splitxyz

       splitxyz  -  filter  to  divide (x,y,z[,distance,heading])
       data into (x,y,z) track segments.

SYNOPSIS

       splitxyz [ xyz[dh]file ] -Ccourse_change [  -Aazimuth/tol­
       erance ] [ -Dminimum_distance ] [ -Fxy_filter/z_filter ] [
       -Ggap_distance ] [ -H[nrec] ] [ -M ] [ -Nnamestem ] [ -S ]
       [ -V ] [ -Z ] [ -: ] [ -bi[s][n] ] [ -bo[s] ]

DESCRIPTION

       splitxyz  reads  a series of (x,y[,z]) records [or option­
       ally (x,y,z,d,h); see -S option] from standard  input  [or
       xyz[dh]file]  and  splits  this  into  separate  lists  of
       (x,y[,z]) series, such that each series has a nearly  con­
       stant azimuth through the x,y plane.  There are options to
       choose only those series which have a certain orientation,
       to  set  a  minimum  length  for  series,  and to high- or
       low-pass filter  the  z  values  and/or  the  x,y  values.
       splitxyz  is  a  useful filter between data extraction and
       pswiggle plotting, and can also be used to divide a  large
       x,y,z  dataset  into segments. The output is always in the
       ASCII format; input may be ASCII or binary (see -b).

       xyz[dh]file(s)
              3 (but see -Z) [or 5] column ASCII file [or binary,
              see  -b]  holding (x,y,z[,d,h]) data values. To use
              (x,y,z,d,h) input, sorted so that d is non-decreas­
              ing, specify the -S option; default expects (x,y,z)
              only.  If no file is specified, splitxyz will  read
              from standard input.

       -C     Terminate  a segment when a course change exceeding
              course_change degrees of heading is detected.

OPTIONS

       -A     Write out only those segments which are within  +/-
              tolerance  degrees  of azimuth in heading, measured
              clockwise from North, [0 -  360].  [Default  writes
              all  acceptable  segments,  regardless  of orienta­
              tion].

       -D     Do not write a segment out unless it  is  at  least
              minimum_distance  units  long.  [Default = 100 dis­
              tance units].

       -F     Filter the z values and/or the x,y values, assuming
              these are functions of d coordinate.  xy_filter and
              z_filter are filter widths in distance units. If  a
              filter  width  is  zero,  the filtering is not per­
              formed. The absolute value of the width is the full
              width  of  a  cosine-arch  low-pass  filter. If the
              width is positive, the data are low-pass  filtered;
              value.  If  z_filter is non-zero, the entire series
              of input z values is filtered before any  segmenta­
              tion is performed, so that the only edge effects in
              the filtering will happen at the beginning and  end
              of  the  complete  data  stream.  If  xy_filter  is
              non-zero, the data is first divided  into  segments
              and  then  the  x,y values of each segment are fil­
              tered separately. This may introduce  edge  effects
              at  the  ends  of  each  segment,  but  prevents  a
              low-pass x,y filter from rounding off  the  corners
              of track segments. [Default = no filtering].

       -G     Do  not let a segment have a gap exceeding gap_dis­
              tance;  instead,  split  it  into   two   segments.
              [Default = 10 distance units].

       -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.  Not used with binary data.

       -M     Use Map units. Then x,y are in  degrees  of  longi­
              tude,   latitude,   and  distances  in  kilometers.
              [Default: distances are cartesian in same units  as
              x,y].

       -N     Create  Named output files, writing each segment to
              a separate file  in  the  working  directory  named
              namestem.profile#,  where # increases consecutively
              from 1. [Default writes entire  output  to  stdout,
              separating segments by sub-headings that start with
              > marks].

       -S     d and h is supplied. In this case,  input  contains
              x,y,z,d,h.  [Default expects (x,y,z) input, and d,h
              are computed from delta x, delta y, according to -M
              option]

       -V     Selects  verbose  mode,  which  will  send progress
              reports to stderr [Default runs "silently"].

       -Z     Data have x,y only (no z-column).

       -:     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 2, 3,
              or 5 input columns as set by -S, -Z].
              sion [Default is double].

EXAMPLES

       Suppose  you want to make a wiggle plot of magnetic anoma­
       lies on segments oriented approximately east-west  from  a
       cruise  called  cag71  in the region -R300/315/12/20.  You
       want to use a 100km low-pass filter to smooth  the  tracks
       and  a  500km  high-pass  filter  to  detrend the magnetic
       anomalies. Try this:

       gmtlist cag71 -R300/315/12/20 -Fxyzdh |  splitxyz  -A90/15
       -F100/-500  -M  -S  -V  |  pswiggle -R300/315/12/20 -Jm0.6
       -Ba5f1:.cag71: -T1 -W3 -G200 -Z200 > cag71_wiggles.ps

       MGD-77 users: For this application we recommend  that  you
       extract  d,  h from gmtlist rather than have splitxyz com­
       pute them separately.
       Suppose you have been  given  a  binary,  double-precision
       file  containing  lat,  lon, gravity values from a survey,
       and you want to split it into profiles  named  survey.pro­
       file# (when gap exceeds 100 km). Try this:

       splitxyz survey.bin -Nsurvey -V -G100 -: -M -bi3

SEE ALSO

       gmt(l), gmtlist(l), pswiggle(l)