Syntax_Recode
This command line argument runs the Recoder
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1 - NO NEED for field data, nor for atmospheric correction
2 - this is demonstrated in this website, using a variety of hyper/multi spectral data
 
Requirements are
1 - homogeneous water body and atmosphere
2 - some coverage of optically deep water
3 - some coverage of dry land
 
Problems are
1 - the precision on estimated depth is found wanting, because the noise-equivalent change in radiance  of accessible data is too high for shallow water column correction work 
2 - radiance data should be preprocessed by the provider at level 1 in order to improve S/N ratio
3 - exponential decay: the deeper/darker the bottom, the poorer the performances
 
So
I keep digging
until suitable data
become available
 



 
Syntax Recode
 
  • Careful
    • save a copy of OutChannel_N: one never knows...
    • you may overwrite InChannel by OutChannel
  • -Recode/OldVal_InChannel_M_into_NewVal_OutChannel_N
    • for the whole image
  • -Recode/OldVal_InChannel_M_into_NewVal_OutChannel_N/shapefile.shp
    • a shapefile is optional: recode only according to the features specified in the shapefile
    • a feature may be either
      • up to 255 separate broken lines
      • up to 255 separate closed polygons
      • separate points
    • maximum 1000 waypoints altogether
    • the .shp suffix is optional in the -Recode... argument
    • do not mix lines and/or polygons and/or points in one same shapefile
    • OpenEV is very good at shapefiles
    • shp2text executable is used by 4SM to convert the shapefile to a textfile, which is then used by 4SM
  • -Recode/LT10_InChannel_4_into_10_OutChannel_4/mask_10
  • -Recode/GT_5... would recode all pixels GreaterThan_OldVal into NewVal...
  • -Recode/LT_5.... would recode all pixels  LesserThan_OldVal into NewVal...
Good luck, and ... don't get confused!

 

  
-Recode/LT10_InChannel_4_into_10_OutChannel_4/mask_10
-Recode/2_InChannel_5_into_3_OutChannel_5

How to Recode

Recode points/lines/polygons to design the mask mSE.
use OpenEV to prepare your point/line/polygon shape file.
4SM shall use shp2txt executable to make use of the shapefile 


 
  • to flag NoDataPixels in raw data:
    • -Recode/0_InChannel_1_into_239_OutChannel_5NoData
    • scan the whole InChannel_1 in order to flag NoDataPixels at 239 in OutChannel_5
  • to flag DubiousPixels in raw data
    • -Recode/LT3_InChannel_1_into_249_OutChannel_5BadData
      • scan the whole InChannel_1 in order to flag BadDataPixels at 249 in OutChannel_5
      • radiances less than 3 are considered bad (less than path radiance?)
    • Recode/GT231_InChannel_1_into_249_OutChannel_5BadData
      • scan the whole InChannel_1 in order to flag SaturatedPixels at 239 in OutChannel_5
      • radiances greater than 231 are considered bad (saturated)
  • to recode polygons
    • -Recode/2_InChannel_5_into_240_OutChannel_5/deep.shp
      • deep.shp contains a series of polygons
    • scan InChannel_5 in order to locate all pixels affected by the polygon deep.shp that are presently coded at OldVal=2
      • and recode them to NewVal=240
    • notice that OutChannel_5 overwrites InChannel_5
  • to recode lines or points
    • -Recode/2_InChannel_5_into_3_OutChannel_5/points.shp points.png
      • points.shp contains a series of points
    • -Recode/248_InChannel_5_into_21_OutChannel_5/lines.shp lines.png
      • lines.shp contains a series of broken lines