• Antelope Release 5.5 Mac OS X 10.8.5 2015-04-21

 

NAME

setdne - sets dnorth and deast fields in a css3.0 database site table

SYNOPSIS

setdne db refsta

SUPPORT


Contributed code: NO BRTT support.
THIS PIECE OF SOFTWARE WAS CONTRIBUTED BY THE ANTELOPE USER COMMUNITY. BRTT DISCLAIMS ALL OWNERSHIP, LIABILITY, AND SUPPORT FOR THIS PIECE OF SOFTWARE.

FOR HELP WITH THIS PIECE OF SOFTWARE, PLEASE CONTACT THE CONTRIBUTING AUTHOR.

DESCRIPTION

In array processing the dnorth and deast fields of a css3.0 database are required to compute plane wave moveout corrections. Modern broadband networks/arrays of stations often don't fill in these fields as when the aperture is large the use of dnorth and deast is usually viewed as a bad approximation of geometry. However, array processing routines still require these fields because the full spherical geometry calculation is cumbersome and, in fact, requires an assumed origin before it can be done correctly. Thus, some programs like dbap and mwap need this field to be set even if it is an approximation. mwap actually computes plane wave statics that correct the moveout for wavefront curvature but still needs dnorth and deast to simplify the moveout computation.

This program uses a simple approximation in using the dist(3) function of Datascope to compute a great circle path distance and bearing from the specified origin. It then uses a simple trigonometric conversion to convert these to distance north and distance east in kilometers.

COMMAND LINE ARGUMENTS

FILES

Only the site table of the named database is accessed.

DIAGNOSTICS

Should be self explanatory.

SEE ALSO

mwap(1), dist(3)

BUGS AND CAVEATS

The appoximation of dnorth and deast gets progressively worse with array aperture. The authors experience is that the moveout computed for teleseismic P waves is accurate to better than 0.1 s for an array with an aperture of about 100 km. This depends on epicentral distance as well as total aperture. Strangely enough the algorithm used should work even if an array spans the pole.

AUTHOR

Gary L. Pavlis
Antelope User Group Contributed Software
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