2020 NOAA/OCM Multibeam Bathymetry: Bayfield, WI

First leg

Second Leg

Third Leg

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Information on the NOAA Office for Coastal Management (OCM)

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

Contractor report

A hydrographic survey was conducted 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). The survey platform was 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.

Bathymetry data were processed in CARIS HIPS (v11.3.8). 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. 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. After the completion of bathymetric data processing, review, and analysis, soundings were gridded using a standard swath angle filter to produce bathymetric surfaces. Bathymetry data were gridded at 2m. Interpolation was applied to fill small gaps. The BAG format contains two data layers: Depth and Uncertainty (standard deviation of depth). Bathymetry products are referenced to NAD83 Universal Transverse Mercator (UTM) Zone 15 North with horizontal units in meters and vertical elevation in meters relative to NAVD88.

NOAA Office for Coastal Management ingested GeoTiff versions of the grid into the Data Access Viewer. The GeoTiff version is the elevation band of the BAG file. The bag file is available through the bulk download.