x_init

       x_init - Initialization of Cross-Over Data Bases.

SYNOPSIS

       x_init -I

DESCRIPTION

       The purpose of x_init is to create two key files that will
       be holding all the  cross-over  information  for  all  the
       cruises  tested.  These  files  are  called  xx_base.b and
       xx_legs.b, and they will contain data for each  cross-over
       and totals for each leg, respectively.  x_init will create
       these two files in the current directory,  and  write  out
       the  fileheader  with a 1 as the next record number in the
       case of xx_base.b. NB! Any previous files  with  the  same
       names in the current directory will be erased, so use with
       caution.

       -I     Must be present form initialization to take effect.

Both files are binary and have fixed record lengths. The formats

       of the files are as follows:
       xx_base.b:
                      Record length = 40 bytes.
                      Rec # 1: fileheader
                      Rec # 2: pairheader
                      Next n recs: crossover-structure
                      Rec # n+3: pairheader etc.
              The fileheader is a 40 byte character string  where
              the last 10 bytes contains the record number of the
              last record in the file.  The pairheader  is  a  40
              byte  character  string which contains the names of
              the two legs in question and  the  number  of  COEs
              generated  between  them.   The crossover-structure
              contains all the information for one COE,  that  is
              lat, lon, time along leg values of gravity, magnet­
              ics, and bathymetry at the  cross-over  point,  the
              heading  of  track #1, and the heading of track #2.
              See program listing for more  details  on  formats.
              The  file  is  sequential  in  that  new  data  are
              appended at the end of the file.

       xx_legs.b:
                      Record length = 204 bytes.

              Each record contains the complete  information  for
              each  leg  that has been checked. The leg-structure
              contains fields like  year  of  cruise,  number  of
              internal/external  COEs for gravity, magnetics, and
              bathymetry, their means  and  standard  deviations,
              and the best fitting regression lines, i.e. the dc-
              shifts and drift-rates computed from the time/error
              data  points.  See  program  listing  for  complete

       gmt(l), x_system(l)

REFERENCES

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