15 m GSD pan-sharpened "on the fly" by 4SM; NO smoothing
Uses CombinedDepth as a seatruth DTM
RMSE=1.05 m
over Isla Espiritu Santo and San Lorenzo Channel |
Seatruth
Data and Deglinting
Modeling
Bottom typing
Profiling |
Caution
A lot of novelties have been introduced in 4SM of late.
Time is needed until these are shown to be consolidated, and stand the test of time! - 15 m GSD: processing pan-sharpened Landsat 8 scenes should become routine, at very low computing cost
- Bottom typing: SAM2 and NDRblues should help for thematic bottom typing
- Combined Depth DTM at 15 m GSD from time series should become routine at low cost
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GSD 15 m - Import:
- Oversampling of MULTI bands from 30 to 15 m upon import in working database.pix
- with weighing of 15 m pixels with their 3 immediate neighbours
- Strict co-registration to the extent possible (quite difficult)
- Processing:
- PAN sharpening if required, "on the fly" on-demand while processing the scene
- note: oversampling and weighing can be implemented here instead of upon Import
- NO smoothing needed
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NDRblues
Normalized Difference Ratio for Blue bands, inspired from Collin et al
NDRblues=100+1000*(CoastalWCC-BlueWCC)/(CoastalWCC+BlueWCC)
see legend for NDRblues |
SAM2
see https://www.watercolumncorrection.com/slcoli-sam.php
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FCC BOA WCC normalized
The Red band is not used in the PAN solution; and it does not exhibit bottom detection beyond 4-6 m.
So I have changed for the following, which is a False Color Composite view: - B=CoastalWCC "normalized" (0-255)
- G=GreenWCC "normalized" (0-255)
- R=BlueWCC "normalized" (0-255)
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Seatruth
I use the Combined Depth as a seatruth DTM
This gives a better estimate of the RMSE of the 4SM method: <=1 m |
Hydrology
This scene shows signs of water flowing from East to West in the deeper channel. - A current of slightly turbid water is seen to flow westward through the channel
- things do not come into place until the deep water reflectance is sampled under the blue rectangle
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Seatruth: RMSE=1.05 m
Seatruth below is limited to Channel and Isla Espiritu Santo |
Data and Deglinting 
Full scene | 
subset | 
TOA TCC: raw image
logarithmic enhancement
Note the swirling plumes
coming westward out of the channel | 
BOA TCC deglinted image
linear enhancement |
Modeling 
BOA TCC: water column corrected
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Retrieved depth
see legend |
Bottom typing 
SAM classified image
see legend for image SAM2 | 
Average bottom brightness
see legend for image B | 
NDRblues200
(CoastalWCC-BlueWCC)/(CoastalWCC+BlueWCC)
see legend for NDRblues
- A current of slightly turbid water is seen to flow westward through the channel
- things do not come into place until the deep water reflectance is sampled under the blue rectangle
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BOA CC normalized
B=CoastalWCC
G=GreenWCC
R=BlueWCC
location of profile_fabio1 and profile_black are shown
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Profiling
In the profiles below:
RED profile is ZDTM: the Combined Depth DTM
BLACK profile is Z4SM: retrieved depth
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