See March 27th 2018


GoogleEarth in November 2017

1300*1300 import area



Location of Profile_RED

I want a display of the panchromatic band,
resampled to 2 m GSD


This profile by Massimo exhibits pure adjacency effect

To be honest,
I should first get used to PLEIADES data
over the Bahamas,
where shallow bottoms are very bright,
and waters very clear.

First thing first: estimate spectral deep water radiances
  • Deep water reflectances increase steadily from North to South
  • Red band exhibits turbid waters all along the waterline, particularly at import ROI
After considerable hesitation, and in view of the modeling results,
a bold compromise is finally adopted: Lsw/194.0/148.3/97.0/95.4/34.6
and a conservative threshold for the Red_solution: -Lm/1.0/1.0/1.0/5.0/255.0
Warning: not for beginners


that's up North
LSW 194.0 148.3  97.0  95.4  34.6

that's down South
All deep water reflectances are much lower  

Something happens between 0 and 400 m:
waters clearer??

Back to normal
keeps decreasing steadily southward

PANchromatic band

With PANchromatic band
  • PAN in channel_3 is quite noisy:
    • resampling from 0.5 to 2.0 m GSD involves averaging over 16 DNs, so should be ultra-smooth, right?
  • Then we shall see that PLEIADES's PAN response curve is not suitable for 4SM modeling

The following parameters were used
Band.....1........2....PAN..... 4........5
  • Circular smoothing kernel : 81 pixel
  • That's a radius=5
  • This results in a ~20 m GSD 
  • No Smart_Smoothing here!
  • So much for the 2 m GSD
  • Beach: Lines 4000, 5000, and 6000: the beach features well
    • I have specified a scaling factor so as to obtain a DN brightness of ~250 over the beach
  • all NIR profiles appear to exhibit distinct atmospheric adjacency effect
    • glint regressions have been estimated over optically deep waters:
      • from Row_3300 to_Row_3600
      • from Line_2800 to Line_3200
    • they appear to be acceptable, in spite of noise
      • except for the Red band

  • Lswred has been boosted by 4 units for all profiles
    • in order to achieve acceptable transition from Red_solution to Green_solution
    • this points to water turbidity all along the waterline
  • Even that is not enough at Line_100
    • depth retrieved by the Red solution is strongly under-estimated
    • I  supect stronger water turbidity by suspended particles in the vicinity of Line_100
  • This precludes the use of the Red band for modeling:
    • the Green solution shall be used at all shallow pixels,
    • unless maybe on a local basis
  • I was hoping that the PAN solution would save our day,as it usually does when using Landat_8 or WorldView_2: alas, it is useless for us!


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