backtracker - Reconstruct points, flowlines and hotspot tracks
] ] [ -C
] [ -Df
] [ -H
] ] [
] [ -Nupper_age
] [ -Sfilestem
] [ -V
] [ -W
] ] [
] ] [
]] ] [
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
No space between the option flag and the associated arguments. Use upper case
for the option flags and lower case for modifiers.
- Data file(s) to be projected. If not given, standard input is 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 -C is set then a total reconstruction
rotation is expected and tstop is implicitly set to 0 and should
not be specified 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.
- Alternatively, specify the longitude, latitude, and opening angle (all in
degrees and separated by /) for a single total reconstruction rotation
that should be applied to all input points.
- 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.
- Expect Total Reconstruction Rotations rather than Forward Stage Rotations
[Default]. File format is similar to the stage pole format except that the
tstart column is not present (assumed to be 0 Ma). Requires
- 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 contains the history of
hotspot motion for the current hotspot. If given, 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].
- Input file(s) has header record(s). If used, the default number of header
records is N_HEADER_RECS. Use -Hi if only input data should
have header records [Default will write out header records if the input
data have them]. Blank lines and lines starting with # are always
- 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 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 -D.
- 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].
- Selects verbose mode, which will send progress reports to stderr [Default
- 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 finite 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 rotation.
- Toggles between (longitude,latitude) and (latitude,longitude) input and/or
output. [Default is (longitude,latitude)]. Append i to select input
only or o to select output only. [Default affects both].
- Selects binary input. Append s for single precision [Default is
d (double)]. Uppercase S or D will force
byte-swapping. Optionally, append ncol, the number of columns in
your binary input file if it exceeds the columns needed by the program. Or
append c if the input file is netCDF. Optionally, append
var1 /var2/... to specify the variables
to be read. [Default is 3 input columns].
- Selects binary output. Append s for single precision [Default is
d (double)]. Uppercase S or D will force
byte-swapping. Optionally, append ncol, the number of desired
columns in your binary output file. [Default depends on settings].
- 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 and -b must set the number
of output columns explicitly. By default the -m setting applies to
both input and output. Use -mi and -mo to give separate
settings to input and output.
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
seamounts.d -Db -E
DC85.d > newpos.d
To project flowlines forward from the (x,y,t) points stored in several 3-column,
binary, double precision files, run
points.* -Df -E
This file can then be plotted with psxy -M
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 (PAC_APM.d), try
echo 204 19 80 | backtracker -Df -C -E
1 > path.d
Data coordinates are assumed to be geodetic and will automatically be converted
to geocentric before spherical rotations are performed. We convert back to
geodetic coordinates for output. Note: If your data already are geocentric,
you can avoid the conversion by using --ELLIPSOID=sphere.
Wessel, P., 1999, "Hotspotting" tools released, EOS Trans. AGU, 80
(29), p. 319.