NAME

       backtracker - Forward and Backward flowlines and hotspot tracks

SYNOPSIS

       backtracker [infile(s)] -Estage_file [ -A[young/old] ] [ -C ] [ -Df|b ]
       [ -H[nrec] ] [ -Lf|bstep ] [ -M[flag] ] [ -Nupper_age ] [ -Qfixed_age ]
       [ -Sfilestem ] [ -Tzero_age ] [ -V ] [ -W[a|t] ] [ -: ] [ -bi[s][n] ] [
       -bo[s] ]

DESCRIPTION

       backtracker reads (longitude, latitude, age) positions from infiles [or
       standard  input]  and  computes projected (x,y,t) coordinates using the
       specified rotation parameters. It can either calculate final  positions
       [Default] or create a sampled track between the initial and final posi-
       tions. 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 rotation poles and opening angles. This file must
              contain one record for each rotation; each record must be of the
              following format:

                      lon lat tstart [tstop] ccw-angle [k a b c d e f g]

              where tstart [and tstop] are in Ma, with lon, lat, and angle  in
              degrees.  For  stage  rotations, the oldest stage must be listed
              first, whereas for total reconstruction rotations  the  youngest
              rotation  is  listed first. tstart (tstop) is the age of the old
              (young) end of the stage. A covariance matrix, if  present,  may
              be  given  in  the  given format.  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 columns 4 and 5 of  the  input
              file.

       -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 (from
              younger to older positions), while -Db will go backward in  time
              (from older to younger positions) [Default].
              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  and
              -bo[s]n must set the number of output columns explicitly.

       -N     Set  the  maximum  age  to  extend the oldest stage back in time
              [Default is no extension].

       -Q     Assign a fixed age to all positions.  Only  lon,  lat  input  is
              expected.

       -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"].

       -W     Rotates  the  given  input (lon,lat,t) and calculates the confi-
              dence ellipse for the projected point. The input point must have
              a  time  coordinate  that  matches  a particular finite rotation
              time, otherwise the point will be skipped. Append t or a to out-
              put  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.

       -:     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].

       -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


GMT4.0                            1 Oct 2004        BACKTRACKER(GMTMANSECTION)