4SM illustrations computed depth

No field data are needed!

	Remopte Sensing can be quite useful in inaccessible locations!!

	Remote sensing can be quite useful for very large scale projects! DTM at Caicos Bank, Bahamas 180 km accross This "combines" computed depths obtained 16 SLCOFF ETM images: clouds have "disappeared" and no-data stripes as well
	One band case can be quite useful in slightly murky waters Computed depth at Tarawa atoll Kiribati, Central Pacific SPOT XS image Making this was only possible because shallow bottoms deeper than 3-5 m are assumed to be very bright bottoms. This is a reasonable assumption, as the bottom is known to be littered with coral/halimedas sand/mud. Certain parts of the lagoon obviously have foul waters: this shows badly in this map, like in the SE end of the lagoon.
	Detail of the above map The use of the NIR band can provide very fine bathymetric features
	One band case can be quite useful in slightly murky waters Computed depth at Arcachon Inlet France SPOT XS image Making this was only possible because shallow bottoms deeper than 3-5 m are assumed to be fairly bright sandy bottoms. This is a reasonable assumption in this highly dynamic environment.

LEFT : potential error on computed depth RIGHT : computed depth	Potential error, alias "uncertainty" can be mapped along with computed depth Computed depth at Caicos Bank Bahamas Landsat TM image Right : computed depth in dm Left : image of sensitivity on computed depth, in dm This is a representation of the degree of uncertainty caused by the 8-bits quantization noise, i.e. by a +/- 0.5 DN uncertainty for all bands used.

	4SM can process all sorts of multispectral imageries AAHIS at Kaneohe Bay Oahu, Hawaii work done in 1998 image courtesy of Eric HOCHBERG

	CASI at Mahone Bay, Nova Scottia, Canada Shallow dark features are mapped to shallow depth, as expected here: <==Upper left BGR composite of raw data <==Lower left computed depths Accounting for water volume reflectance is key to this achievement
	TM at Geraldton, Western Australia Bright bare sand dunes stand a few meters above a very dark vegetated bottoms surrounding Accounting for water volume reflectance is key to this achievement

	Sand dunes at Prince Edward Island, Nova Scottia, Canada Using Jerlov's data to calibrate the diffuse attenuation coefficients 2K is a safe process in the St Laurent Estuary Remember: No field data was used for this calibration!

	CASI at Gezirat Reef, Red Sea <==watercolumn corrected <==computed depth