florida-ETM_2003_01_12


back to Florida


 
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
 


Various water types:
each of these distinct basins has its distinct Jerlov water type
clearest         is OIB+0.7             for open Gulf waters
least clear     is Coastal 4                       under mask_4
the problem of course is that Lsw and Lw cannot be estimated properly



L71015043_04320030112 12 JAN 2003


Raw TCC
 

Deglinted TCC
 
    
  raw ETM1                            raw ETM2
  • negative bottom contrast in the blue band is obvious over the Everglades
    • and also in many of the shallow sounds
  • very high bottom contrast in the blue band
   
raw ETM3                        raw  ETM4
  • negative bottom contrast in the blue band
  • over the Everglades, this denotes healthy vebetation and/or "black waters" high in CDOM
  • in the shallow sounds, we may suspect abundant seagrass and/or very dark bottoms
    
deglinted ETM1              deglinted ETM2 
under mask 6
see profile6
  • deglinted ETM1 shows onlymoderate variations and decreases ~3 DNs below the water volume reflectance of the ocean
  • deglinted ETM2 is highly variable, and remains everywhere well above the water volume reflectance of the ocean
  • deglinted ETM3 decreases towards deep water radiance form NW towards SE

deglinted ETM3
under mask 6
 

Calibration for the whole image
  • no deglinting and no smoothing of BPL pixels
  • water type OIB+0.7
  • WL[green]=572 nm
  • note that the bright pixels of mask 5
  • are present in the biplot of Ls[blue]vsLs[red], but they have been more strongly attenuated

Calibration under mask 10
  • no deglinting and no smoothing of BPL pixels
  • water type OIB+0.7
  • it can be seen that shifting WL[green] from  560 to 572 nm is quite necessary for the BPL assumption to be satisfied for all pairs of bands
  • WL[green] at_midwaveband  without shifting WL[green]: water type OIB+0.4
4SM can calibrate under any mask
specified in a shapefile

as illustrated below

Upon modeling
only pixels under specified mask

are updated,
 while other pixels are left unchanged
Calibration under mask 3
  •  water type C3+0.2
  • WL[green]=562 nm
  • Lsw[blue] was decreased from 61.3 to 57.3: this tends to increase computed depth over dark bottom
  • Depth under mask 3 is reported to reach 6 feet in its southern part
Results under mask 3
  • image B the bottom is extremely dark in the northern part
  • image Z mostly shows swell artifact! Deepens toward the central basin
  • image LBnormalized clearly suggests green spectral signature all over
  • profile3_Z           see also profile3
    • green spectral signature well developped in the deeper basin
    • reaches ~1.6 m at most
    • variations of computed depth are badly affected by the swell
  • Modeling under mask 3
    • seems to make sense
    • lacks a near Blue band in order to ascertain the extent of the decrease in water volume reflectance in the blue region for coastal waters
 
Calibration under mask 4
  • water type C4+0.0
  • WL[green]=583 nm
  • Lsw[blue] was decreased from 61.3 to 58.3: this tends to increase computed depth over dark bottom
  • Depth under mask 4 is reported to reach 6 feet
Results under mask 4
  • image B the bottom is extremely dark in the deeper areas
  • image Z mostly shows swell artifact!
  • image LBnormalized clearly suggests green spectral signatureall over, although less pronounced where bottom is brighter
  • profile4_Z           see also profile4
    • green spectral signature all along
    • reaches ~1.8 m at most
    • variations of computed depth are badly affected by the swell
  • Modeling under mask 4
    • too dark
    • too noisy
    • lacks a near Blue band
    • a frustrating experience!
  • I wish ALI had covered this area
 
Calibration under mask 5
  • water type OIII+0.0
  • WL[green]=578 nm
  • could not ascertain a decrease of Lsw[blue] for lack of negative bottom contrast
  • Depth under mask 5 is reported just to exceed 6 feet locally
Results under mask 5
  • image B the bottom is extremely bright in the central area
  • image Z nicely depicts depth variations
  • image LBnormalized clearly suggests green spectral signature is less pronounced in the central brightest area
  • profile5_Z           see also profile5
  • green spectral signature all along
  • reaches 2 m at most
  • variations of computed depth are slightly affected by the swell

Modeling under mask 5
very bright ==> noise not a problem

 a nice experience

 

Calibration under mask 6
  • water type C3+0.3
  • WL[green]=578 nm
  • Lsw[blue] was decreased from 61.3 to 57.8: this tends to increase computed depth over dark bottom
  • Depth under mask 6 is reported to reach just in excess of 6 feet
 
Results under mask 6
  • image B the bottom is extremely dark
  • image Z shows mostly depth variations caused by the swell
  • image LBnormalized suggests green spectral signature all over
  • profile6_Z           see also profile6
  • modeling is impossible where the Red band reaches the deep water radiance because K[green] and K[blue] are too close
  • variations of computed depth are badly affected by the sewll
  • Modeling under mask 6
    • too dark
    • too noisy
    • lacks a near Blue band
    • a frustrating experience!
 

I wish ALI had covered this area

 
Calibration under mask 7
  • water type C3+0.4
  • WL[green]=562 nm
  • Lsw[blue] was decreased from 61.3 to 57.3: this tends to increase computed depth over dark bottom
  • Depth under mask 7 is reported  just to exceed 6 feet locally
 
Results under mask 7
  • image B the bottom is not too dark
  • image Z nicely depicts the details of this drainage system, althoug the swell artifact shows up where deepest
  • image LBnormalized suggests green spectral signature all over
  • profile7 Z           see also profile7
    • depth reaches ~1.6 m, with some noticeable difference with the Coastview map though
    • variations of computed depth are affected by the swell at depth
  • Modeling under mask 7
    • quite nice, as the area is fairly shallow
    •  and bottoms are not too dark
    • modeling with only the green and blue bands would be impossible: this would require
      • an orange band
      • possibly a near blue band
      • and a much improved SN ratio like with ALI
Calibration under mask 8
  • water type OIII+0.0
  • WL[green]=578 nm
  • Lsw[blue] was decreased from 61.3 to 58.0: this tends to increase computed depth over dark bottom
  • Depth under mask 8  :
    • please note the 12 feet contour line
    • please note the 30 feet contour line
Results under mask 8
  • image B
  • image Z the shallower ridge at waypoint B is dubious
  • image LBnormalized maps the extent and variations of the green spectral signature
  • profile8 Z           see also profile8
    • ?depth  is ~1.6 m at waypoint Cwhere the Coastview map has the 12 feet contour
  • Modeling under mask 8
    • quite nice, as the area is fairly shallow and bottoms are not too dark

 

Calibration under mask 10
  • perfect and straightforward calibration
  • water type OIB+0.7
  • WL[green]=572 nm
Results under mask 10

 
Work is not finished: it would require
  • covering the whole imagewith contiguous masks,
  • and modeling under each mask one after the other
  • and some seatruth
 
Don't be surprised:
work is not finished.

Rather I want to study more ETM images