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


scene LC80340432016061LGN00, March 01rst 2016
DATE_ACQUIRED = 2016-03-01
    SCENE_CENTER_TIME = "17:47:45.1553002Z"

Work done november 2016

GSD 15 m Rstudio_sharpened by Yann
data are scaled into a weird range
No sweat though: 4SM is a "ratio" method

Ground truth
How sad!


March 1th 2016    vs   Sonar Depths
RMSE=1.89 m

Sonar Two Days seatruth depths raster
not corrected for tide

15 m GSD
see depth legend

March 01rst 2016   vs   DTM

DTM from U. of La Paz, Mexico
resampled to 15 m GSD
see depth legend

DTM - March 01rst 2016
see legend 

Data and Deglinting

TOA TCC: raw image
logarithmic enhancement

NOTE the bad green waters flowing
from SE through channel towards NW

BOA TCC deglinted image
logarithmic enhancement
Glint regressions using SWIR1
No pan-sharpening applied

R2 values are fairly high
15 m pansharpening does not increase noise
R_sharpened data include a very large offset


Green Rpansharpened
R-pansharpening slight mis-registration
and five fancy dark pixels
can cause artifacts

Pan band

Optical calibration
for the whole image

16U data are scaled to allow for comfortable screen display

Calibration diagram
for the whole image
for bands Blue, Green, Red and NIR


Calibration diagram
for the whole image
for bands Blue, PAN, Red, NIR
  • 0-15m: KBLUE/KGREEN=0.713
    • Jerlov water type OII+0.3
    • clear waters
  • 15-30m: becoming clearer
Calibration ignores
the "Green" waters
  • which are likely to be less clear
  • which are likely to cause artifacts:
    • depth underestimation
    • dark bottoms

Ready for modeling
A complex situation produces weird results
Combined depths shall be needed

BOA CC WCC normalized
CoefNorm=7.5 (usually 2.5)
BGR color composite:
  • Blue=Coastal band
  • Green=Green band
  • Red=Blue band

Retrieved depth
see legend

Profile Black

Profile Black

Location of Profile Black
  • WEST sections A and B: bad and puzzling results
    • maybe turbid waters play trick
  • EAST sections C and D: very nice results

Bottom typing

SAM classified image
see legend for image SAM

Average bottom brightness
NOTE the very dark bottom artifact

see legend for image B
How weird/nice that the scaling of the data
by the R pan-sharpening routine
does not preclude SAM mapping!

Well: that's what they mean by
a "ratio" method!


Download 52 MB
from my GoogleDrive

Contains the following
Channel Descriptor    file="slcOLI_20160301_15mresults.pix";
 1 U8 SAM bottom typing-----------------------------
 2 U8 image B average bottom brightness (0-200)-----
 3 U8 image Z in decimeters-------------------------
 4 U8 WCC reflectance (0-250) at 440.0 nm-----------
 5 U8 WCC reflectance (0-250) at 480.0 nm-----------

 6 U8 WCC reflectance (0-250) at 560.0 nm-----------
 7 U8 WCC reflectance (0-250) at 590.0 nm-----------
 8 U8 WCC reflectance (0-250) at 655.0 nm-----------
 9 U8 WCCnormalized (0-250) at 440.0 nm>B-----------
10 U8 WCCnormalized (0-250) at 560.0 nm>G-----------
11 U8 WCCnormalized (0-250) at 480.0 nm>R-----------
12 S16 Z4SM in centimeters--------------------------
13 S16 ZDTM in centimeters--------------------------
14 S16 ZDTM-Z4SM in centimeters---------------------



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