step 1: prepare your script for running the Deglinter
Activity : use LINE_2
  • Run the Calibrator script formated by the AutoCAL process
  • Run the Deglinter
  • Experiment with extraction window -E.shp
  • Experiment about TOA/BOA, 
  • Experiment about  Smoothing/NoSmoothing
  • Experiment about choosing/drawing glint.shp
  • Experiment about Deglinting/NotDeglinting
First disable Line_1
#LINE_1: build the database, import data, ....
#nice -20  ./4SM.8.07 -Process/nosu  -Origin/Tarawa_Kiribat.................                           
Then append  #Line_2
LINE 2: Run the Deglinter

Please follow instructions

Order of precedence among 4SM modules
RunMakePIX...........highest precedence
RunDeglinter...............comes before RunCalibrator
RunModeler......................lowest precedence

step 2: extract a new set of glint regressions
Activity : use LINE_2 
  • experiment with the glint shapefile
If a suitable tarawa-subset_m0_255.gli  text file is not available, or if you have deleted it, 
  • maybe you want to modify the glint.shp shapefile, change its shape or its location, try your chance and common sense,
  • then, upon the next execution of your script:
    • 4SM extracts the glint data from the area specified by the glint.shp shapefile
    • 4SM writes a script  which may be launched to display the following plots
  • Lswnir = 6.5   adopted by the AutoCAL process
  • Lsw[bands]=6.5 in the commandline
    • this value is used to derive all other spactral Lsw values
      • Lswred   =14.8
      • Lswgreen=27.4
    • therefore -Lsw/027.4/014.8/006.5 are derived from Glint correlation
  • You may change the 6.5 for any other value that you deem more  appropriate
    • as 4SM shall derive all other values using the glint correlations

The glint shapefile
over a backdrop of NIR band
The cloud is not included
Cloud/Shadow in the NIR band
Glint shapefile is shown in white
  • orange=6: this is the darkest cloud shadow
    • Lswnir=6.5 is a weighted  average of those darkest pixels
  • yellow=7
  • green=8
Including the cloud itself inside the glint shapefile 
  • yields virtually the same set of slope/intercept
  • therefore, the photons backscattered by the cloud 
    • have virtually the same spectral composition as the glitter at the water surface.
  • this is not allways the case though
A similar behaviour is observed over a boat's wake.
 plot of the glint correlations 
without the cloud

plot of the glint correlations 
including the cloud


step 3: FYI, the dark pixel assumption: how it is used
FYI, nothing to do
Then, on any instance, 4SM 
Get Lsw and Lw from glint correlation
  • Because   deglinting is enabled ,
    • 4SM uses  LswNIR=6.5 as a seed value, along with the glint correlations
      • to derive its own estimates of Lswgreen=27.4 and Lswred=14.8
    • this is done as part of the pre-processing for any 4SM execution
  • This may be adjusted at will though,
    • by altering manually the value for LswNIR  
    • either manually in the command line,
    • or by use of the  dLsw argument:  LswNIR = LswNIR + dLswNIR
  • Therefore, the practitioner shall later have to settle for 
    • an optimized operational seed value  for LswNIR
    • upon which the deglinting shall be based.
  • based on the seed value for LswNIR provided in the command line for the NIR band,
  • the glint regression text file is used to derive  spectral Lsw and Lw values
    • to override those provided  for other bands in the command line.

step 4: FYI: deglint the whole image
  • FYI, nothing to do

4SM goes on to Deglint/Smooth the image 
or just part of the image through a  -EfirstRow/lastRow/firstLine/lastLine  argument

Writes a Smoothed/Deglinted image in channels 22 to 24
  • it can be TOA or BOA, as specified in the -B... argument
  • a central area is left not deglinted in this example

TCC TOA deglinted/smoothed


NIR band, BOA deglinted/smoothed


RED band, BOA deglinted/smoothed


GREEN band, BOA deglinted/smoothed

Deglinted Green band, channel_22
 deep.shp shapefile
Deglinting/Smoothing helps to delineate optically deep waters if you want to prepare a deep.shp shapefile

next to Deglint page 2

Créer un site
Créer un site