Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries
 

WorldView 2 image at Waimanalo Beach, Oahu, Hawaii islands
3289x3241, 2 m ground resolution, courtesy of Ron Abileah
home
4SM   vs  NOAA's method
 
 
July 13th
Modeling with NOAA's log ratio method : Stumpf's method


SHOALS DTM:
five BLUE profiles and four YELLOW profiles

 

In 4SM, all visible bands are now used in a generalized version of Stumpf's method: if suitable bottom detection in all WV2 visible bands:

Z=(   Mone[5]*((log(L[1])+log(L[2])+log(L[3])+log(L[4]))
/(4*log(L[5])))   )    -Mzero[5];


In 4SM, Mzero=Mone for Stumpf's method

  • Let Z=0
  • in 4SM, L1=L2=L3=L4=L5, because the Soil Line is normalized
  • therefore ==> Mzero=Mone     
  • sure, you'll like that!


In 4SM, computed depths are used as "seatruth" to estimate a value for Mzero for Stumpf's method

  • no need for field data
  • and no need for segmenting the image into several bottoms substrates, like 'sand' vs 'coral', with separate calibrations
  • sure, you'll like that!
thresholds: -Lm/1.0/1.0/1.0/10.0/10.0/255/255.0/255.0

 
  • From this comparison, it is quite clear that
    • deeper that 15-20 m here, depths become badly underestimated by Stumpf's method (some sort of assymptot)
      • that's ~60% of maximum depth of bottom detection
      • while 4SM yields results over the whole bottom detection depth range
    • 4SM shall easily beat Stumpf's method even when field data are not available
    • nothing shall (ever) beat the LIDAR in terms of accuracy on depth
  • How about very dark bottoms?
    • this image lacks very dark bottom substrates
      • which should yield badly over-estimated  depths by Stumpf's method
  • Atmospheric correction, anyone?
    • now, who shal insist that they do require atmospheric corrections after all?
      • or field data for that matter?
  • Real life conditions?
    • Well, Waimanalo Bay in Hawaii is expected to be  "very clean tropical waters": now, better think twice, as it also has its pollution problems!
    • All this now must be documented rigorously by independent investigators, using a variety of imageries including WV2
Below are the plots for these 9 profiles
by 4SM method
Below are the plots for these 9 profiles
by Stumpf's method
waimanalo_profile_yellow_Z_LB_DTM_4SM
Profile YELLOW by 4SM method
 

Profile YELLOW by Stumpf's method
 

waimanalo_profile_blue_Z_LB_DTM_4SM
Profile BLUE by 4SM method


Profile BLUE by Stumpf's method

waimanalo_deg_2_DTMXYZ_RgrsZZ_wZ_3_4_5
ZC vs ZR regression by 4SM method
 

ZC vs ZR regression by Stumpf's  method
ZC - ZR
ZZRegressor: Statistics of seatruth ZC-ZR

on image waimanalowv2m_deg at Oahu, Hawaii
N=5.609 millions pixels by Morel's 4SM method
Htide=1 Smooth=1_5 Using_bands_1_2_3_4_5 cZ=1.00
 

 1.79% pixels with depth underestimated by more than 5.0 m
 4.17% pixels with depth underestimated by more than 3.0 m
 6.78% pixels with depth underestimated by more than 2.0 m
13.71% pixels with depth underestimated by more than 1.0 m
35.68% pixels with depth underestimated by more than 0.0 m

25.91% pixels with depth  overestimated by less than 1.0 m
 8.15% pixels with depth  overestimated by less than 2.0 m
 2.27% pixels with depth  overestimated by less than 3.0 m
 1.16% pixels with depth  overestimated by less than 5.0 m
 0.37% pixels with depth  overestimated by more than 5.0 m


61.60% of computed depths are within  +-1.0 m of DTM depth
83.46% of computed depths are within  +-2.0 m of DTM depth
92.51% of computed depths are within  +-3.0 m of DTM depth
97.83% of computed depths are within  +-5.0 m of DTM depth
over a total of 100.00% of computed depths
ZC - ZR
ZZRegressor: Statistics of seatruth ZC-ZR
on image waimanalowv2m_deg at Oahu, Hawaii
N=5.574 millions pixels by Stumpf's method
HTide=1 m Smooth=1_5 Using_bands_1_2_3_4_5 cZ=1.00


4.96% pixels with depth underestimated by more than 5.0 m
 8.97% pixels with depth underestimated by more than 3.0 m
 9.79% pixels with depth underestimated by more than 2.0 m
17.07% pixels with depth underestimated by more than 1.0 m
25.60% pixels with depth underestimated by more than 0.0 m

26.13% pixels with depth  overestimated by less than 1.0 m
 6.71% pixels with depth  overestimated by less than 2.0 m
 0.66% pixels with depth  overestimated by less than 3.0 m
 0.10% pixels with depth  overestimated by less than 5.0 m
 0.00% pixels with depth  overestimated by more than 5.0 m


51.73% of computed depths are within  +-1.0 m of DTM depth
75.52% of computed depths are within  +-2.0 m of DTM depth
85.97% of computed depths are within  +-3.0 m of DTM depth
95.04% of computed depths are within  +-5.0 m of DTM depth
over a total of 100.00% of computed depths
waimanalo_deg_2_ZC-ZR_wZ_3_4_5
ZC - ZR
by 4SM

ZC - ZR
by Stumpf's method

 



Créer un site
Créer un site