Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
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4SM FEATURES & OPTIONS


  Garbage in, Garbage out  

4SM is an interactive process that requires a knowledgeable and responsible practitioner

Your comments are invited              VNC : let's work together live!             See you on 4SM blog         
Where is the competition?                          Operational?                  4SM errors



 
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
 

Deal or NoDeal?
 

  • It shall be seen that an acceptable calibration which yields acceptable results
    • is a fuzzy concept in respect of the many parameters involved
    • even though we are using a simplified radiative transfer model
  • What is important is NOT
    • that a physically exact calibration has been achieved
    • leave that for the big boys at NRL
  • Rather what is important to US
    • is that a coherent set of calibration parameters be assembled
    • so that an acceptable and usefull result be produced : DTM and bottom type classification
    • using only the image
  • 4SM offers an integrated set of ergonomic tools to achieve that
    • withing a short time frame


4SM value

Can you afford to wait for a few decades,
untill the semi-analytical methods come of age?

 

  • The value of 4SM is not so much in outstanding concepts
    • which are described if full detail in this website
    • which are fully demonstrated to be safe to use
      • subject to radiometric quality
      • subject to narrow wavebands
      • subject to homogeneous atmosphere and waters
      • provided the deep water radiance may be estimated from the image
  • Rather it stems from the variety and large number of images processed starting 1994
    • which confers to 4SM its "operational and practical" character for commercial operation
      • subject to re-writing of the code by a professional programmer

 


4SM KEY FEATURES

What's new with 4SM?

  • data: read the 8 or 16 bits raw imagery, up to 20 spectral bands at present,
  • glint: remove the sun/skyglint, and the adjacency effect as well to a certain extent, from this raw data,
  • calibration: extract all the necessary calibration information, and processes it to derive all necessary calibration parameters,
  • model: model all shallow water pixels,
  • output: write out various outputs.
  • smoothing: apply a smart smoothing to shallow water pixels,
  • subwindow: any sub-area (rectangular) or sub-zone (mask) may be processed.
  • on the fly: 16>8 bits scaling, mosaic equalization, removal of glint, and smart-smoothing, and modelisation are performed on the fly.
  • The bash commandline . 4SM reads the raw data and applies the whole suite of procedures "on the fly"
 
  • File Structure: PCI Geomatica Band-Interleaved, or File-Interleaved for very large images.
  • Mask : the practitioner interactively prepares a Special_Effects_Mask.
  • License : upon modeling, 4SM checks for Licensed_Image. If applicable, issue a LicenseKey and quit
  • The bash commandline . 4SM reads the raw data and applies the whole suite of procedures "on the fly"
    • from raw data in all cases  all the way to writing final output:
    • see  tmnov.sh for a 4-bands           spectral image,
    • see  mb4.sh    for a 17-bands hyperspectral image
  • Scale 16 bits data into 8 bits data for purpose of display only (CASI, Ikonos, ...).
  • RAW DATA : all computations are conducted on raw original data, in real variables, so that none of its dynamic is lost in the process.
  • Extract calibration data: Brightest_Pixels_Line and Soil_Line, etc  tmnov_m0.cal 
  • Calibrate modeling parameters: calibration using GMT for graphic display  tarawa-subset_1_2_3.eps 
  • Writes 
    • an 8-bits image_WZ: make a note of modeling conditions  tmnov_WZ 
    • an 8-bits image_WR: make a note of smart-smoothing window radius  tmnov_WR 
    • an 8-bits image_Z250: depth from 0 up to 250 decimeters  tmnov_Z250 
    • an 8-bits image_B: average bottom reflectance in the range 0-200  tmnov_B 
    • an 8-bits image of the depth range entailed by a +-0.5 DN variation in radiance (quantization noise):  a "Depth sensitivity" indicator (left)
    • an 8-bits image_LBS of the spectral bottom reflectance in the range 0-250  tmnov_LBS 
    • an 8-bits image_LBS of the spectral bottom reflectance NORMALIZED in the range 0-250  menton_LBS     Lee Stocking island 
    • an 8-bits 3-bands BGR composite of normalized bottom reflectance   mbnorth_RGBCC_LBS_normalized 
    • an 8-bits image of bottom typing  mbnorth_bottom_typing 
  • Update a history textfile
  • 4SM help services for online help to provide the syntax for the commandline

 
4SM OPTIONS
 

  • Correction for variable illumination in raw CASI flight lines                      ILS plot   transient
  • Fill small and isolated NoData holes in a raw CASI 16U_mosaic                 filling 
  • Remove Limb Brightening from raw CASI flight lines                                    delimbing 
  • Equalize flightlines in a CASI mosaic                                                               equalize_a_mosaic 
  • Deglint the data free of sunglint, skyglint, haze, and possibly of adjacency effect
  • Smoothing
    • pain-Smoothing by a fixed radius circular smoothing window prior to processing,
    • smart-Smoothing by dynamic radius circular smoothing window with dynamic smoothing range: sort of an "edge-preserving" smoothing scheme.                                 tmnov_Profile_Raw_Smoothed 
  • Sub-window
    • process only inside any odd-shaped masked zone                                         tmnov_redpolygon 
    • process only inside any rectangular sub-window  
      •                                      tarawa-subset_deglint  (a rectangular windos is not smoothed)]
  • PANmode : model using a SPOT Pan band in addition to XS bands:
    • Z is truly modeled down to ~10 m                                                                           Bora Bora 
  • RLNmode : model depths using  the log(Lblue)/log(Lgreen) algorithm published by               NOAA
  • Bottom Typer : supervised bottom type classification                                                       Heron_CASI
  • Profiler : plot bottom depth and water column corrected bottom reflectance versus distance       Waimanalo
  • Seatruth regressor : Waimanalo
  • Write
    • an 8-bits spectral image of Smoothed and Deglinted data image  LeeStockingIsland 
    • an 8-bits spectral Smoothed_Deglinted_Linearized image  tarawa-subset X (a rectangular windos is not deglinted)]
    • a 16S bits image of depths in centimeters. Non-shallow pixels are coded at -1  tarawa ZG 
    • a 8-bits RGB Color Composite from spectral 8-bits RGB image  mb4 results 
  • Profile
  • Sea-truth regression : use GMT to draw a Postscript display of the linear regression of Computed_Depths versus Seatruth_Depths                                                          caicos    caicos  negril85  moorea 




























 

  • Correction for variable illumination in raw CASI flight lines  ILS plot   transient
  • Fill small and isolated NoData holes in a raw CASI 16U_mosaic  filling 
  • Remove Limb Brightening from raw CASI flight lines  delimbing 
  • Equalize flightlines in a CASI mosaic equalize_a_mosaic 
  • Deglint the data free of sunglint, skyglint, haze, and possibly of adjacency effect  tarawa_XS_deglint  LeeStocking_Ikonos_deglint 
  • Smoothing
    • pain-Smoothing by a fixed radius circular smoothing window prior to processing,
    • smart-Smoothing by dynamic radius circular smoothing window with dynamic smoothing range: sort of an "edge-preserving" smoothing scheme. tmnov_Profile_Raw_Smoothed 
  • Sub-window
  • PANmode : model using a SPOT Pan band in addition to XS bands: Z is truly modeled down to ~10 m  Bora Bora 
  • RLNmode : model depths using the log(Lblue)/log(Lgreen) algorithm published by NOAA Limnology and Oceanography
  • Bottom Typer : supervised bottom type classification                                                
  • Profiler : plot bottom depth and water column corrected bottom reflectance versus distance Waimanalo
  • Seatruth regressor : Waimanalo
  • Write
    • an 8-bits spectral image of Smoothed and Deglinted data image  LeeStockingIsland 
    • an 8-bits spectral Smoothed_Deglinted_Linearized image  tarawa-subset X (a rectangular windos is not deglinted)]
    • a 16S bits image of depths in centimeters. Non-shallow pixels are coded at -1  tarawa ZG 
    • a 8-bits RGB Color Composite from spectral 8-bits RGB image  mb4 results 
  • Profile
  • Sea-truth regression : use GMT to draw a Postscript display of the linear regression of Computed_Depths versus Seatruth_Depths  caicos    caicos  negril85  moorea 









 

 
Busy? 4SM in 10 lines