NIR band at 842 nm
- NIR may not be used for deglinting
- all NIR bands are affected
shall be used for deglinting
- see that the lowest radiance is located in the NorthEastern part of this scene
Blue band 7 at 476 nm raw
- It is quite clear here that a body of very clear waters sweeps Northwards from SouthEast
- We have to remember here that very clear waters exhibit strong water volume reflectance in the Blue region of the solar spectrum
band 2 at 418 nm raw
- Waters on the Mayaguez shelf are under influence of coastal waters which spill over and northwards
- Such waters would exhibit lower water volume reflectance in the Blue region
- superb image, hardly any glint
- see that the lowest radiances are located in the NorthEastern part of this scene
- note the swirl of turbid waters oozing away from the city of Mayaguez
- note a body of slightly turbid southern waters sweeping northwards
- See that areas at depths 10-20 m along the coastline in the LIDAR image often exhibit significant radiance in the deglinted red band.
- This cannot be bottom detection, but rather reveals turbidity in the yellow-red range,
- particularly at La Parguera.
This explains and justifies the details
of the optical calibration below.
RED band at 648 nm, deglinted/smoothed
- LIDAR data shows that most of these areas at depths 10-20 m along the coastline should be optically deep for this deglinted red band.
- see zoom over La Parguera where the bottom cannot be detected deeper than ~4-6 m over the innermost shelf.
- Therefore, what we see is mostly caused by turbidity in the yellow-red range,
|Estimating the deep water reflectance Lsw |
is going to be an impossible task
- unless maybe it is done on a local basis
- using some specific tools in 4SM
- with some knowledge of the bathymetry, like the LIDAR coverage
Blue band 7 at 476 nm, deglinted
- Profile Green is shown
- Turquoise polygon: area for estimating deep water radiance is shown
- Bands at 419, 442, 476, 545 and 694 nm are shown
- Deglinting: band 26 at 694 nm is used for deglinting
- Decline: a strong decline in water volume reflectance is observed from West to East
- Deep waters: between waypoints B1 and B2 of section B, a small area of deep water radiance is sampled. This area was located after close study of the LIDAR data
- Coastal waters: blue radiances decline abruptly as the profiles reach to the surrounding of Mayaguez city
- there is an active point source of turbid waters there