Provided by: gmt_4.5.11-1build1_amd64 bug

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[i][nrec] ] [ -M ] [ -Nnamestem ] [  -Qflags
       ] [ -S ] [ -V ] [ -Z ] [ -:[i|o] ] [ -b[i|o][s|S|d|D[ncol]|c[var1/...]] ] [ -f[i|o]colinfo
       ]

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 [0]

       -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 ignores gaps].

       -H     Input file(s) has header record(s).  If used, the default number of header  records
              is  N_HEADER_RECS.   Use -Hi if only input data should have header records [Default
              will write out header records if the input data have them]. Blank lines  and  lines
              starting with # are always skipped.  Not used with binary data.

       -M     Use  Map  units.   Then x,y are in degrees of longitude, latitude, distances are in
              kilometers, and angles are azimuths.  [Default:  distances are  cartesian  in  same
              units as x,y and angles are counter-clockwise from horizontal].

       -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].

       -Q     Specify your desired output using any combination of xyzdh, in any order.   Do  not
              space  between  the letters.  Use lower case.  The output will be ASCII (or binary,
              see -bo) columns of values corresponding to xyzdh [Default is -Qxyzdh (-Qxydh if -Z
              is set)].

       -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 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 d (double)].
              Uppercase S or D will force byte-swapping.  Optionally, append ncol, the number  of
              columns  in your binary input file if it exceeds the columns needed by the program.
              Or append c if the input  file  is  netCDF.  Optionally,  append  var1/var2/...  to
              specify  the  variables to be read.  [Default is 2, 3, or 5 input columns as set by
              -S, -Z].

       -bo    Selects binary output.  Append s for single  precision  [Default  is  d  (double)].
              Uppercase  S or D will force byte-swapping.  Optionally, append ncol, the number of
              desired columns in your binary output file.  [Default is 1-5 output columns as  set
              by -Q].

       -f     Special  formatting  of  input  and/or  output columns (time or geographical data).
              Specify i or o to make this apply only to  input  or  output  [Default  applies  to
              both].   Give one or more columns (or column ranges) separated by commas.  Append T
              (absolute calendar time), t (relative time in chosen TIME_UNIT since TIME_EPOCH), x
              (longitude),  y  (latitude),  or  f (floating point) to each column or column range
              item.  Shorthand -f[i|o]g means -f[i|o]0x,1y (geographic coordinates).

ASCII FORMAT PRECISION

       The ASCII  output  formats  of  numerical  data  are  controlled  by  parameters  in  your
       .gmtdefaults4    file.     Longitude    and    latitude   are   formatted   according   to
       OUTPUT_DEGREE_FORMAT, whereas other values are formatted according to D_FORMAT.  Be  aware
       that  the  format in effect can lead to loss of precision in the output, which can lead to
       various problems downstream.  If you find the output is not written with enough precision,
       consider  switching to binary output (-bo if available) or specify more decimals using the
       D_FORMAT setting.

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 -R 300/315/12/20 -F xyzdh | splitxyz -A 90/15 -F 100/-500 -M -D 100 -S -V |
       pswiggle -R 300/315/12/20 -Jm 0.6 -Ba  5f1:.cag71:  -T  1  -W  0.75p  -G  gray  -Z  200  >
       cag71_wiggles.ps

       MGD-77  users:  For  this  application  we  recommend that you extract d, h from mgd77list
       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 -N survey -V -G 100 -D 100 -: -M -bi3

SEE ALSO

       GMT(1), mgd77list(1), pswiggle(1)