web-sharkbay

Bathymetry and water column correction
LANDSAT 8 OLIP
at Shark Bay and Hamelin Pool, Western Australia
4395*5915, 30 m pixel size, UTM zone 49
scene LC80090452013133LGN01, April 18th 2013 downloaded from USGS
Work done september 2013

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_1, Blue_2, Green_3, PAN_4, Red_5, NIR_6 and SWIR1_7

Please refer to Bora Bora and Sanaa
for use of the PANchromatic band for water column correction

Please refer to

HICO user’s Annual Report, August 2012 "Determining inherent optical properties, bathymetry and benthic types using HICO imagery within northeast and Western Australia "
HICO User’s Annual Report, April 2014 "Examining the potential of detecting change in HICO-derived bathymetry: a case study of Shark Bay, Western Australia"
Bierwirth & Burne Landsat Shark Bay Onshor.pdf
Burling_thesis.pdf
"Intertidal and Subtidal Microbialites in the Shark Bay World Heritage area" Lindsay Collins, Jahnert & Collins 2011, 2012
WAMSI Shark Bay Project Talk S Blake - 3 Apr 2012 web.pdf

home
The data
Deglinting
Optical calibration
Normalization
Retrieved depth Hamelin Pool
Water column correction
Using the PAN band
Difficulties
Command Line
Download the result

The data
Seven bands are used: Purple, Blue, Green, PAN, Red, NIR and SWIR1

FCC	TCC
GREEN band Offshore: the Leeuwin current carries turbid waters	Panchromatic band, sum-aggregated to 30 m, Note the smal group of clouds East of Cape Peron

Deglinting

Glint regression based on SWIR1 band	Glint regression based on NIR band
Only a few scatters of small clouds need deglinting ast of Cape Peron. Apart from these, no need for deglinting.	The PAN band exhibits very noisy correlation I don't know why Maybe poorly co-registered image after 4*4 sum aggregation Or, as is the case with WV2 images: is there a time gap between PAN and other visible bands?

Optical calibration
Water type OIB of Jerlov
Spectral BOA reflectance of the brightest bottoms:
RM: 0.184 0.233 0.333 0.346 0.437 0.635 0.729
on the scale 0-1, as calibrated using the _MTL.txt textfile

Calibration diagram for bands Blue, Green, Red and NIR	Calibration diagram for bands Purple, Green, Red and NIR
Spectral operational 2K This calibration yields the following operational 2K0.085/0.076/0.169/0.182/0.606/5.084/18.7 2K_blue =0.076 m^-1 2K_green=0.169 m^-1 2K_red =0.606 m^-1 2K_nir =5.1 m^-1 Final_Z *= CoefZZ - Tide_to_Datum**	Operational wavelengths These diagrams demonstrate that a satisfactory fit of the BPL mode has been achieved among all visible bands -WL/440/480/560/590/620/865/1610 This was obtained by setting WL_purple at 440 nm WL_blue at 480 nm WL_green at 560 nm WL_red at 620 nm Only WL_red is set away from mid-waveband, at a very low value like at Caicos This clearly suits the data comfortably, and yield depth results that approximately match those reported in Burling_thesis.pdf
LsM Conversion of LsM to BOA reflectance yields RM: 0.184 0.233 0.333 0.346 0.437 0.635 0.729 this is very close to coral sand reflectance published by S. Maritorena 1994, and by C. Davies 2012 This high reflectance is only represented at very shallow depth: this might be gypsum deposits, as reported in "swwa_microbialites_lcollinsx.pdf"	LsM Conversion of LsM to BOA reflectance This very high reflectance RM/0.184/0.233/0.333/0.346/0.437/0.635 0.729 is slightly less bright than the sand dunes on land It is ~1.4 times brightest than that of the brightest bottoms at depths RM/0.132/0.167/0.228/0.249/0.312/0.454/0.520 Settling for the high LsM carries the following benefits: increases dramatically the S/N ratio of dark pixels which in turn increases the operational depth range
Benefits of normalization of the water column correction process It is therefore desirable to adopt coral sand BOA reflectance as a way to normalize the water column corrected spectral bottom reflectances, and therefore to allow for time series studies to increase the S/N ratio of shallow bottoms, and therefore improve the precision of results at low bottom-reflected signal	Normalization of the water column correction process This requires easy access to suitable metadata like presented in Using the USGS Landsat 8 Product.html Is this available with Wv2 data?