- We ran a new extraction of calibration data over the whole lagoon
- A new calibration file tarawa-subset_m0.cal was extracted
- it overwrites the previous file tarawa-subset_m0.cal
- now the BPL pixels account for all shallow pixels in the lagoon area,
- whether under mSE=3 or mSE=4 all the way to mSE=mSOIL-1=20
- that is: pixels with mSE<3 are excluded.
- The result is a new calibration diagram for the whole lagoon
Bulging BPL pixels
Sure you want to see where in the image those bulging BPL pixels are located
It is quite obvious that very shallow BPL pixels (0-0.5 m)
exhibit a distinctly brighter bottom signature:
In order to avoid saturation upon modeling, we had to increase LsM.
We did this by way of CoefLM in -B... argument
For this reason, in order to avoid excessive saturation of the computed bottom reflectance
- we used a CoefLM=1.15 in the -B... argument
- this "slides" the LsM point up the Soil Line
- a new -LsM... argument is offered on your terminal
- search for NewLsM in your terminal:
- we enabled -LsM/203.4/192.1/178.5_cLM=1.15
- then returned to -B/tclne_2.0/LBref170_100/1/cLM1.00
- this new -LsM... argument now accounts for the very bright bottoms that just showed up at some very shallow locations under mSE=3
The calibration now accounts for this new maximum bottom refelctance
before increase of LsM
after increase of LsM
NewLsM and CoefLM
- See that, if CoefLM is given a value >1 or <1,
- a NewLsM is computed and applied:
- it is obtained by sliding LsM up or down along the Soil Line
- its value is shown in the Postscript display,
- If found satisfactory, it may be used/enabled
- to replace/override the existing -LsM... argument in the command line.
Why locally Brighter bottoms?
- This very shallow extent of pure white bottoms is a very gently sloping lime mudflat
- calcium carbonate precipitation occurs: waters there can be milky at times
- Halimeda sands/muds are ubiquitous in this lagoon
- finer grained entails higher reflectance
- locally cleaner muds entails higher reflectance
Why locally clearer waters?
- This is easier to explain:
- waters over the reef flat are cristal clear oligotrophic ocean waters
- These cristal clear oceanic waters intrude into the lagoon
- through "hoas" across the reef rim:
- nice swimming in those streams!