1X_INIT(1) Generic Mapping Tools X_INIT(1)
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6 x_init - Initialization of Cross-Over Data Bases.
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9 x_init -I
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12 The purpose of x_init is to create two key files that will be holding
13 all the cross-over information for all the cruises tested. These files
14 are called xx_base.b and xx_legs.b, and they will contain data for each
15 cross-over and totals for each leg, respectively. x_init will create
16 these two files in the current directory, and write out the fileheader
17 with a 1 as the next record number in the case of xx_base.b. NB! Any
18 previous files with the same names in the current directory will be
19 erased, so use with caution.
20 -I Must be present form initialization to take effect.
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24 Both files are binary and have fixed record lengths. The formats of the
25 files are as follows:
26 xx_base.b:
28 Record length = 40 bytes.
29 Rec # 1: fileheader
30 Rec # 2: pairheader
31 Next n recs: crossover-structure
32 Rec # n+3: pairheader etc.
33 The fileheader is a 40 byte character string where the last 10
34 bytes contains the record number of the last record in the file.
35 The pairheader is a 40 byte character string which contains the
36 names of the two legs in question and the number of COEs gener‐
37 ated between them. The crossover-structure contains all the
38 information for one COE, that is lat, lon, time along leg values
39 of gravity, magnetics, and bathymetry at the cross-over point,
40 the heading of track #1, and the heading of track #2. See pro‐
41 gram listing for more details on formats. The file is sequential
42 in that new data are appended at the end of the file.
43 xx_legs.b:
45 Record length = 204 bytes.
46 Each record contains the complete information for each leg that
48 has been checked. The leg-structure contains fields like year of
49 cruise, number of internal/external COEs for gravity, magnetics,
50 and bathymetry, their means and standard deviations, and the
51 best fitting regression lines, i.e. the dc-shifts and drift-
52 rates computed from the time/error data points. See program
53 listing for complete description of record format.
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56 GMT(1), x_system(1)
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59 Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers
60 & Geosciences, 15, 333-346.
61GMT 4.5.6 10 Mar 2011 X_INIT(1)