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R E A D M E
doc: Tue May 15 18:10:40 2012
dlm: Thu May 7 13:02:10 2015
(c) 2012 A.M. Thurnherr
uE-Info: 78 38 NIL 0 0 72 3 2 8 NIL ofnI
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This directory contains a re-implementation of the shear method for
LADCP velocity processing, written and copyrighted by A.M. Thurnherr;
the appropriate reference is Thurnherr [J. Tech., 2012, DOI:
10.1175/JTECH-D-11-00158.1].
Essentially, the software is a re-implementation of the shear method
for LADCP velocity processing. Data editing borrows heavily from Eric
Firing's c/Matlab/perl code that was used extensively during the later
stages of the WOCE. However, some of the algorithms were simplified.
In particular,
1) a much simpler gridding algorithm is used, and
2) there is no support for using GPS data for velocity referencing.
In regions of good scattering, the shear output from this software when
applied to data collected with current RDI instruments can be expected
to be very similar to the corresponding output from Eric's code with
PPI editing disabled, except that the high wavenumbers are considerably
less damped in this re-implementation (see Thurnherr [2012]). In
regions of bad scattering, this software simply leaves gaps in the
shear profiles whereas Eric's code uses a low-pass filtered version of
the shear to interpolate across gaps in the high-resolution profiles.
While this software can be used to integrate LADCP shear data
vertically to calculate velocity profiles, velocity referencing must be
done with a single partial-depth velocity profile (e.g. from BT or
SADCP data). While the resulting profiles of absolute ocean velocity
are useful and very easily obtainable "first guesses", much better
profiles can typically be obtained by applying multiple simultaneous
referencing constraints with the the Shear Inversion method [Thurnherr,
J. Tech., 2010; DOI: 10.1175/2010JTECHO708.1].
THIS SOFTWARE CAN BE FREELY USED AND COPIED FOR EDUCATIONAL OR OTHER
NOT-FOR-PROFIT PURPOSES.
Currently, limited documentation is provided in the following set of
files:
[README] This overview
[README.Install] Software installation instructions
[README.ProcessData] A HowTo for obtaining shear, as well as relative
and absolute velocity profiles from CTD/LADCP
data
[README.TimeLagging] The most common problem encountered during
processing of CTD/LADCP data with this software
is failure of the CTD/LADCP time-lagging
routine. This Readme provides additional
information and tips for how to solve
time-lagging problems.
[README.Output] A description of the various files produced by
this software
[README.PostEdit] A HowTo for post-editing shear with different
statistics, e.g. to filter data collected with
the ADCP very close to the surface, where the
ship's magnetic field can degrade the compass
data. Also describes how the shear data can be
gridded with statistics other than simple
arithmetic mean.
[README.YoYo] Notes on how to process data from "non-standard"
casts, such as yoyo's and tow-yo's.
[Slocum-Explorer_HowTo.pdf] Cookbook describing how to process
velocity data collected with Explorer ADCPs on
Slocum gliders
NOTE: Most of the source files use a hard tab of 4 spaces, i.e. they
can be viewed correctly, e.g. with "less -x4".