Optical calibration, bathymetry, water column correction and bottom typing of shallow marine areas, using passive remote sensing imageries

A 1584*1216 SPOT 1 image of Anaa atoll,
Tuamotu Archipelago, French Polynesia

The 4SM license cost for this image is 57 US$
Work done in 2005
return to 4SM Study Cases

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
I keep digging
until suitable data
become available


A very nice image indeed

clear skies, no wind, lots of photons




An excellent calibration, particularly for the Soil Line, thanks to extensive very dark dry marshes.

Jerlov's water type OII+0.8: waters are not very clear in this isolated water mass with no major pass.

Some water masses are locally less clear: they cause some falsely darker bottom reflectances at places.