trusty (1) splitxyz.1gmt.gz

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][n] ]

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)].  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].

       -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(1gmt), gmtlist(1gmt), pswiggle(1gmt)

                                                   1 Jan 2004                                        SPLITXYZ(l)