History of Modern Seafloor Mapping

Over the last century, remotely sensed mapping of continental shelf seafloor topography has had a rich history of applied research with varying techniques, all of which strive to accurately visualize the submarine benthos. Many early techniques (e.g., three-dimensional hachure maps) relied solely on the researcher’s knowledge and cartographic skills in absence of technological advances yet to be made. Acoustic mapping practices were then derived from war-time sonar sweeps that painted a surprisingly vivid picture of the seafloor through the use of sound. Through time, more sophisticated acoustic remote sensing techniques were developed and used as either sidescan sonar, single beam echo sounders, or multibeam reflection sounders. More powerful ground-penetrating seismic techniques have also been used to not only map the surface layer of the seafloor, but to also visualize what lies below the benthic interface. However, aircraft and satellite-assisted techniques enabled researchers to recently make considerable advancements in the visualization of benthic environments. Once mainly used as military reconnaissance procedures for strategic planning, the advent of high-resolution aerial photography and orthoimagery has proven to be among the most effective techniques for visualizing shallow, low turbid waters along continental shelves. Equally as effective for clear waters within the nearshore of the continental margin are airborne laser bathymetry (ALB) methods, which use pulses of light to acquire bathymetric and topographic configurations based on airborne laser reflectance. Lastly, hyperspectral and multispectral sensors onboard orbiting satellites (e.g., IKONOS, Landsat, MODIS, SPOT) provide a continuous stream of benthic environment visualization without the logistical inconveniences of deploying a vessel or aircraft every time images are to be acquired. A historical review of advances in seafloor mapping methods shows that remote sensing techniques led to new ways of visualizing dynamic benthic environments that ranged from broadly generalized geomorphological features to specific biological coverages.