OPR-O193-RA-13Behm Canal, AKBehm CanalNOAA Ship RAINIERH125181Vicinity of Burroughs BayAlaskaUnited States400002013Richard T. Brennan, CDR/NOAANavigable Area2013-04-012013-05-092013-06-18Multibeam Echo SounderMultibeam Echo Sounder BackscattermetersUniversal Transverse Mercator (UTM)UTCPacific Hydrographic BranchNOAAThe area surveyed is referred to as Sheet 1: "Vicinity of Burroughs Bay" within the Project Instructions. The area is in the northern portion of the eastern branch of Behm Canal near Ketchikan, Alaska (Figure 1).56.05131.25833333355.775130.9666666671H12518 survey limits.SupportFiles\Figure_A_1_1_X1_Survey_Limits.pngThe purpose of this project is to provide contemporary surveys to update National Ocean Service (NOS) nautical charting products.The entire survey is adequate to supersede previous data.Data acquired on survey H12518 met complete multibeam echosounder (MBES) coverage requirements, including the 5 soundings per node data density requirements outlined in Section 5.2.2.2 of the HSSDM (Figure 2). In order to extract some descriptive statistics of the data density achievements, the density layer of each finalized surface was queried within CARIS and then examined in Excel (Figure 3). Overall, the required data density was achieved in 98.7% of the nodes and 99.8% of the total area.2H12518 data density.SupportFiles\Figure_A_3_X1_Density_plot.png3Summary table showing the percentage of nodes satisfying the 5 sounding density requirements, sub-divided by the appropriate depth ranges. Note: The final row has a unit of square meters, and sums the number of different resolution nodes into a common unit of area.SupportFiles\Figure_A_3_X1_Density_table.pngSurvey limits were acquired in accordance with the requirements in the Project Instructions and the Hydrographic Survey Specifications and Deliverables Manual (HSSDM).4Acquired survey coverage overlaid on Chart 17424.SupportFiles\Figure_A_4_X1_Survey_Coverage.pngComplete multibeam (MBES) coverage was achieved within the limits of hydrography as defined in the Project Instructions (Figure 4). There are a few gaps in coverage where multibeam data did not meet the sheet limit nor the 4-meter curve. In all cases, these gaps were nearshore and dangerous to approach, and were therefore deemed to be inshore of the NALL. Further, HSD has acknowledged minor gaps along the sheet limits, which the field determines to be non-navigationally significant, need not be acquired (see Supplemental Correspondence - HSD_holidays_on_edge.pdf).2013-05-082013-05-132013-05-142013-05-152013-06-162013-06-1770053029.0S221074.700000002801 (RA-4)0138.400000002802 (RA-5)030.600000002803 (RA-3)010.000000002804 (RA-6)013.40000018.100267.10000018.106.8Refer 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.2801283.52802283.52803283.52804283.5S22123116.5Data was primarily acquired by RAINIER (S221) for the deep central portion of the survey, with limited nearshore mainscheme data acquired with survey launches (2801, 2802, 2803 and 2804) (Table 4). The vessels acquired multibeam echosounder (MBES) soundings, sound speed profiles, and bottom samples.KongsbergEM710MBESReson7125MBESApplanixPOS-MV V4Attitude SystemSeabirdSBE 19 PlusSound Speed SystemODIM Brooke Ocean (Rolls Royce Group)MVP30Sound Speed SystemODIM Brooke Ocean (Rollys Royce Group)MVP200Sound Speed SystemResonSVP 71Sound Speed SystemResonSVP 70Sound Speed SystemMultibeam crosslines were acquired using the Reson 7125 on Launch 2804. Crosslines totaled 18.1 NM, which comprised 6.8% of mainscheme hydrography. An 8-meter CUBE surface was created using strictly the mainscheme lines, while a second 8-meter CUBE surface was created using only crosslines, from which a difference surface was generated at an 8-meter resolution (Figure 5). Statistics were then derived from the difference surface and are shown in Figure 6. The average difference between the depths derived from mainscheme and crosslines was 0.56 meters (mainscheme being deeper) with a standard deviation of 2.41 meters. There is a bimodal distribution in the depth differences (Figure 6), which has a distinct geographic trend (Figure 5). Generally speaking, the crosslines were deeper in deep central portions of the survey area, and shoaler in the shoal waters closer to shore. This deep-biasing in the deeper waters may be a function of the crosslines being acquired with the Reson 7125, which is seldom operationally deployed in waters deeper than 200 meters; in the areas of overlap, crossline depths exceeded 500 meters. For the respective depths, the difference surface was compared to the allowable IHO accuracy standards (Figure 7). In total, 95.6% of the depth differences between H12518 mainscheme and crossline data are within allowable IHO accuracies (Figure 8). The majority of the inconsistencies are on the steep inclines and may simply be an artifact of the gridding algorithm. In addition to performing a crossline comparison using surface differencing, the CARIS QC Report was used to compare the crossline soundings to the depth estimates of the 8-meter resolution surface. The depth differences are calculated between each crossline ping and mainscheme surface; and that depth difference is then compared to allowable IHO uncertainties. The output QC Report classifies the percentage of pings meeting IHO orders by beam angle. This table was copied and examined in Excel (Figure 9). Only 90% of the pings up to 40-degrees from nadir satisfy IHO Order 2. The relatively low percentage of pings meeting IHO standards is largely due to the depth of water (averaging 263 meters in the area of overlap), which exceeds the operational limits of the Reson 7125 (which will seldom return a full swath in depths greater than 200 meters).5H12518 crosslines.SupportFiles\Figure_B_2_1_Crossline_overview_PN.png6Crossline comparison with mainscheme lines.SupportFiles\Figure_B_2_1_X2_Crossline_table.png7Depth differences between H12518 mainscheme and crossline data as compared to allowable IHO accuracy standards for the associated depths.SupportFiles\Figure_B_2_1_X3_Crossline_IHO.png8Summary table showing percentage of difference surface nodes between H12518 mainscheme and crossline data that meet allowable IHO accuracy standards for the associated depths.SupportFiles\Figure_B_2_1_X4_Crossline_IHO_table.png9CARIS QC Report comparing crossline soundings to depth estimates.SupportFiles\Figure_B_2_1_X5_Crossline_QCreport.png00.0728013.1528023.1528033.15280431.15S2211.05In addition to the usual a priori estimates of uncertainty, some real-time and post-processed uncertainty sources were also incorporated into the depth estimates of survey H12518. Real-time uncertainties from both the EM710 and Reson 7125 were recorded and applied in post-processing. Applanix TrueHeave files are recorded on all survey vessels, which includes an estimate of the heave uncertainty, and are applied during post-processing. Finally, the post-processed uncertainties associated with vessel roll, pitch, gyro and navigation are applied in CARIS HIPS via an SBET RMS file generated in POSPac. Uncertainty values of submitted finalized grids were calculated in CARIS using the "Greater of the Two" of uncertainty and standard deviation (scaled to 95%). To visualize the locations in which accuracy requirements were met for each finalized surface, a custom predicted IHO-compliance layer was created, based on the difference between calculated uncertainty of the nodes and the allowable IHO uncertainty (Figure 10). To quantify the extent to which accuracy requirements were met, the preceding predicted IHO-compliance layers were queried within CARIS and then examined in Excel (Figure 11). Overall 100.0% by node and 100.0% by area of survey H12518 met the accuracy requirements stated in the HSSDM.10H12518 met IHO accuracy standards for 99.8% of the survey area.SupportFiles\Figure_B_2_2_X1_IHO_overview.png11Summary table showing the percentage of nodes satisfying the indicated IHO accuracy level, sub-divided by the appropriate depth ranges. Note: The final row has a unit of square meters, and sums the number of different resolution nodes into a common unit of area.SupportFiles\Figure_B_2_2_X2_IHO_table.pngOne junction comparison was completed for H12518 (Figure 12). The junctioning survey, H12519, was acquired concurrently with this survey. Depth comparisons were performed using the CARIS Difference Surface and CARIS Subset Editor.H12519400002013NOAA Ship RAINIERNOverlap with survey H12519 was 400 meters wide along the 4,000 meter southern boundary of H12518 (Figure 13). Depths in the junction area range from 20 to 350 meters. A 16-meter CARIS Difference Surface analysis between CUBE depth surfaces for each survey showed H12518 to be an average of 0.04 meters shoaler than H12519, with a standard deviation of 2.06 meters (Figure 14). For the respective depths, the difference surface was compared to the allowable IHO accuracy standards (Figure 15). In total, 91.2% of the depth differences between H12518 and junctioning survey H12519 are within allowable IHO accuracies (Figure 16). Inspection of the data in CARIS Subset Editor (Figure 17), shows great agreement between the two surveys, suggesting the majority of the inconsistencies seen in the difference surfaces are just artifacts of the gridding algorithm.12Overview of junctions with survey H12518.SupportFiles\Figure_B_2_3_X0_Junction_overview.png13Difference surface between H12518 (purple) and junctioning survey H12519 (orange).SupportFiles\Figure_B_2_3_X1_Junction_diff_surface.png14Difference surface statistics between H12518 and H12519 CUBE depth layers (16-meter grid size). H12518 is an average of 0.04 meters shoaler.SupportFiles\H12519_H12518_JNX_graph.png15Depth differences between H12518 and junctioning survey H12519 as compared to allowable IHO accuracy standards for the associated depths.SupportFiles\Figure_B_2_3_X3_H12518_Junction_IHO_compliance.png16Summary table showing percentage of difference surface nodes between H12518 and junctioning survey H12519 that meet allowable IHO accuracy standards for the associated depths.SupportFiles\Figure_B_2_3_X3b_H12518_Junction_IHO_table.png17Subset view of sonar data between H12518 (yellow) and junctioning survey H12519 (red).SupportFiles\Figure_B_2_3_Junction_subset2.pngSonar system quality control checks were conducted as detailed in the quality control section of the DAPR.Loss of GAMS solution.On DN167 (16 June), Launch 2802 experienced numerous drops in position throughout the day; this was likely due to a combination of high PDOP and satellite masking by the surrounding mountains. The post-processing of position via POSPac was able to remedy some, but not all, of the errors in the trajectory file (Figure 18). Every line from this day was closely scrutinized for potential errors in navigation or attitude records. All cases in which the affected lines diverged from neighboring data, the affected soundings were flagged as rejected. The lines requiring editing were DN167-1821, 1831, 1835, 1857 and 1928.18Example of the effects of GPS drop outs and loss of GAMS solution on a single survey line: upper inset shows artifact during loss of GAMS solution, while lower inset shows agreement between datasets while GAMS is in use.SupportFiles\Figure_B_2_5_X1_GPS_dropping.pngEllipsoid-to-Tidal surface comparisonUsing the GPS height determined from the SBET file, data from H12518 was referenced to the ellipse and gridded. By differencing this ellipsoidally-referenced surface (ERS) from the traditional tidally-referenced surface, one should only see the ellipsoidal slope across the length of the survey. Any deviations from this slope would therefore be the result of an error intrinsic to either the ERS or tidal processing work flow. For example, misprojected SBETs, current-induced dynamic draft, incorrect waterline measurements, corrupt True Heave files, or poorly-modeled water levels are all examples of artifacts that can be identified through the difference of the ERS and tidally-referenced surfaces. Figure 19 shows the gentle slope of the ellipse from north to south in the vicinity of survey H12518. Given there were no major "bright spots" in the difference surface, none of the artifacts mentioned in the previous paragraph are likely present, in any substantial amount, in survey H12518. Extending the ellipsoidal-to-tidal surface across the entire Behm Canal project (Figure 20), one can see the ellipsoid slope seen in survey H12518 continues through junctioning survey H12519.19Difference surface between the ellipsoidally-referenced and tidally-referenced surfaces.SupportFiles\Figure_B_2_6_X1_ERS_diff_MLLW.png20Difference surface between the ellipsoidally-referenced and tidally-referenced surfaces across the entire Behm Canal project.SupportFiles\Figure_B_2_6_X2_ERS_diff_MLLW.pngSurface Sound SpeedSurface sound speed values were observed to vary temporally and spatially throughout the survey area, with the largest variations being near the Unuk and Klahini Rivers at the head of Burroughs Bay (Figure 21). A fresh water lens spread across the length of Burroughs Bay leading to sound speed changes of up to 30 meters/second. To mitigate the potential refraction errors, extra sound speed profiles were acquired in the upper arm of Burroughs Bay (for further details, see Section B.2.7 - Sound Speed Methods).21Plot of surface sound speed as recorded on a single day while acquiring crossline data. Fresh water inflow from rivers at the head of Burroughs Bay, lead to a fresh water lens and corresponding drop in surface sound speed.SupportFiles\Figure_B_2_6_X3_Surface_SV.pngFor data collected by launches, sound speed profiles were acquired using the SBE 19plus CTDs at discrete locations within the survey area at least once every four hours, when large changes in surface sound speed were apparent, and when moving to a new area. For data collected on S221 (RAINIER), sound speed profiles were acquired using the Rolls Royce MVP200 approximately every 15 minutes or when recommended by "CastTime", a cast frequency program developed at the University of New Hampshire. All casts were concatenated into a master file for the entire survey and (with the exception of one line) applied to lines using the "Nearest in distance within time (4 hours)" profile selection method (Figure 22). On DN135 (15 May) a line of opportunity was acquired by S221 without deploying the MVP (Line 0024). The most appropriate cast was acquired by a survey launch which was working in the same area at a different time. In order for this cast to be applied, the survey line was processed using the "Nearest in distance within time (6 hours)" profile selection method. The affected line was examined in Subset Editor, which showed good agreement between neighboring lines.22Distribution of sound speed profiles acquired for survey H12518.SupportFiles\Figure_B_2_7_X1_Cast_Locations.pngAll equipment and survey methods were used as 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.Backscatter data was acquired, but not formally processed by RAINIER personnel. However, periodic spot checks were performed to ensure backscatter quality. A preliminary backscatter mosaic of data acquired by S221 is shown in Figure 23. Backscatter was logged as 7k or .ALL files and submitted to NGDC, but is not included with the data submitted to the Branch.23H12518 backscatter mosaic of S221 lines.SupportFiles\Figure_B_4_X1_Backscatter.pngNOAA Extended Attribute Files Version 5_3_2All final data processing was performed using CARIS HIPS and SIPS 7.1.2.6. It should be noted that all Kongsberg EM710 data was intentionally processed without the Simrad Sound Velocity Correction (SVC) module. This was done in order to avoid a known error in the SVC module associated with reverse-mounted transducers. To accomplish this, a custom CARIS license file was used, which excluded the licensing for the Simrad SVC. For further details, refer to the DAPR.H12518_1mCUBE1-2600NOAA_1mComplete MBESH12518_2mCUBE2-2600NOAA_2mComplete MBESH12518_4mCUBE4-2600NOAA_4mComplete MBESH12518_8mCUBE8-2600NOAA_8mComplete MBESH12518_16mCUBE16-2600NOAA_16mComplete MBESH12518_32mCUBE32-2600NOAA_32mComplete MBESH12518_1m_-10to40_FinalCUBE1-240NOAA_1mComplete MBESH12518_2m_18to80_FinalCUBE21880NOAA_2mComplete MBESH12518_4m_36to160_FinalCUBE436160NOAA_4mComplete MBESH12518_8m_72to320_FinalCUBE872320NOAA_8mComplete MBESH12518_16m_144to500_FinalCUBE16144500NOAA_16mComplete MBESH12518_32m_288to600_FinalCUBE32288600NOAA_32mComplete MBESH12518_Combined_32mCUBE32-2600NOAA_32mComplete MBESIn order to prevent apparent coverage gaps resulting from the gridding algorithm in the "steep and deep" bathymetry found in H12518 (Figure 24), finalized surfaces were extended beyond the depth thresholds specified in the HSSDM. For example, rather than gridding the data at a 2-meter resolution between 18 and 40 meter depths; the depth range was extended to between 18 and 80 meter depths. All other finalization depth ranges are stated in Table 10.24(Top) Finalized surfaces created using depth thresholds specified in the HSSDM; notice the gaps between depth resolutions. (Bottom) The same region gridded at the finest resolution shows the data is free of coverage gaps.SupportFiles\Figure_B_5_2_X1_Surface_Resolutions.pngAdditional information discussing the vertical or horizontal control for this survey can be found in the accompanying HVCR.Mean Lower Low WaterDiscrete ZoningKetchikan, AK9450460Burroughs Bay, AK94509179450917.tidVerified ObservedH12518CORP.zdfFinal2013-06-212013-08-02The operating NWLON primary tide station in Ketchikan, AK (9450460), as well as a subordinate tide station installed by RAINIER personnel at Burroughs Bay, AK (9450917) served as the controls for datum determination and water level reducers for survey H12518. A complete description of the vertical and horizontal control for this survey can be found in the accompanying OPR-O193-RA-13 Horizontal and Vertical Control Report (HVCR), submitted under a separate cover.North American Datum of 1983 (NAD83)UTM - 09 NorthSingle BaseChannel Island, AKN/AIn conjunction with this project, a GNSS base station was established by RAINIER personnel on Channel Island near the center of the survey area. Vessel kinematic data was post-processed using Applanix POSPac processing software as described in the DAPR. Single Base processing was used from DN133 to DN134 while the site was installed.The PPK base station on Channel Island was removed on DN135 to relocate to the next project area. Therefore, a PPK solution was not possible for DN135, DN167, and DN168. To provide enhanced positioning data, a PPP solution was used for those days. Data processed by PPP correlated well with surrounding data processed with PPK. Additionally, for testing purposes, DN129 was processed using PPP. The lines showed high correlation with surrounding data and was never reprocessed using PPK.Biorka Island, AK (305 kHz)Level Island, AK (295 kHz)Annette Island, AK (323 kHz)DGPS was used for primary positioning during acquisition. Following PPK or PPP processing, DGPS position data was replaced with improved SBET navigation data.Two principle methods were used in comparing survey H12518 to the contemporary charts. From the survey data, contours and soundings were generated and compared to the raster chart. For the Electronic Navigation Chart (ENC), a TIN was generated from all soundings and contours within the ENC (Figure 25). From this TIN, an interpolated surface was generated, which was then differenced from the survey data for the purposes of visualization and computing statistics. For specific details on the chart comparisons for survey H12518, refer to Section D.1.1 - Raster Charts, and Section D.1.2 - Electronic Navigation Charts.25TIN and interpolated surface generated from ENC US4AK43M and US4AK44M for the purposes of a chart comparison to survey H12518.SupportFiles\Figure_D_1_X1_ENC_TIN.png1742427378000092009-102013-08-142013-08-14A comparison was performed between survey H12518 and Chart 17424 (1:80000) using CARIS sounding and contour layers derived from the 32-meter combined surface. The contours and soundings have been overlaid on the chart, and a representative area is shown in Figure 26. Throughout the survey, the 100-fathom contour is closely followed by the survey data; however the charted 3-fathom contour has likely been pulled offshore for cartographic reasons and is seldom correctly modeled. Given the extreme steep and deep nature of the bathymetry, the 3-fathom contour is inappropriate for this area and the Hydrographer recommends removing it from the chart. For a further discussion of the surveyed depths to charted sounding comparison, refer to Section D.1.2 - Electronic Navigation Charts. It is recommended that H12518 data supersede all charted depths on Chart 17424. 26Close-up of Burroughs Bay, showing comparison of contours derived from survey H12518 and those depicted on Chart 17424.SupportFiles\Figure_D_1_1_X1_Contours.png1742227318000092006-022013-08-142013-08-14In the vicinity of survey H12518, Chart 17422 is equivalent to Chart 17424. Please refer back to the previous section for a comparison of survey H12518 and Chart 17424.US4AK44M8000022011-12-122011-12-12falseENC US4AK44M coincides with raster Chart 17424 (with a small contribution from US4AK43M). To compare soundings, a TIN surface was created from the ENC depth features (soundings and contours). A 16-meter surface from H12518 was then differenced from the ENC TIN (Figure 27). Positive (red) values show where survey H12518 is shoaler than the TIN and negative (blue) values show where survey H12518 is deeper than the TIN. Overall, the surveyed depths and charted soundings agree well in the center of the channel; otherwise, there is a tendency for the chart to express a shoal biasing in the soundings (sometimes by over 10 fathoms). Figure 28 shows a close-up of the depth comparisons in the vicinity of Fitzgibbon Cove and Saks Cove. One can see how all the soundings near shore (shoaler than 100 fathoms) are typically much shoaler than H12518 depths (likely because the soundings were pulled offshore for cartographic reasons). Figure 28 also shows that, generally, the survey and chart agree in the two coves.27Difference surface between depth estimates from survey H12518 and an interpolated surface created from the soundings and contours of ENC US4AK44M (with a small contribution from US4AK43M).SupportFiles\Figure_D_1_2_X1_ENC_diff.png28Close-up view of Fitzgibbon and Saks Coves and difference surface between depth estimates from survey H12518 and the TIN surface. Charted nearshore soundings (except within the coves) appear to have been pulled offshore for cartographic reasons.SupportFiles\Figure_D_1_2_X2_ENC_diff_inset.pngUS4AK43M8000022012-09-202012-09-20falseENC US4AK43M only intersects with a small portion of survey H12518 (Figure 23). For the purposes of the chart comparison, both US4AK43M and US4AK44M were compiled into the TIN discussed previously that was used to create the difference surface. Please refer back to the previous section for a comparison of survey H12518 and ENC US4AK44M.No AWOIS items were assigned for this survey.No Maritime Boundary Points were assigned for this survey.Within the extents of survey H12518, Chart 17424 reports "tide rips" in two locations (Figure 29). Though the RAINIER worked in the area through two spring tides, with daily tidal ranges exceeding five meters, no tidal rips were observed in the project area.29Tide rips reported on Chart 17424.SupportFiles\Figure_D_1_5_X1_Charted_Feature.pngNo uncharted features exist for this survey.No Danger to Navigation Reports were submitted 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.Eighteen bottom sample locations were identified in the Project Reference File. Eleven assigned bottom samples, where depths exceeded 100 meters, were not acquired due to equipment limitations. Seven bottom sample locations were selected based on feasibility and distribution throughout the survey area (Figure 30). Acquired bottom samples are addressed, as required, with S-57 attribution and recorded in the Final Features File accompanying this submission.30Bottom samples in H12518.SupportFiles\Figure_D_1_10_Bottom_Samples.pngShoreline verification was conducted near predicted low water in accordance with the applicable sections of the NOAA HSSDM and FPM. There were 56 assigned features for this survey. All features were addressed as required with S-57 attribution and recorded in the H12518 Final Features File to best represent the features at chart scale.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.Originating at the head of Burroughs Bay, and wrapping around Pt Fitzgibbon is, what appears to be, an ancient submerged riverbed (Figure 31). This meandering riverbed is pronounced in depths of up to 400 meters, and, in places, has scoured a trench in the seafloor of up to 50 meters.31Ancient submerged riverbed located at the head of Burroughs Bay.SupportFiles\Figure_D_2_8_Significant_Feature.pngNo 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 Manual, Field Procedures Manual, Standing and 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.Richard T. Brennan, CDR/NOAACommanding Officer, NOAA Ship RAINIER2013-08-15Michael O. Gonsalves, LT/NOAAField Operations Officer, NOAA Ship RAINIER2013-08-15James B. JacobsonChief Survey Technician, NOAA Ship RAINIER2013-08-15Damian Manda, LTJG/NOAAJunior Officer, NOAA Ship RAINIER2013-08-15