backtracker - Generate forward and backward flowlines and hotspot tracks
] ] [ -Df
] [ -Lf
] ] [
] [ -Qfixed_age
] [ -Tzero_age
] ] [ -W
] ] [ -b
nodata ] [ -e
regexp ] [ -h
headers ] [ -i
] [ -o
flags ] [ -:
No space is allowed between the option flag and the associated
reads (longitude, latitude, age) positions from
[or standard input] and computes rotated (x,y,t) coordinates
using the specified rotation parameters. It can either calculate final
positions [Default] or create a sampled track (flowline or hotspot track)
between the initial and final positions. The former mode allows additional
data fields after the first 3 columns which must have
(longitude,latitude,age). See option -:
on how to read
- Give file with rotation parameters. This file must contain
one record for each rotation; each record must be of the following format:
lon lat tstart [tstop] angle [ khat a b c d e f g df ]
where tstart and tstop are in Myr and lon lat angle are
in degrees. tstart and tstop are the ages of the old and
young ends of a stage. If tstop is not present in the record then a
total reconstruction rotation is expected and tstop is implicitly
set to 0 and should not be specified for any of the records in the file.
If a covariance matrix C for the rotation is available it must be
specified in a format using the nine optional terms listed in brackets.
Here, C = (g/khat)*[ a b d; b c e; d e f ]
which shows C made up of three row vectors. If the degrees of
freedom ( df) in fitting the rotation is 0 or not given it is set
to 10000. Blank lines and records whose first column contains # will be
ignored. You may prepend a leading + to the filename to indicate you wish
to invert the rotations. Alternative 1: Give the filename composed of two
plate IDs separated by a hyphen (e.g., PAC-MBL) and we will instead
extract that rotation from the GPlates rotation database. We return an
error if the rotation cannot be found. Alternative 2: Specify
lon/lat/angle, i.e., the longitude, latitude, and
opening angle (all in degrees and separated by /) for a single total
- One or more ASCII (or binary, see
-bi[ncols][type]) data table file(s) holding a number
of data columns. If no tables are given then we read from standard
- Used in conjunction with -Lb|f to limit the
track output to those sections whose predicted ages lie between the
specified young and old limits. If -LB|F is
used instead then the limits apply to the stage ids (id 1 is the youngest
stage). If no limits are specified then individual limits for each record
are expected in columns 4 and 5 of the input file.
- Set the direction to go: -Df will go backward in
time (from younger to older positions), while -Db will go forward
in time (from older to younger positions) [Default]. Note: For -Db
you are specifying the age at the given location, whereas for -Df
you are not; instead you specify the age at the reconstructed point.
- Supply a file with lon, lat, age records that describe the
history of hotspot motion for the current hotspot. The reconstructions
will only use the 3rd data input column (i.e., the age) to obtain the
location of the hotspot at that time, via an interpolation of the hotspot
motion history. This adjusted location is then used to reconstruct the
point or path [No drift].
- Specify a sampled path between initial and final position:
-Lf will draw particle flowlines, while -Lb will draw
backtrack (hotspot track) paths. Append sampling interval in km. If
step < 0 or not provided then only the rotation times will be
returned. When -LF or -LB is used, the third output column
will contain the stage id (1 is youngest) [Default is along-track
predicted ages]. You can control the direction of the paths by using
- Set the maximum age to extend the oldest stage rotation
back in time [Default is no extension].
- Assign a fixed age to all positions. Only lon, lat input is
expected [Default expects longitude, latitude, age]. Useful when the input
are points defining isochrons.
- 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.
- Set the current time [Default is 0 Ma].
- -V[level] (more ...)
- Select verbosity level [c].
- Rotates the given input (lon,lat,t) and calculates the
confidence ellipse for the projected point. The input point must
have a time coordinate that exactly matches a particular total
reconstruction rotation time, otherwise the point will be skipped. Append
t or a to output time or angle, respectively, after the
projected lon, lat. After these 2-3 items, we write azimuth, major, minor
(in km) for the 95% confidence ellipse. See -D for the direction of
- -bi[ncols][t] (more ...)
- Select native binary input. [Default is 3 input
- -bo[ncols][type] (more ...)
- Select native binary output. [Default is same as
- -d[i|o]nodata (more ...)
- Replace input columns that equal nodata with NaN and
do the reverse on output.
- -e[~]"pattern" |
-e[ ~]/regexp/[i] (more ...)
- Only accept data records that match the given pattern.
- Skip or produce header record(s).
- Select input columns and transformations (0 is first
- -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 just use -).
- -+ 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 all options, then exits.
All spherical rotations are applied to geocentric coordinates. This means that
incoming data points and grids are considered to represent geodetic
coordinates and must first be converted to geocentric coordinates. Rotations
are then applied, and the final reconstructed points are converted back to
geodetic coordinates. This default behavior can be bypassed if the ellipsoid
setting PROJ_ELLIPSOID is changed to Sphere.
To backtrack the (x,y,t) points in the file seamounts.txt to their origin
(presumably the hotspot), using the DC85.txt Euler poles, run
gmt backtracker seamounts.txt -Db -EDC85.txt > newpos.txt
To project flowlines forward from the (x,y,t) points stored in several 3-column,
binary, double precision files, run
gmt backtracker points.\* -Df -EDC85.txt -Lf25 -bo -bi3 > lines.b
This file can then be plotted with psxy. To compute the predicted Hawaiian
hotspot track from 0 to 80 Ma every 1 Ma, given a history of hotspot motion
file (HIdrift.txt) and a set of total reconstruction rotations for the plate
echo 204 19 80 | gmt backtracker -Df -EPAC_APM.txt -Lb1 > path.txt
GMT distributes the EarthByte rotation model
Global_EarthByte_230-0Ma_GK07_AREPS.rot. To use an alternate rotation file,
create an environmental parameters named GPLATES_ROTATIONS
to an alternate rotation file.
gmt , gmtpmodeler, grdpmodeler, grdrotater, grdspotter, hotspotter, mapproject,
originator, project, psxy
Wessel, P., 1999, "Hotspotting" tools released, EOS Trans. AGU, 80
(29), p. 319.
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe