Twof Landsat 8 images
at Gulf of Laganas, Zakynthos Island, Greece
LANDSAT 8 OLIP 
Using the Panchromatic band for water column correction
to derive water depth and spectral bottom signature:
Landsat 8 OLIP bandset used for this work
Purple=1, Blue=2, Green=3, PAN=4, Red=5, NIR=6 and SWIR1=7
home
 
 

 LUT 
still a lot needs to be mastered/understood!

some seatruth
Bathymetry from Schofield_MEPS_2007.pdf
Bottom types by Pasqualini et al, 2005
 
 
Landsat 8 data aquired August 1rst 2015
work done october 2021

TCC raw data
most variable atmosphere
BOA TCC deglinted
BOA deep water reflectance is quite variable
 

 		 Glint regressions are excellent
Deglinting is excellent

Adjacency effect is fairly strong,
several kilometers wide

Deglinting along yellow profiles
from South to North: sections A, B, C and D
TCC deglinted
  • Note the low radiance over the Blue range along the western waterline of Zakynthos island
  • This happens at various locations in this scene, and is illustrated along the yellow profiles
what's that?





Calibration over the whole image
 Calibration over the whole image
 
  • deeper than ~5 m:
    • Kblue/Kgreen=0.32
    • extremely clear waters 
    • Jerlov's OI water type
    • this exhibits the clearest waters which exist in this very large scene?
 
  • 0-~5 m: 
    • Kblue/Kgreen in excess of 1.0


Waters happen to be less clear
at specific sites, 
as documented below




Calibration over Missolonghi Lagoon, Gulf of Patras
 "Its maximum depth is 5 to 6 metres" 
 
Calibration over purple ROI:
explains the above mentioned weird aspects
 
Kblue/Kgreen>=1.30
mainly exhibits Coastal type 3 waters
which contaminate the Gulf of Patras
view the LUT result
 







Calibration  under three ROIs over Zakinthos Island

 
RED ROI
Kblue/Kgreen=0.32		 very very very clear waters over bright sands
Jerlov type OI+0.7

Calibration Blue vs Green
 
  • BPL pixels: display as a straight line with a slope Kblue/Kgreen=0.32
  • Kblue/Kgreen=0.32   
    • this is Jerlov water type OI+0.7
    • this is very-very-very clear,
    • just below Jerlov type OI A
    • upwelling is at work here
  • Deepest bottom detection for this bottom: ~28 m
    • BUT deepest bottom detection for coral sand would be ~47 m
  • Shallowest pixels are at ~7.5 m
    • this sandy slope stretches from 7.5 m down to 28 m
  • Very few pixels in this ROI exhibit darker bottoms
  • Land pixels provide a clear view of the SOIL Line assumption
    • Lwcoastal~=63       Lacoastal ~=249
    • Lwblue   ~=38       Lablue    ~=152
    • Lwgreen ~=1.5       Lagreen  ~=  68
    • Lwpan     ~=1.3     Lapan     ~= 56
Calibration Coastal vs Green
UltraBlue band is under tight control



Calibration Blue vs PAN
Panchromatic band is under tight control
 
Blue ROI
Kblue/Kgreen=0.45		 very very clear waters over sparse veg
Jerlov's type OIB+0.1  

Calibration Blue, Green, Red, NIR
  • Kblue/Kgreen is ~=0.45  
  • Bottom brightness is 0.35 times that of Red area 
  • The shallow range 0-5 m is present; 
 
GREEN ROI
Kblue/Kgreen=0.60		 very clear waters over dense vegetation
Jerlov's type OIB+0.8

Calibration Blue, Green, Red, NIR
  • Bottom brightness is only 0.35 times that of  Red area 
  • The shallow range 0-5 m is present



Ready for Modeling

Retrieved depth in centimeters
see full scene
see legend
CC BOA WCC
B=Coastal
G=Green
R=Blue

B average bottom brightness
 LUT:
map of the ratio Kblue/Kgreen







January 24th 2016

Calibration over Zakinthos
Zakinthos
 LUT: 
map of the ratio Kblue/Kgreen


 



Créer un site
Créer un site