High-Resolution Multibeam Mapping Products, Python-Based Geomorphic Derivatives, and Raw Data from Mischley Reef in Thunder Bay, Lake Huron, 2019

Multibeam echosounder surveys can be used to gather a variety of physical lakebed properties including bathymetry, substrate, and habitat characteristics, by comparing the backscatter and signal intensity to ground truth data. Multibeam data collected at shallow depths (<25m) and with sufficient overlap between survey lines can produce high resolution surfaces, with a high degree of spatial accuracy of lakebed features. Multibeam data was collected at Mischley Reef in Thunder Bay, Lake Huron due to its importance as a historical fish spawning reef that has experienced a rapid decline in the abundance of commercial and recreational species of interest over the past 25 years. Bathymetric accuracy and uncertainty were evaluated using empirical crosscheck analyses, post-processed POSPac navigation-quality metrics, patch test calibration values, and propagated uncertainty estimates generated in QPS Qimera. Crosscheck analysis of 193,800 comparison points resulted in test acceptance with no rejected observations and yielded a root mean square error (RMSE) of 0.051 m, a mean absolute residual of 0.040 m, and a 95th percentile absolute residual of 0.088 m. Propagated Qimera uncertainty statistics from approximately 63.5 million bathymetric soundings resulted in a mean THU of 0.351 m, a 95th percentile THU of 0.616 m, a mean TVU of 0.101 m, and a 95th percentile TVU of 0.114 m.Raw echosounder data were processed into bathymetry and backscatter raster layers gridded at 0.25m, 0.5m and 1m horizontal resolutions to verify reef extents and support development of additional derived geomorphic products including slope, aspect, roughness, Topographical Ruggedness Index (TRI), Topographical Position Index (TPI), Hillshade, 4,5,6 and 10 class geomorphic classification, Local Binary Pattern 21-4 and four classes of Shannon Index. These high-resolution map products can be used to accurately compare reefs and support additional analyses and geographic targeting of future research and restoration efforts.