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

 
 




 



 
LE70180472000025EDC00
25 january 2000


TCC


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
Kblue/Kgreen=0.53

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
Kblue/Kgreen=0.60
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


TCC_WCC_BOA_normalized


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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