1X2SYS_SOLVE(1) Generic Mapping Tools X2SYS_SOLVE(1)
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6 x2sys_solve - Determine systematic corrections from crossovers
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9 x2sys_solve -Ccolumn -TTAG -Emode [ COE_list.d ] [ -V ] [ -W ] [ -Z ] [
10 -bi[s|S|d|D[ncol]|c[var1/...]] ]
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13 x2sys_solve will use the supplied crossover information to solve for
14 systematic corrections that can then be applied per track to improve
15 data quality. Several systematic corrections can be solved for using a
16 least-squares approach. Note: Only one data column can be processed at
17 the time.
18 -T Specify the x2sys TAG which tracks the attributes of this data
20 type.
21 -C Specify which data column you want to process. Needed for
23 proper formatting of the output correction table and must match
24 the same option used in x2sys_list when preparing the input
25 data.
26 -E The correction type you wish to model. Choose among the follow‐
28 ing functions f(p), where p are the m parameters per track that
29 we will fit simultaneously using a least squares approach:
30 c will fit f(p) = a (a constant offset); records must contain
31 cruise ID1, ID2, COE.
32 d will fit f(p) = a + b * d (linear drift; d is distance;
33 records must contain cruise ID1, ID2, d1, d2, COE.
34 g will fit f(p) = a + b sin(y)^2 (1980-1930 gravity correc‐
35 tion); records must contain cruise ID1, ID2, latitude y, COE.
36 h will fit f(p) = a + b cos(H) + c cos(2H) + d sin(H) + e
37 sin(2H) (magnetic heading correction); records must contain
38 cruise ID1, ID2, heading H, COE.
39 s will fit f(p) = a * z (a unit scale correction); records must
40 contain cruise ID1, ID2, z1, z2.
41 t will fit f(p) = a + b * (t - t0) (linear drift; t0 is the
42 start time of the track); records must contain cruise ID1, ID2,
43 t1-t0, t2-t0, COE.
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46 No space between the option flag and the associated arguments.
47 COE_list.d
49 Name of file with the required crossover columns as produced by
50 x2sys_list. NOTE: If -bi is used then the first two columns are
51 expected to hold the integer track IDs; otherwise we expect
52 those columns to hold the text string names of the two tracks.
53 -V Selects verbose mode, which will send progress reports to stderr
55 [Default runs "silently"].
56 -W Means that each input records has an extra column with the com‐
58 posite weight for each crossover record. These are used to
59 obtain a weighted least squares solution [no weights].
60 -Z For -Ed and -Et, determine the earliest time or shortest dis‐
62 tance for each track, then use these values as the local origin
63 for time duration or distance calculations. The local origin is
64 then included in the correction table [Default uses 0].
65 -bi Selects binary input. Append s for single precision [Default is
67 d (double)]. Uppercase S or D will force byte-swapping.
68 Optionally, append ncol, the number of columns in your binary
69 input file if it exceeds the columns needed by the program. Or
70 append c if the input file is netCDF. Optionally, append
71 var1/var2/... to specify the variables to be read.
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74 To fit a simple bias offset to faa for all tracks under the MGD77 tag,
75 try
76 x2sys_list COE_data.txt -V -TMGD77 -Cfaa -Fnc > faa_coe.txt
78 x2sys_solve faa_coe.txt -V -TMGD77 -Cfaa -Ec > coe_table.txt
79 To fit a faa linear drift with time instead, try
81 x2sys_list COE_data.txt -V -TMGD77 -Cfaa -FnTc > faa_coe.txt
83 x2sys_solve faa_coe.txt -V -TMGD77 -Cfaa -Et > coe_table.txt
84 To estimate heading corrections based on magnetic crossovers associated
86 with the tag MGD77 from the file COE_data.txt, try
87 x2sys_list COE_data.txt -V -TMGD77 -Cmag -Fnhc > mag_coe.txt
89 x2sys_solve mag_coe.txt -V -TMGD77 -Cmag -Eh > coe_table.txt
90 To estimate unit scale corrections based on bathymetry crossovers, try
92 x2sys_list COE_data.txt -V -TMGD77 -Cdepth -Fnz > depth_coe.txt
94 x2sys_solve depth_coe.txt -V -TMGD77 -Cdepth -Es > coe_table.txt
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97 x2sys_binlist(1), x2sys_cross(1), x2sys_datalist(1), x2sys_get(1),
98 x2sys_init(1), x2sys_list(1), x2sys_put(1), x2sys_report(1)
99GMT 4.5.6 10 Mar 2011 X2SYS_SOLVE(1)