Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
4SM What's new

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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
I keep digging
until suitable data
become available

4SM What's new 

Fully Automatic 4SM process
Combined depths
Make a PCIDSK formated database.pix
SuperUser: done with LicenseKey babbling!
Linux workstation
Bottom Type Classifier
Download a mirror copy of 4SM website ==> 4SM HELP services: work offline!



To users of

is a great free software.
This means that it is not necessary
to have/use the PCI Geomatica software to use 4SM.
Your own favorite image processing software will do, along with Openev.
  • Openev is available for Windows and for Linux.
  • Ensure your computer has AcceleratedX or the screen hangs/freezes!
  • Image format: 4SM uses the image format of PCI Geomatica database.pix, whether BAND or FILE interleaving.
  • Openev can read quite a great number of image formats, in particular TIFF, PCI, ENVI, ERDAS, ILLWIS, ERMapper, IDRISI.
    • OpenEV uses GDAL (Geospatial Data Abstraction Library) for accessing raster files, so any file formats supported by GDAL should be supported by OpenEV. The original, and authoritative list of GDAL Supported Formats should be checked for a current format list, and details of each format.
  • Openev can export from any of these formats to PCIDSK database.pix.
  • 4SM then reads from and writes to database.pix.
  • 4SM now uses only Openev for display of the image.
  • The mask_mSE is now entirely prepared using 4SM.
  • Then when finished, Openev is used to write out the database.pix preferably to ERDAS.lan or TIFF.
  • Georeferencing is supported.
This means that it is not necessary
to have/use the PCI Geomatica software to use 4SM.

Your own favorite image processing software will do, along with Openev.


Use      to
  • create a georeferenced database.pix
  • load it with your own raw image data from a TIFF file
  • make a mask mSE with 4SM only
This shall be the start of the first 4SM tutorial.
  • Get ready
    • Directory: make a new working directory
      • Change to that directory
  • DownLoads: bring in that directory a copy of  4sm_tutorial_xs_tarawa.zip
    • Unzip them: "4sm_tutorial_xs_tarawa.zip"
  • Yourimage: copy yourimage.tif from where it resides into that directory
    • That's if you want to work on another image
    • yourimage.tif is no georeferenced: do not try to overlay shapefiles provided yet!
  • launch OPENEV and export yourimage.tif or yourimage.img or etc... into yourimage.pix in PCIDSK format:
    • "openev -h &"
  • Command Line: write an executable bash command line script: see Prepare_your_working_environment
    • That's if you want to work on another image: you would customize an existing script to the specifics of your own image
    • Actually, it is provided for the tarawa-subset image: tarawa-subset.sh
      • "gedit tarawa-subset.sh &"
  • 4SM executable:
    • bring a copy of the 4SM executable file
    • actually, it is provided for this tutorial
    • chmod: check that both are made executable: "chmod a+rwx 4SM tarawa-subset.sh"
  • MakePIX: create a georeferenced PCIDSK database
    • see Syntax_MakePIX
    • at the prompt on your screen: enter "tarawa-subset.sh" to run tarawa-subset.sh to create a PCIDSK database tarawa-subset .pix
    • -dB/tarawa-subset/27_1_0_0/3_1/650_600/714.5_162.54/1_1 with 27 8U channels, followed by one 16S channel, 650 rows and 600 lines.
      • /714.5_162.54/1_1: the georeferencing provided is the coordinates of the center of the Upper Left pixel
      • the georeferencing pixel needs not to be the UL pixel
      • /714.5_162.54/100_250: would tell 4SM that the georeferencing information referes to Row_100 and Line_250
    • -MIS/Tarawa/Kiribati/SPOT/XS/NA/UTM_19_E008/.02_.02/01_JAN_1986
      • UTM_19_E008 gives the projection, UTM zone, and ellipsoid
      • .02_.02 gives the sizeXpixel and the sizeYpixel in same units as coordinates of UL pixel center, either meters or kilometers
    • -MakePIX  this shall create the tarawa-subset .pix database in PCIDSK format, with FILE interleaving, and eight pseudo color tables
  • Import your raw data: run tarawa-subset.sh to import raw image data
    • see Syntax_Import
    • -Import/yourimage/dbnc_3_0_0_0/650_600/1,3_1,3/dbiw_0_0_650_600
    • from channel_1_to_3 of yourimage.pix
    • into channel_1_to_3 of tarawa-subset.pix
    • ==> your raw data have been loaded into channels 1, 2 and 3 of database tarawa-subset.pix:
    • ==> check it out by displaying with Openev.
    • You may use the Openev project file tarawa-subset.opf
to prepare mask mSE in channel_4