4SM CASI seychelles

4SM processing january 2006
I want to redo it in 2014: shall be much better: see CASI at Heron Island!!
see Sarah Hamylton's paper on CASI at Alphonse Atoll, Seychelles 2011

4SM processing january 2006

go to bottm typing

SUNGLINT
This image is marred with heavy sunglint,
which should have been avoided by flying into or away from the sun.
Removing most of the sunglint has been a challenge,
as sunglint does not have the same properties as the usual skyglint.
Much has been learned in this regard, and 4SM has been improved accordingly.

DEEP SOUTH
The southern half of this image lies at approx 30 m.
it appears to be scattered with very dark towering mounds at approx 4-6m.
In order to yield some results in spite of adverse sunglint, the model had to be operated beyond reasonable limits.

AMAZING
Altogether, I think these results are amazing:

no fancy gimmicks such as derivative spectroscopy, spectral libraries, neural network classifier, principal components analyzis, you name it
- just a simple empirical "ratio" method inspired by Lyzenga's and Maritorena's work
- although sub-pixel analysis is a way forward
no atmospheric corrections needed
- most of heavy sunglint effectively is removed
- although removal of the adjacency effect would be a way forward
no field data needed/used
- yields both computed depth and water column corrected "low-tide" image which is ready for bottom type classification
- an exclusivity of 4SM!
- results down to ~30 m of depth in these clear tropical waters

from left to right:

raw TCC
deglinted TCC
"low-tide" TCC
"low-tide normalized" TCC
10 bottom types
computed depth

Below is a zoom window

TCC raw image	TCC deglinted image
TCC bottom reflectance a "low tide" view	TCC normalized bottom reflectance enhances the visibility of contrasted bottom signatures
Computed depth Z10	Computed depth Z250
Bottom signatures classified into 10 bottom types raw image	Bottom signatures classified into 10 bottom types a modal filter has been applied
Calibration diagram	FAIRLY CLEAR WATERS, BRIGHT IMAGE, BRIGHT SANDS excellent calibration Jerlov optical marine water type ~OII

Bottom Typing

STATISTICS OF SHALLOW BOTTOM TYPING in BOA radiance 0-200

CoefSTD=3.00 nbMISS=3 -E1/1950/1/12233 on Fri Jan 20 08:57:12 2006

The Classifier tool in 4SM is under development: these results should be taken with precautions

Type_0 is Land pixel
Type_1 is Unclassified Shallow pixel
Type_2 is Optically Deep water pixel
Type_3 is No Data pixel
Type_4 is Wave Breaker pixel
Type_5 is Cloud/Shadow pixel
Type_6 and above is for Classified Shallow pixel

1.40% as type_1   UnClassified shallow pixels

2.42% as type_6   SIG   4.9   4.7   4.5   3.3   3.7   4.2   4.4   4.5   5.2   5.0   4.7   4.9   4.9   4.0   8.5   0.0   0.0
BGSL   4            STD   0.4   0.3   0.3   0.3   0.3   0.3   0.4   0.4   0.4   0.4   0.4   0.4   0.5   0.4   0.6   0.0   0.0

7.45% as type_7   SIG   7.7   7.9   7.7   6.3   6.8   7.1   7.1   7.3   7.6   7.6   7.6   8.7   9.9   9.3 14.2   0.0   0.0
BGSL   7            STD   0.5   0.5   0.6   0.6   0.6   0.5   0.7   0.6   0.6   0.6   0.6   0.6   0.6   1.3   0.7   0.0   0.0

6.02% as type_8   SIG 10.4 10.6   9.6   8.8   8.4   8.6   8.7   8.7   9.1   9.0   8.9   9.3   9.6   8.7 15.6 11.4   0.0
BGSL 9            STD   0.8   0.9   0.9   0.9   1.0   1.0   1.0   1.1   1.1   1.1   1.1   1.0   1.0   1.1   1.4   1.7   0.0

13.35% as type_9   SIG 15.8 17.9 16.7 15.7 15.7 16.6 15.4 15.5 16.1 15.9 16.1 17.8 21.9 19.3 23.5   0.0   0.0
BGSL 16            STD   1.2   1.4   1.3   1.6   1.4   1.5   1.3   1.3   1.4   1.3   1.3   1.3   1.5   1.2 0.2   0.0   0.0

23.13% as type_10 SIG 23.8 26.2 26.2 25.7 26.0 26.7 26.1 27.4 27.9 27.5 26.3 26.4   0.0   0.0   0.0   0.0   0.0
BGSL 26           STD   1.9   2.1   2.2   2.3   2.2   2.3   1.9   2.0   2.1   1.9   1.7 0.5   0.0   0.0   0.0   0.0   0.0

19.25% as type_11 SIG 38.3 41.2 41.9 42.6 42.2 40.5 40.5 40.7 41.8 39.8 31.6   0.0   0.0   0.0   0.0   0.0   0.0
BGSL 41            STD   2.8   3.1   3.4   3.2   3.0   2.8   2.3   2.2   2.1   1.9   1.3   0.0   0.0   0.0   0.0   0.0   0.0

7.02% as type_12 SIG 54.8 57.9 57.0 54.8 57.2 60.1 60.1 62.7 64.3 62.4 65.9 64.1 65.3 59.5 73.0 35.4   0.0
BGSL 58            STD   2.7   3.0   2.9   2.7   2.8   2.6   2.4   2.4   2.7   2.6   2.8   2.7   3.1   3.3   3.3   6.3   0.0

9.21% as type_13 SIG 65.9 69.8 74.5 76.9 78.4 76.2 76.7 78.9 81.0 78.5 71.1 70.9 94.0   0.0   0.0   0.0   0.0
BGSL 77            STD   3.1   3.4   3.8   4.1   3.7   4.9   4.6   3.8   4.4   4.2   3.7   5.0   1.9   0.0   0.0   0.0   0.0

7.68% as type_14 SIG 88.2 103.0 96.5 107.5 105.2 100.6 104.9 101.9 107.0 103.9 93.3 88.8 108.4   0.0   0.0   0.0   0.0
BGSL 105            STD   3.7   4.6   4.6   4.9   4.2   4.4   5.5   4.4   5.1   4.8   3.4   2.8   5.3   0.0   0.0   0.0   0.0

3.07% as type_15 SIG 114.8 124.8 121.1 132.2 131.2 125.7 130.7 137.6 146.5 146.3 112.1   0.0   0.0   0.0   0.0   0.0   0.0
BGSL 130            STD   6.4   5.9   5.6   5.3   5.7   5.0   5.4   6.0   6.8   6.4   5.0   0.0   0.0   0.0   0.0   0.0   0.0

Band setting: EXCELLENT

   1 [16U] 434.5nm+/- 10.3nm (rows 278-288) DNSRU:1000.000000 a b        First time I see these near blue bands
   2 [16U] 452.0nm+/- 7.6nm (rows 270-277) DNSRU:1000.000000 a b           having a great radiometric quality
   3 [16U] 467.7nm+/- 6.6nm (rows 262-268) DNSRU:1000.000000 a b
   4 [16U] 481.6nm+/- 7.6nm (rows 254-261) DNSRU:1000.000000 a b
   5 [16U] 497.3nm+/- 8.5nm (rows 245-253) DNSRU:1000.000000 a b
   6 [16U] 513.2nm+/- 7.6nm (rows 237-244) DNSRU:1000.000000 a b
   7 [16U] 528.1nm+/- 7.6nm (rows 229-236) DNSRU:1000.000000 a b
   8 [16U] 543.0nm+/- 7.6nm (rows 221-228) DNSRU:1000.000000 a b
   9 [16U] 558.0nm+/- 7.7nm (rows 213-220) DNSRU:1000.000000 a b
10 [16U] 573.0nm+/- 7.7nm (rows 205-212) DNSRU:1000.000000 a b         One or two more bands
11 [16U] 588.0nm+/- 7.7nm (rows 197-204) DNSRU:1000.000000 a b        inside this range
12 [16U] 603.0nm+/- 7.7nm (rows 189-196) DNSRU:1000.000000 a b should be an adavantage
13 [16U] 634.1nm+/- 6.8nm (rows 173-179) DNSRU:1000.000000 a b
14 [16U] 654.9nm+/- 4.9nm (rows 163-167) DNSRU:1000.000000 a b
15 [16U] 700.4nm+/- 4.9nm (rows 139-143) DNSRU:1000.000000 a b
16 [16U] 740.3nm+/- 6.8nm (rows 117-123) DNSRU:1000.000000 a b        TWO near-infrared in this range
17 [16U] 849.8nm+/- 9.7nm (rows 058-067) DNSRU:1000.000000 a b        are a great help for deglinting