Very High Resolution Seafloor Classification and Satellite Derived Bathymetry of Lancelin, Australia (IMSA)

Full description

Mapping of benthic habitat and seafloor bathymetry of Lancelin, WA derived from satellite imagery captured on 17 July 2017 at a spatial resolution of 2 m.

Mapping extent covered as much of the Defence gazetted waters as possible, to a depth of approximately 18 m based on water clarity. Recently dead or senesced (e.g. winter dieback of leaves) and mobile seagrass have the same satellite signature as live seagrass at spectral resolutions of the sensor (WorldView-2). This ensured areas of winter dieback and/or senescence were captured as areas of seagrass for the purposes of impact assessment.

Lineage

Statement: The data provides bathymetric and seafloor classification information based on optical satellite image data. Imagery data were processed by the Modular and Inversion System (MIP) by EOMAP GmbH & Co.KG. The MIP is designed for the physically based assessment of hydro-biological parameters from multi- and hyperspectral remote sensing data. EOMAPs Satellite-Derived Bathymetry (SDB) method relies on the reflected light energy which is measured at the satellite sensor in space. In order to measure the water column thickness, the sea bottom reflection must be separated from all other simultaneously measured portions of light. Other contributors of light scattered to the sensor are atmospheric molecules and aerosols, adjacent scattering from land, the water surface reflection, and light scattered and absorbed due to particular properties of water constituents and the pure water itself. The pure water itself also absorbs light in a spectrally specific manner and therefore leaves unique signatures in the signal while the light passes through the water column and returns after reflection at the sea bottom. This property is relevant to estimate water depth from optical satellite imagery. As many properties can vary over space and time, effective correction, regularisation and retrieval algorithms must be applied to avoid unstable results. EOMAP developed and maintains these unique algorithm and its workflows for almost two decades. The maximum depth the system is able to sense is related to the complex interaction of radiance of bottom material, incident sun angle and intensity, and the type and quantity of organics or sediments in the water column. As a rule-of-thumb, satellite-derived bathymetry should be capable of sensing bottom to depths equal to one to one point five times the Secchi depth. EOMAP's Seafloor Classification (SFC) method is based on seafloor reflection at different wavelengths, which is being used to run an object-based classification procedure grouping objects of similar spectral characteristics, shape and texture into different classes of seafloor coverage. Correction modules applied to the satellite imagery: - Corrected for Satellite sensor noise: Yes - Corrected for atmospheric effects: Yes - Corrected for the effect of adjacent land reflectance: Yes - Corrected for effects of turbidity: Yes - Corrected for water refraction effect: No - Ground-control points accessed to improve horizontal accuracy: No - Local in-situ data accessed for calibration and validation purposes: Yes Datum: Mean Sea Level based on Admirality Total Tide Station Lancelin, 6225 (HAT: +1.1m above LAT, MSL: +0.48m above LAT, LAT: 0m)

Notes

Credit
EOMAP, 2019. Very High Resolution Seafloor Classification and Satellite Derived Bathymetry of Lancelin, Australia. Seefeld, Germany: EOMAP GmbH & Co. KG