x_init (1gmt)

x_init -I

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, magnetics, 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 description of record format.

GMT(1), x_system(1)

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