1X_SOLVE_DC_DRIFT(1)          Generic Mapping Tools         X_SOLVE_DC_DRIFT(1)
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NAME

6       x_solve_dc_drift - Find Best-fitting D.C.-shift and Drift Estimates
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SYNOPSIS

9       x_solve_dc_drift  [  -Xxbase  ]  [  -Llbase ] [ -Iignorefile ] [ -S ] [
10       -Citeration ] [ -Mmin_nx ] [ -Rwest/east/south/north ] [  -Uuselegsfile
11       ] [ -V ] [ -Bbinfile ]  [ -AASCIIfile ]
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DESCRIPTION

14       x_solve_dc_drift  will  read the database files and, by iterating, find
15       the best-fitting regression line to the <time,COE> points for each  leg
16       that  minimizes  the  overall  standard  deviation of the data set in a
17       least squares sense. Finally, correction file(s) are created.
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19       -X     Indicate an alternate database to read. [Default is xx_base.b].
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21       -L     Indicate an alternate legbase to read. [Default is xx_legs.b].
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23       -I     Ignore information for certain legs (that might be bad, etc).
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25       -S     Reset the old d.c.-shift and  drift  estimates  to  zero  before
26              iterating.
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28       -C     Specify  how  many iterations to do. Default is interactive ses‐
29              sion.
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31       -M     Solve for drift only if the leg  has  more  than  min_nx  cross-
32              overs.
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34       -R     Only  take  COEs  inside  this  region into account. [Default is
35              world].
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37       -U     Solve for corrections involving COEs from legs in  the  uselegs‐
38              file only.
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40       -B     Create a binary correction file (which can be read by x_list and
41              gmtlist).
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43       -A     Create an ASCII correction table. At least one of -A and -B must
44              be specified.
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46       -V     Operate in verbose mode.
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BEWARE

49       The  reason for the -M  option is that if the COEs are few, then a sta‐
50       ble estimate of the slope may not be obtained (e.g. when  most  of  the
51       COEs  occur  midway  between ports). However, in most cases the bulk of
52       the COEs do occur near the ports so that a drift estimate can  be  com‐
53       puted.  Conventional wisdom recommends plotting the time-series and the
54       computed regression line to see if it makes sense.
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SEE ALSO

57       GMT(1), x_system(1)
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REFERENCES

60       Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers
61       & Geosciences, 15, 333-346.
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65GMT 4.3.1                         15 May 2008              X_SOLVE_DC_DRIFT(1)
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