Layer: Lakebed Rugosity (ID: 28)

Parent Layer: Lakebed Surface

Name: Lakebed Rugosity

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Description: <DIV STYLE="text-align:Left;font-size:12pt"><DIV><DIV>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. 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. The ESRI grid of source bathymetry was input into the Rugosity Builder Tool, a component of the ArcGIS Benthic Terrain Modeler (BTM). The BTM tool, a collection of ArcGIS terrain visualization tools developed by the Oregon State University (OSU) Department of Geosciences and the National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center, calculated the rugosity of that bathymetric grid based on an algorithm developed by Jeff Jenness. A short summary of the process, quoted directly from the BTM's documentation, is as follows: "...rugosity derivation relies, in part, on a neighborhood analysis using a 4 grid cell by 4 grid cell neighborhood. An algorithm is passed through the Raster Map Algebra Operation object within Spatial Analyst that calculates the planar distance between the center point of the center cell and of each of the eight surrounding cells in the neighborhood. Next, using the Pythagorean Theorem, the surface distance is calculated for each planar distance using the difference in elevation between the cells. The result of this function is sixteen separate grid data sets with each cell value equal to this surface distance. The next step in the process is to calculate the area formed by three adjacent sides. The result is eight triangular surface area grids. These grid datasets are combined to obtain a surface area data set for the input bathymetric data set. The final step in the process is to create a data set that represents the ratio of surface area to planar area. This final data set represents rugosity for the study area." More information on the specific algorithms used, and contact points for questions, can be found in the BTM's documentation. Rugosity values near 1 represent flat smooth terrain, while higher values reflect increasing rugosity or terrain roughness.</DIV></DIV></DIV>

Copyright Text: National Oceanic Atmospheric Administration (NOAA), National Centers for Coastal Ocean Science (NCCOS), Great Lakes Research Initiative (GLRI).

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