Landsat 8 OLIP at Shuwayhat Island, UAE
from Qatar towards Abu Dhabi
images courtesy of USGS
6747*6082, pixel size=30 m
work done in october 2014
Waters not so clear: watch these Youtube video  and Youtube video
see also the Marawaah island studycase

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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
 

Shuwayhat Island AOI






6SBK-Ab-Gulf-bathmap.jpg : isobaths in fathoms


Bathymetry map of the the Arabian Gulf
with a spatial resolution of 2 km from NOAA






Riegl & Purkis (ed) 2012 fig 2.1




200k--g39-35_760.png: isobaths in meters

 
With the help of these two bathymetric maps,
I know where to place the 18-20 m isobath (see black contours)
Consequently, as of october 2014, I can
  • rule out the "need" to increase the effective wavelength of the Green wideband
    • this is only acceptable if we accept to decrease dramatically the effective wavelength for the Red wideband
    • this yields depths which are 1.4 times deeper
    • if it can be confirmed, it should prove to be a generic finding for widebands
    • if it can be confirmed, it warrants thorough investigation using HYDROLIGHT
  • be less conservative when setting thresholds
 
 
 
EFFECTIVE WAVELENGTH

PAN solution is applied for all images

shuwayhat_20131207
shuwayhat_20140329
shuwayhat_20140820
shuwayhat_20140905
shuwayhat_20140921
Four results
Error on retrieved depth