Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
Bathymetry and water column correction
LANDSAT 8 OLIP 
at Caicos Bank, Bahamas
4018*4149, 30 m pixel size, UTM zone 18, downloaded from USGS

 
Panchromatic band
Using the Panchromatic band for water column correction to derive water depth and spectral bottom signature:

Landsat 8 OLIP bandset used for this work

Coastal_1Blue_2Green_3PAN_4Red_5NIR_6 and SWIR1_7

Please refer to Bora Bora and Sanaa
for use of the PANchromatic band for water column correction


 
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
 

  scene LC80090452016110LGN00
May 21rst  2016
work done september 2016

home

This is spring time in the Bahamas

 



DTM seatruth RMSE=0.64 m
        ZDTM+0.8m - Z4SM
 
     ZDTM+0.8m - Z4SM
see legend
 
 
<==This histogram is a good way 
to estimate a tide height,
rather than the regression






Data and Deglinting

TOA TCC: raw image

BOA TCC deglinted image


Calibration
16U data are scaled to allow for comfortable screen display

Calibration diagram for the whole scene
for bands Coastal, Green, Red and NIR
KBLUE/KGREEN=0.56 => Jerlov water type OIB+0.58

 

Calibration diagram for the whole scene
for bands Blue, PAN, Red, NIR

 




Ready for modeling

BOA TCC: water column corrected
 

Retrieved depth
see legend

 



Bottom typing

SAM classified image
see legend for SAM

Average bottom brightness
notice several super_brightness spots