4SM others 5

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**(semi)analytical methods**
Hedley & Mumby 2003 Hedley et al 2009: ALUT BRILLIANT : Mishra Ikonos at Roatan Island Sagar using ALOS and Sambuca in the GBR Heege et al: hyperspectral at Ningalo reef and Rotnest Island, WA 2007 Goodman, Lee and Ustin 2008 Aviris at Kaneohe Bay, Hawaii Heege's EOMAP cluster and classification approach WV2 and Ikonos 2011 Fearns et al Hyperspectral mapping at JurienBay HYMAP 2011 Mobley: Moreton Bay Hyperspectral Alexey Castrodad Carrau

**Hedley and Mumby 2003**
A remote sensing method for resolving depth and subpixel composition of aquatic benthos "The technique requires knowledge of the reflectance spectra of m pure substrata in n (n>m) spectral bands at depth 0 and the water diffuse attenuation coefficients for the site in the same bands. Depth, z, can be entirely unknown."

Mishra Ikonos at Roatan Island
bottom_typing_Roatan_Mishra_Article_JGR

PHD work done in 2005 at U of Nebraska Ikonos image

Great reading indeed : a fine "digest" of the whole bio-optical theories!

An all-included service!
I just wish I had that culture and those brains!
I just wish I had a few months for delivering
a bathymetric map and a bottom type classification
for just one Ikonos image for my PHD assignement
at an affordable price!
Shows that a more operational solution is still wanted!

Depth + bottom typing : aims at mapping both water depth and bottom type classification using an Ikonos image of coral reef environment
Atmospheric correction : to estimate the water-leaving radiance (equation 13), a "first order" atmospheric correction goes in great details through
- L_R : computation of Rayleigh path radiance
- L_A : computation of Aerosol path radiance
- t : computation of diffuse atmospheric transmittance
- BOA : L=(L_TOA-L_R-L_A)/t in units of radiance

Computing depth
a ratio method calibrated using depth points measured along five transects of various bottom types
K_blue/K_green~=0.85
"different bottom albedos at constant depth still have the same ratio"
second order polynomial using known depths along five transects
- explains in excess of 97% of variation

Computing bottom albedo
requires an estimate of the water column contribution to the water leaving radiance,
based on Lee et al's model (1998) and further simplified for a 3 visible wideband bands image
- involving absorption, diffusion, backscattering, solar zenith angle, you name it!!!!!!!!!
Brilliant
Not operational by lay practionners for quite a long while though

Bottom type classification
- ISODATA iterative self-organizing data algorithm
- Five shallow bottom classes + deep water
- Comprehensive evaluation of the classification acuracy

BRILLIANT
Not operational by lay practionners for quite a long while though

While waiting, use 4SM

needs no field data for estimating operational attenuation coefficients
is quite happy with the dark pixel substraction :
- 4SM needs optically deep water to be sampled to represent an homogeneous water body
does not require calibration in physical units of radiance
estimates contribution by water column backscatter radiance, and accounts for it in estimating bottom albedos
computes bottom albedos in units of DNs
offers a very simple classifier
is capable of "same-day" operation in advance of any field work,
- for just a fraction of the cost

Sagar using ALOS and Sambuca
Great Barrier Reef
Presentation

Another grand approach to the bathymetric problem
Here we get a taste of CSIRO's Sambuca software
- for computing shallow water depth and water column corrected bands
- using ALOS multispectral BGRN data, 8-bits, 10 m resolution, swath 70 km
LADS laser bathymetry, tide correction
Fig 3 exhibits great performances
- although Fig 4 points to the need for smoothing
~30 scenes to cover the whole GBR

4SM

I wish I'd be given the opportunity to show what 4SM can do on this image
- 4SM would also deliver water column corrected spectral image

Combined depth would be in order for al all-GBR project
- Such a project would take just a few months of 4SM processing
- with NO NEED for LADS data to calibrate the model
- as 4SM is a non-site-specific method
I can't see what the problem is in respect of deglinting
4SM can deal with situations where the whole scene is submerged under water

JurienBay CSIRO HYMAP

Fearns et al Hyperspectral mapping at Jurien bay 2011
Klonowski

This really is a grand approach using Lee et al's semianalytical model! and the collection of library spectra
Figure 2 comes in support of the way I estimate the water volume reflectance in 4SM with refelctance being approximately equal in the blue and the red bands for shallow dark vegetation/bottoms
Fig 6 depth comparison is great : Lee's model works very well, too bad it is so complex
- although the seatruth depth dataset lacks the 0-4 m, and also deeper than 10 m
- these two depth ranges are where any misfit are likely to happen when using less elaborate approachs

Compare with CASI in Nova Scotia, Canada

I just wish I'd be given the oportunity
to show what 4SM can do with this HYMAP imagery
over a week or so.
I'm afraid though that the Hymap lines might not include proper deep waters.

Goodman, Lee and Ustin 2008
Alexey Castrodad Carrau

"Influence of atmospheric and sea-surface corrections on retrieval of bottom depth and reflectance
using a semi-analytical model: a case study in Kaneohe Bay, Hawaii"

Preprocessing of Aviris hyperspectral data followed by the grand semi-analytical approach to model inversion, by the Naval Researh Laboratory...
- adverse viewing and illumination geometries
- four atmospheric correction options and two glint correction methods
- seatruth over sand areas
- "We next implemented the inversion model using 12 different preprocessing scenarios and performed
  a quantitative analysis of model estimated bathymetry for each scenario using the SHOALS bathymetry data as ground truth"

Near Nadir viewing by spaceborne sensors are less of a problem
It's a long way .... to Tiperari, until such niceties actually mature into a set of operational processing tools for use by the lay practioner using commercialy affordable data with limited resources and demanding deadlines
==>> Until then, use 4SM!

Heege, Hausknecht, and Kobryn 2007
see Albert & Mobley

Great reading

No need for such analytical niceties for case 1 waters though:
4SM can process several tens of bands in clear waters
in a matter of just a few days

Ohlendorf, Heege et al 2011 :
EOMAP’s cluster and classification approach
Geisler et al 2011: EOMAP
see Albert & Mobley
Wiki by Thomas Heege
GBR 2013
Proteus FZC

quite a team work, on the long term
use Albert and Mobley's approach : standardized physics-based data processing
use several WV2 and Ikonos images for several sites of the Carribean and Australian coasts
reference MODIS data : even adjacency effect is corrected for
use a spectral library of bottom types to produce a spectral bottom reflectance
this yields both
- shallow depth
- spectral bottom reflectance, for further bottom type classification
seatruth is echosounding

quite a grand approach: fully analytical at that, no petty parameter is left behind!
- yields beautifull "all encompassing"results
- this of course raises the question of operationality for day to day life of an operational project : meet you in a few decades
- until then, something more simple is needed when the product must be delivered to the client in a matter of weeks, possibly even when no field data is available
YES : you got it! 4SM is there: offering to fill the gap!

I wish I would be given the opportunity
to show what 4SM can do
with these IKONOS images
in just a fraction of the time

PROTEUS FZC
uses
EOMAP's MIPS fully analytical technology
based on Albert and Mobley's approach