• Antelope Release 5.5 Linux 2.6.32-220.el6.x86_64 2015-04-21

 

NAME

dbproject_covariance- compute confidence-ellipse from covariance matrix

SYNOPSIS

dbproject_covariance [-v] [-c conf] dbname

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

dbproject_covariance reads the covariance matrix out of the origerr table of a CSS3.0 or related database. A confidence ellipse is then calculated (smajax, sminax, and strike, as well as sdepth and stime) based on a Chi-squared model and the specified confidence level. If no confidence level is specified, dbproject_covariance uses 0.683, i.e. 1 sigma. If any of smajax, sminax, strike, sdepth, and stime are non-null, the origerr row is skipped. If any of the covariance-matrix elements are null, the origerr row is skipped. dbproject_covariance also uses ndef and dtype out of the origin table to determine the number of degrees of freedom of the solution. When the projected confidence region has been computed, the origerr table is updated with the new smajax, sminax, sdepth, stime, strike, and conf values.

OPTIONS

EXAMPLE


% dbproject_covariance -v testdb
orid 1  ndef 41 dtype f conf 0.683      chi2 40.54
        smajax  0.95 sminax  0.55       strike 149.5
        sdepth  3.61    stime  0.30
orid 2  ndef 56 dtype f conf 0.683      chi2 56.31
        smajax  3.53 sminax  2.24       strike  18.9
        sdepth  6.30    stime  0.53
orid 3  ndef 21 dtype f conf 0.683      chi2 19.20
        smajax  9.10 sminax  4.01       strike 114.0
        sdepth  9.38    stime  0.93
orid 4  ndef 60 dtype f conf 0.683      chi2 60.49
        smajax  0.64 sminax  0.58       strike  98.6
        sdepth  5.33    stime  0.33
orid 5  ndef 41 dtype f conf 0.683      chi2 40.54
        smajax  1.59 sminax  0.60       strike 121.6
        sdepth  2.87    stime  0.20
% 

SEE ALSO

dbgenloc(1)

BUGS AND CAVEATS

The number of degrees of freedom is based on ndef and dtype. If array data are included (azimuth and slowness information in addition to arrival-time), more than one degree of freedom is added per incoming phase, so using the number of defining phases is not exact. To do this properly, the timedef, azdef, and slodef fields would have to be examined in the assoc table. This has not been done in the current program. There is another way to calculate the confidence level, namely with an F-distribution statistical model rather than the chi-squared. In principle this would be possible however it would probably require a recomputation of residuals from the assoc table.

AUTHOR

Kent Lindquist
Antelope User Group Contributed Software
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