introduction to icor and acolite atmospheric correction for … · 2017. 11. 23. · ac in ocean...
TRANSCRIPT
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Dimitry Van der Zande - RBINS Clémence Goyens – VITO
Quinten Vanhellemont – RBINS Liesbeth De Keukelaere - VITO
Introduction to iCOR and ACOLITE atmospheric correction for Landsat-8
and Sentinel-2
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ATMOSPHERIC CORRECTION
Ozone layer
Absorption by aerosols
& molecules
Scattering by aerosols & molecules
Scattering from the
target
Rayleigh
Aerosols
θ𝑠𝑠 θ𝑣𝑣
Scattering from the
background
Atmosphere
Δφ
𝐿𝐿 𝑇𝑇𝑇𝑇𝑇𝑇 = 𝐿𝐿𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 + 𝐿𝐿𝑡𝑡𝑡𝑡𝑎𝑎−𝑝𝑝𝑡𝑡𝑡𝑡𝑝 + 𝐿𝐿𝑏𝑏𝑡𝑡𝑏𝑏𝑏𝑏𝑡𝑡𝑡𝑡−𝑝𝑝𝑡𝑡𝑡𝑡𝑝
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
AC in Ocean Color
Courtesy of PJ Werdell
𝐿𝐿 𝑇𝑇𝑇𝑇𝑇𝑇 = 𝐿𝐿𝑤𝑤𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 + 𝐿𝐿𝑡𝑡𝑡𝑡𝑎𝑎−𝑝𝑝𝑡𝑡𝑡𝑡𝑝 + 𝐿𝐿𝑏𝑏𝑡𝑡𝑏𝑏𝑏𝑏𝑡𝑡𝑡𝑡−𝑝𝑝𝑡𝑡𝑡𝑡𝑝 In the NIR
Gordon and Wang, 1994 Black Pixel Assumption
Ignored
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
AC in Ocean Color
Courtesy of PJ Werdell
𝐿𝐿 𝑇𝑇𝑇𝑇𝑇𝑇 = 𝐿𝐿𝑤𝑤𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 + 𝐿𝐿𝑡𝑡𝑡𝑡𝑎𝑎−𝑝𝑝𝑡𝑡𝑡𝑡𝑝 + 𝐿𝐿𝑏𝑏𝑡𝑡𝑏𝑏𝑏𝑏𝑡𝑡𝑡𝑡−𝑝𝑝𝑡𝑡𝑡𝑡𝑝
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ATMOSPHERIC IMAGE CORRECTION
- Use a NIR modelling scheme and remove ρW(λNIR) from ρt(λ) → apply GW94 e.g., Siegel et al. (2000), Stumpf et al. (2003), Bailey et al. (2010), Wang et al. (2012) - Fix aerosol contribution from nearby pixels and model to determine the ρW(λNIR) e.g., Hu et al. (1999) and Ruddick et al. (2000, 2006)
- Using Short Wave Infrared (SWIR) bands in highly turbid waters e.g., Wang and Shi (2007) and Wang et al. (2009)
- Coupled Ocean-Atmosphere optimization/inversion e.g., Gordon et al. (1997) (spectral matching); Chomko and Gordon (1998), Chomko et al.
(2003) and Kuchinke et al. (2009) (spectral optimization method); Jamet et al. (2005) and Brajard et al. (2012) (spectral optimization including NN); Doerffer and Schiller (2008, 2007), Schroeder et al.(2007) (NN inversion); Steinmetz et al. (2010) (polynomial atmospheric path radiance).
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ICOR, ATMOSPHERIC IMAGE CORRECTION
- Sensor generic (S2, L8, hyperspectral, … ) - Scene generic (Land and Water) - Focus on operationability - Handle land and water pixels - Focus on coastal and inland waters Previously known as OPERA
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
𝐿𝐿 𝑇𝑇𝑇𝑇𝑇𝑇 = 𝐿𝐿𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 + 𝐿𝐿𝑡𝑡𝑡𝑡𝑎𝑎−𝑝𝑝𝑡𝑡𝑡𝑡𝑝 + 𝐿𝐿𝑏𝑏𝑡𝑡𝑏𝑏𝑏𝑏𝑡𝑡𝑡𝑡−𝑝𝑝𝑡𝑡𝑡𝑡𝑝
De
Keu
kela
ere
et a
l. (s
ubm
itted
)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
• Using external sources OR image based • Image based
– Guanter et al., 2005 – Derived above land – Spatially extended over water pixels – Fixed rural aerosol model
Latm−path & AOT retrieval
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
As seen by the satellite
Rayleigh scattering
ρw(λ) ?
Lbackgr.−path over water
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Lbackgr.−path over water
NIR similarity spectrum Ruddick et al. (2006 )
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Lbackgr.−path over water
Lake Marken - 15/09/16 Lake Marken - 15/09/16
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Lake Marken - 15/09/16
Transect – 865 nm (9km)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Mantua Lakes - 23/09/14
No SIMEC SIMEC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Lbackgr.−path over land
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
iCOR in SNAP
Let’s try it during 11:00 Practical hands-on session: iCOR atmospheric correction using the SNAP toolbox
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE Atmospheric Correction for High-Resolution Satellites
To develop AC algorithms for Sentinel-2, Landsat-8 taking TOA radiance data and auxiliary data as input and provide bottom of
atmosphere water reflectance as output.
L8 20140716
TOA radiances Rayleigh corrected radiances water reflectance
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE aims at
ρ Rayleigh
TOA
ρ aerosol
Rayleigh corrected
Retrieve water-leaving radiance reflectance, ρw, for turbid waters - use dark SWIR pixels to establish estimate of aerosol reflectance - SWIR threshold delineates water/non water - exponential extrapolation using 1.6/2.2 SWIR ratio (smoothed) - no direct AOT/Ta estimation
Sensitive to adjacency effects (inland waters), water surface effects (glint)
water reflectanc
e
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE processor
L1 Imagery
Rayleigh corrected imagery
Rayleigh correction: LUT based on 6SV and sun and sensor geometry
Land/cloud masking
ρc 6 > 0.0215 Cloud shadow detection
-in development-
Rayleigh corrected imagery with water
pixels
Height of lake
Elevation automatically extracted from DE
Select clear water pixels
SWIR (1609,2201)
ε spatially
fixed or variable
NIR (655,865nm)
ε spatially
fixed
SWIR (865,1609nm)
ε spatially
fixed
SWIR (865,2201nm)
ε spatially
fixed
Aerosol type (ε) selection
ρw=𝟏𝟏𝒕𝒕
(𝝆𝝆𝒄𝒄 − 𝜺𝜺. ρam)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Currently at version ‘2070718’ • Binary distribution of L8/S2 AC processor for Windows, Linux and MAC • Simple and fast processing of L8/S2 images for marine and inland water applications • AC is image based, no need for external Inputs!! • ε constant over scene (crop), aerosol multiple scattering reflectance varies per pixel • Use of settings file (created by acolite) batch processing
‘idl –rt=acolite.sac –args image=imagelist.txt sttings=acolite_settings_file’
ACOLITE software
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Standard Features • Atmospheric correction of L8/S2 • RGB image generation (TOA, RCO, pan sharpened), RGB scaling • extraction of rectangular regions • Mapping options: next to NetCDF, GeoTIFF, PNG now also KMZ • L2 processing products:
ACOLITE software
Rhow
CHL_OC2, CHL_OC3
SPM_NECHAD 561, 655, 865
SPM_Balaton
RTOA, LTOA DEM T_NECHAD_645
RRC, LRC FAI (floating algae index)
T_DOGLIOTTI (red, NIR, mix)
RHOAM NDVI, NDVI_TOA, NDVI_RCO
QAA_a QAA_bb QAA_Kd
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Qualitative inspection of ACOLITE products for L8-OLI
ACOLITE products for L8
Lake Balaton (20140716)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Qualitative inspection of ACOLITE products for L8-OLI
ACOLITE products for L8
Lake Balaton (20140716)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2
S2 10m resolution 16/1/2016
Ice
Ice
Thin cloud
Submerged ice
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2
S2 10m resolution 16/1/2016 Submerged
ice
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2
S2 665nm 10m resolution 16/1/2016
Cloud shadow
High reflectance by ice (cracks)
Striping in RGB bands
Water visible through ice?
Clouds flagged
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2 Cyanobacterial bloom in Lake Mulwala (Australia)
705 nm reference
665 nm chla absorption
9x9 pixels
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2 Cyanobacterial bloom in Lake Mulwala
9x9 pixels
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 & S2 AC
Lake Balaton (20140716) *WISP-ASD-RAMSES-HyperSAS
Lake Mantua (20140923) *ASD, SE Curonian Lagoon (20140902)
*WISP
Inter-comparison exercise of AC procedures for L8 • In situ remote sensing reflectance gathered by CNR (and INFORM consortium) in
Balaton Lake, Kis, Lake Mantua and Curonian Lagoon • Match up time difference max 2h • Every match up QC for cloud, cloud shadow, glint
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Inter-comparison exercise of AC procedures • In situ Rrs data was QC and processed by individual partners responsible for data
acquisition 1 hyperspectral Rrs measurement per station
• Resampled to L8-OLI bands and S2-MSI to enable direct comparison (using SRF)
Validation of L8 & S2 AC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Balaton 20160721 L8-OLI
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8-OLI 443nm
490nm
ACOLITE
iCOR
ACOLITE Slope = 0.927 R² = 0.921 rmse = 0.004
iCOR / iCOR-SIMEC Slope = 1.075 / 1.114 R² = 0.934 / 0.939 rmse = 0.004 / 0.004
iCOR-SIMEC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2-MSI
ACOLITE Slope = 1.166 R² = 0.752 rmse = 0.003
iCOR / iCOR-SIMEC Slope = 0.920 / 0.630 R² = 0.950 / 0.812 rmse = 0.0002 / 0.001
ACOLITE ACOLITE
iCOR iCOR-SIMEC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
• Atmospheric correction could be considered the most important step in the generation of L2W products.
• iCOR (SNAP) & ACOLITE (stand alone) open access software provides AC for water applications with land-sensors
• iCOR & ACOLITE show good results in many cases but limitations have been identified (e.g. noisy SWIR bands S2)
• Limitations due to sensor characteristics have been mentioned in the recommendations for future Copernicus missions
• BEL-Ponder: development of new AC approach (multi-band dark pixel fitting) to deal with AC issues for current sensors
Summary
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Bonus slides
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 with MOW1 data
Validation of ACOLITE using BE AERONET
Match-up analysis Zeebrugge-MOW1 station (prelim results): • AERONET-DATA from Febr 2014-Febr
2016 + Aug-Sept 2016
• Level 1 13 match ups • Level 1.5 1 match up • Level 2 1 match up
• ACOLITE v20160602v2 (SubF_Unity) • Actual pixel value • < 1h time difference
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 with MOW1 data
T5.1.3 Validation of ACOLITE
443nm
490nm
560nm
665nm
865nm
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2-MSI with AERONET-OC data
T5.1.3 Validation of ACOLITE
• AERONET-DATA 2016 MOW1: since Aug 2016 Cpower: full S2-MSI mission
• Level 1.5 16 match ups (15 Cpower, 1 MOW1) • 8 Cpower and 1 MOW1 matchup remained after quality control (clouds,
haze, wave effects, glint, …) • ACOLITE v20161123v1.0 (SWIRvar_Unity)
• 300m by 300m (31x31 pixels)
• < 1h time difference
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
T5.1.3 Validation of ACOLITE
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
T5.1.3 Validation of ACOLITE
Increased scatter towards shortest blue band (bug in ACOLITE?)
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
T5.1.3 Validation of ACOLITE
665nm: Increased scatter in clear water match-ups due to differences between SRFs of narrow AERONET-band and
wide S2-MSI band
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
T5.1.3 Validation of ACOLITE
Difficulties to measure a very low NIR signal in clear waters show the limits of the sensor and atmospheric correction
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 AC –ACOLITE- 560nm 443nm
490nm 665nm
865nm
MAPE
ACOLITE
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 AC –iCOR- 560nm 443nm
490nm 665nm
865nm
MAPE
iCOR
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of L8 AC –iCOR SIMEC- 560nm 443nm
490nm 665nm
865nm
MAPE
iCOR-SIMEC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2 AC –ACOLITE- 560nm 443nm
490nm 665nm
865nm
MAPE
ACOLITE
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2 AC –iCOR- 560nm 443nm
490nm 665nm
865nm
MAPE
iCOR
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2 AC –iCOR SIMEC- 560nm 443nm
490nm 665nm
865nm
MAPE
iCOR-SIMEC
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Validation of S2-MSI
490nm
ACOLITE Slope = 0.952 R² = 0.767 rmse = 0.003
iCOR / iCOR-SIMEC Slope = 0.920 / 0.630 R² = 0.950 / 0.812 rmse = 0.0002 / 0.001
ACOLITE
iCOR
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
Inter-comparison exercise of AC procedures • In situ remote sensing reflectance gathered by CNR (and INFORM consortium) in
Balaton Lake, Kis, Lake Mantua and Curonian Lagoon, Lake Garda, Lake Iseo, Lake Marken
Validation of L8 & S2 AC
ACOLITE (RBINS) –Based on approach of Ruddick et al. (2000) • Input: target altitude; sun-target geometry • Aerosol model and aerosol reflectance estimated from spectral imagery • No adjacency correction • Water applications
iCOR (VITO) – Based on MODTRAN • Input: target altitude; sun-target geometry; • Visibility with land approach • Fixed rural aerosol model • Spatially extended over water pixels • procedure for adjacency effects • Land and water applications
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2 Lake Garda
17/8/2016 12/9/2015 1/7/2016
Rrs664
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2
S2 443nm 60m resolution 16/1/2016
Mis-alignment of lenses for 443 band?
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User Uptake Workshop
16-17 November 2017
European Environment Agency, Copenhagen, Denmark
ACOLITE products for S2
S2 497nm 10m resolution 16/1/2016
NO Mis-alignment of lenses for 497 band
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