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PROGRAM:

NAME

gmtvector - Basic manipulation of Cartesian vectors

SYNOPSIS

gmtvector [ tables ] [ m[conf]|vector ] [ [i|o] ] [ ] [ ] [ vector ] [
a|d|D|paz|r[arg|R|s|x] ] [ [level] ] [ -b<binary> ] [ -d<nodata> ] [ -f<flags> ] [
-g<gaps> ] [ -h<headers> ] [ -i<flags> ] [ -o<flags> ] [ -:[i|o] ]

Note: No space is allowed between the option flag and the associated arguments.

DESCRIPTION

gmtvector reads either (x, y), (x, y, z), (r, theta) or (lon, lat) [or (lat,lon); see -:]
coordinates from the first 2-3 columns on standard input [or one or more tables]. If -fg
is selected and only two items are read (i.e., lon, lat) then these coordinates are
converted to Cartesian three-vectors on the unit sphere. Otherwise we expect (r, theta)
unless -Ci is in effect. If no file is found we expect a single vector to be given as
argument to -A; this argument will also be interpreted as an x/y[/z], lon/lat, or r/theta
vector. The input vectors (or the one provided via -A) are denoted the prime vector(s).
Several standard vector operations (angle between vectors, cross products, vector sums,
and vector rotations) can be selected; most require a single second vector, provided via
-S. The output vectors will be converted back to (lon, lat) or (r, theta) unless -Co is
set which requests (x, y[, z]) Cartesian coordinates.

REQUIRED ARGUMENTS

None.

OPTIONAL ARGUMENTS

table One or more ASCII [or binary, see -bi] file containing lon,lat [lat,lon if -:]
values in the first 2 columns (if -fg is given) or (r, theta), or perhaps (x, y[,
z]) if -Ci is given). If no file is specified, gmtvector, will read from standard
input.

-Am[conf]|vector
Specify a single, primary vector instead of reading tables; see tables for possible
vector formats. Alternatively, append m to read tables and set the single, primary
vector to be the mean resultant vector first. We also compute the confidence
ellipse for the mean vector (azimuth of major axis, major axis, and minor axis; for
geographic data the axes will be reported in km). You may optionally append the
confidence level in percent [95]. These three parameters are reported in the final
three output columns.

-C[i|o]
Select Cartesian coordinates on input and output. Append i for input only or o for
output only; otherwise both input and output will be assumed to be Cartesian
[Default is polar r/theta for 2-D data and geographic lon/lat for 3-D].

-E Convert input geographic coordinates from geodetic to geocentric and output
geographic coordinates from geocentric to geodetic. Ignored unless -fg is in
effect, and is bypassed if -C is selected.

-N Normalize the resultant vectors prior to reporting the output [No normalization].
This only has an effect if -Co is selected.

-S[vector]
Specify a single, secondary vector in the same format as the first vector. Required
by operations in -T that need two vectors (average, bisector, dot product, cross
product, and sum).

-Ta|d|D|paz|s|r[arg|R|x]
Specify the vector transformation of interest. Append a for average, b for the pole
of the two points bisector, d for dot product (use D to get angle in degrees
between the two vectors), paz for the pole to the great circle specified by input
vector and the circle's az (no second vector used), s for vector sum, rpar for
vector rotation (here, par is a single angle for 2-D Cartesian data and
lon/lat/angle for a 3-D rotation pole and angle), R will instead rotate the fixed
secondary vector by the rotations implied by the input records, and x for
cross-product. If -T is not given then no transformation takes place; the output
is determined by other options such as -A, -C, -E, and -N.

-V[level] (more ...)
Select verbosity level [c].

-bi[ncols][t] (more ...)
Select native binary input. [Default is 2 or 3 input columns].

-d[i|o]nodata (more ...)
Replace input columns that equal nodata with NaN and do the reverse on output.

-f[i|o]colinfo (more ...)
Specify data types of input and/or output columns.

-g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more ...)
Determine data gaps and line breaks.

-h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
Skip or produce header record(s).

-icols[l][sscale][ooffset][,...] (more ...)
Select input columns (0 is first column).

-ocols[,...] (more ...)
Select output columns (0 is first column).

-:[i|o] (more ...)
Swap 1st and 2nd column on input and/or output.

-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows
use just -).

-+ or just +
Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.

-? or no arguments
Print a complete usage (help) message, including the explanation of options, then
exits.

--version
Print GMT version and exit.

--show-datadir
Print full path to GMT share directory and exit.

ASCII FORMAT PRECISION

The ASCII output formats of numerical data are controlled by parameters in your gmt.conf
file. Longitude and latitude are formatted according to FORMAT_GEO_OUT, whereas other
values are formatted according to FORMAT_FLOAT_OUT. Be aware that the format in effect can
lead to loss of precision in the output, which can lead to various problems downstream. If
you find the output is not written with enough precision, consider switching to binary
output (-bo if available) or specify more decimals using the FORMAT_FLOAT_OUT setting.

EXAMPLES

Suppose you have a file with lon, lat called points.txt. You want to compute the spherical
angle between each of these points and the location 133/34. Try

gmt vector points.txt -S133/34 -TD -fg > angles.txt

To rotate the same points 35 degrees around a pole at 133/34, and output Cartesian 3-D
vectors, use

gmt vector points.txt -Tr133/34/35 -Co -fg > reconstructed.txt

To rotate the point 65/33 by all rotations given in file rots.txt, use

gmt vector rots.txt -TR -S64/33 -fg > reconstructed.txt

To compute the cross-product between the two Cartesian vectors 0.5/1/2 and 1/0/0.4, and
normalizing the result, try

gmt vector -A0.5/1/2 -Tx -S1/0/0.4 -N -C > cross.txt

To rotate the 2-D vector, given in polar form as r = 2 and theta = 35, by an angle of 120,
try

gmt vector -A2/35 -Tr120 > rotated.txt

To find the mid-point along the great circle connecting the points 123/35 and -155/-30,
use

gmt vector -A123/35 -S-155/-30 -Ta -fg > midpoint.txt

To find the mean location of the geographical points listed in points.txt, with its 99%
confidence ellipse, use

gmt vector points.txt -Am99 -fg > centroid.txt

To find the pole corresponding to the great circle that goes through the point -30/60 at
an azimuth of 105 degrees, use

gmt vector -A-30/60 -Tp105 -fg > pole.txt

ROTATIONS

For more advanced 3-D rotations as used in plate tectonic reconstructions, see the GMT
"spotter" supplement.

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