Lee, Chengfa Benjamin

Institute of Transport Research:Publications

A full cloud-native dive into regional-scale seagrass mapping in the Mediterranean using Sentinel-2 multitemporal dataLee, Chengfa BenjaminPhD Candidate, German Aerospace Centre (DLR)Global Seagrass WatchRapid & global loss of seagrass215 sites29% loss since 18793 seagrass bioregions poorly representedSource: Accelerating loss of seagrasses across the globe threatens coastal ecosystems, Waycott M, et al. (2009)Seagrass DatasetsSeagrass DatasetsAnalysis Ready Dataset (ARD)1. Expanded spatial extent2. Processing large datasets3. Monitoring changes (temporal)1. Easy scalability2. Cloud computing capabilities3. Multitemporal analyticsSentinel-2 L1Ccollection1 Jan 2015 – 31 Dec 2019Pre-processing• Cloud mask• Multitemporal composition• Atmospheric correction• Land & deep water mask• Turbid maskMultitemporal compositeTraining polygons(GEE composite)(n = 50712)Validation points (WorldView-2, field data)(n = 3165)Seagrass mapof theMediterraneanGoogle Earth EngineClassification• Random Forest(‘Probability‘ output)• Convert to hardclassificationValidationStatisticsScalabilityNo. of tiles used ~280,000Total area of basin covered ~56,000 km2Estimated total seagrass area ~19,000 km2AccuracySeagrass PA 55.0 %Seagrass UA 61.8 %Overall accuracy 72.1 %Bastia, Corsica, FranceRGB compositeUNEP-WCMC seagrassSoft to hardclassificationSeagrassmapSandSeagrassDeepwaterSource: Own work (2020)Challenges1. Spectral normalisation (regional)Source: Own work (2020)2. Spectral artifacts(local)Source: Own work (2020)3. Optical depthSource: Mapping coastal marine habitats and delineating the deeplimits of the Neptune’s seagrass meadows using very high resolutionEarth observation data, Poursanidis D, et al. (2018)Works1. GEE App showcaseSeagrass meadows of Corsica (France)https://leechengfa.users.earthengine.app/view/geo-for-good-2020-mapping-mediterranean-seagrasses2. Work in progressCloud-native advances in Earth Observationreveal the pan-Mediterranean extent of the P.oceanica seagrass ecosystemTraganos, Lee, Poursanidis et al. (2020). Manuscript in preparation.3. Future ventures• Carbon stock estimates• Change detection• Species identificationThank you for your attention.Dr. Alexander BornPoint of ContactRainer Schüller-FenglerProject CoordinatorDimos TraganosProject ManagerAvi Putri PertiwiResearch ScientistBenjamin LeePhD candidate

A full cloud-native dive into regional-scale seagrass mapping in the Mediterranean using Sentinel-2 multitemporal data

https://elib.dlr.de/188089/1/Geo4Good_lightningtalk.pdf

A full cloud-native dive into regional-scale seagrass mapping in the Mediterranean using Sentinel-2 multitemporal data

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Institute of Transport Research:Publications