| Date: | 2005-10-25 00:09:00 | |
| Sender: | Jim Ray <Jim Ray (NGS 301-713-2850 x112) <jimr@ngs.noaa.gov>> | |
| Subject: | [SLR-Mail] No. 1401: OTL routine available for testing | |
| Author: | Jim Ray | |
| Content: | ******************************************************************************** SLR Electronic Mail 2005-10-25 00:09:00 UTC Message No. 1401 ******************************************************************************** Author: Jim Ray Subject: OTL routine available for testing Dear Analysis Colleagues, As you might have noticed, the IERS Conventions (2003) are highly ambiguous on many points concerning implementation of a model for ocean tidal loading displacments. No routine was provided to compute the displacements and it is doubtful that any international standard can be said to exist for this effect currently. Fortunately, Duncan Agnew (UCSD) has provided a program of his to compute the ocean tidal loading displacements for a site given the usual amp & phase values as generated by the Bos-Scherneck website (in BLQ format). Duncan´s implementation considers a total of 119 constituent tides whose amps & phases are found by spline interpolation of the tidal admittance based on the 11 main tides. He says this gives a precision of about 0.1% (which is far better than that of the tidal models, the Earth model information, or the displacement convolution calculation). As part of the process to evaluate this routine for possible inclusion in the future IERS Conventions, it would be very helpful if several groups could test it against any others regarded as high-accuracy implementations. A copy of Duncan´s code can be obtained at: ftp://ftp.ngs.noaa.gov/dist/jimr/hardisp.f Please let me know if you encounter any problems or if you have any questions. Your feedback is needed to resolve this important issue. Thanks for your help. And special thanks to Duncan. --Jim Run without imputs, the routine hardisp.f returns: -------------------------------------------------------------------------- Usage: hardisp yr [d-of-yr | month day] hr min sec num samp Where the UTC date given is the time of the first term output num is the number of output epochs to be written out samp is the sample interval (seconds) The harmonics file (amp and phase of displacement) is read from standard input in the BLQ format used by Scherneck and Bos Results are written to standard output (units = m): dU dS dW using format: 3F13.5 -------------------------------------------------------------------------- From: Jim Ray ”(NGS” 301-713-2850 ”x112)” ******************************************************************************** |