NAME

       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.

BEWARE

       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  gener-
              ated  between  them.   The  crossover-structure contains all the
              information for one COE, that is lat, lon, time along leg values
              of  gravity,  magnetics, and bathymetry at the cross-over point,
              the heading of track #1, and the heading of track #2.  See  pro-
              gram 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 description of record format.

SEE ALSO

       gmt(GMTMANSECTION), x_system(GMTMANSECTION)

REFERENCES

       Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers