Tarawa, Kiribati,  is a 30 km wide
in the eastern equatorial Pacific. 
SPOT XS image, 1986


We shall use a 650*600 subset 
inside the white polygon: 
please note that a heavy sky glint
is evidenced by the enhancement.

An introduction to 4SM modeling  
 return to 4SM tutorials                         Om symbol.svg                             continued  

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
The flow chart of this tutorial
  • Prepare your image                                              
    • Prepare shapefiles
    • Prepare your database
    • Prepare the AutoCAL script
    • Run the AutoCAL script
    • About the marine/land segmentation of the image
  • Investigate your image
    • About the PATH in OpenEV projects
    • Learn from your image, and segment it
    • Sample your image: the -DN... tool
    • Inspect the result of the AutoCAL process
  • Deglint your image                                                          
    • The dark_pixel_assumption
    • Smooth_Deglint_Linearize the image
    • Investigate your image
    • Make a deglinted profile
    • Play a bit with 4SM!
Work on the full image   of Tarawa atoll.
Don't be mistaken:   it's really worth consolidating tour training
Install your workstation
Install your 32 bits Ubuntu Linux 4SM workstation
As of April 2018, my environment is:
ASUS ROG STRIX 17" laptop  with Windows 10
Oracle VirtualBox (4 cores, 4 GB RAM)
Ubuntu 14 LTS virtual 32 bits machine

I used  FWTools-linux-2.0.6.tar.gz 
to install OpenEV as directed in
Not any additional or proprietary driver.
No -h option to launch OpenEV.
Then I upgraded my virtual machine to Ubuntu 16 LTS,
which is supported until 2021.
see also a tutorial by Fabio Favoretto;
do not bother about GuidosToolBox though
Please trash any previous tutorial material.
Please download the latest  tarawa-tutorial zipfile, dated April 2018
Move it to a directory  ~/Work,  and unzip it.

My environment 



alias openev="~/FWTools-2.0.6/bin_safe/openev &"
alias dir="   ls -l    -k --color "

alias dirw="      ls -l    -k --color; pwd "
alias dira="      ls -l -a -k --color ; dir *sh"
alias dirs="      ls    -a -k --color "
alias cpr="       bzip2 "
alias ucp="       bunzip2 "
alias zip="        zip -r "
alias te="         gedit "
alias mv="        mv -i  "
alias cp="         cp -i  "
alias rm="        rm -i  "
alias gimp="    gimp &"

#home2: to mount my main disk shared file as home2
alias home2mount=" sudo mount -t vboxsf home2   ~/home2; dir ~/home2"
Export data to PCIDSK image format  
 video LINE_1
  • cd /your_path_to/4sm_tutorial_tarawa/data
  • launch openev
  • in OpenEV: File/Export tarawa-full.tif into tarawa-full.pix in PCIDSK format
  • in OpenEV: Image/Compose/LoadFile to display a false color composite of tarawa-full.pix 
4SM is a 32 bits binary: must be made executable 
Idem for system calls
4SM checks that they are all working fine
  • cd /your_path_to/4sm_tutorial_tarawa   
  • chmod a+x      ./4sm.calls/*     ./4SM.8.07  
  • launch    ./4SM.8.07
    • 4SM shall check that all are working fine             


Set your script tarawa-subset.sh
do as directed below
Reference script
for a reference, a full copy of my script is available:   tarawa-subset-tutorial-script-txt
update your command line script
Ensure you have one antislash 
at the end of each sub-line
If your script gets messed up, or you lost control
next get acquainted with your working database

 return to 4SM tutorials