Hydrographic Mapping for Alaskan & Canadian Arctic Waters
What is Space-Based Laser Bathymetry?
Satellite Derived Bathymetry (SDB) is a practical and economical solution in filling in the “white ribbon” data gap.
SDB relates the water-leaving reflectance measured by Earth observing satellites to the depth of the water column. Therefore it can provide bathymetry data for the shallow coastal regions without having to do airborne lidar surveys which can be expensive and time consuming.
Image: 20m SDB of coastal Espenberg within the Bering Land Bridge National Preserve
"We visually inspect candidate imagery to have the least amount of atmospheric influence including: cloud cover, shadow, haze, and sun glint and water surface or water column influences such as ice, waves, turbidity, CDOM, Algae, NAP and any floating vegetation as these factors influence the ability to see the seafloor bottom". - TCarta Remote Sensing Analyst
Clouds present in imagery are difficult to mask out over water but have a direct influence on false depth retrievals.
Sun-glint resulting from offset geometries between the sun and satellite during acquisition saturate the image overall and lead to homogeneous depth retrievals.
SDB feasible imagery is usually clear, free from clouds and cloud shadow, haze, and bi-directional reflectance (BRD) effects.
Fortunately, TCarta has multiple methods in place for analyzing imagery for water quality/clarity to determine whether SDB is possible for a given location.
"Due to the lack of in situ validation turbidity measurements, water clarity is classified by modeling suspended particle backscatter from the water-leaving reflectance using the red-edge channels of the electromagnetic spectrum. Identified turbid regions are then masked out so they are not included in SDB calibration". - TCarta Remote Sensing Analyst
Slider: Identification of turbidity (yellow and red) covering coastal bottom in a Worldview-2 image.
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