4SM shallow water column correction: 
demonstration using a CASI image

from import of raw data all the way to seatruth

only 54 minutes on my new machine

4SM versus ALLUT
see 4SM on USB3 stick/SSD
Demonstration is now final as of May 2nd 2014

4SM deliverable

From now on, I can very easily produce a demo
for my "customer" to produce the 4SM results in-house for any future project:
It is just a matter of customizing the 4SM script to the current project.

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
HYPHOON license

Directory structure
this demonstration uses a 17 bands CASI dataset
at Heron Island, GBR, Australia
downloaded in december 2013 from HYPHOON
Heron Reef data provided courtesy of
the Center for Spatial Environmental Research at the University of Queensland

  1. this demo starts by reading the commandline script
  2. then erases all image-specific files in the current directory
  3. then proceeds to create the database structure in PCIDSK format
  4. then proceeds to import and check the raw data
  5. then proceeds to use various shapefiles to create a mask
  6. then proceeds to run the AutoCalibrator process
    1. which specifies spectral values for the commandline
  7. then proceeds to proper optical calibration of spectral bands,
    1. displays calibration plots
  8. then proceeds to optical calibration of the Panchro band,
    1. displays calibration plot for Panchro
  9. then proceeds to extract and display 13 bottom type signatures,
    1. using 13 ROI shapefiles
  10. then proceeds to model/classify the image
  11. then proceeds to run a modal filter
    1. on the bottom typing classified image
  12. then proceeds to import the seatruth DTM
  13. then proceeds to run a seatruth assessment

The purpose of this demonstration
  • 4SM is operational: it only took me 3 days to post my results:
  • 4SM uses modest computing resources:
    • a 4 years old Toshiba Satellite laptop, 17" screen, 32 bits, Intel Icore 3, 4GB RAM
  • 4SM only uses OpenSource:
    • Ubuntu Linux, OpenEV, and a few GMT executables
  • 4SM uses an empirical approach which goes beyond research
    • by Lyzenga
    • and then by Maritorena
  • 4SM delivers the same results as much more sophisticated semi-analytical approaches
  • 4SM relies on information that is contained in the image data itself,
    • and the optical properties of oceanic and coastal waters published by Jerlov
  • 4SM does not require formal atmospheric correction,
    • works with the original image DNs
  • 4SM water column correction includes
    • shallow depth mapping
    • bottom type mapping
    • and seatruth evidence, as "seatruth" DTM is available

please refer to 
This dataset is under Creative Commons license
CC BY 3.0 Unported license
originally from HYPHOON
  • Share — copy and redistribute the material in any medium or format
  • Adapt — remix, transform, and build upon the material for any purpose, even commercially.
  • The licensor cannot revoke these freedoms as long as you follow the license terms.
So, you are allowed get a copy of the data from me under the same license
and use it as you like under the license terms

Download the the demonstration environment, data and script
The original dataset is available for download at HYPHOON
  • It contains
    • data/HeronReef_2002_CASI_hyperspectral_v00.pix the original CASI image data 
    • seatruth/HeronReef_2002_BATHY_derived_v00.pix which I exported/subsetted , and imbedded into a PCIDSK image so that it overlays the CASI image
    • seatruth/HeronReef_2002_BATHY_derived_subset.pix  
  • contains a copy of the directory structure
    • complete with data and seatruth, and all necessary bits and pieces
    • including my Heron Island CASI demonstration script