the empiric way is impractical
 - The empiric way is far from easy, as the effective diffuse attenuation coefficient for the panchromatic band decreases steadily
- from very high values at very shallow depths
- to Kpan ~1.7*Kblue in very clear waters at extinction for a WV02 image.
- Once the Red, Yellow and Green solutions are calibrated to satisfaction, the image is processed in order to derive the experimental law of variation of the ratio Kblue/Kpan as a function of bottom depth for the current image.
- Now that this experimental law is available, the PAN solution is applied to all shallow pixels which exhibit suitable signal.
- as all this refers to a "ratio method" where radiances remains in units of uncalibrated DNs,
- Isobath curves at 1 m interval are shown
- Note that the experimental BPL is "bumpy"
- this yields "bumpy" depth results
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As opposed to the empiric way,
the optical way is ideal
- As of august 26th 2014
- This this only uses the radiance response curve for the PAN band along with the optical calibration model for the Multi/Hyperspectral bands of the current image.
- Therefore, it is a generic process which makes it quite easy to add the PAN band to the Multi/Hyperspectral dataset for shallow water processing of any image.
- Still not quite satisfactory here using a WV2 image at Princess Cays!
- Isobath curves at 1 m interval are shown
- note that they are packed very closed to each other deeper than 5-6 m: results shall become quite noisy at depth
- Note that the BPL model is very smooth:
- this yields smoother results
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see Landsat 8 PAN response curve
This applies to Landsat 8 OLIP as well
as illustrated below
Note that the Landsat 8 Panchromatic band - only covers the Green_to_Red range
- this excludes the Blue and the NIR ranges
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Calibrating the PAN solution
for a hyperspectral image - All visible bands in a hyperspectral image may be binned together to produce a synthetic Panchromatic band.
- This was done with complete success for the Heron Island study case, then on Hyperion and HICO data
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Results - The whole depth range is processed in a very homogeneous way:
- processing time remains the same: a same day service can be achieved.
- no more of these disturbing and unacceptable gaps.
- The overall accuracy on retrieved depth shall be shown to have distinctly improved.
- The precision on retrieved depth shall be shown to have
- increased dramatically wherever the GREEN solution was the only recourse (think of Stumpf et al's method).
- The homogeneity shall be shown to be outstandingly improved.
- Processing pan-sharpened images might become routine:
- please improve the radiometric quality of the image, rather than indefinitely reducing the pixel footprint.
Using HYPERION at Fakarava atoll
Blue vs PAN for a Hyperion image
of Fakarava atoll, French Polynesia
work done october 2014
see also HICO at Lee Stocking Island |
