NAME¶
x_solve_dc_drift - Find Best-fitting D.C.-shift and Drift Estimates
SYNOPSIS¶
x_solve_dc_drift [
-Xxbase ] [
-Llbase ] [
-Iignorefile ] [
-S ] [
-Citeration ] [
-M min_nx ] [
-Rwest/east/south/north ] [
-U uselegsfile ] [
-V ] [
-Bbinfile ] [
-A ASCIIfile ]
DESCRIPTION¶
x_solve_dc_drift will read the database files and, by iterating, find the
best-fitting regression line to the <time,COE> points for each leg that
minimizes the overall standard deviation of the data set in a least squares
sense. Finally, correction file(s) are created.
- -X
- Indicate an alternate database to read. [Default is
xx_base.b].
- -L
- Indicate an alternate legbase to read. [Default is
xx_legs.b].
- -I
- Ignore information for certain legs (that might be bad,
etc).
- -S
- Reset the old d.c.-shift and drift estimates to zero before
iterating.
- -C
- Specify how many iterations to do. Default is interactive
session.
- -M
- Solve for drift only if the leg has more than min_nx
cross-overs.
- -R
- Only take COEs inside this region into account. [Default is
world].
- -U
- Solve for corrections involving COEs from legs in the
uselegsfile only.
- -B
- Create a binary correction file (which can be read by
x_list and gmtlist).
- -A
- Create an ASCII correction table. At least one of -A
and -B must be specified.
- -V
- Selects verbose mode, which will send progress reports to
stderr [Default runs "silently"].
BEWARE¶
The reason for the
-M option is that if the COEs are few, then a stable
estimate of the slope may not be obtained (e.g. when most of the COEs occur
midway between ports). However, in most cases the bulk of the COEs do occur
near the ports so that a drift estimate can be computed. Conventional wisdom
recommends plotting the time-series and the computed regression line to see if
it makes sense.
SEE ALSO¶
GMT(1),
x_system(1)
REFERENCES¶
Wessel, P. XOVER: A Cross-over Error Detector for Track Data,
Computers &
Geosciences, 15, 333-346.