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     Selects verbose mode, which will send progress reports to stderr
47              [Default runs "silently"].
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BEWARE

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

58       GMT(1), x_system(1)
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REFERENCES

61       Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers
62       & Geosciences, 15, 333-346.
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66GMT 4.5.6                         10 Mar 2011              X_SOLVE_DC_DRIFT(1)