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.................                           
 
#exit
LINE 2
Then append  #Line_2
LINE 2: Run the Deglinter

Please follow instructions

Order of precedence among 4SM modules
RunMakePIX...........highest precedence
RunImporter
RunScaler
RunRecoder
RunDN
RunDeglinter...............comes before RunCalibrator
RunExtractor
RunCalibrator
RunClassifier
RunABProfiler
RunZZProfiler
RunZZRegressor
RunTyper
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 glint_regression.sh 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
-Lsw/27.4/14.8/6.5 


 
plot of the glint correlations 
including the cloud
-Lsw/26.9/13.9/6.5 

 
 
 



 
  
step 3: FYI, the dark pixel assumption: how it is used
Activity
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
Activity
  • 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 raw
 

TCC TOA deglinted/smoothed

 

NIR band, BOA deglinted/smoothed

 

RED band, BOA deglinted/smoothed

 

GREEN band, BOA deglinted/smoothed

 
Zoom
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
 



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