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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