Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using
World View 2 at Lee Stocking Island, Bahamas
the "PAN solution" uses the PANCHRO band
bands 1, 2, 3, Panchro, 4, 5, 6, 7 and 8
become
bands 1, 2, 3, 4, 5, 6, 7, 8 and 9
9178*8864 scene dated december 9th 2009, pixel size 1.8 m, geographic projection
Winter image is quite dark
Lots of clouds
Nadir viewing, sun elevation 40°
"(c) DigitalGlobe, Inc. All Rights Reserved"
"Includes copyrighted material of DigitalGlobe, Inc., All Rights Reserved" This dataset from Digital Globe,
under a "Data exchange agreement", courtesy of Gregory Miecznik
  • six MULTI...........tiles 09DEC07154605-M2AS_R1C1-052963315020_01_P001
    • tiles R1C1 to R3C3
  • six PANCHRO...tiles 09DEC07154605-P2AS_R1C1-052963315020_01_P001
    • tiles R1C1 to R3C3
    • 4x4 sum-aggregated by myself using Openev
  • mosaicked by myself using 4SM
Please refer to countless papers by the COBOP research group

For other 4SM investigations using the panchromatic band:
see my PANCHROMATIC web page

 


 
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
 

TCC

TCC deglinted_smoothed





Deglinting

NIR1
exhibits some vertical banding
  • Blue, Green, Red and PAN are deglinted by NIR1
  • the noise in NIR1 is transfered  upon deglinting!!

NIR2
does not exhibit noticeable banding
  • Purple, Yellow, RedEdge are deglinted by NIR2

PAN deglinted_smoothed

YELLOW deglinted_smoothed




 

Optical calibration

water type is OII of Jerlov

Calibration diagram for bands 2, 3, 5 and 6
that is Blue, Green, Yellow and Red

Calibration diagram for bands 2, 4, 5 and 6
that is Blue, PAN, Yellow and Red
  • The BPL for the pair Blue/Green is seen to be a straight line
    • as Kblue =O.128 m-1 and Kgreen=0.175 m-1 are assumed to retain the same value over the whole scene, over the whole shallow depth range
  • The BPL for the pair Blue/PAN is seen to be a curved line
    • as Kpan decreases continuously as depth increases
    • while Kblue remains constant at 0.128 m-1
 
  • Once
    • the glint regressions are secured, 
    • the deep water radiances are secured, 
    • some bare ground is masked
    • suitably "clean" shallow areas of interest are masked,
  • Then the extraction of all calibration data is done automatically by 4SM
    • this now includes the "curved" BPL line for the pair Blue/PAN
  • And the many aspects of the above diagrams are fine-tuned manually