A time series of landsat 8 images
at San Lorenzo Channel, Baja California

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

work done december 2016


scene LC80340432016349LGN00, December 12th 2016
DATE_ACQUIRED = 2016-12-14
    SCENE_CENTER_TIME = "17:48:08.0454640Z"

Work done december 2016

15 m GSD by 4SM. No PANsharpening

Ground truth
limited to Isla Espiritu Santo and San Lorenzo Channel
Seatruth DTM is Combined Depth raster

December 14th  2016   vs   DTM
tide correction applied: Htide=0.80m

LswPAN might be reduced a wee bit
in order to reduce over-estimation of depths
in the 15-25 m range


DTM - December 14th
tide correction applied: Htide=0.80m
RED: this vast area of underestimated depths
signals the westward flow
of slightly more turbid waters:
this corresponds to brown-green areas in image B
see legend 

tide correction applied: Htide=0.80m
0-10 m: depths are correct
10-20 m: depths are under-estimated
20-25 m: depths are over-estimated

this is Combined Depth 15 m GSD

Data and deglinting
Complex hydrology:
Blooming Sea of Cortez is pouring westwards into Bay of La Paz

TOA TCC: raw image
logarithmic enhancement

BOA TCC deglinted, histeq enhancement
complex hydrology

Glint regressions

Clearly suggests flow of waters
from SE Sea of Cortez through the channel,
into the Bay of La Paz.
ROI is where deep water radiance is sampled


Look at those lineaments in the PAN image
  • are they real, scoured by currents?
  • do they signal microtopography?

Optical calibration
for the whole image

Calibration diagram
for bands Blue, Green, Red and NIR
Water type OII+0.7

Calibration diagram
for bands Blue, PAN, Red and NIR


Type10 WCC signature
is promoted to the local reference for SAM
see its location at Bahia San Gabriel
  • It represents the brightest bottom substrate at shallow depth around
  • It is expected and assumed to be free of significant chrophyll pigments
  • Calibration of the Soil Line is optimized so as to obtain WCC reflectance at 200 in all blue-green bands for type10 WCC signature:
    • this is done by tweaking LsM
    • it yields SAref=(0.199+0.257)/(2*0.366)
  • So, SAreference=0.62 for this image,
    • and we know that SACoralSand=0.78
  • So, upon modeling in 4SM, all SA values
    • are scaled as  SA=SA*0.75/0.62
    • then rescaled as SA=100*SA
  • to be displayed using SAM2 color table
SAM: Type10 signature
  • Calibration of the Soil Line is optimized so as to obtain WCC reflectance at 200 in all blue-green bands:
    • this yields SAreference=0.62 for this image
  • We know that SACoralSand=0.78

SAM: remember
  • SAM has nothing to do with brightness
  • SAM is only concerned to map how green stands out in the WCC bottom signature,
    • whatever the brightness
SAM and Soil Line
  • dull signatures=Soil Line: so, all water column corrected pixels which do not exhibit an excess -or a deficit- of Green reflectance belong to the family of the Soil Line, from dark to bright
  • contrasted signatures
    • High Green signatures: shall map in the 0.0-0.7 classes of the SAM2 color table
    • Low Green signatures: shall map in the 0.8-1.3 classes of the SAM2 color table

Ready for modeling

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

Retrieved depth
see legend

Profile Black

Profile Black

Location of Profile Black
backdrop is Z4SM
  • WEST sections A and B
  • EAST  sections C and D

Bottom typing

SAM classified image
see legend for image SAM

Average bottom brightness
dark green-brown:
looks like the whole channel
is affected by more turbid waters flowing westwards
see legend for image B

see legend for NDRblues

Download from my GoogleDrive
 slcOLI_20161214_15mresults.zip   52 MB 
Channel Descriptor    file="slcOLI_20161214_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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