OPERA: An Operational Atmospheric Correction for Land and Water

OPERA: An Operational Atmospheric Correction for Land and Water

16/06/2015
OPERA : An Operational Atmospheric
Correction for Land and Water
Sindy Sterckx, Els Knaeps, Ils Reusen, Stefan Adriaensen,
Liesbeth De Keukelaere (VITO )
Peter Hunter (University of Stirling)
Daniel Odermatt (Odermatt-Brockmann)
Claudia Giardino (CNR)
Sentinel-3 for Science, 2-5 June 2015
SENTINEL-3
L1 data
Land/Sea
Mask
L2 LAND processing
L2 MARINE processing
Oceans
Coastal areas
Land
Estuaries ?
Lakes ?
Rivers ?
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Typical marine atmospheric
correction schemes might not
work
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Need to account for non-zero altitude
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Need to account for non-zero NIR reflectance
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Knaeps et al., 2014
Need to account for non-zero NIR reflectance (even at 1020 nm) !
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Need to account for non-water spectra
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80
70
reflectance (%)
60
50
40
30
20
10
0
400
450
500
550
600
650
700
750
800
850
900
wavelength (nm)
Need to account for adjacency effects
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950
Typical land atmospheric
correction schemes might not
work over water
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Need to account for non-lambertian reflection
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OPERA: OPERational Atmospheric correction
» Sensor generic ( Sentinel-3 , Sentinel-2, Landsat, Hyperspectral missions,
…)
» Scene generic allowing to correct both land and water areas
» including turbid, high altitude, tidal or macrophyte dominated waters
» Requires to account for surface elevation variation, adjacency effects,
non-Lambertian reflection of water surfaces
» Focus on operationability, minimal manual interaction, processing
efficiency
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OPERA overview
TOA SCENE
LAND/WATER
MASKING
LAND BASED AOT
RETRIEVAL
SZA,VZA,RAA
DEM
WATER VAPOR
RETRIEVAL
MODTRAN5
LUT
ADJACENCY CORR.
WATER: SIMEC
LAND: RANGES
ATMOSPHERIC CORR.
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L2 SCENE
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Land-based AOT retrieval
TOA SCENE
Based on
Guanter et al. (2008) RSE
SZA,VZA,RAA
DEM
Cloud & Water masking
Tiles creation
Select Lmin(VIS)
MODTRAN5
LUT
NDVI selection
Endmember inversion
AOT tiles
Inverse distance
interpolation
Resize (bilinear)
Spatial smoothing
AOT SCENE
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Adjacency correction : SIMEC (over water pixels)
» Basic assumption :
Invariant shape of water reflectance
in NIR, ie ‘‘similarity’’ NIR reflectance
spectrum (Ruddick et al., 2006)
» No assumption on NIR albedo
Sterckx et al. (2015) RSE
Sterckx et al. (2011) IJRS
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Adjacency correction : SIMEC (over water pixels)
» Basic assumption :
Invariant shape of water reflectance
in NIR, ie ‘‘similarity’’ NIR reflectance
spectrum (Ruddick et al., 2006)
Sterckx et al. (2015) RSE
Sterckx et al. (2011) IJRS
» No assumption on NIR albedo
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OPERA on MERIS FR
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WO
HO
MO
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OPERA on LANDSAT 8 (OLI)
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0.04
Mantua lakes (Italy)
0.07
P1 OPERA with
SIMEC
0.03
Rw
P1 OPERA
without SIMEC
0.02
0.05
0.03
0.01
0
600
700
Wavelength (nm)
0.05
P2
0.04
P3
P4
800
900
P2 OPERA
without SIMEC
0.02
600
700
Wavelength (nm)
800
900
P6 insitu
P6 OPERA with
SIMEC
0.05
0.04
P5 OPERA
without SIMEC
0.03
0.02
0.01
0.01
0
0
500
600
700
Wavelength (nm)
0.05
800
P3 OPERA with
SIMEC
0.03
Rw
P3 OPERA
without SIMEC
0.02
500
600
700
Wavelength (nm)
0.05
P3 insitu
0.04
400
900
800
900
P7 insitu
0.04
P7 OPERA with
SIMEC
P7 OPERA
without SIMEC
0.03
Rw
400
0.02
0.01
0.01
0
0
400
500
600
700
Wavelength (nm)
0.05
800
900
400
500
600
700
Wavelength (nm)
800
P4 insitu
0.04
P4 OPERA with
SIMEC
0.03
P4 OPERA
without SIMEC
Rw
Landsat 8
23 Sept 2014
500
0.06
P2 OPERA with
SIMEC
0.03
400
0.07
P2 insitu
Rw
P5
500
Rw
400
P6
P5 OPERA
without SIMEC
0.04
0
P1
P5 OPERA with
SIMEC
0.06
0.02
0.01
P7
P5 insitu
0.08
P1 insitu
Rw
0.05
0.02
0.01
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0
400
VITO NV 700
500 © 2014,
600
19
800
900
900
Mantua lakes (Italy)
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Belgian coast
Aeronet OC (RBINS)
+/- 4.5 km
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OPERA without SIMEC :
Reflectance Landsat8 865 nm band
OSLO
LC81970192014205LGN00
0.004
0.032
Image LC81970222014205LGN00
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OPERA with SIMEC :
Reflectance Landsat8 865 nm band
LC81970192014205LGN00
0.004
0.032
Image LC81970222014205LGN00
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OPERA without SIMEC :
Reflectance Landsat8 655 nm band
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OPERA with SIMEC :
Reflectance Landsat8 655 nm band
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OPERA without SIMEC :
Landsat8 TSM MAP based on 655nm
Nechad et al, 2010
0
8 mg/l
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OPERA with SIMEC :
Landsat8 TSM MAP based on 655nm
Nechad et al, 2010
0
8 mg/l
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OPERA without SIMEC :
Reflectance Landsat8 865 nm band
Image: LC81990242014075LGN00
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OPERA with SIMEC :
Reflectance Landsat8 865 nm band
Image: LC81990242014075LGN00
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OPERA without SIMEC :
Landsat8 TSM MAP based on 865nm
Nechad et al, 2010
0
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100 mg/l
30
OPERA with SIMEC :
Landsat8 TSM MAP based on 865nm
Nechad et al, 2010
0
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100 mg/l
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Conclusions
» Atmospheric correction : complex
» Variability of inland waters adds more complexity
 Remote sensing : underutilised
 Need for adequate atmospheric correction algorithms
» OPERA : step forward
» SIMEC mainly neutral or positive effect. Adjacency effect not
always clearly present.
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Outlook
» Mountainous regions :
» Stability of AOT retrieval need to be improved
» Alternative AOT retrieval specific for water areas
» Use of SWIR bands
» BUT
»SNR issues ?
»Accuracy of SWIR bands ?
» eg. Pahlevan et al (2014) gains for OLI:
(1.034 SWIR 1, 1.21 SWIR2 )
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