Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries

Landsat ETM 4 bands image 
of Chinchorro atoll, Gulf of Mexico

Work completely updated in january 2016
return to 4SM Study Cases


LE70180472000089SGS00 29 march 2000

work in progress



TCC deglinted
There is hardly any sea surface glint in this image

Special effect mask
  • Green areas are excluded from calibration data extraction: deep waters and clouds
  • Blue areas represent the outer reef slopes
    • they are processed using the general calibration  optical model
  • Orange areas represent the lagoon
    • they are processed using the lagoon calibration  optical model

Optical calibration
for the full image

Optical water type OIA+0.59
Open waters are very clear

This is nearly
Sargasso Sea waters!


Depth over bright bottoms exceeds 32 m
K1=0.061 m-1   K2=0.157 m-1   K3=0.740 m-1

Optical calibration under mask_3
excludes the reef slopes
i.e. only inside the lagoon

Optical water type OIA+0.59
There is no sign
that lagoon waters are less clear


Depths inside the lagoon do not exceed ~13 m

is only slightly lowered.
This is needed in order to achieve
a nice fit of the Ki/Kj slopes
with the observed BPL pixels

whereas ETM 25 january 2000
required a value of CoefK=1.0
as at HYPERION Fakarava

Could it be that this parameter
is correlated to water clarity?
This now needs to be investigated.

Profile Blue
Retrieved depth
and water column corrected
spectral bottom reflectance
The red profile represents
depth retreived for Chinchorro_20000125
minus a tide height=1 m


Profile Blue
Raw and deglinted/smoothed radiances


TCC water column corrected, BOA


deltaZ  =  Z_january  -  Z_march
a tide height of 1 m
was subtracted from Z_january



This regression compares
Z_29MAR2000 with Z_25JAN2000


This histogram compares
Z_29MAR2000 with Z_25JAN2000



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