NAME
backtracker - Forward and Backward flowlines and hotspot tracks
SYNOPSIS
backtracker [infile(s)] -Estage_file [ -A[young/old] ] [ -C ] [ -Df|b ]
[ -H[nrec] ] [ -Lf|tstep ] [ -M[flag] ] [ -Nupper_age ] [ -Sfilestem ]
[ -Tzero_age ] [ -V ] [ -: ] [ -bi[s][n] ] [ -bo[s][n] ]
DESCRIPTION
backtracker reads (longitude, latitude, age) positions from infiles [or
standard input] and computes projected (x,y,t) coordinates using the
specified stage pole (Euler) rotations. You can either calculate just
final positions [Default] or create a sampled track between initial and
final position. The former mode allows additional data fields after the
first 3 columns which must have (longitude,latitude,age). See option
-: on how to read (latitude,longitude,age) files.
No space between the option flag and the associated arguments.
Use upper case for the option flags and lower case for modifiers.
infile(s)
Data file(s) to be projected. If not given, standard input is
read.
-E Give file with stage poles and opening angles. This file must
contain one record for each stage; each record must be of the
following format:
lon lat tstart tstop ccw-angle
where time is in Ma and the rest is in degrees. Oldest stage
must be listed first. tstart is the time when the stage begins
(oldest age). Blank lines and records whose first column con-
tains # will be ignored.
OPTIONS
-A Used in conjunction with -Lb|f to limit the track output to
those sections whose predicted ages fit between the young and
old limits. If -LB|F is used instead then the limits apply to
the stage ids. If no limits are supplied then individual limits
for each seamount are expected in the input file’s columns 4 and
5.’
-C Expect Total Reconstruction Poles (Finite Poles) rather than
Backward Stage Poles [Default] File format is similar to the
stage pole format except the youngest rotation must be listed
first and that the tstart column is optional (assumed to be 0
Ma).
-D Set the direction to go: -Df will go forward in time, while -Db
will go backward in time [Default].
-H Input file(s) has Header record(s). Number of header records can
be changed by editing your .gmtdefaults file. If used, GMT
default is 1 header record.
-L Specify a sampled path between initial and final position: -Lf
will draw flowlines, while -Lb will draw backtrack (hotspot
track) paths. Append sampling interval in km. When -LF or -LB
is used, the third output column will contain the stage id (1 is
youngest) [Default is along-track ages].
-M Multiple segment file(s). Segments are separated by a special
record. For ASCII files the first character must be flag
[Default is ’>’]. For binary files all fields must be NaN.
-N Set the maximum age to extend the oldest stage back in time
[Default is no extension].
-S When -L is set, the tracks are normally written to stdout as a
multisegment file. Specify a filestem to have each track written
to filestem.#, where # is the track number. The track number is
also copied to the 4th output column.
-T Set the current time [Default is 0 Ma].
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-: Toggles between (longitude,latitude) and (latitude,longitude)
input/output. [Default is (longitude,latitude)]. Applies to
geographic coordinates only.
-bi Selects binary input. Append s for single precision [Default is
double]. Append n for the number of columns in the binary
file(s). [Default is 3 input columns].
-bo Selects binary output. Append s for single precision [Default is
double].
EXAMPLES
To backtrack the (x,y,t) points in the file seamounts.d to their origin
(presumably the hotspot), using the DC85.d Euler poles, run
backtracker seamounts.d -Db -EDC85.d > newpos.d
To project flowlines forward from the (x,y,t) points stored in several
3-column, binary, double precision files, run
backtracker points.* -Df -EDC85.d -Lf25 -bo -bi3 > lines.b
This file can then be plotted with psxy -M.
SEE ALSO
gmt(GMTMANSECTION), project(GMTMANSECTION), mapproject(GMTMANSECTION),
hotspotter(GMTMANSECTION) originator(GMTMANSECTION)
REFERENCES
Wessel, P., 1999, "Hotspotting" tools released, EOS Trans. AGU, 80
(29), p. 319.
1 Jan 2004 BACKTRACKER(l)
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