## 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 ] [ -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 (longi
           tude,latitude,age).  See option -: on how to  read  (lati
           tude,longitude,age) files.
                   No  space  between the option flag and the associ
           ated arguments. Use upper case for the  option  flags  and
           lower case for modifiers.

           infile(s)
                  Data  file(s)  to be projected. If not given, stan
                  dard 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 contains #
                  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 .gmt
                  defaults  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  sam
                  pling  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].

           -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  (lati
                  tude,longitude) input/output. [Default  is  (longi
                  tude,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 preci
                  sion [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(l),  project(l), mapproject(l), hotspotter(l) origina
           tor(l)

## REFERENCES

           Wessel, P., 1999, "Hotspotting" tools released, EOS Trans.
           AGU, 80 (29), p. 319.

                                1 Mar 2002             BACKTRACKER(l)