• which followed time intensive processing of a series of 12 Landsat ETM images in Tanzania, and many more, early in 2009
• after 9 years, it now seems to work to satisfaction

4SM GUI
The AutoCAL feature paves the way for the preparation of a graphic user interface
Several aspects had to be addressed

• Specify default values for most of the command line arguments
• Automatic creation of desired database structure
• Automatic import of raw data channels from original image
• Automatic preparation of special effect mask mSE
• Automatic specification of glint regression, if applicable
• Automatic extraction of calibration data
• Automatic preliminary calibration,
  • and, if allowed, deglinting and modeling
• Wavelength specification
• Preparation of a detailed command line, complete with a choice of supplementary tools

Automatic Mode of 4SM
the next step after importing the raw data:
from raw data to a preliminary calibration (and deglinting/modeling) 

Prerequisites

The AutoCAL process won't work unless

• LsM.shp: at least a few non-saturated pixels of bright land may be sampled using the LsM.shp shapefile
• Lsw.shp: an area of optically deep water pixels may be sampled using a Lsw.shp shapefile
  • optically deep is to mean : optically deep in all wavebands
• glint.shp: if conspicuous clouds or glint is observed over optically deep water in the image,
  • an area of glinted pixels may be sampled using a glint.shp shapefile
  • this area must include from very low-glint to higher-glint

• bright and homogeneous bottoms are expected to exist at various depths
• suitable default values are available and applicable

• Apart from image-specific metadata which need to be specified in -DB..., -Mis... and -Import... arguments,
  • many commandline argument variables are given a default value in the 4SM code
  • any such default value can be overridden in the command line itself
• Upon the first execution of 4SM in the current directory,
  • 4SM writes a 4sm.def editable textfile to contain such default values
  • default values are read at the end of decoding the -Mis... argument
  • default values are then eventually overridden upon reading the rest of the commandline

• Either purge the work directory if -MakePIX/PISA has been specified
  • then creates the database, import raw data, scale to 8 bits
• Or erase existing mask mSE in channel bands+1
  • then write a new one
• Recode
  • NoData........recode to 239 in mask mSE all pixels which read 0 in any of the raw data bands
  • baddata.......recode to 239 in mask mSE all pixels which are included in shapefile baddata.shp
  • cloud...........recode to 234 in mask mSE all pixels which are included in shapefile cloud.shp
  • wave...........recode to 233 in mask mSE all pixels which are included in shapefile wave.shp
• Lsw and LsM
  • Lsw.............if a -Lsw... argument is not provided in the commandline,
  • 4SM reads shapefile Lsw.shp to compute and specify provisional spectral Lsw
• LsM.............if a -LsM... argument is not provided in the commandline,
  • 4SM reads shapefile LsM.shp to compute and specify provisional spectral LsM
• Glint regression
  • if a shapefile named glint.shp is available, 4SM reads it
  • to specify the glint regression correlations
  • which are used to specify the -Lsw... argument
• Make Land, Marine, Wave  and Cloud....
  • A provisional Soil Line is defined using provisional LsM and Lsw values in the Red and Nir bands
  • The image is then segmented as explained elsewhere
    • recode land pixels       to   248
    • recode shallow pixels  to   2
    • recode cloud pixels     to   234 (if a cloud.shp shapefile is not available)
    • recode wave breakers to   233 (if a wave.shp shapefile is available)
• Recoder
  • Clean the land area
    • land.shp: recode to 248 pixels which are included in shapefile land.shp
  • Clean the marine area
    • shallow.shp............recode to 2 all pixels which are included in shapefile shallow.shp
    • badwaters.shp..................recode to 249 all pixels which are included in shapefile badwaters.shp
    • deep.shp..........................recode to 249 all pixels which are included in shapefile deep.shp
    • mask_1.shp......................recode to 1 all pixels which are included in shapefile mask_1.shp
    • mask_3.shp......................recode to 3 all pixels which are included in shapefile mask_3.shp
    • mask_4.shp......................recode to 4 all pixels which are included in shapefile mask_4.shp
    • mask_5.shp......................recode to 5 all pixels which are included in shapefile mask_5.shp
    • etc, up to mask_20.shp
    • mask_20.shp....................recode to 20 all pixels which are included in shapefile mask_20.shp
    • negative.shp.....................recode to 244 areas where negative bottom contrast is allowed
• Extractor:
  • if a suitable calibration textfile is not available, 4SM runs the extraction

• KIKJ Regressor: only works for most favorable images
  • estimates the ratio Kblue/Kgreen by regression on the linearized BPL pixels
    • and  use the linearized BPL, the optical calibration, and the provisional Soil Line to specify final LsM
  • if the coefficient of determination is too low (R2<R2KKmin),a default value is enforced:
    • KIKJ=Kblue/Kgreen=0.50
      • or
    • KIKJ=Kgreen/Kred=0.25 for SPOT 1 images

• All parameters are now specified
• 4SM proceeds to compute and display the calibration plot

• 4SM writes and displays a textfile named autoCAL.txt
  • which contains, among other things, a complete detailed commandline
  • which may in turn be used for the practioner to take full control of all aspects of the 4SM process