April 20th NIR band
Highest tide in the NIR band: 1.2 m to Chart Datum
July 9th NIR band
Lowest tide in the NIR band: 0.8 m to Chart Datum
|May 22nd, June 7th and July 23rd : |
NIR shows decreasing tide height
between these two extremes
4SM satellite derived bathymetry (SDB)
Last August, the first 5 scenes had been processed hastily.
For this new exercise,
I worked all 9 scenes: all calibration parameters have been estimated aknew and more rigorously.
Hopefully, all scenes have been processed in a consistent way.
All results using the PAN solution, which yields a "no-gap" depth result.
That is: the NIR solution, the Red solution and the Green solution were disabled altogether.
|Calibration of the PAN band |
Proper results depend on proper and very detailed calibration of the PAN solution.
To a degree that I did not suspect.
All this was done manually: I learned a lot, under operational pressure and time constraint.
After all those manual calibrations, I now have an idea for automatically and finely calibrating the PAN band.
But then it needs to be implemented...
In the course of this UAE exercise,
I think I have identified a more secure and practical way
of estimating the all-important water volume reflectance Lw.
I need a way to validate how I estimate water volume reflectance Lw=Lsw-La
this is all-important for very dark pixels.
|Surrounding of Marawaah Island |
The quality of the result very much depends on the specific area
I focused on your stated project: the surrounding of Marawaah Island.
The PAN solution procedure is still very new.
I keep discovering how to handle it practically.
But I predict it shall become VERY popular, with WV2 as with OLI,
to the extent that its calibration can be refined and hard-coded.
|By adding new scenes to this sort of exercise, |
and with your fine post-processing,
maybe we can work out a scene-wise commercial product
One key to such project is strict co-registration: your call.
Smothing or NotSmoothing, that is the question.
I had rather smooth, but it is your call.
|Adding the Green solution or not? |
It would extend the depth range,
but would exhibit gaps which might be severe locally, depending on the actual bottom signature.
As for enabling the Red solution, I think a well calibrated PAN solution is just as good.
This need to be tested though: your call, but mind the gaps.
|BOA reflectance (0-1) |
|marawaah20130420F_depth4.pix||Purple, Blue and Green against PAN |
|marawaah20130522F_depth4.pix||Purple, Blue and Green against PAN |
|marawaah20130607F_depth4.pix||Purple, Blue and Green against PAN |
no smoothing, homogeneous atmosphere, excellent deglinting
THIS POSSIBLY IS THE BEST IMAGE
certainly the best calibration of the PAN solution, with the least compromise or "spying" on the nautical chart
FinalZ = CoefZ*Z + HtideToDatum
|marawaah20130623F_depth4.pix||Purple, Blue and Green against PAN |
|marawaah20130709F_depth4.pix||Purple, Blue and Green against PAN |
|marawaah20130725F_depth4.pix||Purple, Blue and Green against PAN |
CAUTION: swirls of turbid waters in the channel north of Marawaah island
|marawaah20130810.................||can't get suitable glint regressions: no results|
|marawaah20130826_depth4.pix||Purple, Blue and Green against PAN |
No smoothing; I see that this might be a problem: result is bumpy, and there are deep pixel artifacts, but you sure have your ways at cleaning/smoothing!
|marawaah20130911_depth4.pix||Purple, Blue and Green against PAN |
I have a problem of strict co-registration of the 2*2 sum-aggregated PAN channel: this produces deep pixel artifacts such as at pixel 2702/5030 in marawaah20130911