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<title>SPLITXYZ</title>
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<h1 align="center">SPLITXYZ</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#OPTIONS">OPTIONS</a><br>
<a href="#ASCII FORMAT PRECISION">ASCII FORMAT PRECISION</a><br>
<a href="#EXAMPLES">EXAMPLES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<hr>
<h2>NAME
<a name="NAME"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">splitxyz
− filter to divide (x,y,z[,distance,heading]) data
into (x,y,z) track segments.</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>splitxyz</b>
[ <i>xyz[dh]file</i> ] <b>−C</b><i>course_change</i> [
<b>−A</b><i>azimuth</i>/<i>tolerance</i> ] [
<b>−D</b><i>minimum_distance</i> ] [
<b>−F</b><i>xy_filter</i>/<i>z_filter</i> ] [
<b>−G</b><i>gap_distance</i> ] [
<b>−H</b>[<b>i</b>][<i>nrec</i>] ] [ <b>−M</b> ]
[ <b>−N</b><i>namestem</i> ] [
<b>−Q</b><i>flags</i> ] [ <b>−S</b> ] [
<b>−V</b> ] [ <b>−Z</b> ] [
<b>−:</b>[<b>i</b>|<b>o</b>] ] [
<b>−b</b>[<b>i</b>|<b>o</b>][<b>s</b>|<b>S</b>|<b>d</b>|<b>D</b>[<i>ncol</i>]|<b>c</b>[<i>var1</i><b>/</b><i>...</i>]]
] [ <b>−f</b>[<b>i</b>|<b>o</b>]<i>colinfo</i> ]</p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>splitxyz</b>
reads a series of (x,y[,z]) records [or optionally
(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
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.
<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><br>
xyz[dh]file(s)</i></p>
<p style="margin-left:22%;">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-decreasing, 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.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−C</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Terminate a segment when a course change exceeding
<i>course_change</i> degrees of heading is detected.</p></td></tr>
</table>
<h2>OPTIONS
<a name="OPTIONS"></a>
</h2>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−A</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">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 orientation].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−D</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not write a segment out unless it is at least
<i>minimum_distance</i> units long [0]</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−F</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Filter the z values and/or the x,y values, assuming
these are functions of d coordinate. <i>xy_filter</i> and
<i>z_filter</i> 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
<i>z_filter</i> 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 <i>xy_filter</i> 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].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−G</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not let a segment have a gap exceeding
<i>gap_distance</i>; instead, split it into two segments.
[Default ignores gaps].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−H</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Input file(s) has header record(s). If used, the default
number of header records is <b><A HREF="gmtdefaults.html#N_HEADER_RECS">N_HEADER_RECS</A></b>. Use
<b>−Hi</b> 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.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−M</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>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].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−N</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>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].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Q</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Specify your desired output using any combination of
<i>xyzdh</i>, in any order. Do not space between the
letters. Use lower case. The output will be ASCII (or
binary, see <b>−bo</b>) columns of values
corresponding to <i>xyzdh</i> [Default is
<b>−Q</b><i>xyzdh</i> (<b>−Q</b><i>xydh</i> if
<b>−Z</b> is set)].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−S</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>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]</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−V</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Z</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Data have x,y only (no z-column).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−:</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Toggles between (longitude,latitude) and
(latitude,longitude) input and/or output. [Default is
(longitude,latitude)]. Append <b>i</b> to select input only
or <b>o</b> to select output only. [Default affects
both].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−bi</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects binary input. Append <b>s</b> for single
precision [Default is <b>d</b> (double)]. Uppercase <b>S</b>
or <b>D</b> will force byte-swapping. Optionally, append
<i>ncol</i>, the number of columns in your binary input file
if it exceeds the columns needed by the program. Or append
<b>c</b> if the input file is netCDF. Optionally, append
<i>var1</i><b>/</b><i>var2</i><b>/</b><i>...</i> to specify
the variables to be read. [Default is 2, 3, or 5 input
columns as set by <b>−S</b>, <b>−Z</b>].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−bo</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects binary output. Append <b>s</b> for single
precision [Default is <b>d</b> (double)]. Uppercase <b>S</b>
or <b>D</b> will force byte-swapping. Optionally, append
<i>ncol</i>, the number of desired columns in your binary
output file. [Default is 1-5 output columns as set by
<b>−Q</b>].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−f</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Special formatting of input and/or output columns (time
or geographical data). Specify <b>i</b> or <b>o</b> 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 <b>T</b> (absolute calendar time),
<b>t</b> (relative time in chosen <b><A HREF="gmtdefaults.html#TIME_UNIT">TIME_UNIT</A></b> since
<b><A HREF="gmtdefaults.html#TIME_EPOCH">TIME_EPOCH</A></b>), <b>x</b> (longitude), <b>y</b>
(latitude), or <b>f</b> (floating point) to each column or
column range item. Shorthand
<b>−f</b>[<b>i</b>|<b>o</b>]<b>g</b> means
<b>−f</b>[<b>i</b>|<b>o</b>]0<b>x</b>,1<b>y</b>
(geographic coordinates).</p></td></tr>
</table>
<h2>ASCII FORMAT PRECISION
<a name="ASCII FORMAT PRECISION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The ASCII
output formats of numerical data are controlled by
parameters in your .gmtdefaults4 file. Longitude and
latitude are formatted according to
<b><A HREF="gmtdefaults.html#OUTPUT_DEGREE_FORMAT">OUTPUT_DEGREE_FORMAT</A></b>, whereas other values are
formatted according to <b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b>. 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 (<b>−bo</b> if
available) or specify more decimals using the
<b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b> setting.</p>
<h2>EXAMPLES
<a name="EXAMPLES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">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:</p>
<p style="margin-left:11%; margin-top: 1em"><b><A HREF="gmtlist.html">gmtlist</A></b>
cag71 <b>−R</b> 300/315/12/20 <b>−F</b> xyzdh |
<b>splitxyz −A</b> 90/15 <b>−F</b> 100/-500
<b>−M −D</b> 100 <b>−S −V</b> |
<b>pswiggle −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> 0.75p <b>−G</b> gray <b>−Z</b>
200 > cag71_wiggles.ps</p>
<p style="margin-left:11%; margin-top: 1em">MGD-77 users:
For this application we recommend that you extract d, h from
<b><A HREF="mgd77list.html">mgd77list</A></b> rather than have <b>splitxyz</b> compute
them separately.</p>
<p style="margin-left:11%; margin-top: 1em">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>.profile<i>#</i>
(when gap exceeds 100 km). Try this:</p>
<p style="margin-left:11%; margin-top: 1em"><b>splitxyz</b>
survey.bin <b>−N</b> survey <b>−V −G</b>
100 <b>−D</b> 100 <b>−: −M
−bi3</b></p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b><i><A HREF="GMT.html">GMT</A></i></b>(1),
<i><A HREF="mgd77list.html">mgd77list</A></i>(1), <i><A HREF="pswiggle.html">pswiggle</A></i>(1)</p>
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