Abstract
The establishment of multibeam echosounders (MBES), as a mainstream tool in ocean mapping, has facilitated integrative approaches towards nautical charting, benthic habitat mapping, and seafloor geotechnical surveys. The combined acoustic response of the seabed and the subsurface can vary with MBES operating frequency. At worst, this can make for difficulties in merging the results from different mapping systems or mapping campaigns. However, at best, having observations of the same seafloor at different acoustic wavelengths allows for increased discriminatory power in seabed classification and characterization efforts. Here, we present the results from trials of a multispectral multibeam system (R2Sonic 2026 MBES, manufactured by R2Sonic, LLC, Austin, TX, USA) in the Bedford Basin, Nova Scotia. In this system, the frequency can be modified on a ping-by-ping basis, which can provide multi-spectral acoustic measurements with a single pass of the survey platform. The surveys were conducted at three operating frequencies (100, 200, and 400 kHz), and the resulting backscatter mosaics revealed differences in parts of the survey area between the frequencies. Ground validation surveys using a combination of underwater video transects and benthic grab and core sampling confirmed that these differences were due to coarse, dredge spoil material underlying a surface cover of mud. These innovations offer tremendous potential for application in the area of seafloor geological and benthic habitat mapping.
Highlights
The effective management of the earth’s natural resources requires knowledge regarding the extent, geographical range, and ecological characteristics of the resource of interest—and maps are the pre-eminent means of recording and communicating this information
The results from this study have demonstrated the benefits that such a system can offer for improved understanding of seafloor geological characteristics
The intermittent ping cycle of the R2Sonic multispectral multibeam echosounders (MBES) provides backscatter at multiple frequencies from a single pass of the survey platform. This ability offers significant advantages, as it allows the same patch of seafloor to be imaged very close to the same grazing angle
Summary
The effective management of the earth’s natural resources requires knowledge regarding the extent, geographical range, and ecological characteristics of the resource of interest—and maps are the pre-eminent means of recording and communicating this information. Multispectral satellite remote sensing, which acquires data from reflected light across a wide spectrum of electromagnetic wavelengths, has enabled scientists to develop classification routines to objectively map patterns of land cover and features (i.e., vegetation type, surface geology, man-made structures, etc.) [3]. By integrating this information with terrestrial digital elevation models (DEMs), Geosciences 2019, 9, 126; doi:10.3390/geosciences9030126 www.mdpi.com/journal/geosciences. Geosciences 2019, 9, 126 elevation models (DEMs), along with other environmental data sets (e.g., climate and surficial geology), sophisticated modelling of species distributions can be attained [2].
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