Quickbird at Shiraho Reef, Japan
image acquired July 2nd 2007, courtesy of Antoine COLLIN (23 december 2014)

4SM      on  a PAN-sharpenned        QUICKBIRD image,
and also on a GoogleEarth-derived QUICKBIRD image

0.5x0.6 m GoogleEarth-derived QB mosaic
no NIR band: WHY IS THAT?
would appear to have been pansharpenned using FuzeGo software

How can it be 0.6 m footprint?
The answer is:
by "positioning the virtual Google Earth eye at the proper altitude and geometry"
against a backdrop of a 0.6 m panchromatic image
0.5x0.6 m footprint
No NIR band   
NIR-based deglinting is impossible.
Lucky there is no adverse wind-generated sea surface clutter over the reef system.
This is a severe limitation of GE-derived images for shallow water work.
Dynamic range
This data fills the whole 0-255 dynamic range: this helps a lot
I used strictly the same mask into channel_4  already used in shirahoQBPS_20070702.pix

Optical calibration

Calibration diagram
  • The calibration data only samples the reef moat and crest: that's the 0-5 m depth range in BLUE, as the GREEN areas are excluded.
    • deeper than that, over the outer reef slope, deglinting would be absolutely necessary, but is impossible.
Noise/Dynamic range
GE image is much easier to calibrate, thanks to the wider dynamic range and lesser level of noise
Lsw and Lw
The main features of a satisfactory calibration are available
  • it requires a seasonned practioner though
  • the estimation of deep water reflectance Lsw and water volume reflectance Lw is more a question of experience and logic with this image...


GE-derived image exhibits a very weird bi-dimensional histogram
Blue vs Red raw radiances here.
This has nothing to do with Mother Nature!!
Do you have a clue?
Is it caused by 0-255 scaling at GoogleEarth? Or their pan-sharpenning process?

Water column correction
raw data
Please note : linear enhancement
water column corrected data

Please note : enhancement is identical
to that of the raw TCC
GE retrieved depth



Créer un site
Créer un site