X_UPDATE(1gmt) Generic Mapping Tools X_UPDATE(1gmt)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 command 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 Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. Reports the pair currently being pro-
cessed.
-W Prints a warning if the number of COEs generated by any pair of legs exceed max.
BEWARE
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 duplica-
tion 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 x_system data base files. Now we can pass the pairs that need to be redone through
x_over/x_update again.
SEE ALSO GMT(1), x_system(1)REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers & Geosciences, 15, 333-346.
GMT 4.5.7 15 Jul 2011 X_UPDATE(1gmt)
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X_INIT(1gmt) Generic Mapping Tools X_INIT(1gmt)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 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 com-
plete description of record format.
SEE ALSO GMT(1), x_system(1)REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers & Geosciences, 15, 333-346.
GMT 4.5.7 15 Jul 2011 X_INIT(1gmt)