Bathymetry and water column corection World View 2 at Saint Croix, US Virgin Islands 8967*8805, MULTI, UTM zone 8 LIDAR seatruth of 4SM computed depths at Buck Island Reef, US Virgin Islands Investigation of Wavelengths and Tide Height, etc home

Seatruth

image wZ

The "RED solution" from 0 to ~5 m: wZ=5
Get things straight when modeling by Red against Purple, Blue, Green and Yellow: this is wZ=5
The goal is to get a nice diagonal fit for the 0-5 m scatter of depth points

 Smoothing is OFF RMSE=0.66 m (0-5m, N=18311) 1 in 25 DTM grid points are investigated wZ=5 for 18311 of those points without smoothing Deglinting is ON Smoothing is OFF WLred   is at mid-waveband Lswred   is increased from 19.7 to 20.5 Lmred   stays at 2 Tide height is set to 0.6 m, and tide correction is applied to Zcomputed Smoothing is ON RMSE=0.49 m (0-5m, N=18024) 1 in 25 DTM grid points are investigated wZ=5 for 18024 of those points with smoothing Deglinting is ON Smoothing is ON WLred   is at mid-waveband Lswred   is increased from 19.7 to 20.5 Lmred   stays at 2 Tide height is set to 0.6 m, and tide correction is applied to Zcomputed A small number of scattered depth points report Zcomputed depths less than 3 m where Zrecorded depths are in excess of 4 m this is commonly caused by locally turbid waters or cloud shadow

The "YELLOW solution" from 0 to ~9 m: wZ=4
Get things straight when modeling by Yellow against Purple, Blue, and Green: this is wZ=4
The goal is to get a nice diagonal fit for the 0-9 m scatter of depth points

 Smoothing is OFF RMSE=1.00m (0-9m, N=43062) 1 in 25 DTM grid points are investigated wZ=4 for 43062 of those points without smoothing Deglinting is ON Smoothing is OFF WLyellow   is at 603.6 nm Lswyellow   is increased from 28.0 to 29.2 Lmyellow   stays at 1.5 Tide height is set to 0.6 m, and tide correction is applied to Zcomputed Smoothing is ON RMSE=0.85m (0-9m, N=42890) 1 in 25 DTM grid points are investigated wZ=4 for 42890 of those points with smoothing Deglinting is ON Smoothing is OFF WLyellow   is at 603.6 nm Lswyellow   is increased from 28.0 to 29.2 Lmyellow   stays at 1.5 Tide height is set to 0.6 m, and tide correction is applied to Zcomputed

The "GREEN solution" from 0 to ~50 m: wZ=3
Get things straight when modeling by Green against Purple and Blue: this is wZ=3
The goal is to get a nice diagonal fit for the 0-50 m scatter of depth points

 Smoothing is OFF RMSE=2.24m (N=346299, 0-50m) 1 in 25 DTM grid points are investigated wZ=3 for 346299 of those points without smoothing Deglinting is ON Smoothing is OFF WLgreen   is at 550.9 nm Lswgreen  stays at 44.9 Lmgreen   stays at 0.5  Tide height is set to 0.6 m, and tide correction is applied to Zcomputed Smoothing is ON RMSE=1.80m (N=345339, 0-50m) 1 in 25 DTM grid points are investigated wZ=4 for 345339 of those points with smoothing Deglinting is ON Smoothing is OFF WLgreen   is at 550.9 nm Lswgreen  stays at 44.9 Lmgreen   stays at 0.5 Tide height is set to 0.6 m, and tide correction is applied to Zcomputed coral heads coral heads are deglinted and smart-smoothed correctly coral heads are so dark that yellow and red bands are extinct: they are modeled by the 3 bands case: wZ=3 their computed depth is commonly overestimated by several meters this shows in the above regression plot in the 4-10 m depth range I can't think of a way to counter that in 4SM

The "PAN solution"
unfortunately, I have not been given the PAN band

Profile RED
 4SM Blind test for a reference Blind test on profile_red: reference Red profile is LIDAR seatruth depth Black profile is Zcomputed by 4SM 4SM Final is much improved Profile_red: final Red profile is LIDAR seatruth depth Black profile is Zcomputed by 4SM Reduce RMSE The challenge is: how to get to final without the use of any seatuth data Reduce RMSE using 4SM As confirmed by this seatruth exercise, the following should help WL (this is outdated: see Hyperion at Fakarava) increase WLgreen away from mid-waveband decrease WLyellow away from mid-waveband keep  WLred at mid-waveband Lsw check on screen for radiance at extinction of shallow bottom tune according to depth results Turbid watch for extremely dark watercolumn corrected reflectances: they are likely to signal that Lsw should be increased, and mask out areas with locally turbid waters altogether Deglint apply deglinting, mask out non-deglinted bright-cloud pixels if at all possible Aliens mask out cloud/shadows manually mask out all alien pixels manually Smooth apply smart-smoothing