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 LC80340432014295LGN00, October 22nd 2014
DATE_ACQUIRED = 2014-10-22
    SCENE_CENTER_TIME = 17:48:05.3137776Z

Work done november 2016

GSD 15 m resampled
No sharpening

Ground truth

October 22th 2014    vs   Sonar Depths
RMSE=0.95 m


Sonar Two Days seatruth depths raster
not corrected for tide

15 m GSD
see depth legend

October 22nd 2014    vs   DTM

DTM from U. of La Paz, Mexico
resampled to 15 m GSD
see depth legend
Depth residuals ZDTM- Z4SM
DTM - October 22nd 2014 
see legend 

Data and Deglinting

TOA TCC: raw image
logarithmic enhancement

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

R2 values are fairly high
15 m resampling does not increase noise


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
  • 0-20m: KBLUE/KGREEN~=0.63
    • Jerlov water type OIB+0.9,
    • nice linear BPL line: denotes homogeneous brightest bottom in homogeneous waters
  • 20-30m: clearing  to OIB

Water appears to be distinctly clearer
deeper than 20 m

Reflectance max at SanLorenzoChannel
It appears to be much darker than coral sand: terrigenous sediment
Coral sand is ~1.7 times brighter than Brightest bottom in this scene

ReflectanceMax slcOLI_20141022......-RM/0.167/0.215/0.304/0.332/0.335/0.415/0.430

Ready for modeling

BOA CC WCC normalized
BGR color composite:
  • Blue  =Coastal band
  • Green=Green  band
  • Red    =Blue   band

Retrieved depth
see legend

Bottom typing

SAM classified image
see legend for image SAM

Average bottom brightness

see legend for image B
  • GREEN colour denotes a green WCC reflectance compared to average Coastal+Blue WCC reflectance,whatever the bottom brightness
  • conversely
  • PINK colour denotes a weak green WCC  reflectance compared to average Coastal+Blue WCC reflectance,whatever the bottom brightness
What I call
"average bottom brightness"

is actually the average
WCC reflectance

scaled 0-200

What we see here: 
seasonal variation?
spectral angle mapper
R values are reflectances (0-1)
(SA is usually converted into radians)
  • SA for the current pixel is compared with SA for type10 signature (which is the brightest bottom signature)
  • Reflectances for the type10 signature are noted on the plot:
    • Rcoastal=0.167
    • Rblue    =0.215
    • Rgreen  =0.303
  • SAtype10     =0.630
  • SAcoralsand=0.784
I hope you get familiar with classifications,
particularly with the art of
spectral angle mapping
type 12 pixel: SA=0.550
  • Rcoastal=0.050
  • Rblue    =0.061
  • Rgreen  =0.101
type 32 pixel SA=0.672
  • Rcoastal=0.149
  • Rblue    =0.190
  • Rgreen  =0.253


Download 48 MB
PAN sharpened by Yann using R
updated November 13th 2016
from my GoogleDrive
Contains the following
Channel Descriptor    file="slcOLI_20141022_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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