Bathymetry and water column correction
LANDSAT 8 OLIP 
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

home


 
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
 

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!

Regression

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

Regression
March 01rst 2016   vs   DTM

 
slcOLI_15m_DTM
DTM from U. of La Paz, Mexico
resampled to 15 m GSD
see depth legend

ZDTM - Z4SM
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
CoefKPan=1.05
  • 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!


continued


Download
slcOLI_20160301_15mresults.zip 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---------------------


continued