SPOT-5 1700*1000 pan-sharpened image of Sanaa, Yemen
The original image is 8061*11954 pixels, pixel size 5 m


work done in 2003 and 2007 on the Al Bodhi island (Al Bawdi)
and in 2012 on the whole image
This image subset, pan-sharpened to a pixel size of 5 m,
is a courtesy of IGN-Espace, Toulouse, France (Denis TOUTSOU, october 2002).

The radiometric quality of this 8-bits image is outstanding.


see also PAN-sharpened Quickbird at Shiraho Reef

return to 4SM Study Cases
 


 
1 - NO NEED for field data, nor for atmospheric correction
2 - this is demonstrated in this website, using a variety of hyper/multi spectral data
 
Requirements are
1 - homogeneous water body and atmosphere
2 - some coverage of optically deep water
3 - some coverage of dry land
 
Problems are
1 - the precision on estimated depth is found wanting, because the noise-equivalent change in radiance  of accessible data is too high for shallow water column correction work 
2 - radiance data should be preprocessed by the provider at level 1 in order to improve S/N ratio
3 - exponential decay: the deeper/darker the bottom, the poorer the performances
 
So
I keep digging
until suitable data
become available
 
Water type is found to be OIII+0.9 of Jerlov: this is Coastal water type 3 of Jerlov
PANCHRO:
this work used the panchro band in addition to the three XS bands

for another such comparison, see also Bora Bora


XS wavelengths are 550, 650 and 850 nanometers,
plus a SPOT 5 Panchromatic band which is given a wavelength of 590 nm.
bands 1, 2, 3 and PAN become bands 1, PAN, 3 and 4

Unfortunately, the Panchromatic waveband of SPOT 5 does not extend
over the Green range of the solar spectrum:
this severely limits its water penetration,
more so here because of the distinctly coastal water type.


For lack of a blue band, modeling is limited to a depth of ~8 m over bright bottoms
-instead of ~5 m without the panchromatic band.


It should be noted though that with a wider panchromatic band,
one would expect an even deeper depth range.


 

 


FCC
histeq enhancement

Panchro
histeq enhancement

Location of Profile_Blue
against a backdrop of the NIR band

this shows the regular increase of the adjacency effect as the profile approaches the waterline, from KM 10 tyo KM 45 in the profile

Location of Profile_Blue
against a backdrop of the RED band

this shows the regular increase of the adjacency effect as the profile approaches the waterline, from KM 10 tyo KM 45 in the profile

Profile_Blue
  • The PANCHRO band is assigned WL=590 nm and stored as band 2
  • Note: extremely high level of path radiance
  • Note: excellent "deglinting" of the adjacency effect

 

Profile_Blue zoom

  • System noise is at most one DN in raw data over deep waters,
    • maybe due to very high level of path radiance (a milky sky)
    • although might be the result of re-sampling??
  • No swell modulated sea-surface glint
  • glint is mostly comprised of the path radiance:
    • a strong sky radiance at LaNIR~=45
    • a strong adjacency effect ranging from LaNIR~=~45 to LaNIR~= ~60
  •  ==> deglinted profile is quite smooth





 

Glint regressions are excellent
 
Sanaa image has a PAN band
Optical water type appears to be OIII+0.9,
 i.e. next to Coastal 3

For some weird reason,
it would appear that the NIR band exhibits
an unexpected water penetration:
2KNIR~=3.2 here,
instead of ~4.5 usually expected.


Although the illumination is maximum in june,
and becaus eof the adjacency effect,
this image only enjoys a ~100 DNs dynamic range
over the deep water radiance
in the Panchro and Green bands.




Subset at Al Bodhi island

The subset below is part of the very large image on the left

Note that the whole area is affected
by a very strong atmospheric adjacency effect,
which is caused by a high content in areosols in the atmosphere and the presence of a very bright continentental mass. This effect gets stronger closer to the coast. This case of adjacency effect is strongly correlated among wavebands, and very easy to remove through the deglinting process.

With atmospheric path radiances
at -La088.5/63.8/59.5/47.3
in the Green, PAN, Red and NIR bands,
this is quite a stuffy atmosphere
on June the 12th 2002 in the Red Sea! 


This nice enhancement does not show
much of the adjacency effect


Deglinting efficiently removes the adjacency effect

 


Image_Z250
Modeling down to 8 meters,
thanks to the use of the panchromatic band

 


Image_Z250_stepped
Modeling down to 8 meters,
thanks to the use of the panchromatic band

 


Image_B
Modeling down to 8 meters,
thanks to the use of the panchromatic band

 


Image_LBS
Modeling down to 8 meters,
thanks to the use of the panchromatic band

 

Sanaa image has a PAN band
Optical water type appears to be OIII+0.9,
i.e. next to Coastal 3

For some weird reason,
it would appear that the NIR band exhibits
an unexpected water penetration:

2KNIR~=3.2 m-1 here,
instead of ~4.5 
m-1 usually expected.


Although the illumination is maximum in june,
and because of the adjacency effect,
this image only enjoys a ~100 DNs dynamic range
over the deep water radiance
in the Panchro and Green bands.

nice -0 4SM.2.07 -PROCESS/01_AUG_2007/IGN               
-dB/PCI/sanaa_island/27_1_0_0/4_1/1700_1000/2.5_2.5/1_1  
@dB/PCI/sanaa/27_1_0_0/4_1/8061_11954/225948_1746774/1_1 -TP/1/2
-Origin/IGN-E_J1_12_06_02.IMA_YEMEN_RedSea        
-MIS/IGN-E/Sanaa/SPOT5/XSP/IGN-E/UTM_38_008/.005_0.005/12_JUN_2002        
-makePIX/FILE/8/Z20      
-import/toto/dbnc_9_0_0_0/8192_11954/1,5_1,5/dbiw_0_0_8061_11954
-recode/0_InChannel_5_into_2_OutChannel_5  
-makeLand/2.0/1.5/showLand    
-WL000550/00590/00650/00850    
-M@000001/00002/00003/00004    
-LsM00200/00160/00172/00185    
@LsM243.0/198.2/217.2/239.8_1.400   
@LsM232.2/188.6/205.9/226.1_1.300   
@LsM221.5/179.1/194.6/212.7_1.200   
@LsM00200/00160/00158/00185    
@LsM221.5/179.1/177.8/212.7_1.200   
@Lsw095.6/066.0/059.1/046.6_DN15_15_deepwater  
-Lsw095.4/066.6/058.9/046.6_Deglint_correlation_smoothed
-La0089.9/064.6/058.9/046.6    
-La0092.5/064.6/058.9/046.6    
-dLsw00.0/000.0/001.0/002.5    
-Lm000002/001.0/00008/00005    
-Lm000002/0020p/0020p/0005p    
-KK/1_3_0.40/4.5/500_600_700    
@KK/1_3_0.44/4.5/500_600_700    
-Z/1.18/.1/0.00/0.0/1.0/PAN_1_4/SIG_3w5/n_1/1.0000 
-B/tclNE_3.0/200_100/1/1.0/7              
-prepare/scale/delimb/1/40/51/10/Dr/fill/4/41/linearize 
-deglintFlv/1.5/4_70/FN/2_255/700_1700_1_50   
-extractv/U8/4Max255/mBPL_1/mSOIL_21/mSHAL /470_950_330_580_Mask_3
-calibratev/BDSMpZ/4_3_2_1/BDh_12_13_14                 
-model/Smooth_3Db/Smart+1/mask_3   
@-Lm000002/0005p/0010p/00005_Mask_3   
@-KK/1_3_0.55/4.5/500_600_700_Mask_3   
@-Model/Smooth_3Db/Smart+1/Mask_3/470_950_330_580 
@-Classify_7.0_0/mode_5_26_24    
-WriteU88/lfilled/lequalized/ldelimbed/Ldeglinted/LSB/lscaled
@-E/470/950/330/450 @-E1/1700/800/850 @-DN15/15_deepwater -Archive