CATS : GPS coordinate time series analysis software -- by Simon D. P. Williams
The technical paper which describes this code is published in
GPS Solutions, Volume 12, Number 2, March 2008, pages 147-153,
"CATS : GPS coordinate time series analysis software"
by Simon D. P. Williams
Proudman Oceanographic Laboratory, 6 Brownlow Street, Liverpool, L3 5DA, UK
sdwil@pol.ac.uk
Abstract
Over the last 10 years, several papers have established that daily estimates of
GPS coordinates are temporally correlated and it is therefore incorrect to
assume that the observations are independent when estimating parameters
from them. A direct consequence of this assumption is the over-optimistic
estimation of the parameter uncertainties. Perhaps the perceived
computational burden or the lack of suitable software for time series
analysis has resulted in many heuristic methods being proposed in the
scientific literature for estimating these uncertainties. We present a
standalone C program, CATS, developed to study and compare stochastic
noise processes in continuous GPS coordinate time series and, as a
consequence, assign realistic uncertainties to parameters derived from
them. The name originally stood for Create and Analyse Time Series.
Although the name has survived, the creation aspect of the software
has, after several versions, been abandoned. The implementation of the
method is briefly described to aid understanding and an example of typical
input, usage, output and the available stochastic noise models are given.
CATS is available here:
Tar/Zip file with CATS software, examples, and documentation. (cats_v3.1.2.tar.gz)
Installation instructions for CATS are available here:
Link to installation instructions. (http://web.mit.edu/mfloyd/www/computing/cats/)
Future
CATS will continue to evolve with time. There is already a development
version (4.0.0) available that is, in places, very different to this
stable version. The following are the most obvious changes: a new program,
CHEETAH, that uses the fast error analysis method described in
Bos et al. (2007); incorporation of the atlas routines; capability for
threading; the ability to read a file containing the functional model so
that more complex functions can be used; estimating the uncertainties of
all the estimated parameters (in CHEETAH).
Links
CATS http://www.pol.ac.uk/home/staff/?user=WillSimoCats
ATLAS http://www.netlib.org/atlas
BLAS http://www.netlib.org/blas
CLAPACK http://www.netlib.org/lapack
Portland compiler http://www.pgroup.com
GCC http://gcc.gnu.org/
POL http://www.pol.ac.uk
PSMSL http://www.pol.ac.uk/psmsl
References
Bos MS, Fernandes RMS, Williams SDP, Bastos L (2007) Fast error analysis
of continuous GPS observations, J Geod doi:10.1007/s00190-007-0165-x
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