Syntax_WL
Syntax_dWL
Syntax_cWL

Specify the WaveLength in nanometers for all spectral bands in the image
HowTo WaveLengths

As of 2016, see 4SM 2K
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Syntax_WL
• HYPERSPECTRAL: all wavelengths for narrow hyperspectral bands are set at mid-waveband
• spectral K values are conveniently interpolated at mid waveband
• but a -dK... parameter must be applied in the 575 to 600 nm range: this is very sensitive
• MULTISPECTRAL: all wavelengths for wide multispectral bands are set at mid-waveband
• but a -dK... parameter must be applied in the 575 to 600 nm range: this is very sensitive

Specify the WaveLength in nanometers for all spectral bands in the image
This is of no interest when using SPOT images:
by default, WL for SPOT images are set at 550, 650 and 850 nm
HowTo WaveLengths

 We are talking wavelength in water Quotation from Kirk, page 5   The refractive index of vacuum is 1 by definition.  The refractive index of air is 1.00028.  The refractive index of water may with sufficient accuracy be regarded as equal to 1.33 for all natural waters.  Assuming that the velocity of light in vacuum is 300,000 km/s, the velocity in water is therefore about 225,000 km/s.  The frequency of the radiation remains the same in water,  but the wavelength diminishes in proportion of the decrease in velocity.  WL=c/f with f=frequency and c=velocity of light Any idea what to do with this regarding shallow water modeling? like: forC WL[c]=WL[c]*225000/300000. Should I do that in 4SM? Apparently NO,  otherwise Jerlov would have made a strong statement about it.
Wavelengths in  nanometers may be specified in one of two ways:
• either : -WL/0490.5/550.8/650.2/850.4.... at mid waveband
• or.......: -WLm and WLM: the alternative is to specify the waveband
• -WLm/0452/0529/0624/0776.....Wavelength_Minimum for waveband
• -WLM/0492/0595/0675/0820.....Wavelength_Maximum for waveband
• ==> WL=WLmin+(WLmax-WLmin)/2
DEFAULTS
• For SPOT XS, wavelengths of 550, 650 and 850 nm are provided internally by default
• For TM, ETM, OLI, ALI, IKONOS and WV02:  WLmin and WLmax are provided by default

 Outdated: As of 2016, WL is set at mid-wavelength: please see 4SM 2K The "effective wavelength" refers to the color of the sea, considering the visible part of the solar spectrum Similarly, we can speak of the "effective wavelength" of a given waveband, as the result of the integration of all radiances captured by the sensor over the span of this waveband Subject to the particular shape of the diffuse attenuation curve for the water type considered, and to the particular waveband considered the "effective wavelength" for that waveband may concievably be offset from the mid-waveband position this apparently is the case for the Green waveband of multispectral imageries The problem of Wavelength versus Response Curve of Waveband In 4SM, wavelengths have to be specified in nanometers This is necessary in order to use the KiKj ratio observed in the image for deriving spectral K values using Jerlov's data, as we need a seed value for K Wavebands are characterized by their specific response curve One discrete wavelength must be specified to represent that response curve: this is not trivial The problem   Under the "BPL assumption"   in 4SM , i.e. clean homogeneous brightest bottom substrate is present at various depths, if at all as isolated patches, and waters are homogeneous over the study area once satisfied that a consistent set of Ki/Kj ratios among all pairs of bands has been derived from the image data, and because next 4SM accesses Jerlov's data in order to derive spectral K values in units of m-1  in the visible range beware though that Jerlov's data  refers explicitly to clear skies, sun high in the sky we need a specific operational wavelength for each spectral waveband: this is a problem with wideband multispectral imageries with all imageries in the 575-600 nm region of Jerlov's classification of marine waters These questions are under constant scrutiny, and warrant careful R&D detail is wanted in the 575-600 nm range of Jerlov's data more careful seatruthing is wanted with all imageries 4SM computed depths must be multiplied by a final depth correcting factor How do we choose an operational wavelength from a response curve? Specific benchmark study cases must be arranged, using bright imageries over extensive homogeneous bright/clean sandy/oozy (or maybe ice?) very gently sloping bottoms in clear marine/lake waters, with suitable seatruth. As of mid-2014 and after considerable efforts to see through All wavelengths are set at mid-waveband Using Ki/Kj ratio observed for bands i and j, all spectral K values are interpolated at mid waveband for all visible bands a -dK... commandline argument is used to tune spectral K - other than Ki and Kj - in order to achieve a strict fit with observed BPL pixels in the optical calibration plots dK is set to 0 in the Blue/Green and Red ranges a good fit must be achieved/observed dK is commonly set to some slightly negative value in the 575 to 600 nm range so as to achieve a good fit :  K=K+dK this practice is derived from consistent evidence when using hyperspectral data anyway     FinalDepth=coefZ * RetrievedDepth - Htide with coefZ and Htide to be derived from some seatruth evidence todate, all seatruth on hyperspectral images yielded coefZ=1.00 for all bands