HICO at Lee Stocking Island
November: lsihico_20101123 
Level 1B, in ENVI format downloaded from http://hico.coas.oregonstate.edu/datasearch on december 17th, 2014

go to the june image
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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
 
So
I keep digging
until suitable data
become available
 
Bottom Typing
  Download


The data
TCC
logarithmic enhancement
lsihico_20101123_FCC
FCC
logarithmic enhancement
_deglintedlsihico_20101123_TCC
TCC deglinted
same logarithmic enhancement
"Glint" actually is caused by variable atmospheric path
_deglintedlsihico_20101123_FCC
FCC deglinted
same logarithmic enhancement
"Deglinting" efficiently removes variable atmospheric path,
thanks to excellent correlations between NIR band and all other HICO bands:
see glint regressions text file
       
       
 


lsihico_20101123 
The AutoCalibration process
lsihico_20101123 special effect mask
Special effect mask
This is prepared automatically.

Note that threshold on deglinting
leaves some critical area not-deglinted;
therefore, threshold should be upped a bit.

Lands and Clouds
are mapped automatically
by the AutoCalibration process,
with some manual editing
through shapefiles.
 
Image preparation 
and AutoCalibration
is comprised of the following steps:
  • create the working database.pix in PCIDSK format
  • import raw data in 16U channels
  • create a synthetic Panchromatic band and writes it as band 27 in database.pix
  • scale 28 raw 16U data bands to 28 raw 8U range
  • use various shapefiles to prepare a special effect mask in channel 29 (see left)
  • estimate spectral LsM, Lsw, and some other stuff
  • estimate glint regressions
  • extract deglinted calibration data
  • format and display a AutoCalibration diagram and display it
  • format a Autocal.txt textfile which contains a proposed command line, ready for fine-tuning


 

The AutoCalibration diagram

The proposed AutoCalibration command line
now needs attention:
changes are to be fine-tuned to suit
the real life image calibration case.
 
   
   
 


lsihico_20101123 
The calibration process 

Calibration for bands
blue=7, green=13, red=22 and NIR=28

Calibration for bands
blue=7, 12, 21 and PAN
All combinations of bands must be investigated,
in order to fine tune
the simplified radiance transfer model


In 4SM,
other than Jerlov's table
of diffuse attenuation coefficients for irradiance 400-700 nm
for marine waters,
no "field" data is used
in the process of calibrating
any shallow scene
  • My experience is that wavelength for the Blue and Green bands are to be left unchanged, so that Jerlov's dataset is interpolated using the observed Kblue/Kgreen=0.60 ratio of diffuse attenuation coefficients with WLblue=457.7 nm and WLgreen=544.4 nm
  • Except of course for the PAN band, all other wavelengths are to be fine tuned, so as to obtain the best possible fit for all pairs of bands
    • this involves significant decrease of effective 2K values, in the near blue range, in the far green range, and in the whole red range
    • see Jerlov's quotation
  • As for the PAN band, it is modelled using the optical properties observed for all other wavebands involved
   
 


lsihico_20101123 
Deglinting along Profile Red
lsihico_20101123_m0.sig textfile
Deglinting along Profile Red
 
No smoothing applied: this shows the real amount of noise
See Profile Red locator
  • LOWER: from waypoint 1 to waypoint 2, the profile runs over a very dark-bottomed seagrass bed
  • UPPER: from waypoint 5 onwards, the profile runs over optically deep waters
I have come to suspect that deep water radiances for bands in the red range are significantly higher over shallow areas than over eastern oceanic waters