| Simon, I beg for indulgence, as I lack the deep water coverage
which is required for estimating deep water radiances.
When I get some seatruth data, then I can use it to ascertain blue-green deep water radiances.
The deeper/darker the bottom, the more hazardous the results.
The least bands usable, the more hazardous the results.
No tide correction applied.
Smart-smoothing applied.
FinalZ = CoefZ * ComputedZ - HTide
CoefZ and Htide to be derived from seatruth regression |
- I used only the MULTI bands, so far
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- I used all the experience gained since november 2011 when I pocessed a Geraldton W2 image: this involves
- estimating the spectral deep water radiances Lsw for the purple, blue and green bands
- estimating the spectral water volume reflectances Lw for the purple, blue, green and yellow bands
- estimating operational wavelenghts for the yellow and red bands
- This was made possible thanks to the absence of adverse surface glint
- and lso needed masking all those countless alien objects that populate the image: boats and wakes, all sorts of objects at the sea surface in this Marine Park
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- The nice radiometic quality of the image allowed me to operate the smart smoothing scheme
- It shall be observed that the smart smoothing does a good job of smoothing homogeneous features while respecting their sharp limits
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| Existing depth data - As a general rule, keeping secret the existing depth data does not serve any purpose
- By making it available along with the image data, the end user can save the practioner a lot of time and anguish, particularly when the image is a hard case
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| No optically deep waters -
The lack of optically deep waters is a real pain for operating the simplified RTE -
as it relies on the estimation of the so-called "bottom contrast" LsB-Lsw, or LB-Lw, where the deep water radiance takes a dominant role over darker or deeper bottoms -
TOA : Ls=Lsw + (LsB-Lsw)/exp(K*Z) or BOA : L=Lw + (LB-Lw)/exp(K*Z) -
I TUNED THE CALIBRATION SO AS TO OBTAIN COHERENT RESULTS -
So it would be required that the dataset extends farther seaward so as to reach areas where the water is optically deep in the blue-green range, where to ascertain the value of Lsw for these bands (and therefore also the value of Lw) |
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| Sewage outfall |
| Failed |
| Dark vs Bright |
| Aliens |
| Altogether
I can get NOOO sa-tis-fac-tion! -
A frustrating experience, like at Geraldton. -
After days of battling, I give up: the results are hazardous, to say the least; although the southern part of the image might be less of a problem because the pollution does not seem to affect it. -
The data is not at its best: -
The site is a difficult one: -
most of the shallow area is deeper than 6 m: the Yellow band is of little help over those very dark bottoms, even more as it needs a high threshold because it is affected by pollution. -
most bottom substrates are very dark, even the "bright" one, apart from a few small areas. -
the topography is quite hard to guess: dark vs bright. Seems we have a dark rocky platform upon which stand hydraulic sandwaves a few meters higher. -
Essential calibration parameters cannot be estimated to satisfaction: -
deep water radiances Lsw for the Purple, Blue and Green bands: I need optically deep water coverage. -
atmospheric path radiance La: La=Lsw-Lw : I need more land coverage. |
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