## 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