La Parguera, Puerto Rico
a time series of images, courtesy of US Geological Survey, and of OSU
with LIDAR DTM from NOAA

Please refer to
"Deriving Bathymetry from Multispectral Remote Sensing Data",
William J. Hernandez and Roy A. Armstrong , J. Mar. Sci. Eng. 2016, 4(1)
Habitat composition and coverage mapping in La Parguera, Puerto Rico, using AVIRIS and IKONOS imagery,  Ramon Lopez Rosado

sensor acquired   processed
HYPERION 20020815   feb  2014
HYPERION 20030113   feb  2014
HICO 20130926 **** april 2016
LANDSAT8 20130618   feb  2014
LANDSAT8 20130805 *****LUT mar  2021
LANDSAT8 20131227 ** may 2016
LANDSAT8 20151030 *** may 2016

LIDAR DTM data reveals that this is a success for 4SM,
although vast expanses are affected by turbid waters
  • it demonstrates that
    • no need for field data, although the LIDAR data helped me a lot in deciphering this case
    • the generic optical calibration of the PAN band works fine
  • good depth retrievals down to 25 m,
    • subject to minor adjustment of the deep water radiance
    • using Kblue/Kgreen with wavelengths WLblue and WLgreen at mid-waveband
    • so that: no need for field data:   CoefZ=1.0

Thanks to the DTM,  I can decide 
  • which operational practices in 4SM should be ruled out, 
  • which are confirmed

These scenes are NOT worthy of shallow water work by 4SM,
  • apart from isolated  ROIs.

Another nice case for "semi-analytical" methods to show their supremacy: see DigitalGlobe and EOMAP
4SMLUT: a final challenge to map the spatial variations of waters optical properties


But I note that Hernandez's 2016 PhD work
  • was done in 2014-2016 at UPRM, home of Prof. Roy Armstrong and Dr James Goodman
  • resorted to not so "analytical" or physical ways, in favor of mathematical ways
  • required a select/suitable formal atmospheric correction
  • required/used an existing LIDAR coverage for its calibration
    • using a simple Blue/Green band ratio (not using Coastal?)
  • focused precisely, and commented only, on the very area where 4SM obtained its best results: ROI5 
  • produced a "depth-invariant" index of bottom brightness in place of a real spectral water column correction
  • and finaly did not use the Panchromatic band of WV2 imagery

With a DTM at hand, I can decide 
which operational practices in 4SM should be ruled out
and which are worth investigating further

I've done my best to try and make sense of these images under 4SM,
using Landsat 8 and Hyperion images: NO WAY!
Looks like there is a curse on La Parguera!

with NOAA's LIDAR seatruth dataset    PR_BATHY_4M_Mean_NNresample


This scene is marred by heterogeneous waters, under the dual influence of
coastal pollution from lands masses, rivers and cities
 and west-bound flow of very clear oceanic waters from the Sargasso Sea.
See original image

From "Geologic maps of the southwestern Puerto Rico Parguera to Guanica insular shelf"
Jack Morelock, Elizabeth A. Winget, and Carlos Goenaga


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