Observing coastal and inland waters with Landsat-8

Observing coastal and inland waters with Landsat-8

Processing very high resolution
satellite data for coastal applications
Quinten Vanhellemont and Kevin Ruddick
RBINS/DO Nature
Presented 5th May 2015 at the Liège Colloquium
http://odnature.naturalsciences.be/remsem/
Examples of high resolution satellite
imagery from Belgian waters
Landsat-8/OLI 2014-03-16
Rayleigh corrected RGB
high SPM
Zeebrugge
Landsat-8/OLI 2014-03-16
Rayleigh corrected RGB
high SPM
Zeebrugge
Landsat-8/OLI 2014-03-16
CPower wind farm
Rayleigh corrected RGB
Landsat-8/OLI 2014-03-16
white wake (foam)
Rayleigh corrected RGB
ships
brown wake (sediment)
Landsat-8/OLI 2014-03-16
Rayleigh corrected RGB
wave breaking
L8/OLI 2014-03-16
L8/OLI 2014-05-19
Landsat-8/OLI 2014-03-16
Rayleigh corrected RGB
wave breaking
CPower wind farm
high SPM
ships
Zeebrugge
Belgium/AOC Zeebrugge – 2013-08-04
Landsat-8 / RBINS processing
Aeronet-OC MOW1
Belgium/AOC Zeebrugge – 2013-10-07
Landsat-8 / RBINS processing
Aeronet-OC MOW1
Belgium/AOC Zeebrugge – 2014-09-08
Landsat-8 / RBINS processing
Aeronet-OC MOW1
C-Power / Pléiades 2015-04-14 – RBINS processing
C-Power Wind Turbine
Pléiades
2015-04-14
/ RBINS–processing
C-Power
/ Pléiades
2015-04-14
RBINS processing
C-Power Offshore Transformer Station
Pléiades 2015-04-14 / RBINS processing
Aeronet-OC
C-Power / Pléiades 2015-04-14 – RBINS processing
Foam (Phaeocystis?)
Pléiades 2015-04-14 / RBINS processing
C-Power / Pléiades 2015-04-14 – RBINS processing
RV Belgica
Pléiades 2015-04-14 / RBINS processing
C-Power / Pléiades 2015-04-14 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Zeebrugge – harbour entrance
Pléiades 2014-09-08 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
www.deme-group.com
Zeebrugge – dredger
Pléiades 2014-09-08 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Zeebrugge – patchy SPM
Pléiades 2014-09-08 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Zeebrugge – MOW1 tidal wake
Pléiades 2014-09-08 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Blankenberge yacht harbour
Pléiades 2014-09-08 – RBINS processing
ADD PLÉIADES IMAGES YOU LAZY
BASTARD
Zeebrugge / Pléiades 2014-09-08 – RBINS processing
Landsat-8 and Pléiades
processing at RBINS
cirrus band
Red/NIR
-> SPM
SWIR bands (AC)
15 m pan band
Landsat-8 and Sentinel-2 bands (adapted from ESA)
L8: 30 m multispectral, 15 m pan, 16 day track repeat
Red band -> SPM
red + NIR bands (AC)
Pléiades bands (source: http://www.satpalda.com/)
2.8 m multispectral, 0.7 m pan, on-demand tasking
Atmospheric correction
Rayleigh reflectance:
air molecules, LUT + geometry
(atm. pressure)
Top Of Atmosphere
𝜌𝑇𝑂𝐴 = 𝜌𝑎 + 𝜌𝑟 + 𝑡 ⋅
0+
𝜌𝑤
water-leaving radiance
reflectance or
marine reflectance
two-way diffuse
atmospheric transmittance
Aerosol reflectance:
particles in the atmosphere
variable in space, time, and composition
Rayleigh-corrected reflectance
0+
𝜌𝑐 = 𝜌𝑇𝑂𝐴 − 𝜌𝑟 = 𝜌𝑎 + 𝑡 ⋅ 𝜌𝑤
Aerosol correction?
Aerosol correction?
0+
𝜌𝑐 = 𝜌𝑇𝑂𝐴 − 𝜌𝑟 = 𝜌𝑎 + 𝑡 ⋅ 𝜌𝑤
𝜌𝑐 = 𝜌𝑎
where
0+ = 0
𝜌𝑤
Landsat-8/Pléiades
red + NIR bands (L8: 4,5)
4
𝜌𝑐4 = 𝜌𝑎4 + 𝑡 4 𝜌𝑤
5
𝜌𝑐5 = 𝜌𝑎5 + 𝑡 5 𝜌𝑤
clear waters
𝜌𝑐4
𝜌𝑐5
4
𝜌𝑎
=
𝜀 4,5
5
𝜌𝑎
=
4
𝜌𝑤
5
𝜌𝑤
=α
4 −𝜀 4,5 𝜌5 )
α(𝜌
𝑐
𝑐
4 =
𝜌𝑤
𝑡 5 (γα − ε)
assume fixed aerosol type over (sub)scene
fixed ratio between red+NIR water reflectance
Landsat-8: α=8.7
Pléiades: α=8.7
(see algebra in Ruddick et al., 2000)
Rayleigh-corrected reflectance in red and NIR bands
water (+aerosol)
𝜌𝑐 655 nm
aerosol
𝜌𝑐 865 nm
Aerosol correction?
0+
𝜌𝑐 = 𝜌𝑇𝑂𝐴 − 𝜌𝑟 = 𝜌𝑎 + 𝑡 ⋅ 𝜌𝑤
𝜌𝑐 = 𝜌𝑎
where
0+ = 0
𝜌𝑤
Landsat-8
SWIR + SWIR bands (L8: 6,7)
6 = 0)
𝜌𝑐6 = 𝜌𝑎6 (𝜌𝑤
7 = 0)
𝜌𝑐7 = 𝜌𝑎7 (𝜌𝑤
𝜌𝑐6
𝜌𝑐7
=
6
𝜌𝑎
=
𝜀 6,7
7
𝜌𝑎
5 =
𝜌𝑤
1
5
(𝜌
𝑐
𝑡5
per pixel
or fixed
− 𝜀 5,7 𝜌𝑐7 )
epsilon is extrapolated using aerosol model
(80 models in SeaDAS, exponential in ACOLITE)
No assumption on water reflectances! (other than 𝜌𝑤 SWIR = 0)
𝜌𝑐 1.6 µm
Rayleigh-corrected reflectance in SWIR bands
aerosol
“non water” mask
>2.15% at 1,6µm
𝜌𝑐 2.2 µm
Landsat-8/OLI 2014-03-16
Rayleigh corrected RGB
high SPM
Zeebrugge
Landsat-8/OLI 2014-03-16
Water reflectance (655 nm)
Landsat-8/OLI 2014-03-16
Aerosol reflectance (865 nm)
C-Power wind farm
surface effects
Validation of OLI Rrs (655 nm) with MODIS Aqua and Terra 250m (645 nm)
- both using SWIR correction
L8/OLI
Terra/MODIS -0:35
Aqua/MODIS +1:15
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour
processing: examples from Landsat-8. http://dx.doi.org/10.1016/j.rse.2015.02.007
Practical application (1):
Mapping of turbidity in coastal waters
largest operational
offshore wind farm
175 turbines
630MW
Vanhellemont, Q., Ruddick, K., 2014a. Turbid wakes associated with offshore wind turbines
observed with Landsat 8. Remote Sens. Environ. 145, 105–115.
Vanhellemont, Q., Ruddick, K., 2014a. Turbid wakes associated with offshore wind turbines
observed with Landsat 8. Remote Sens. Environ. 145, 105–115.
Landsat-8/OLI 2014-03-16
SPM-Nechad (655 nm)
dredger
flood tide
Practical application (2):
Detection of black dredged sediments
Rayleigh corrected RGB
Landsat-8/OLI 2013-10-30
dumped dredged
sediments
ship
port discharge
Oostende
Spuikom
J.P. Vogt (RBINS) 2014-01-24
Vanhellemont, Q., Ruddick, K., 2014b. Landsat-8 as a Precursor to Sentinel-2: Observations of
Human Impacts in Coastal Waters., in: ESA Special Publication SP-726.
Simple detection algorithm for high
concentrations of absorbing sediments
the NIR marine reflectance is greater than a threshold for turbid waters:
5 > 0.01
𝜌𝑤
the maximum marine reflectance in three visible bands is low for this
turbidity:
2 , 𝜌 3 , 𝜌 4 ) < 0.07
max(𝜌𝑤
𝑤 𝑤
NIR-VISMAX
absorbing sediment flag
L8/OLI 2014-03-16
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour
processing: examples from Landsat-8. http://dx.doi.org/10.1016/j.rse.2015.02.007
Landsat-8/OLI 2013-10-30
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour
processing: examples from Landsat-8. http://dx.doi.org/10.1016/j.rse.2015.02.007
Landsat-8/OLI 2013-10-30
𝝆𝟓𝒘 > 0.01
𝒎𝒂𝒙(𝝆𝟐𝒘 , 𝝆𝟑𝒘 , 𝝆𝟒𝒘 ) < 0.07
dredger plume
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour
processing: examples from Landsat-8. http://dx.doi.org/10.1016/j.rse.2015.02.007
Landsat-8/OLI 2013-10-30
𝝆𝟓𝒘 > 0.01
𝒎𝒂𝒙(𝝆𝟐𝒘 , 𝝆𝟑𝒘 , 𝝆𝟒𝒘 ) < 0.07
low VIS, background NIR
dredger plume
𝝆𝟓𝒘 > 0.001 ≈ ambient
𝒎𝒂𝒙(𝝆𝟐𝒘 , 𝝆𝟑𝒘 , 𝝆𝟒𝒘 ) < 0.07
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour
processing: examples from Landsat-8. http://dx.doi.org/10.1016/j.rse.2015.02.007
Conclusions
-
Landsat-8 is excellent for coastal and inland water monitoring, thanks to 30
m resolution and good SNR.
- 16-day track repeat, complements moderate resolution data
- two atmospheric correction schemes were developed at RBINS, using
the red+NIR band (VR2014) and the SWIR bands (VR2015).
-
Pléiades imagery shows promise in retrieving water quality information at
even higher resolution, at reasonable cost. 70 cm resolution from a
satellite orbiting at 700 km!
-
With (very) high resolution imagery:
- Remotely sensed water quality information near the coast and in
inland waters (WFD!)
- Small scale features are resolved in coastal and inland waters: e.g.
sediment transport, human impacts, algal blooms.
- Assessment of sub pixel variability of moderate resolution sensors
ACOLITE
-
Fast L8 image processing
- full tile or cropped to region
- batch mode option
-
Makes RGB images
- TOA or Rayleigh corrected
- Pan-sharpening
-
V&R NIR or SWIR atmospheric correction
- Output in NetCDF / GeoTIFF / PNG
- Possible outputs:
- marine reflectance
- aerosol reflectance
- extra: rtoa, rrc, spm, t, chl_oc, fai,
ndvi …
- Tweakable AC settings
http://odnature.naturalsciences.be/remsem/acolite-forum/
Acknowledgments
NASA/USGS: Landsat-8/OLI data  http://earthexplorer.usgs.gov/
Airbus DS: Pléiades Imagery
EU: funding of the HIGHROC project
BELSPO: funding of the JELLYFOR project
References -> http://odnature.naturalsciences.be/remsem/
Ruddick, K.G., Ovidio, F., Rijkeboer, M., 2000. Atmospheric correction of SeaWiFS imagery for turbid coastal
and inland waters. Appl. Opt. 39, 897–912.
Vanhellemont, Q., Ruddick, K., 2014. Turbid wakes associated with offshore wind turbines observed with
Landsat 8. Remote Sens. Environ. 145, 105–115.
Vanhellemont, Q., Ruddick, K., (2015). Advantages of high quality SWIR bands for ocean colour processing:
examples from Landsat-8. Remote Sens. Environ. 161, 89–106