HICO
at La Parguera, Puerto Rico

500*900, 100 m pixel size, not georeferenced
scene iss.2013269.0926.124759.L1B.Puerto_Rico.v04.14765.20130926181516.100m.hico.bil, September 26th 2013.
Image courtesy of OSU

28 narrow wavebands
 
 
work done april 2016
home
 


 
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
 




Because we have a LIDAR coverage,
we can research the conditions which may yield correct results:
The outcome is:
  • one must be very strict to ensure consistency of the model
  • this can be achieved without use of the LIDAR data
  • tools in 4SM have been developped to that effect
  • This image is not worthy of 4SM work

Optical calibration
under mask_3
Under mask 3

Calibration diagram for bands_27_22_13_7
only under mask 3 colored orange:
this excludes the outer slopes colored red

It shows
Mask 3 is colored orange
First, to achieve a good linear fit below
for the BLUEvsGREEN pair,
I had to raise substantially LswGREEN
BEFORE: LswGREEN=23.7

BLUE vs GREEN
BEFORE
This does not involve knowledge of bathymetry


AFTER: LswGREEN=30.4

BLUE vs GREEN
AFTER

 
Then, to achieve the good fit below,
I had to raise substantially LswPAN
BEFORE: LswPAN=19.8

GREEN solution vs PAN solution
BEFORE
This does not involve knowledge of bathymetry

AFTER: LswPAN=21.9

GREEN solution vs PAN solution
AFTER





Optical calibration
under mask_6
Under mask 6

Calibration diagram for bands_27_22_13_7
only under mask 6 colored red
this is the outer reef ridge colored red

It shows
  • 12_30 m: assumes a ratio Kblue/Kgreen=0.70
    • same as under mask_3
Mask 6 is colored red
First, to achieve a good linear fit below
for the BLUEvsGREEN pair,
I had to raise substantially LswGREEN
BEFORE: LswGREEN=25.5

BLUE vs GREEN
BEFORE

Under mask 6 colored red


 
This does not involve knowledge of bathymetry

AFTER: LswGREEN=29.3

BLUE vs GREEN
AFTER
Under mask 6 colored red

 
 
Then, to achieve the good fit below,
I had to raise substantially LswPAN
BEFORE: LswPAN=19.8

GREEN solution vs PAN solution
BEFORE
This does not involve knowledge of bathymetry
AFTER: LswPAN=21.6

GREEN solution vs PAN solution
AFTER




Calibration diagram
for the whole image
For mask_3 and mask_6 combined

Calibration diagram for bands_27_22_13_7
for the masks 3 and 6 combined
using mask_3 calibration

QUITE CONFUSING
  • Try and error
  • It took me a long while, many errors, and constant reference to LIDAR data,
  • until a workable/consistent set of calibrations finally evolved
For the whole scene

Calibration diagram for bands_27_22_13_7
for the whole image
using mask_3 calibration

MUCH THE SAME
  • LsM: finally set at the radiance of coral sands, as per experience gained using Landsat 8 at La Parguera
  • Only the outer ridge exhibits such bright bottoms at some low lying spots or as isolated pixels, while the rest is 3 to 4 times darker, being commonly covered vith seagrass or corals
 
Spectral 2K in m-1 
  • White dots: this set up of spectral 2K in the Orange-Red range of the solar spectrum
    • was derived from calibration work on this image 
    • white dots are experimental
  • Thick black line: it consolidates previous findings
    • thick black line is derived from observation at Fakarava, using HYPERION and CoefK=1.5