Bathymetry and water column correction
at Lee Stocking Island, Bahamas
Image courtesy of the U.S. Geological Survey
7671*7841 30 m pixel size, UTM zone 18

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


As I don't have seatruth data, apart from the above speaker_harris_fig_01.png,
I used results obtained on lsiOLI_20140129 as a seatruth DTM
The result is astounding,
knowing that part of the fuzziness is caused by slight misregistration of the PAN band.
No smoothing applied

April 8th 2016    vs   Jan 29th 2014
This is a test of the robustness of 4SM

ZR + 0.60m - ZC
February 4th 2016   -   April 8th 2016
Three specific sources of discrepancies must be considered
  • Cloud shadows: they cause over-estimation of retrieved depths. I could not find a way to avoid it.
  • Misregistration: the 30 m re-sampled PAN band is misregistrated by one pixel in both row and line. This causes fuzziness, and overestimated depths on occasion.
  • Variation of water optical properties: they cause local over -or under- estimation of retrieved depth
The results are much more robust than I expected! I intend to produce
a Combined Depth raster 
out of all these results.

and Deglinting
by NIR

TOA TCC: raw image
logaritmmic enhancement

BOA TCC deglinted image
logaritmmic enhancement

BOA deglinted PAN
logaritmmic enhancement
discoloured water:
total extinction

of PAN, Blue and Coastal bands
BOA deglinted Coastal
logaritmmic enhancement

Bad deglinting
BOA deglinted Green
logaritmmic enhancement
very faint signal
over discoloured water
BOA deglinted Red
logaritmmic enhancement
poor deglinting
on west side

Optimized calibration
16U data are scaled to allow for comfortable screen display
Calibration diagram for the whole scene
for bands Blue, Green, Red and NIR

Calibration diagram for the whole scene
for bands Coastal, PAN, Red and NIR

Ready for modeling
No Smoothing
BOA TCC: water column corrected

Retrieved depth
see legend


Bottom typing

SAM classified image
see legend for SAM

Average bottom brightness



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