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4SM : advantages
4SM : pluses
4SM : requirements
4SM : challenges
4SM : where's the catch?
4SM : errors
4SM: conclusions
please also refer to CSIRO's SAMBUCA and to Heege's EOMAP
4SM advantages |
No need for conversion of raw image DNs to apparent reflectance in units of reflectance using image metadata
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No need for a formal atmospheric correction
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No need for existing depth points to achieve the optical calibration Best seatruth in town
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Calibration makes great use of a graphical plot of the simplified radiative transfer equation applied to the specifics of the current study case
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Water column correction of the image is performed in the same process: this yields a "low tide" view of the shallow areas of the scene, "on the fly" along with a DTM
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4SM can make good use of a panchromatic band along standard spectral bands
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All this same day if required, ahead of any field work
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Accounts for the water volume reflectance |
Reads form the raw image in PCIDSK format, then proceeds to writing a segmentation mask, extracting of calibration data, then to calibrating the optical model
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All computations are performed using data in units of DN!!!!!!!!!!!!! |
All this ahead of any field work!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! |
4SM has processed a wide range of multi/hyper spectral imageries, up to ~20 spectral bands |
4SM is ~50,000 lines of dense C code by an amateur programer; it includes tools for
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A one-stop workshop : all this ergonomy for sake of operationality |
For operating 4SM, the following are required |
4SM needs some coverage of optically deep waters, like all other empirical ratio methods apart from Stumpf's log ratio method |
4SM needs some coverage of bare dryland as well, but still can do without any |
4SM requires a seasonned practioner, well versed in things optical and underwater |
4SM is a supervised process: the practitioner is in command and takes full responsibilities, while ensuring that the basics of radiative transfer theories are accounted for : garbage in -> garbage out Disclaimer
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4SM does not require the use of any proprietary software, and reads/writes from/to PCIDSK image format
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4SM faces many challenges |
Contrary to widely accepted views expressed by respected gurus, it is demonstrated in this website that there is NO NEED for
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On top of it, 4SM performs the water column correction of spectral shallow bottom signatures, while computing depth in meters
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Apart from quite some SPOT archive images, and also CASI datasets, most images processed todate are Landsat, ALI and HYPERION
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Propper working conditions imply a team work, where the practioner can interact in-house with knowledgeable colleagues
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4SM uses the Linux/bash open source environment and has no graphical user interface
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4SM code in C MUST be recoded by professionals, into a cross-platform open source application with suitable GUI
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We are talking big $$$ Once acknowledged sometime in the (near!) future, 4SM shall become the ultimate craze for a few decades, until semi-analytical methods take over for dual use operational purposes |
Universities shall set out to research, experiment and teach the 4SM method, and set networked R&D groups for the purpose of thorough cal/val activities |
Research funding agencies shall want to see through |
Government organisations shall progressively want to use it for themselves |
Inter-governmental organisations shall want to follow suite, by devising large projects for tender and also training programmes |
Hydrographic and defense services shall want to use 4SM on their own
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RS consulting firms shall be hard-pressed to compete for sizeable tenders based on the use of 4SM and imageries like Ikonos, Quickbird, and now WV2, SPOT6 or Pleiades |
Vendors of RS image processing packages shall need to offer their own version of 4SM |
Vendors of RS imageries might even want to try and sell 4SM results along with the raw data |
In my view, and after studying hundreds of multispectral and hyperspectral images and used limited seatruth datasets for eighteen years, I have come to the following conclusions: | |||
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