Assessing an Atmospheric Correction Algorithm for Time Series of Satellite-Based Water-Leaving Reflectance Using Match-Up Sites in Australian Coastal Waters

Abstract

An atmospheric correction algorithm for medium-resolution satellite data over general water surfaces (open/coastal, estuarine and inland waters) has been assessed in Australian coastal waters. In situ measurements at four match-up sites were used with 21 Landsat 8 images acquired between 2014 and 2017. Three aerosol sources (AERONET, MODIS ocean aerosol and climatology) were used to test the impact of the selection of aerosol optical depth (AOD) and Ångström coefficient on the retrieved accuracy. The initial results showed that the satellite-derived water-leaving reflectance can have good agreement with the in situ measurements, provided that the sun glint is handled effectively. Although the AERONET aerosol data performed best, the contemporary satellite-derived aerosol information from MODIS or an aerosol climatology could also be as effective, and should be assessed with further in situ measurements. Two sun glint correction strategies were assessed for their ability to remove the glint bias. The most successful one used the average of two shortwave infrared (SWIR) bands to represent sun glint and subtracted it from each band. Using this sun glint correction method, the mean all-band error of the retrieved water-leaving reflectance at the Lucinda Jetty Coastal Observatory (LJCO) in north east Australia was close to 4% and unbiased over 14 acquisitions. A persistent bias in the other strategy was likely due to the sky radiance being non-uniform for the selected images. In regard to future options for an operational sun glint correction, the simple method may be sufficient for clear skies until a physically based method has been established.

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“…Thankfully, because of ARD, all that has changed. GA has published extensively on the science behind the creation of ARD, and in collaboration with researchers at the Commonwealth Scientific Research Organisation (CSIRO), created the first open data cube (ODC) [6,[11][12][13][14]. The advantage of the ODC, where data are indexed as spatial stacks over time, is that consistent temporal analysis is now possible using the entire DEA ARD ODC archive, which now includes a substantial portion of all Landsat and Sentinel-2 data over Australia.…”

“…BRDF and terrain shade correction do not usually apply, except when nearby mountains may cast shadows. Instead, the adjacency effects, as well as Sun and sky glint corrections, are applied simultaneously with the Lambertian atmospheric correction [14,[29][30][31]. These can be applied to the whole image.…”

“…These can be applied to the whole image. If the target reflectance is very different from the surrounding area (it often happens in water surfaces near the land and inland waters), the remote sensing reflectance can then be calculated [14].…”

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“…The Great Barrier Reef is a world-famous natural heritage for the beautiful coral scenery and the water is clear. The special water environment also makes it a typical area for coastal research (Li et al, 2021).…”

Satellite Multi/Hyper Spectral HR Sensors for mapping the <em>Posidonia oceanica</em> in South Mediterranean Islands

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