CASI image of Blue Lagoon, Rangiroa atoll, French Polynesia

Image courtesy of HDI , collected at low altitude in 1998 from the small seaplane Golden Eye from vessel Golden Shadow.
These are 10 bands images; pixel resolution is1 meter.
Flight #2 is 7 km long 4SM license cost is 1050 Euros
Flight #4 is 9 km long 4SM license cost is 1169 Euros
-WL0435/462/490/525/547/577/654/666/680/850 in nanometers
Unfortunately, this dataset lacks bands in the red-yellow region of the solar spectrum.
This does not help for an optimal deglinting, and also for calibrating/modeling!
A difficult case, interpretation is questionable.

Work done in 2005


SPOT XS image_RGB at Blue_Lagoon
SPOT XS, image_Z in grey-shades at Blue_Lagoon
One-band case: deeper than 4-6 m, dark bottomed areas are mapped with depths in great excess:
this explains the apparent "moat" around the coral growths.


  Casi flights #2 & 4 false color composites

Casi flights #2 & 4 false color composites, histeq enhancement
Please notice numerous -and ominous- cloud shadows,
and also skyglint -or is it cloudglint, at the far right?
Deglinting quite efficient though: see below.


Casi flights #2 & 4 image_Z

Casi flights #2 & 4 image_B

Please refer to Rangiroa_ETM: this dark-bottomed area is present also in the ETM image
A difficult case, interpretation is questionable.
It is reassuring to see bright bottomss reappearing at depth inside the main lagoon in Flight #4!


Casi flights #2 & 4 Color composite of normalized bottom reflectance, 490-557-645 nm

Flight #2: a close-up view of the shadowed/glinted area
These shadows/glint, combined with complex bottom topography/history,
make for a challenging interpretation!


Jerlov's water type inside the atoll lagoon is OII+0.15
waters are very clear

Flight #2: false color composite, 
histeq enhancement

 Flight #2: image_B
The "sandy plain" at depth is mapped 
in excess of 30 m at the base of the outer reef slope

 Flight #2: image_Z

Local "spurr and groove" morphology appears
to be the result of erosion of the reef outer slope:
this cause the reef rim to move back by approx 20 m

Many coral growths grace most of theBlue_Lagoon floor, except inside the three basins
Flight #2: normalized bottom reflectance

3D views of Blue_Lagoon flight #2
(processed in 1999)

  • 3D_1: Blue Lagoon

  • 3D_2: towards Deep Lagoon



  • 3D_1: Deep Lagoon

  • 3D_2: Deep Lagoon



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