Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
Four Landsat ETM 4-bands images of Andros, Bahamas


 
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
 
 

andros_2000-03-26

-LK/G434583041P30N80810TY5190X/andros_2000-03-26/1484_Euros/-LE/1/7764/1/7096/7.422/4       

This work was done in 4 hours, including the preparation of this web page


True color composite of raw data

this image exhibits extensive greennish areas
which are likely to be dense seagrass beds

 

False color composite of raw data

 

 

 


Computed depth
most of this image exhibits
bottom detection in the red band

Bottom brightness

Lots of vegetation

Water column corrected image :  a "low tide view"

 

OII water type
-cWL/0.500/0.760/0.500/0.500
Note the bad saturation in the blue band


Fairly good, hey!

 

 

 

-Z/MSL0.00/n_1/RLBgb1.150_0.500/mask_3

Profile_red

Obviously, the upper profile requires
some alteration of calibration

in order to increase depths computed
by the two-bands case
in the eastern half of the image:

seagrass is greener there

==> -Z/MSL0.00/n_1/RLBgb1.300_0.500/Mask_3


Z and spectral bottom reflectance
along profile_purple

Location pf profile_purple

The water column corrected image
probably depicts the variations
of seagrass cover density
 

 

nice -20  4SM.4.08  -Process  -Origin/BILKO   
-DB/andros_2000-03-26/31_1_0_0/4_1/7764_7096/106.515_2825.415/1_1               
-Mis/Bahamas/Andros/Landsat/ETM/TIF/UTM_18_008/0.030_0.030/26_MAR_2000       
-CK/9KHgHxFH3F9ggK}g_{KFl7fxg9/andros_2000-03-26       
-LS/0255.0/255.0/255.0/255.0           
-cWL/0.500/0.760/0.500/0.500_AutoCAL       
-M/@000001/00002/00003/00004           
@CP/0000.0/000.0/000.0/000.0_0.68m       
-LsM/380.9/394.9/475.3/265.9_cLM=1.600   
-Lsw/074.2/039.4/027.6/010.9_AutoCAL       
-dLsw000.0/000.0/000.0/000.0           
-Lw/0009.5/001.5/000.0/000.0_AutoCAL       
-Lm/0001.0/001.0/002.0/255.0           
-KK1_2_0.4400/Knir4.500/mask_3       
-Z/MSL0.00/n_1/RLBgb1.150_0.500/mask_3   
-Z/MSL0.00/n_1/RLBgb1.300_0.500/Mask_3   
-B/tclNe/Bmin0/cLM1 .6 0.88 .60           
-deglint/vRbaD/GlintM25.0       
-extract/v/mBPL2/mask_3           
-calibrate/v/BdSNpZG/BDh_12_13_34       
-Model /mask_3               
-Smooth/1/D/Smart+           
@-E1/7764/1/7096    -E4300/7764/800/6000_Mask_3               
@-DN300/100/3/comment  @-DD550/125/4/comment               
@ProfileAB/R/profile_red/chAB_2_3/2_3/0_201/0_30_2.0/*           
@ProfileAB/R/profile_green/chAB_2_3/2_3/0_201/0_30_2.0/*           
@ProfileAB/R/profile_blue/chAB_2_3/2_3/0_201/0_30_2.0/*           
@ProfileAB/R/profile_black/chAB_2_3/2_3/0_201/0_30_2.0/*           
@Recode/2_InChannel_5_into_3_OutChannel_5/mask_3