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                    R E A D M E 

                    doc: Tue May 15 18:10:40 2012

                    (c) 2012 A.M. Thurnherr

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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

considerably, in particular

1) a much simpler gridding algorithm is used

2) no PPI editing is carried out

3) 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

README files:

[README]		This overview

[README.Install]	Installation instructions

[README.ProcessData]	A HowTo for obtaining shear, as well as relative

			and absolute velocity profiles from CTD/LADCP

			data

[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.

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".