4SM on OLI at Caicos Bank, Bahamas

This is a time series of Landsat 8 OLI+PAN images
work done july-september 2016

Seatruth DTM was purchased
from Harris-Ellis_Knowledge_Transfer
The Harris-Ellis dataset was used for research on carbonate sands bodies on the Bahamas: Satellite Imagery and Visualization of the Caicos Platform	Location of depth soundings used to produce a crude DTM Purple depth points are satellite derived Others are derived from soundings and nautical chart
DTM DTM indicates that optical calibration using Jerlov data is correct and suitable NO NEED FOR FIELD DATA And also that using the PAN solution is correct NEXT USE PAN-SHARPENED IMAGES: OLIP or WV2P Co-registration is excellent Three main sources of error: DTM very coarse Biased retrieval: Htide is un-realistic; this still needs investigation Genuine depth change over time	DTM DTM is too coarse for a fair estimation of RMSE there is nothing like a LIDAR or MBES DTM for estimating RMSE This DTM only useful in the 1-17 m depth range lacks depths 17-30 m DTM allows for invaluable insight into 4SM modeling practise 4SM now tuned for Landsat 8 OLIP data, next WV2P Conclusion on DTM seatruth

**Remarkable findings and improvements**
This series of images offers a good opportunity for strengthening 4SM tools	Regressions: the slope of the regressions is found to be ~=1 : this owes nothing to the existing DTM, but rather offers a nice confirmation that YES: thanks to Jerlov's data, no need for field data for optical calibration?		SAM: water column corection results mapped to spectral angle offer a good opportunity for time series studies
		MAY 2013 RMSE=0.52 m SWIR deglinting very good RED bottom detection down to ~8-9 m==>low KRED Excellent calibration PAN solution better than GREEN solution DTM seatruth: no need for field data BOA reflectance==>SAM bottom classification
		JANUARY 2014 RMSE=0.57 m SWIR deglinting very good RED bottom detection down to ~8-10 m==>low K_RED Excellent calibration BOA reflectance==>SAM bottom classification
		FEBRUARY 2014 RMSE=0.61 m
		MARCH 2014 RMSE=0.63 m PAN solution safer, avoids artifacts "Whiting" or resuspension?
		AUGUST 2014 RMSE=0.59 m
		SEPTEMBER 2014 RMSE=0.73 m A bad image: complex atmosphere, poor deglinting Stratified waters are correctly accounted for in 4SM: very clear in the SE corner DTM is faulty in the SE corner KB_LUE/K_GREEN=0.42 ==> WaterType OIB+0 ==> No need to decrease K_RED Something is very wrong: deeper than ~10 m: calibration not under control CoefKPAN=1.25
		NOVEMBER 2014 RMSE=0.59 m
		JANUARY 2015 RMSE=0.93 m Bad atmosphere 4SM model is not under good control
		MAY 2015 RMSE=0.62 m Vegetation Line==>Lw=Lsw-La==>BOA==>BOA Reflectance
		JULY 2015 RMSE=0.69 m Bad atmosphere Htide=1.5 m: something's wrong!
		AUGUST 2015 RMSE=0.65 m Very green in august
		SEPTEMBER 2015 RMSE=0.57 m Htide=0.7 m
		BEST IMAGE OCTOBER 2015 RMSE=0.56 m Vegetation Line==>Lw=Lsw-La==>BOA==>BOA Reflectance K₁/K₂=(K₁/K₃)/(K₂/K₃) must be satisfied
		NOVEMBER 2015 RMSE=0.62 m Bottom typing K_COASTAL must be slightly decreased
		JANUARY 2016 RMSE=0.67 m
		APRIL 2016 RMSE=0.66 m very dense and heterogeneous atmosphere several very bright spots Lsw for PAN needs some increase
		MAY 2016 RMSE=0.66 m The histogram is a better way to estimate a tide height, rather than the regression