Layer: MBES - Depth (ID: 19)

Parent Layer: Bathymetry and Elevation

Name: MBES - Depth

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Description: <DIV STYLE="text-align:Left;font-size:12pt">During July-September 2020, Cardinal Point Captains (CPC) hydrographers conducted hydrographic survey operations in three survey areas located on the western side of Bayfield Peninsula in southwestern Lake Superior. Survey operations took place over three legs: Leg 1 (7/25-8/5), Leg 2 (8/25-9/2), and Leg 3 (9/16-9/28). CPC utilized the Research Vessel (R/V) Echo, which was equipped with a Teledyne-Reson SeaBat 7125 multibeam echosounder for simultaneously acquiring bathymetry and acoustic backscatter imagery. During survey operations, DEA provided remote technical support to assist CPC with vessel setup, system calibrations, and initial hydrographic data testing and quality control, and coordinated transfers of raw hydrographic data. After initial data assessments were complete, the raw multibeam data were prepared for import into CARIS Hydrographic Information Processing System (HIPS) software (version 11.3.8). Upon import into CARIS HIPS software, the raw multibeam data were converted from native Teledyne-Reson s7k file format into CARIS HDCS format. The converted multibeam data were stored logically by survey day. Soundings with a Reson quality flag of 0 or 1 (indicating poor brightness and/or collinearity of data) were rejected automatically on import. These soundings were reviewed later during manual inspection. A CARIS HIPS Vessel File (HVF), which stored sensor offsets for the survey vessel, was constructed using values for the Echo as provided and documented by CPC hydrographers. Multibeam patch test data (conducted 7/25/2020) were analyzed and alignment corrections were calculated and applied to soundings. Vessel attitude (heading, pitch, roll, heave) and position data (global navigation satellite system (GNSS) corrections) were manually reviewed and verified. Applanix POSPac software was used to calculate Smoothed Best Estimate of Trajectory (SBET) files, which combined the vessel attitude and position data to produce a corrected horizontal position solution and to extract ellipsoidally referenced heights. Soundings were converted from ellipsoid heights (North American Datum of 1983; NAD83) to the project vertical datum (North American Vertical Datum of 1988; NAVD88) in CARIS HIPS using the GEOID12B model. Sound speed profiles were incorporated to correct multibeam slant range measurements and compensate for refraction in the water column. Sound speed profiles were imported into CARIS HIPS and applied to soundings using the “closest in distance and time” function. Static draft measurements were conducted periodically during hydrographic survey operations. Draft measurements were used to compute Global Positioning System (GPS) tides relative to the ellipsoid and to obtain an approximate waterline for the application of sound speed profiles. After position, motion, waterline, and sound velocity corrections were applied, soundings were gridded for review and directed editing. Preliminary grid resolution was 2 meters (m). Review of bathymetric data was conducted by reviewing multiple bathymetry child layers (e.g. standard deviation, density) in CARIS HIPS and using editing and QC tools to view and edit erroneous soundings (“fliers”), systematic biases, timing errors, or alignment offsets. Upon completion of directed editing, soundings were gridded at 2m and interpolated using the ArcGIS Focal Statistics tool for geospatial analysis. A final surface was generated from the interpolated results for the NCCOS Apostle Island Digital Atlas. Soundings were converted again from the NAVD88 projection to the IGLD85 projection using NOAA Vdatum v4.3. Once the data was projected to IGLD85, the surface was converted from projected height above sea level to the Lake Superior Water Level Datum from July - September, 2020. The average IGLD85 Lake Level height obtained from the GLERL Great Lakes Dashboard (https://www.glerl.noaa.gov/data/dashboard/GLD_HTML5.html) for July - September, 2020 was 183.86 m above sea level. Using the ESRI Raster Calculator, the IGLD85 elevations were subtracted by the GLERL Lake Superior water level. The result is a water depth model relative to the shoreline of Lake Superior (0m) as the base height. </DIV>

Copyright Text: David Evans and Associates Inc. (DEA), Woolpert, Inc., Cardinal Point Captains (CPC), National Oceanic Atmospheric Administration (NOAA), National Centers for Coastal Ocean Science (NCCOS), Great Lakes Research Initiative (GLRI).

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