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7.4. Backscatter Data. The format for backscatter data (measured, for example, by a
HOBILabs HydroScat-6 or WETLabs bb-9 instrument) is similar to that for a and c data,
except that the data records 12 and onward now contain the depth and backscatter coefficient
values (rather than a and c values). See file HE52\data\examples\HydroScat6.txt for an
example data file. The HE52 data processing, e.g., interpolating or extrapolating in depth
and wavelength, is similar to that just described for ac-9 data.
Note. There does not seem to be any convention on removing pure water values when
processing HydroScat-6, bb-9 or similar backscatter data (because the scattering contribution
by pure water is usually a small contribution to the total, except in very clean water). The
UI therefore requires you to indicate whether or not your file of backscatter data has had
pure-water backscatter removed. HE52 will then know whether or not to subtract pure-water
backscatter from your data in order to determine the particle backscatter fraction for use in
defining a Fournier-Forand phase function.
7.5. Bottom Reflectance Data. As explained in §3.1, for finite-depth water a physical
bottom is placed at depth zmax. Light and Water Eq. (4.81) then gives the needed bidirectional radiance reflectance of the physical bottom. The irradiance reflectance for a
physical bottom is most easily communicated to HE52 by placing measured wavelengthdependent reflectances on a file in the HE52 standard format for bottom reflectances and then
giving the file name to the UI. The format for reflectance data is the same as for
concentration-specific data, except that the data records are now pairs of wavelength and
reflectance values, rather than wavelength and concentration-specific a or b values. See any
of the files in directory HE52\data\botmrefl for an example of such a data file.
For bottom reflectances, you can add your data file to the list of files in the UI pull-down
menu for bottom reflectances. This is done as follows:
•
Place the wavelength vs. reflectance data on a file with the HE52 standard format seen
in the file HE52\examples\template\Rbottom.txt.
•
Give the file a meaningful name, e.g. Rmud.txt, and place the file in the
HE52\data\botmrefl directory.
•
Use a text editor (such as Notepad or Wordpad) to add the name of your file to the
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