Baytap08: A Program for Analyzing Tidal Data

Baytap08 is a modified version of the Bayesian Tidal Analysis Program - Grouping Model program developed by M. Ishiguro, Y. Tamura, T. Sato and M. Ooe, which is known as BAYTAP-G. This program uses a Bayesian modeling procedure (based on work by H. Akaike) to analyze time series that contain both tidal and other variations: this includes tidal gravity, ocean tides, and strain and tilt data. Baytap08 is basically the same program, but has been modified (by D. C. Agnew) to make it somewhat easier to use than the original.

The program can:


Estimate tidal amplitudes and phases.


Determine a long-period component of the data (the ‘‘drift’’ or ‘‘trend’’) and calculate its power spectrum using an ARMA model.


Include in its modeling the effect of partially correlated data, such as atmospheric pressure.


Interpolate missing data and estimate sizes of known offsets.


Perform a rough search for abnormal data.

The figure below shows the result of analyzing some strainmeter data (from a quartz-bar instrument at the Esashi Observatory. The original data is decomposed into a tidal part, a part correlated with the local air pressure, a white-noise part (the ‘‘residual’’) and a lower-frequency part (the ‘‘drift’’): the last two are the nontidal signal.

Baytap08 is a stand-alone program written in Fortran-77. The only system-dependent features are calls to the Unix functions argc{} and getarg to get arguments from the command line, and fdate to get the current time (for timestamping the output file). On most systems the program can simply be compiled with a Fortran compiler, and the resulting executable run directly.

The download package is a gzipped tarfile that contains the source code, the Baytap08 manual (in PDF) and several examples, both to show how the program can be run, and to allow checking of it after it is installed.

For questions, contact dagnew dot at-sign dot ucsd dot edu

Since the intitial distribution, the following changes have been made:

30 Jan 2009: line 1664 changed from call getarg(2+i,dum) to call getarg(2+i,dum) (thanks to Luca Crescentini for spotting this).

If you make use of Baytap08 in producing published work, please cite the main paper on BAYTAP-G, and also the Baytap08 manual; since the latter is at a stable URL, it may be referenced in, for example, AGU journals.

Image esashi.png