NAME

     X_UPDATE - Archiving of Cross-Over Information


SYNOPSIS

     x_update cross-overfile [ -Xxbase ] [ -Llegbase ] [ -V  ]  [
     -Wmax ]


DESCRIPTION

     x_update reads the ASCII file produced by x_over and  writes
     the   information   to  the  database  files  xx_base.b  and
     xx_legs.b (unless other filenames are specified on the  com-
     mand  line)  using  a  compact,  binary  format. The options
     recognized are:

     -X   Indicate alternate xx_base.b file.

     -L   Indicate alternate xx_legs.b file.

     -V   Verbose. Reports the pair currently being processed.

     -W   Prints a warning if the number of COEs generated by any
          pair of legs exceed max.


     For security reasons the  xx_legs.b  are  first  renamed  to
     xx_legs.b_old, to prevent loss of information if a black-out
     or system crash should  occur  during  writing  of  the  new
     xx_legs.b  file. It is recommended that the old file is left
     on the disk in case of other disasters. Note  that  x_update
     does  not  check  if  a  pair  of  legs already exist in the
     xx_base.b file. It is the user's  responsibility  to  ensure
     that  duplication of information does not occur. Should some
     pairs already in the database need to be re-examined,   then
     run x_remove which will wipe out all traces of the specified
     cruises from the xsystem data base files. Now  we  can  pass
     the  pairs  that  need  to be redone through x_over/x_update
     again.


SEE ALSO

     gmt(l), x_system(l)


REFERENCES

     Wessel, P. XOVER: A  Cross-over  Error  Detector  for  Track
     Data, Computers & Geosciences, 15, 333-346.