Optical calibration, bathymetry, water column correction and bottom typing of shalClipperton Atoll, Francelow marine areas, using passive remote sensing imageries
Landsat 8 at Clipperton Atoll, France

Landsat January 19th 2020, 360*374 pixels, 15 m GSD


BOA deglinted TCC
glint regressions

calibration Nir, Red, Green, Blue

calibration Red, Pan, green, blue

map of the ratio 100*Kblue/Kgreen

satellite derived bathymetry, in cm

BOA TCC of water column corrected radiances 
Ublue, Green, Blue RGB

Landsat December 2nd 2020
work done june 2021

Clipperton atoll
 Blue waters over the ocean 
Ultrablue and Blue bands shine       Green, Pan and Red bands are low
 Green waters inside the lagoon 
UltraBlue and Blue bands are low    Green, Pan, and Red bands     shine
The purpose of the LUT approach is, among other things, 
to account for such variations of the optical properties of the shallow waters

 upon operating the water column correction, pixel-wise

Deglinted/smoothed data
With Coastal C5 water type, the central lagoon is most probably optically deep

is extinct


is slightly depressed

glows strongly


glows slightly

a neat and very small scene 

image size: 360*374, 15m GSD
Glint regressions based on SWIR
shows PAN vs SWIR

a good start: regressions are excellent
calibration NIR, Red, Green, Blue
full image, clear oceanic waters
K2/K3=0.65 related to Oceanic II water type

calibration Red, Pan, Green, Blue
full image, under satisfactory control

Map of the ratio Kblue/Kgreen


TCC BOA deglinted

SDB in cm
Relates reasonably well with existing bathymetric maps

TCC BOA WCC Ublue, Green, Blue RGB 
TCC of water column corrected radiances:
the ultimate goal


A 1371*1160 IKONOS 4 bands image of Clipperton atoll
Wavelengths at midresponse curve are 480, 551, 665 and 805 nm
Strong sky and sun glints. Clouds not masked. Confined fresh waters in the lagoon 
 Work done in 2000, updated in 2005, image courtesy of S.  Andrefouet

Raw image, BGR TCC
histeq enhancement

Raw image, full resolution
histeq enhancement

Deglinted image, BGR TCC
histeq enhancement
No smoothing over the deep ocean

Deglinted image, full resolution
histeq enhancement
No smoothing over the deep ocean



image_LBS normalized

histeq enhancement


Blue vs Green

Blue vs Green

Optical calibration
of outer slopes

Fairly straightforward, although 
2K[red]=0.38 at 665 nm is a physical nonsense,
therefore the range of computed depths is problematic
  • Wavelengths must be set so that all ratios Ki/Kj fit nicely the slopes observed in this calibration diagram
  • Kblue/Kgreen=0.762
  • Kblue/Kred and Kgreen/Kred are very easy to check
  • Quite likely WLgreen must be increased and WLred must be decreased

Optical calibration
inside the lagoon

Quite difficult, as the lagoon bottom substrates
would appear to be extremely dark

The following is adopted:
Jerlov water type Coastal 3+0.14


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