A series of four ETM images of Zirku Island, Abu Dabi
Work done in July 2009.  Co-registered images provided by FUGRO-NPA

this shows that there is moderate water penetration through the year in these  ETM images
although 16 bits data imageries should allow for somewhat deeper penetrations in these waters.

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1 - NO NEED for field data, nor for atmospheric correction
2 - this is demonstrated in this website, using a variety of hyper/multi spectral data
 
Requirements are
1 - homogeneous water body and atmosphere
2 - some coverage of optically deep water
3 - some coverage of dry land
 
Problems are
1 - the precision on estimated depth is found wanting, because the noise-equivalent change in radiance  of accessible data is too high for shallow water column correction work 
2 - radiance data should be preprocessed by the provider at level 1 in order to improve S/N ratio
3 - exponential decay: the deeper/darker the bottom, the poorer the performances
 
So
I keep digging
until suitable data
become available
 




AutoCalibration now works to satisfaction in many occasions,
although calibrations still need to be fine-tuned manually.

 

Zirku20090701.zip (18 MB): I have uploaded my Zirku work directory as of July 2nd, hoping you execute the scripts, as they are.
 
september 2001 october 2001 january 2002 july 2002

Most of what we see is probably the wandering and buildup of turbid plumes: they were building fancy artificial islands off Dubai at the time.

Thresholds would need to be raised at some locations.

The atmosphere in these four images seems to be fairly nice, apart from the eastern part of the july image.

Optical properties of the waters do not seem to vary that much through the year: maximum bottom detection down to ~15 meters over bright bottoms.

For maping land habitats, an image in spring is probably wanted.

There is definitevely a potential for bottom typing

september 2001 october 2001 january 2002 july 2002

July 2002     


ETM2002-07-03_rawCC

July 2002

Raw image, true color composite

 

July 2002     


ETM2002-07-03_Z250

July 2002

Computed depth

see legend for computed depth

ETM2002-07-03_B
July 2002

Average bottom reflectance      

ETM2002-07-03_LBSnormalized
July 2002

image LBS "normalized"

  • This image is intended as a contribution towards habitat mapping efforts by more established procedures
   

January 2002 

ETM2002-01-24_rawCC
January 2002

Raw image, true color composite

January 2002   

ETM2002-01-24_Z250
January 2002

Computed depth

see legend for computed depth

ETM2002-01-24_B January 2002

Average bottom reflectance      

 

 

ETM2002-07-03_LBSnormalizedJanuary 2002

image LBS "normalized"

  • This image is intended as a contribution towards habitat mapping efforts by more established procedures

 

   

October 2001 

ETM2001-10-04_rawCC
October 2001

Raw image, true color composite

October 2001 

ETM2001-10-04_Z250
October 2001

Computed depth

see legend for computed depth

ETM2001-10-044_B
October 2001

Average bottom reflectance

ETM2001-10-04_LBSnormalized
October 2001

image LBS "normalized"

  • This image is intended as a contribution towards habitat mapping efforts by more established procedures
   
September 2001 

ETM2001-10-04_rawCC
September 2001

Raw image, true color composite

 

September 2001 

ETM2001-09-18_Z250
September 2001

Computed depth

see legend for computed depth

 

ETM2001-09-18_B
September 2001

Average bottom reflectance

 


ETM2001-09-18_LBSnormalized
September 2001

image LBS "normalized"

  • This image is intended as a contribution towards habitat mapping efforts by more established procedures

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