OPR-K379-KR-15 Approaches to Atchafalaya Bay, LA Approaches to Atchafalaya Bay, LA C&C Technologies, An Oceaneering International Company H12791 5 22 NM S of Point Au Fer Louisiana USA 40000 2015 Tara Levy Navigable Area 2015-07-14 2015-09-06 2016-03-26 meters Universal Transverse Mercator UTC Atlantic Hydrographic Branch Contractor The survey area is located 22 NM S of Point Au Fer off the coast of Louisiana, USA. 29.023 91.425 28.934 91.321 The purpose of this survey is to provide a contemporary survey to update National Ocean Service (NOS) nautical charting products. Survey H12791 covers 27.34 square nautical miles (SNM) near the Atchafalaya River. The river is the only expanding river delta in North America and the Port of Morgan City has been working to deepen and maintain the channel. The project potentially covers altered area where depth contours may have migrated. The entire survey is adequate to supersede previous data. Survey coverage for H12791 (Figure 1) was collected in accordance with the requirements outlined in the Project Instructions and HSSD (2015). 100% side scan sonar (SSS) coverage was acquired with concurrent multibeam echosounder (MBES) data. A combination of complete MBES with backscatter and/or water column data and/or SSS data was collected for feature investigations. Figure 1.  H12791 Survey Coverage. SupportFiles\H91_Fig1_SurveyCoverage.tif LAZ74232C313 0 0 0 0 0 546.82 0 0 0 1237094 0 0 0 0 0 84.48 0 52.48 0 JQN00023E708 0 0 0 0 0 0 0 0 0 0 0 0 0 0 631.30 0 52.48 0 8.31 8 0 0 57 0 27.34 2015-09-06 2015-09-07 2015-09-08 2015-09-09 2015-09-10 2015-09-16 2015-09-17 2015-09-18 2015-09-19 2015-09-20 2015-09-21 2015-09-26 2015-10-09 2015-10-28 2015-10-29 2015-10-30 2015-11-30 2015-12-01 2015-12-02 2015-12-08 2015-12-09 2015-12-10 2016-01-25 2016-01-30 2016-01-31 2016-02-01 2016-02-20 2016-02-21 2016-02-22 2016-03-26 The following table lists the mainscheme and crossline acquisition mileage for this survey. Note that these statistics exclude investigation, fill-in, feature disproval and rerun line mileage. Detached positions include position fixes associated with bottom samples, CTD’s, leadlines and platform fixes. Refer to the OPR-K379-KR-15 Data Acquisition and Processing Report (DAPR) for additional information regarding survey systems as well as operational, processing and quality control procedures. A summary of the equipment and vessels used for this survey is provided below. LAZ74232C313 5.8 0.9 1237094 40.84 1.98 JQN00027E708 9.14 0.76 Kongsberg EM2040C MBES Kongsberg EM3002 MBES Klein 5000 V2 SSS EdgeTech 4200 P 300/600kHz SSS EdgeTech 4125 SSS Coda Octopus F180 Attitude and Positioning System Forum OCTANS 3000 Gyrocompass and motion sensor C-Nav 3050 Positioning System AML SV*Xchange Sound Speed System YSI Electronics 600R-BCR-C-T Sound Speed System Sea-Bird Electronics, Inc SBE 19 and SBE 19 plus Sound Speed System The following major systems were used for data acquisition during this survey: Crosslines were run perpendicular to mainscheme lines so that quality control statistics could be performed on the data after completion of mainscheme survey lines. The total crossline miles were 52.48 NM and the total mainline miles were 631.30 NM; investigation lines were not included in mainline totals. The crosslines comprise 8.31 percent of the total mainline miles. Mainlines were compared to crosslines for which there was overlapping data (for Kongsberg .all files only) using C & C’s proprietary Hydromap software. The graphs generated from the comparison show the mean difference, RMS difference and confidence interval for each beam. Refer to the DAPR for additional information and Separates II Digital Data for sample graphical documentation. The surface difference tool in CARIS HIPS was used to evaluate crossline and mainscheme line agreement; investigations were not included in the comparisons. The mainline BASE surface was used as Surface 1 and the crossline BASE surface as Surface 2. Statistical information about the difference surface was generated using the compute statistics tool (Figure 2). The analysis shows that greater than 97% of depth difference values are between -0.41 and 0.39 m. This is within the maximum allowable TVU for the depths of the comparison area (5.17 – 12.74 m) which ranges from ±0.504 to ±0.527 m. Factors contributing to depth difference values greater than ±0.50 meters, include the following: changes bathymetry, which appears more prominently in the eastern portion of the survey area, overlap of the edges of MBES swaths and overlap of data with motion artifacts, which is evident in the southern portion of the survey area. Statistical crossline information was also generated by comparing each of the crosslines to the depth layer of the 1-m BASE surface of the mainscheme survey lines using the CARIS QC report utility. In general, greater than 99% of crossline soundings fall within the selected Order 1a survey order, as outlined in the CARIS User Manual. Crossline comparisons generated with the CARIS QC report utility as well as the difference BASE surface are shown in the Separates II Digital Data\Checkpoint Summary & Crossline Comparisons folder. Figure 2. Crossline comparison statistical information and histogram output from CARIS compute statistics tool. SupportFiles\H91_Fig2_CrosslineComparison.jpg The areas of overlap between Sheets (Figure 3) were evaluated using the CARIS Difference Tool to ensure general agreement of depths. Junction analyses were conducted using 1 or 2 meter BASE surfaces and/or .bag files of all the Sheets. If necessary, data was further reviewed in Subset Editor. Figure 3. H12791 Junctions. SupportFiles\H91_Fig3_SurveyJunctions.tif H12433 40000 2012 C&C Technologies, Inc. SE The northwest margin of H12433 borders the southeast margin in H12791. Two meter BASE surfaces were used for comparison purposes. Figure 4 shows statistical information for the junction generated with the CARIS compute statistics tool. Depths from survey H12791 generally agree well with depths from survey H12433 with 89% of depth difference values within ±0.35 m. Figure 4. Statistical information and histogram output from CARIS Compute Statistics tool for the difference surface generated between H12791 and H12433 2-meter surfaces. SupportFiles\H91_Fig4_Junction_H12433.jpg H12434 40000 2012 C&C Technologies, Inc. E The western margin of survey H12434 borders the eastern margin of survey H12791. Two meter BASE surfaces were used for comparison purposes. Figure 5 shows statistical information for the junction generated with the CARIS compute statistics tool. Depths from survey H12791 generally agree well with depths from survey H12434 with 88% of depth difference values within ±0.30 m. In the southern portion of overlap, survey H12434 shows depressions that are not present in H12791. Surveyed soundings from H12791 are shallower than those of H12434 in these areas. However, the majority of depth differences show a slight trend towards more positive values. This indicates that depths from H12791 are generally deeper than those of H12434, with nearly 95% of values between -0.19 and 0.41 m. Figure 5. Statistical information and histogram output from CARIS Compute Statistics tool for the difference surface generated between H12791 and H12434 2-meter surfaces. SupportFiles\H91_Fig5_Junction_H12434.jpg H12436 40000 2012 C&C Technologies, Inc. S The northern margin of survey H12436 borders the southern margin of survey H12791. Two meter BASE surfaces were used for comparison purposes. Figure 6 shows statistical information for the junction generated with the CARIS compute statistics tool. The difference values exhibit a positive bias, which indicates overall deeper depths recorded in H12791 than in H12436 with nearly 90% of values falling in between 0.04 and 0.54 m. Figure 6. Statistical information and histogram output from CARIS Compute Statistics tool for the difference surface generated between H12791 and H12436 2-meter surfaces. SupportFiles\H91_Fig6_Junction_H12436.jpg H12556 40000 2013 C&C Technologies, Inc. SW The eastern margin of survey H12556 borders the western margin of survey H12791. One meter BASE surfaces were used for comparison purposes. Figure 7 shows statistical information for the junction generated with the CARIS compute statistics tool. Depths from survey H12791 are generally shallower than those recorded from survey H12556 with 94% of depth differences between -0.54 and 0.06 m. Figure 7. Statistical information and histogram output from CARIS Compute Statistics tool for the difference surface generated between H12791 and H12556 1-meter surfaces. SupportFiles\H91_Fig7_Junction_H12556.jpg H12789 40000 2015 C&C Technologies, Inc. An Oceaneering International Company NW The southeast margin of survey H12789 borders the northwest margin of survey H12791. One meter BASE surfaces were used for comparison purposes. Figure 8 shows statistical information for the junction generated with the CARIS compute statistics tool. Depths from survey H12791 agree well with depths from survey H12789 with 99% of depth difference values within ±0.30 m. Figure 8. Statistical information and histogram output from CARIS Compute Statistics tool for the difference surface generated between H12791 and H12789 1-meter surfaces. SupportFiles\H91_Fig8_Junction_H12789.jpg Odom single beam echosounders were continuously operated and monitored during the survey as an independent check on the multibeam bottom-detect. The R/V Sea Scout (Hull ID 1237094) is equipped with an Echotrac MK III, and the R/V C-Wolf (Hull ID JQN00027E708) is equipped with an ODOM CV-100. The C-Worker 6 (Hull ID LAZ74232C313) was not equipped with a single beam echosounder. However, a series of patch tests conducted by the C-Worker 6 and verification lines collected with the R/V Sea Scout over the same contact demonstrated the repeatability of depths obtained from the C-Worker 6; refer to the System Accuracy Test Reports for additional information. Equipment Effectiveness The angular coverage of the multibeam sonars was modified in order to moderate the effects of factors such as increased sea state or to increase coverage, if necessary. Any changes are documented in the acquisition logs. An 80 meter line spacing and operation of the SSS at 50 m range ensured 100% SSS coverage. Split lines were run in the event that environmental factors limited the effective range of the side scan sonar. Factors Affecting Soundings Weather, sea state, water column sound speed, thermoclines, and fish/marine life were all temporary factors that affected the data periodically throughout the duration of the survey; these are noted in the acquisition and processing logs. Two times daily. Sea Bird Electronics SBE19 and SBE19plus CTDs were used for speed of sound measurements in the water column. Casts were conducted at least twice daily aboard the R/V Sea Scout and aboard the mothership associated with the C-Worker 6 ASV operations. Casts were conducted at least once daily on board the R/V C-Wolf. Casts were conducted more often as needed on all vessels. The multibeam data was corrected for the water column sound speed in real-time using the SIS control software. To determine the sound speed at the transducers, an Endeco YSI sonde was used on board the R/V C-Wolf, and AML SV•Xchange systems were used on board the R/V Sea Scout and C-Worker 6. The sound speed data and confidence checks are located in Separates II Digital Data\Sound Speed Data Summary. Complete Coverage, Option 2: SSS data and concurrent MBES data, as outlined in the HSSD (2015) was acquired in the survey area. 100% SSS coverage was acquired in accordance with the requirements stated in the project instructions for this survey. On board the R/V Sea Scout and C-Worker 6, MBES data was acquired with Kongsberg EM2040C echosounders and on board the R/V C-Wolf, MBES data was acquired with a Kongsberg EM3002 echosounder. A Klein 5000 V2 side scan sonar was used aboard the R/V Sea Scout, an EdgeTech 4200P side scan sonar was used aboard the R/V C-Wolf and an EdgeTech 4125 was used aboard the C-Worker 6. A combination of complete MBES with backscatter and/or water column data and/or SSS data was collected for feature investigations. Density According to section 5.2.2.2 of the HSSD (2015) at least 80% of all nodes on the surface shall be populated with at least 5 soundings for Complete Coverage Option 2 surveys. The Compute Statistics tool in CARIS HIPS was used to generate statistics about the density child layer for the following surface: H12791_MB_1m_MLLW_Final (Figure 9). A bin size of 1 was used and the data exported in ASCII format. The number of nodes in the first 4 bins were added together to determine the number of nodes that contain less than 5 soundings. The H12791_MB_1m_MLLW_Final surface contains a total of 39,815,728 nodes and 39,663,416 nodes contain at least 5 soundings. Therefore, greater than 99.6% of all nodes on the surface contain at least 5 soundings. Figure 9. Statistical information about the density child layer of the H12791_MB_1m_MLLW_Final BASE surface, generated from the CARIS Compute Statistics tool. SupportFiles\H91_Fig9_Density.jpg 0.037 0.075 0.1873 0.000 1237094 2 n/a 0.8 JQN00023E707 2 n/a 0.8 LAZ74232C313 2 n/a 0.8 Uncertainty of all components of the sounding measurement are included in the CARIS vessel file and detailed in the DAPR. CARIS HIPS was used to compute the Total Propagated Uncertainty (TPU) for each sounding. Data collected in 2015 (and in 2016 by the R/V C-Wolf) was processed with final verified tides and the zoning file. Specific TPU parameters for data processed with tide correctors are shown in the first row in Table 7. Data collected in 2016 by the R/V Sea Scout was processed using ellipsoid derived vertical correctors. Specific TPU parameters for data processed using ellipsoid derived vertical correctors are shown in the second row of Table 7. An Uncertainty layer child layer is generated during BASE surface creation that shows the uncertainty at each node of the surface. For additional review and quality control, two new layers were generated for each BASE surface that would become a finalized BASE surface. The two new layers were generated for the following surface: H12791_MB_1m_MLLW. The first layer was named <TVU_Maximum> and shows the maximum TVU at each node. The following formula was used during layer creation: ((0.5^2)+((0.013* Depth)^2))^0.5 The second layer generated was named <Uncertainty_QC> and defined as the difference between the TVU_Maximum and Uncertainty layers. Positive values indicate that the uncertainty is less than the TVU_Maximum and that the data meet specifications, while negative values indicate that the uncertainty is greater than the TVU_Maximum and that the data do not meet specifications. The two layers could have been combined into one for the Uncertainty_QC, as was done for the finalized surfaces, but the TVU_Maximum layer also aided in determining the designation or examination status of critical soundings. The uncertainty for the H12791_MB_1m_MLLW BASE surface ranges from 0.02 – 0.65 meters. There are four nodes of the H12791_MB_1m_MLLW BASE surface where the Uncertainty_QC layer of the BASE surface shows negative values. This indicates that the uncertainty values at these four nodes are greater than the maximum allowable TVU for each node. These four nodes are located in close proximity on line 262_5066_001 (Fig 10). An Uncertainty_QC_Final layer was also generated for all finalized surfaces, defined by the equation below: (((0.5^2)+(0.013* Depth)^2)^0.5)- Uncertainty The uncertainty for the H12791_MB_1m_MLLW_Final surface ranges from 0.2 to 1.29 meters. A text file was exported from CARIS and run through a python script to determine the percentage of Uncertainty_QC_Final values that are less than zero, which indicates that the uncertainty values at those nodes exceed specifications. Analysis of the Uncertainty_QC_Final layer for the H12791_MB_1m_MLLW_Final BASE surface indicates that less than 0.0002% of nodes have an uncertainty greater than the maximum allowable TVU. It was observed that the majority of uncertainty values are within specification for the un-finalized surfaces, but there is a larger portion of values that are out of specification when finalized. The reason is due to the finalization parameter, where the uncertainty is defined as the greater of either the standard deviation or uncertainty for a particular node. Note that when the surfaces are finalized, the TVU_Maximum and Uncertainty_QC layers are retained but Uncertainty_QC layer does not reflect the new Uncertainty values of the finalized surface. These layers can be removed, but if the finalized BASE surface is recomputed, it appears that these layers will be regenerated (after closing and re-opening the project). For this reason, the layers were not removed from the finalized surfaces. Figure 10. Four nodes of the H12791_MB_1m_MLLW surface where the uncertainty is greater than the maximum allowable TVU. SupportFiles\H91_Fig10_Uncertainty.jpg All corrections to echo sounding (instrument corrections, static and dynamic draft, speed of sound, and attitude corrections) follow the procedures outlined in the accompanying Data Acquisition and Processing Report (DAPR). Prior to initiating survey operations, a standard patch test was performed for each vessel to determine correctors for pitch, roll, and heading (additional calibrations were performed as necessary or for verification purposes). Squat and settlement tests were also conducted to determine the dynamic draft of the vessels. Refer to the Data Acquisition and Processing Report for additional information. Patch Test - Sea Scout 2015-04-29 Multibeam calibration Patch Test - C-Wolf 2015-09-06 Multibeam calibration Patch Test - C-Worker 6 2015-09-06 Multibeam calibration Patch Test - C-Worker 6 2015-09-26 Multibeam Calibration Patch Test - C-Worker 6 2015-11-30 Multibeam Calibration Patch Test - C-Worker 6 2015-12-08 Multibeam Calibration Squat Test - C-Worker 6 2015-09-01 Determine squat of vessel due to speed Squat Test - Sea Scout 2015-06-11 Determine squat of vessel due to speed Squat Test - C-Wolf 2016-01-15 Determine squat of vessel due to speed Backscatter was logged within each Kongsberg EM file collected aboard the R/V Sea Scout and R/V C-Wolf. This data was imported during CARIS conversion and reviewed when necessary. Backscatter mosaics of the EM3002 data were able to be generated using CARIS 9.0. The EM2040C data was unable to be processed in CARIS 9.0. CARIS correspondence indicates that EM2040C backscatter data should be able to be processed in CARIS 9.1 but this has not been tested internally. The Kongsberg .all files were imported and backscatter mosaics generated using FMGT version 7.5.1. Several errors were encountered with the following lines: 344_5084a, 052_5019a-2.0, 053_5001a, H91-CB-11.0. Mosaics would not process with these lines and they were removed from the project. Processing limitations necessitated the generation of several small mosaics instead of a mosaic of the entire area. Backscatter was logged within each .HSX file collected aboard the C-Worker 6. Although extensive testing and correspondence with Hypack and QPS was conducted, at this point in time the HSX files (converted to HS2 files) were only able to be processed in Hypack. Processing limitations necessitated the generation of mosaics by day instead of a mosaic of the entire area. Correspondence with QPS indicates that Qimera was able to make a GSF file for importation into FMGT, but this was not verified internally. The following Feature Object Catalog was used: NOAA Extended Attribute Files V5_3_2. Software updates are detailed in the DAPR. No further software updates occurred after the submission of the DAPR. H12791_MB_1m_MLLW Uncertainty 1 5.17 12.74 QC/Complete Coverage H12791_MB_1m_MLLW_Final Uncertainty 1 5.17 12.73 Complete Coverage H12791_MB_2m_MLLW Uncertainty 2 5.22 12.63 Junction Analysis H12791_MB_Mainlines_1m_MLLW Uncertainty 1 5.17 12.74 QC H12791_MB_Crosslines_1m_MLLW Uncertainty 1 5.44 12.14 QC Data Cleaning Methodology Data collected aboard the C-Worker 6 in particular was affected by inclement weather and considerable motion artifacts are present in some of the data. This was problematic for data cleaning. In an effort to expedite the cleaning and review process, the MBES data was cleaned utilizing a slightly different methodology than what is outlined in the DAPR. An uncertainty surface was generated and a surface filter used with the following parameters: Threshold Type: Standard Deviation and Threshold value: 3.00. Deviations to this method as well as additional filtering on a line by line basis are detailed in the processing log. After the filter was applied, each line was reviewed individually in swath editor to ensure that the filter cleaned the data appropriately and did not remove any contacts. This accelerated the processing time while ensuring each line was reviewed. Data Quality Control After initial data cleaning, the surfaces were reviewed a second time for fliers using the standard deviation layer and the 3D display window, when necessary. All areas with a standard deviation of 0.25 m or higher were specifically examined. Higher standard deviation is generally associated with bathymetric features, contacts and/or areas of bathymetric change. Areas of noisy MBES data, although cleaned, can also show higher standard deviation as can areas of overlapping lines where depths do not compare well. The highest standard deviation of 0.80 m on the H12791_MB_1m_MLLW surface is located at 29.973 N, 91.415 W. This high standard deviation is associated with a contact that was submitted as a DtoN for survey H12791. Additional Data Processing Notes. When initially opening the project on a new computer with a new directory letter, CARIS cannot resolve the data sources for day 160326 collected with the R/V C-Wolf (Figure 11). The user must reset the raw data location for this day only (Figure 12). This does not appear to affect data processing in any way. Figure 11. Display window from CARIS upon initially opening the project on a new computer/different directory. SupportFiles\H91_Fig11_CannotFindRawData.jpg Figure 12. Reset raw data location window. SupportFiles\H91_Fig12_ResetRawDataLocation.jpg A complete description of the horizontal and vertical control for the OPR-K379-KR-15 surveys is located within the accompanying Horizontal and Vertical Control Report (HVCR). A summary of the horizontal and vertical control is provided below. Mean lower low water (MLLW) Discrete Zoning LAWMA, Amerada Pass, LA 8764227 8764227.tid Verified Observed K379KR2015CORP.zdf Final 2016-01-25 2016-01-25 Preliminary zoning is accepted as the final zoning for project OPR-K379-KR-15 as outlined in the Tides and Water Levels Statement of Work section 1.5.1. This zoning was used for data collected in 2015 only. VDatum GPS_HAE_Reduction_to_MLLW_SeaScout.tid The file (Ellispoid to Chart Datum) used to correct the data collected by the R/V Sea Scout in 2016 data is: GPS_HAE_Reduction_to_MLLW_SeaScout.tid Data collected in 2016 by the R/V Sea Scout was corrected using primary C-Nav GPS ellipsoid heights reduced to MLLW. Refer to the DAPR for a detailed explanation. North American Datum of 1983 (NAD83) 15N Single Base Post- Processed Kinematic (PPK) GPS data was not used during post processing. C & C Technologies’ C-Nav network was used during survey operations. The C-Nav® Corrections Service is a global system for the distribution of dynamic DGNSS Precise Point Positioning corrections. Real Time Kinematic DGPS was not used during survey operations. C & C Technologies’ C-Nav network was used during survey operations The C-Nav GPS systems aboard the vessels receive corrections through the C-Nav Subscription Services. This is “a premier worldwide subscription service providing 5 cm or better positioning accuracy. GNSS corrections are broadcast via Inmarsat geostationary satellites, providing highly accurate and reliable positioning coverage from 72 degrees north to 72 degrees south latitude.” (http://www.cnavgnss.com/products) A combination of user defined color range charts and a selected sounding layer were used to compare surveyed soundings to charted depths. The selected sounding layer was generated as shoal-biased with a single defined radius of 150 meters to produce sufficient sounding density for comparisons purposes. 11340 49 458596 79 2016-02 2016-03-22 2016-03-26 No Local Notices to Mariners were issued within the survey bounds subsequent to the date of the project instructions and before the end of the survey. The last Local Notice to Mariners reviewed was LNM 15/16 8th Dist - Chart: 11340, Current Edition: 79 Print Date: Feb. /2016, Mississippi River to Galveston. Surveyed soundings range from 2.83 – 6.97 fathoms (5.17 – 12.74 meters). Depths increase from northeast to southwest within the survey area. There are three charted depths within the survey bounds that are not associated with charted features such as obstructions. There is a 5 ¾ fathom depth in the southern portion of the survey area, a 2 ¾ fathom depth in the northeast corner of the survey area and a 4 fathom depth in the northwest corner of the survey area. Surveyed soundings generally compare well to within 1 – 1.5 feet of the 4 and 5 ¾ fathom charted depths. Surveyed soundings are generally deeper than the 2 ¾ fathom charted depth by 1.5 – 4.5 feet. The 3 fathom contour on chart 11340 only just extends into the survey area in the far northeast portion of the survey area and an isolated region bounded by the 3 fathom contour extends into the survey area in the northeast corner of the survey area. The 5 fathom contour extends from northwest to southeast through the southwest corner of the survey area. A color range chart was used to compare surveyed soundings to charted depths (Figure 13). The color range chart in CARIS can only be populated by values in meters. The following equations were used to determine the fathoms/feet/meters conversion: 3 fathoms = 18 feet = 5.4864 meters 5 fathoms = 30 feet = 9.144 meters However, according to section 5.1.2, the NOAA cartographic rounding (0.75 round value) can be applied when directly comparing to charted depths. For this reason, the following equations were used to determine the 0.75 round values for the contour comparison. 2.75 fathoms = 16.5 feet = 5.0292 meters 4.75 fathoms = 28.5 feet = 8.6868 meters It is evident from survey data, with the 0.75 soundings rounding used (Figure 13), that the 3 fathom contours are no longer present within this area and the 5 fathom contour has shifted northeast of its currently charted position (Figure 14). Figure 13. User defined color range chart to compare surveyed soundings to 11340 charted contours. SupportFiles\H91_Fig13_ColorRangeChart_11340.jpg Figure 14. Comparison between surveyed soundings and charted 3 and 5 fathom contours. Light blue represents area between 2.75 fathoms (5.029 meters) and 4.75 fathoms (8.687 meters). Dark blue represents area where surveyed soundings are greater than 4.75 fathoms (8.687 meters). H91_Fig14_ChartComparison_11340.tif 11356 62 80000 41 2014-07 2016-03-22 2016-03-26 No Local Notices to Mariners were issued within the survey bounds subsequent to the date of the project instructions and before the end of the survey. The last Local Notice to Mariners reviewed was LNM 15/16 8th Dist - Chart: 11356, Current Edition: 41 Print Date: Jul. /2014, Isles Dernieres to Point au Fer. Surveyed depths range from 16.98 to 41.82 feet (5.17 – 12.74 meters). In general, surveyed soundings are 1 – 3 feet deeper than charted depths throughout the survey area except in the east and northeast portions of the survey area where surveyed soundings can be 1 – 2 feet shallower than charted depths (Figure 15). The 18 foot contour of chart 11356 extends north-south in the far northeast portion of the survey area and there are several isolated regions bounded by the 18 foot contour in the northeast corner of the survey area. The charted 30 foot contour extends from northwest to southeast through the southwestern corner of the survey area. The color range chart in CARIS can only be populated by values in meters. The following equations were used to determine the fathoms/feet/meters conversion: 3 fathoms = 18 feet = 5.4864 meters 5 fathoms = 30 feet = 9.144 meters However, according to section 5.1.2, the NOAA cartographic rounding (0.75 round value) can be applied when directly comparing to charted depths (Figure 16). For this reason, the following equations were used to determine the 0.75 round values for the contour comparison: 17.75 feet = 5.4102 meters 29.75 feet = 9.0678 meters It is evident from survey data that the isolated 18 foot contours in the north-central portion of the survey area are no longer present. However, there are some isolated areas in the northeast corner of the survey area where surveyed soundings are less than 17.75 feet. The 30 foot contour has shifted northeast of the currently charted position (Figure 17). Figure 15. Comparison of surveyed soundings to charted depths. Areas in blue polygons represent areas where surveyed soundings are shallower than charted depths by 1 – 2 feet. SupportFiles\H91_Fig15_ChartComparison_11356_1.tif Figure 16. User defined color range chart to compare surveyed soundings to 11340 charted contours. SupportFiles\H91_Fig16_ColorRangeChart_11356.jpg Figure 17. Comparison between surveyed soundings and 11356 charted depths, including the 18 and 30 foot contours. Yellow (inside red polygon) represents area where surveyed soundings are less than 17.75 feet (5.410 meters) Light blue represents area where surveyed soundings are between 17.75 feet (5.410 meters) and 29.75 feet (9.068 meters). Dark blue represents area where surveyed soundings are greater than 29.75 feet. SupportFiles\H91_Fig17_ChartComparison_11356_2.tif 11351 63 80000 43 2012-03 2016-03-22 2016-03-26 No Local Notices to Mariners were issued within the survey bounds subsequent to the date of the project instructions and before the end of the survey. The last Local Notice to Mariners reviewed was LNM 15/16 8th Dist - Chart: 11351, Current Edition: 43 Print Date: Mar. /2012, Point au Fer and Marsh Island. Chart 11351 covers the northern two-thirds of the survey area. Charted depths and contours closely match those of chart 11356 and the comparisons observed between surveyed soundings are charted depths of chart 11356 are generally valid for chart 11351. One exception exists in the chart overlap in the far eastern portion of the survey area where chart 11356 shows shallower depths than chart 11351 and a wider area encompassed by the 18 foot contour. Surveyed soundings are 2 feet shallower than the charted 20 foot depth of chart 11351. Figure 18. Chart 11351 (bold charted depths) over chart 11356 (faded charted depths) with survey bathymetry and selected soundings (in blue). Yellow polygon shows area where charted depths differ. SupportFiles\H91_Fig18_ChartComparison_11351.tif US4LA21M 80000 27 2015-03-25 2016-04-01 false ENC US4LA21M covers the northern two-thirds of the survey area. Depths on ENC US4LA21M generally match those of chart 11351 or are 1 foot shallower, particularly in the northeast corner of the survey area. Contours of ENC US4LA21M also match those of chart 11351. The observations made between surveyed soundings and depths on chart 11356 and 11351 are generally valid for the ENC. US4LA25M 80000 17 2013-09-19 2016-01-29 false ENC US4LA25M covers the southern third of the survey area. Depths and contours on ENC US4LA21M generally match those of chart 11356 and the observations made between surveyed soundings and depths on chart 11356 are generally valid for the ENC. One exception where an ENC depth is greater than the charted depth of 11356 exists at 29.948 N, 91.326 W. Surveyed soundings more closely match the charted 24 foot depth of 11356 rather than the 26 foot charted depth of the ENC. AWOIS item investigations were not assigned for this project. Maritime Boundary Points were not assigned for investigation within H12791 survey bounds. Chart 11340 In addition to three charted depths and the 3 and 5 fathom contours charted within the survey area (refer to the chart comparisons section above), there is one charted 4 fathom obstruction in the survey area. This obstruction was submitted as a DtoN for this survey. Refer to section D.1.7 and the Final Feature File for additional information. Chart 11356 In addition to the charted depths and 18 and 30 foot charted contours (refer to the chart comparisons section above) there is one charted 25 foot obstruction within the survey area. This obstruction was submitted as a DtoN for this survey. There are also four charted pipelines that extend to some degree through the survey area and four charted platforms (one PA) within the survey area. Refer to sections D.1.7, D.2.5 and D.2.7 as well as the Final Feature File for additional information. Chart 11351 No additional charted features than what was previously described for charts 11340 and 11356 exist on chart 11351. Previously described feature remarks are valid for chart 11351. US4LA21M No additional features are observed on the ENC that are not charted on RNC 11356 or 11351. Previously described feature remarks are valid for ENC US4LA21M. US4LA25M No additional features are observed on the ENC that are not charted on RNC 11356 or 11351. Previously described feature remarks are valid for chart ENC US4LA25M. One uncharted Danger to Navigation was submitted for survey H12791. Refer to the Final Feature File for additional information. 1 One Danger to Navigation was submitted for survey H12791. Refer to the Final Feature File for additional information. No additional shoal or hazardous features were observed visually or within survey data that have not been discussed in sections D.1.6, D.1.7, D.2.4, D.2.6 or D.2.7. No channels are currently charted within the survey limits, and none were observed during survey operations. Eight bottom samples were collected within the limits of H12791. Refer to Separates\Acquisition_&_Processing_Logs\Detached_Positions and the Final Feature File for additional information. There is no Shoreline Verification for this survey. Prior survey data was not required to be evaluated for this survey. No Aids to Navigation are currently charted within the survey area, and none were observed either visually or within survey data. Overhead features do not exist for this survey. Four charted submarine pipelines extend to some degree through the H12791 survey area. A series of SSS contacts were identified along the pipeline that extends southwest-northeast through the central portion of the survey area (Fig 19). These contacts were insignificant and not pipeline exposures (Figure 20). Figure 19. Series of SSS contacts identified along a pipeline within the survey bounds of H12791. SupportFiles\H91_Fig19_Pipelines_SSS_Contacts.tif Figure 20. Typical SSS signature of contacts identified along a pipeline within the survey bounds of H12791 SupportFiles\H91_Fig20_Pipelines_SSS.jpg No ferry routes or terminals are currently charted within the survey limits, and none were observed during survey operations. There are four platforms charted within the bounds of H12791. One platform was observed visually and within survey data near a currently charted platform. The three other platforms were not observed visually or within survey data and the hydrographer recommends removal from the chart. The CSF file contains two platforms associated with the one charted PA platform, which the hydrographer also recommends to remove. Feature disprovals were conducted over charted platforms that no longer exist. It is recognized that only a 120 m radius around the charted PA platform was covered with 200% SSS. No contacts were observed in either the 100% or 200% SSS data. Refer to the Final Feature File for additional information as well as Separates\I_ Acquisition_ &_Processing_Logs\Detached_Positions. The Final Feature File includes one additional obstruction that was not submitted as a Danger to Navigation. This obstruction meets the minimum measurement requirements according to surveyed soundings (2 m x 2 m x 1 m) for the Final Feature File. The north/northeast portion of the survey area in particular is a dynamic area. Changes in SSS signatures and bathymetry over time were observed, for example, changes are evident between the time that the C-Worker 6 ASV collected data and the R/V Sea Scout collected split line data. These changes do not pose a danger to navigation. Refer to mosaics H12791_SSS_1of5 and H12791_SSS_3of5 in particular. No active dredging or construction was observed during survey operations. No new surveys or investigations are recommended for this area. No new insets are recommended for this area. Field operations contributing to the accomplishment of the H12791 survey were conducted under my direct supervision with frequent personal checks of progress and adequacy. This report and CARIS project have been closely reviewed and are considered complete and adequate as per the Statement of Work. This report is accompanied by the Data Acquisition and Processing Report for project OPR-K379-KR-15. Tara Levy Chief of Party 2016-04-28 Nicole Galloway Geoscientist 2016-04-28