GGPSA

This program can be used for automatic filtering and differentiation using
the power spectrum assessment method. The sequence can briefly be described
as:

The cut-off frequency is calculated in the frequency domain based on some
parameters. The signal is extrapolated using the linear prediction method.
The extrapolated signal is filtered using a N order Butterworth digital
filter. Higher derivatives are calcualted using first order finite
differences.

The program would illustrate the power spectrum of the signal, the
extrapolated signal and the higher derivatives. In case you have a reference
acceleration signal you can see this also with the filtered acceleration.

This is not a black box program, as there is not a single automatic
filtering technique appropriate for all signals. All the filtering
parameters are open and can be adjusted. It is suggested to initially
experiment with some signals of the same movements ,and as long as you
are happy you can keep the same parameters for all the rest. Some of the
parameters are:sampling frequency, number of extrapolated points, order
of filter, etc.

There is no limitation on the number of columns (signals) and the number
of data -as far as I know- that each input file can have.

The input file must have only numbers (no headings). The output of the
program comes as three files, one for each derivative: OUT0.txt, OUT1.txt,
OUT2.txt


DISCLAIMER
Even though GGPSA has been tested and used in the past, nothing is for
granted. The use of this software is at your own risk. 


USAGE POLICIES
GGPSA can be used free of charge. The author however request proper credit
(citation or acknowledgments), if GGPSA is used in publications or in any
other forms of communication. 


SUPPORT
GGPSA is not supported, however, if you find errors, have suggestions,
contact Giannis Giakas (ggiakas@fs1.ho.man.ac.uk).


UPDATES
You can always download the latest version of this software via my home page
http://www.hop.man.ac.uk/geri/giannis/
Section --> Software --> GGPSA

REFERENCES
Giakas G (1999). Automatic data filtering in Sports Biomechanics:
Filtering Solutions. Data Filtering Workshop. XVII International Symposium
of Biomechanics in Sports. Organised by International Society of
Biomechanics in Sports. Perth, Australia.

Giakas G, V Baltzopoulos and R M Bartlett (1998). Improved extrapolation
techniques in recursive digital filtering: a comparison of least squares
and prediction. Journal of Biomechanics 31(1), 87-91.

Giakas G and V Baltzopoulos (1997). A comparison of automatic filtering
techniques applied to biomechanical walking data. Journal of Biomechanics
30(8), 847-850.