Bathymetry and water column correction
at SanLorenzoChannel, Baja california
Image courtesy of the U.S. Geological Survey
7671*7841 30 m pixel size, UTM zone 12
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


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
I keep digging
until suitable data
become available

Applying ZDTM

Applying ZDTM
see legend for image SAM
As I have an estimate of water depth through the existing (and crude) DTM,
I can use it in the inversion of the RTE.
This means that there is no Soil Line assumption any more:
the result only depends on
the water optical properties
and the measured spectral radiances.

To me, this result is astounding, as it means that
  • FIRST, produce a combined depth image using all scenes available over the study site
    • very detailed at a 15 m GSD and free of weird artifacts
    • without any smoothing thanks to R_pan-sharpening
  • THEN use this detailed combined depth image as a DTM as above,
    • and get a very detailed time series of SAM result like this one above
    • for each of the scenes available
    • at a 15 m GSD without any smoothing
    • free of artifacts caused by bad/crude depths
    • but still suffering from horizontal variations of water optical properties

NOTE the greenneness flowing through the channel