Banc d'Arguin, Arcachon
a 500*630 subset of a SPOT XS image
of the Atlantic coast of France

updated july 2011 then october 2017
please refer to
http://kalideos.cnes.fr/spip.php?article46
 026_Capo_Sylvain.pdf
back to 4SM tutorials           next to Prepare your image
 
 

    

A nice 1-band study case

This is a bad case of foul coastal waters, with a lot of wave breakers
Quite interesting though for training,
for the following reasons:
  • Foul waters: plumes of suspended sediments abound. Therefore optical modeling of this image is a "Natural Hazard"!
  • Wave breakers: shoals exposed to oceanic swell exhibit wave breakers: this shall be a challenge for optical calibration
  • Aliens: aliens can play bad tricks for one who undertakes shallow water modeling
    • popular aliens are clouds and their shadows, lumps of haze, sun and sky glint, wave breakers, sailing boats, artificial calibration targets submerged or on the beach, floating/drifting vegetal mats
    • each requires a specific attention
  •  Narrow dynamic range:  radiance of damp bright sands at null depth is approx DN=70 only
    • bottom contrast in the green band is at most 70-30=40
  • Coastal: coastal waters with fairly poor water penetration
  • Seatruth: still, the optical calibration of the water type using Jerlov's data works well, 
  • One-band case: therefore, 
    • and because the bottom is mostly clean sands in this highly dynamic environment , 
    • this image is a good illustration of the one-band case.
  • Jerlov's data: this case demonstrates clearly that 
  • Reference: this site has been extensively investigated by V. Lafon, J. M. Froidefond, F. Laher, and P. Castaing, "SPOT shallow water bathymetry of a moderately turbid tidal inlet based on field measurements", Remote Sensing of Environment, 81, 2002, 136-148 .
     
 

  Prepare the image

 First Calibration

First Modeling

  Second Calibration

 Final  Modeling   

  What we learned

 

The sea-truth is extracted from "Teledetection et gestion du milieu cotier", Prud'homme R, Froidefond J. M. and Castaing P., Memoire de l'Institut Oceanographique de Monaco, 1994; 18, 1994, pp53-65 
It is a depth contour map surveyed by the Port Authority of Bordeaux one year after the SPOT image was acquired.

 
The end


 



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