NAME

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

SYNOPSIS

      splitxyz [ xyz[dh]file ] -Ccourse_change [ -Aazimuth/tolerance ] [
      -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 optionally
      (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 constant 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-decreasing, 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
           orientation].

      -D   Do not write a segment out unless it is at least minimum_distance
           units long.  [Default = 100 distance 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 performed.  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; if negative, the data
           are high-pass filtered by subtracting the low-pass value from the
           observed value.  If z_filter is non-zero, the entire series of
           input z values is filtered before any segmentation 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 filtered 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_distance; 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 .gmtdefaults 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 longitude, 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 (latitude,longitude)
           input/output.  [Default is (longitude,latitude)].

      -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].

      -bo  Selects binary output.  Append s for single precision [Default is
           double].

EXAMPLES

      Suppose you want to make a wiggle plot of magnetic anomalies 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 compute 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.profile# (when gap exceeds 100 km).  Try this:

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

SEE ALSO

      gmt, gmtlist, pswiggle