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



25 january 2000


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
mostly represents the outer reef slopes

Optical water type OIB+0.27
Open waters are very clear

Depth over bright bottoms exceeds 30 m
K1=0.084 m-1   K2=0.158 m-1   K3=0.614 m-1

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

Optical water type OIB+0.55
Lagoon waters are distinctly less clear
Depth inside mask_3 does not exceed ~13 m
K1=0.100 m-1    K2=0.167 m-1   K3=0.626 m-1


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

This confirms what was observed
using HYPERION image
at Fakarava Atoll

Profile Blue
Retrieved depth
and water column corrected
spectral bottom reflectance


Profile Blue
Raw and deglinted/smoothed radiances


TCC water column corrected, BOA


image B
Average bottom brightness



Retrieved depth

see bathymetric map
by Garci_a-Gil et al. 2003
A tide height of ~1.5 m appears suit this scene

Bottom typing: image classified


Bottom typing legend

see Bottom type signatures


Bottom type signatures

type 10

type 11

type 12

type 13

type 14

type 15

type 16

type 17

type 18

type 19


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