requirements as set forth in the NOS Hydrographic Surveys Specifications and Deliverables document as well as the Hydrographic Survey Project Instructions and Statement of Work. This data is adequate to supersede charted data in their common areas. This survey is complete and no additional work is required with the exception of deficiencies--if any--noted in the Descriptive Report.Andrew Orthmann, C.H.TerraSond Charting Program Manager2018-12-29Marine Mammal Observers Training Logsheet and Observation Logs2018-08-28NCEI Sound Speed Data Submission2018-11-07Coast Pilot Review Report2018-12-17