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Glint Removal Assessment to Estimate the Remote Sensing Reflectance in Inland Waters with Widely Differing Optical Properties
摘要： The quality control of remote sensing reflectance (Rrs) is a challenging task in remote sensing applications, mainly in the retrieval of accurate in situ measurements carried out in optically complex aquatic systems. One of the main challenges is related to glint effect into the in situ measurements. Our study evaluates four different methods to reduce the glint effect from the Rrs spectra collected in cascade reservoirs with widely differing optical properties. The first (i) method adopts a constant coefficient for skylight correction (ρ) for any geometry viewing of in situ measurements and wind speed lower than 5 m·s?1; (ii) the second uses a look-up-table with variable ρ values accordingly to viewing geometry acquisition and wind speed; (iii) the third method is based on hyperspectral optimization to produce a spectral glint correction, and (iv) computes ρ as a function of wind speed. The glint effect corrected Rrs spectra were assessed using HydroLight simulations. The results showed that using the glint correction with spectral ρ achieved the lowest errors, however, in a Colored Dissolved Organic Matter (CDOM) dominated environment with no remarkable chlorophyll-a concentrations, the best method was the second. Besides, the results with spectral glint correction reduced almost 30% of errors.
关键词： remote sensing accuracy,inland waters,optically complex systems
更新于2025-09-23 15:23:52
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Estimating the Optical Properties of Inorganic Matter-Dominated Oligo-to-Mesotrophic Inland Waters
摘要： Many studies over the years have focused on bio-optical modeling of inland waters to monitor water quality. However, those studies have been conducted mainly in eutrophic and hyper-eutrophic environments dominated by phytoplankton. With the launch of the Ocean and Land Colour Instrument (OLCI)/Sentinel-3A in 2016, a range of bands became available including the 709 nm band recommended for scaling up these bio-optical models for productive inland waters. It was found that one category of existing bio-optical models, the quasi-analytical algorithms (QAAs), when applied to colored dissolved organic matter (CDOM) and detritus-dominated waters, produce large errors. Even after shifting the reference wavelength to 709 nm, the recently re-parameterized QAA versions could not accurately retrieve the inherent optical properties (IOPs) in waterbodies dominated by inorganic matter. In this study, three existing versions of QAA were implemented and proved inefficient for the study site. Therefore, several changes were incorporated into the QAA, starting with the re-parameterization of the empirical steps related to the total absorption coefficient retrieval. The re-parameterized QAA, QAAOMW showed a significant improvement in the mean absolute percentage error (MAPE). MAPE decreased from 58.05% for existing open ocean QAA (QAALv5) to 16.35% for QAAOMW. Considerable improvement was also observed in the estimation of the absorption coefficient of CDOM and detritus from a MAPE of 91.05% for QAALv5 to 18.87% for QAAOMW. The retrieval of the absorption coefficient of phytoplankton (aφ) using the native form of QAA proved to be inaccurate for the oligo-to-mesotrophic waterbody due to the low aφ returning negative predictions. Therefore, a novel approach based on the normalized aφ was adopted to maintain the spectral shape and retrieve positive values, resulting in an improvement of 119% in QAAOMW. Further tuning and scale-up of QAAOMW to OLCI bands will aid in monitoring water resources and associated watershed processes.
关键词： water quality,bio-optics,quasi-analytical algorithm,Brazilian reservoir,inland waters,inherent optical properties
更新于2025-09-19 17:15:36
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Bio-optical Modeling and Remote Sensing of Inland Waters || Bio-optical Modeling of Total Suspended Solids
摘要： Suspended solids play a fundamental role in the aquatic ecosystem as they regulate two major transport routes of materials and contaminants: the dissolved transport in the pelagic water and the particulate benthic sedimentation route (Wetzel, 1983; Ha?kanson, 2006). The presence of total suspended solids (TSS) in water has an impact on primary producers (Zhang et al., 2008), through affecting the amount of light penetrating through the water column that restricts the rate at which benthic algae, phytoplankton, and macrophytes can assimilate energy through photosynthesis.
关键词： Inland Waters,Bio-optical Modeling,Remote Sensing,Total Suspended Solids,Water Quality
更新于2025-09-10 09:29:36
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Bio-optical Modeling and Remote Sensing of Inland Waters || Atmospheric Correction for Inland Waters
摘要： Light received by a passive Earth-observing remote sensor goes through the Earth’s atmosphere twice—from the Sun to the Earth’s surface and from the surface to the sensor—before it reaches the sensor. As such, the light received at the sensor is invariably affected by absorption and scattering by gaseous molecules and particulate matter in the atmosphere. The process of correcting for the atmospheric effects and retrieving the reflectance of a target on the Earth’s surface is called atmospheric correction. The atmospheric effect on the radiance received by a remote sensor is significantly large over water bodies because water is highly absorptive and contributes to only 20% or less of the total at-sensor radiance (e.g., Hovis and Leung, 1977). Correcting for these atmospheric effects is an essential prerequisite to retrieving accurate estimates of water-leaving radiance, which is the basis for deriving quantitative estimates of biophysical parameters from remotely sensed data.
关键词： remote sensing,biophysical parameters,Atmospheric correction,inland waters,water-leaving radiance
更新于2025-09-09 09:28:46