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<HTML>
<HEAD>
<TITLE>splitxyz</TITLE>
</HEAD>
<BODY>
<H1>splitxyz</H1>
<HR>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
splitxyz - filter to divide (x,y,z[,distance,heading])
data into (x,y,z) track segments.
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>splitxyz</B> [ <I>xyz[dh]file</I> ] <B>-C</B><I>course</I><B>_</B><I>change</I> [ <B>-A</B><I>azimuth</I>/<I>tol</I>
<I>erance</I> ] [ <B>-D</B><I>minimum</I><B>_</B><I>distance</I> ] [ <B>-F</B><I>xy</I><B>_</B><I>filter</I>/<I>z</I><B>_</B><I>filter</I> ] [
<B>-G</B><I>gap</I><B>_</B><I>distance</I> ] [ <B>-H</B>[<I>nrec</I>] ] [ <B>-M</B> ] [ <B>-N</B><I>namestem</I> ] [ <B>-S</B> ]
[ <B>-V</B> ] [ <B>-Z</B> ] [ <B>-:</B> ] [ <B>-bi</B>[<B>s</B>][<I>n</I>] ] [ <B>-bo</B>[<B>s</B>] ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>splitxyz</B> reads a series of (x,y[,z]) records [or option
ally (x,y,z,d,h); see <B>-S</B> option] from standard input [or
<I>xyz[dh]file</I>] 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.
<B>splitxyz</B> is a useful filter between data extraction and
<B><A HREF="pswiggle.html">pswiggle</A></B> 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>-b</B>).
<I>xyz[dh]file(s)</I>
3 (but see <B>-Z</B>) [or 5] column ASCII file [or binary,
see <B>-b</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 <B>-S</B> option; default expects (x,y,z)
only. If no file is specified, <B>splitxyz</B> will read
from standard input.
<B>-C</B> Terminate a segment when a course change exceeding
<I>course</I><B>_</B><I>change</I> degrees of heading is detected.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-A</B> Write out only those segments which are within +/-
<I>tolerance</I> degrees of <I>azimuth</I> in heading, measured
clockwise from North, [0 - 360]. [Default writes
all acceptable segments, regardless of orienta
tion].
<B>-D</B> Do not write a segment out unless it is at least
<I>minimum</I><B>_</B><I>distance</I> units long. [Default = 100 dis
tance units].
<B>-F</B> Filter the z values and/or the x,y values, assuming
these are functions of d coordinate. <I>xy</I><B>_</B><I>filter</I> and
<I>z</I><B>_</B><I>filter</I> 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 <I>z</I><B>_</B><I>filter</I> 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 <I>xy</I><B>_</B><I>filter</I> 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].
<B>-G</B> Do not let a segment have a gap exceeding <I>gap</I><B>_</B><I>dis</I>
<I>tance</I>; instead, split it into two segments.
[Default = 10 distance units].
<B>-H</B> Input file(s) has Header record(s). Number of
header records can be changed by editing your .gmt
defaults file. If used, <B><A HREF="GMT.html">GMT</A></B> default is 1 header
record. Not used with binary data.
<B>-M</B> 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].
<B>-N</B> Create Named output files, writing each segment to
a separate file in the working directory named
<I>namestem</I>.profile<I>#</I>, where <I>#</I> increases consecutively
from 1. [Default writes entire output to stdout,
separating segments by sub-headings that start with
> marks].
<B>-S</B> 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 <B>-M</B>
option]
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
<B>-Z</B> Data have x,y only (no z-column).
<B>-:</B> Toggles between (longitude,latitude) and (lati
tude,longitude) input/output. [Default is (longi
tude,latitude)]. Applies to geographic coordinates
only.
<B>-bi</B> Selects binary input. Append <B>s</B> for single precision
[Default is double]. Append <I>n</I> for the number of
columns in the binary file(s). [Default is 2, 3,
or 5 input columns as set by <B>-S,</B> <B>-Z</B>].
sion [Default is double].
</PRE>
<H2>EXAMPLES</H2><PRE>
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 <B>-R</B>300/315/12/20 <B>-F</B>xyzdh | splitxyz <B>-A</B>90/15
<B>-F</B>100/-500 <B>-M</B> <B>-S</B> <B>-V</B> | pswiggle <B>-R</B>300/315/12/20 <B>-Jm</B>0.6
<B>-Ba</B>5<B>f</B>1:.cag71: <B>-T</B>1 <B>-W</B>3 <B>-G</B>200 <B>-Z</B>200 > cag71_wiggles.ps
MGD-77 users: For this application we recommend that you
extract d, h from <B>gmtlist</B> rather than have <B>splitxyz</B> 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 <I>survey</I>.pro
file<I>#</I> (when gap exceeds 100 km). Try this:
splitxyz survey.bin <B>-N</B>survey <B>-V</B> <B>-G</B>100 <B>-:</B> <B>-M</B> <B>-bi</B>3
</PRE>
<H2>SEE ALSO</H2><PRE>
<I>gmt</I>(l), <I>gmtlist</I>(l), <I><A HREF="pswiggle.html">pswiggle</A></I>(l)
</PRE>
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