Bathymetry and water column correction
LANDSAT 8 OLIP 
at SanLorenzoChannel, Baja california
Image courtesy of the U.S. Geological Survey
 
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=1Blue=2Green=3PAN=4Red=5NIR=6 and SWIR1=7

Work done july 2018
GSD 15 m
 


 
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
 

4SM and attenuation coefficient 2K

19/4/16


What about the operational attenuation 2K in the simplified RTE?
  • This all important question is discussed in detail by Maritorena et al, 1994, in their paper "Diffuse reflectance of oceanic shallow waters: influence of water depth and bottom albedo".
  • I have come to suspect that shallow areas in a deglinted remote sensing image allow the practioner to derive a very good estimation of the value of spectral operational 2K in units of m-1 :
    • Radiances in units of native image DNs may used: conversion into reflectances (0-1) is not a requirement when operating a "ratio method".
    • Retrieved depths are computed in units of m, without the need/use of any field data for calibration of the simplified RTE.
    • Water column corrected spectral bottom signatures are computed in units of native image DNs.
  • This is presented in my new web page 4SM 2K Jerlov.

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