Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
The Smart-Smoothing Process

Your comments are invited                            See you on 4SM blog

return to Illustrations
  • Smoothing is absolutely necessary, more so for deeper/darker pixels.
  • Smoothing must preserve the edges of sea-bottom features,
    • while applying a larger smoothing window to darker pixels with low S/N ratio.

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

Smart-Smoothing preserves the edges

Smart-Smoothing preserves the edges
  • Smart-Smoothing preserves the edges of the dark and shallower patch
  • The profile compares
    • RAW in thin blue
    • DEGLINTED in thin red
    • Smart-Smoothed in thin green
    • FINAL in fat black

<== Smart-Smoothing improves SeaTruth regression

This plot compares the sea-truth regression

  • LEFT : NO smoothing applied
  • RIGHT :Smart-Smoothing applied

<<==Smart-Smoothing yields an acceptable DTM

<<==Smart-Smoothing yields an acceptable DTM
CASI data