Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
WorldView 2 image at Waimanalo Beach, Oahu, Hawaii islands
3289x3241, 2 m ground resolution, courtesy of Ron Abileah
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New tools in 4SM
 
 

Some new tools in 4SM: depth over dryland

 


Depth applied over land : 1 meters

Let's paly a bit:

  • let's apply a 1 m water depth exponential decay to all dryland pixels spectral signatures

  • then see what computed depth we obtain by inverse modeling

    • the answer is : using the current calibration, computed depths are unerestimated by an average of ~ 0.67 meter, as illustrated in the plot to the left which crosses a variety of vegetation patches across the whole image from west to east
    • estimated depth over bright targets is very close to seatruth (bright targets are not vegetated)
    • estimated depths over dark vegetated targets is underestimated
    • this is only the begining: using this kind of display, it should be possible to devise yet another trick to alleviate this problem: still more work to do!
  • This new tool shall allow to investigate various aspects of what is done in 4SM.

  • It shall prove invaluable

    • for fine-tuning various parameters

    • and for validating some recent WV2-specific 4SM tricks

  • Although it ignores

    • the system noise aspect

    • the spatial variations in water quality

    • the deviations of sensor response from faithfull linearity


Depth applied over land : 2 meters


Depth applied over land : 5 meters


Depth applied over land : 10meters


Depth applied over land : 15meters





Some new tools in 4SM: glint regressions for WV2 images

We have established that

  • NIR band 8 is well correlated with bands 6, 4 and 1

  • NIR band 7 is well correlated with bands 5 , 3 and 2

Therefore,

  • NIR band 8 is used in 4SM to estimate spectral deep water radiances for bands 6, 4 and 1, and the amount of glint to be subtracted from those bands

  • NIR band 7 is used in 4SM to estimate spectral deep water radiances for bands 5, 3 and 2, and the amount of glint to be subtracted from those bands

  • -Lsw/044.7/029.3/010.6/009.3/009.5/000.0/000.1/000.1

 

 



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