NDLI: Google Earth Engine Sentinel-3 OLCI Level-1 Dataset Deviates from the Original Data: Causes and Consequences

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Google Earth Engine Sentinel-3 OLCI Level-1 Dataset Deviates from the Original Data: Causes and Consequences

Content Provider	MDPI
Author	Prikaziuk, Egor Yang, Peiqi van der Tol, Christiaan
Copyright Year	2021
Abstract	In this study, we demonstrate that the Google Earth Engine (GEE) dataset of Sentinel-3 Ocean and Land Color Instrument (OLCI) level-1 deviates from the original Copernicus Open Access Data Hub Service (DHUS) data by 10–20 W m $^{- 2}$ sr $^{- 1}$ μ $μ$ m $^{- 1}$ per pixel per band. We compared GEE and DHUS single pixel time series for the period from April 2016 to September 2020 and identified two sources of this discrepancy: the ground pixel position and reprojection. The ground pixel position of OLCI product can be determined in two ways: from geo-coordinates (DHUS) or from tie-point coordinates (GEE). We recommend using geo-coordinates for pixel extraction from the original data. When the Sentinel Application Platform (SNAP) Pixel Extraction Tool is used, an additional distance check has to be conducted to exclude pixels that lay further than 212 m from the point of interest. Even geo-coordinates-based pixel extraction requires the homogeneity of the target area at a 700 m diameter (49 ha) footprint (double of the pixel resolution). The GEE OLCI dataset can be safely used if the homogeneity assumption holds at 2700 m diameter (9-by-9 OLCI pixels) or if the uncertainty in the radiance of 10% is not critical for the application. Further analysis showed that the scaling factors reported in the GEE dataset description must not be used. Finally, observation geometry and meteorological data are not present in the GEE OLCI dataset, but they are crucial for most applications. Therefore, we propose to calculate angles and extraterrestrial solar fluxes and to use an alternative data source—the Copernicus Atmosphere Monitoring Service (CAMS) dataset—for meteodata.
Starting Page	1098
e-ISSN	20724292
DOI	10.3390/rs13061098
Journal	Remote Sensing
Issue Number	6
Volume Number	13
Language	English
Publisher	MDPI
Publisher Date	2021-03-13
Access Restriction	Open
Subject Keyword	Remote Sensing Google Earth Engine Gee Sentinel-3 Ocean and Land Color Instrument Olci Medium Resolution Imaging Spectrometer Meris Copernicus Open Access Data Hub Service Dhus European Space Agency Esa Pixel Uncertainty Snap Time Series Copernicus Atmosphere Monitoring Service Cams
Content Type	Text
Resource Type	Article

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