sinusoidal vs. geographic projec6on · sinusoidal vs. geographic projec6on nima pahlevan 1,2,...
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SinusoidalVs.GeographicProjec6on
NimaPahlevan1,2,SudiptaSarkar1,2,VirginiaKalb2,EricVermote2,SadashivaDevadiga1,2,,GaryLin1,RobertE.Wolfe2,
MiguelRoman2,andChrisJus6ce3
1Science,Systems,AndApplica6ons,Inc.(SSAI)2NASAGoddardSpaceFlightCenter(619)
3DepartmentofGeographicalSciences,UniversityofMaryland
MODIS/VIIRSScienceTeamMee1ng,LandbreakoutSilverSpringMD
June2016
Introduc6on
• Sinusoidalprojec6onwasadopted…– Itwasrecommendedbyclimatemodelers– Itpreservesthearea– Thereislessdistor6onovertropicalareas– Thereislesscomputa6onoverhigh-la6tudeareas
• Geographicprojec6on,ontheotherhand,facilitateseasierintegra6onwithvariousgeo-visualiza6ontoolsavailablenowadays
2ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
SinusoidalProjec6on
3ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
RasterMosaicDatasetfromscaledEVITOC,defined'nodata’,withunderlyingshadedreliefDEMat30arcseconds(USGS)
GeographicProjec6on
4ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
RasterMosaicDatasetfromscaledEVITOC,defined'nodata’,withunderlyingshadedreliefDEMat30arcseconds(USGS)
Objec6ve
• Evaluatetheimpactofchangeinprojec6ononLandSurfaceReflectanceandNDVIProductsover“GoldenTiles”
5ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
Method:SimulateDailyMODIS/VIIRSProducts
MODIS
OLIscene
185km
185km
OLI-derivedsurfacereflectanceproducts
ScanOLIdataaccordingtoVIIRSandMODIS
• ViewinggeometriesforoneorbitcycleAND• ThePointSpreadFunc6ons
1kmgridding(GEOVS.SIN)
intercomparison
Swath-levelsimulatedMODISandVIIRSproducts
6ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
Spa6alSamplingUsedinSimula6ons
Agg.3X1 Agg.2X1 Agg.1X1
MoredetailsonthemethodinPahlevan,N,Sarkar,S.,Devadiga,S.,Wolfe,R.E.,Román,M.O.,Vermote,E.,Lin,G.,andXiong,X.(2016).ImpactofSpa6alSamplingonCon6nuityofMODIS-VIIRSLandSurfaceReflectanceProducts:ASimula6onApproach.Submi&edtoIEEETransac4onsofGeoscienceandRemoteSensing(underreview).
8
SampleSimulatedNDVIs(SINVs.GEO)
ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
h30v11 ï d2014016 ï t0502030
0
0.05
0.1
0.15
0.2h31v11 ï d2014016 ï t0502030
0
0.05
0.1
0.15
0.2
Metrics• Histogram-basedanalysisofdifferencegridsofSINandGEOforLSRandNDVI
– Per-pixel(i):PercentDifference(PD)andAbsolutePD(APD)
– Per-area:histogrammean(PD&APD)andRMSD– Median/min/maxofmeanvalues(mul6pleSIN-GEO)
9ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
−20 −10 0 10 200
50
100
150
200C:NIR
Bias = 0.005%Kurtosis = 3.3PoP @ ±1% = 37.1%
±1%
±5%
±10%
PD (%)
Freq
uenc
y
Australia(barren)
10ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
NWCanada(boreal)
11ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
NorthernChile
12ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
NDVI
13ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
• Ensembleofsimulateddifferenceimages(variousorbitsandlandcovers)
Conclusion
• SIN>GEOyield,onaverage,insignificantdifferences(PD<0.5%&difference<1e-3)inLSRandNDVIproducts.
• RecommendaMon– Dependingonuserneeds,itispossibletotransiMontogeographicprojecMonwithveryminimalimpactonlandproducts.
– FurtheranalysesoftheimpactcanbedonebysciencePIs(ifneeded)
14ImpactsofChangeinProjec6ononLandProducts-NimaPahlevanSSAI/NASAGSFC
Backup
ImpactsofSpa6alSamplingonProducts-NimaPahlevanSSAI/NASAGSFC 15
SampleSimulatedSwaths
16
ThesimulatedMODISLSRswathsre-projectedandoverlaidontogriddedMODISLSRs(MYD09)showninRGBfortheSWUSA(left)andNEChina(DOY=247)sites.CourtesyofPeteMa(NASAGSFC/SSAI).
ImpactsofProjec6onChangeonLandProducts-NimaPahlevanSSAI/NASAGSFC
MoredetailsonthemethodinPahlevan,N,Sarkar,S.,Devadiga,S.,Wolfe,R.E.,Román,M.O.,Vermote,E.,Lin,G.,andXiong,X.(2016).ImpactofSpa6alSamplingonCon6nuityofMODIS-VIIRSLandSurfaceReflectanceProducts:ASimula6onApproach.Submi&edtoIEEETransac4onsofGeoscienceandRemoteSensing(underreview).