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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>
<a name="NAME"></a>
<h2>NAME</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>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</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>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</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 style="margin-top: 1em" valign="top"><b>−C</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Terminate a segment
when a course change exceeding <i>course_change</i> degrees
of heading is detected.</p></td>
</table>
<a name="OPTIONS"></a>
<h2>OPTIONS</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" valign="top"><b>−A</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−D</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Do not write a
segment out unless it is at least <i>minimum_distance</i>
units long [0]</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−F</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−G</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−H</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−M</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−N</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−Q</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−S</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−V</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects verbose
mode, which will send progress reports to stderr [Default
runs "silently"].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−Z</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Data have x,y only
(no z-column).</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−:</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−bi</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−bo</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−f</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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>
</table>
<a name="ASCII FORMAT PRECISION"></a>
<h2>ASCII FORMAT PRECISION</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>
<a name="EXAMPLES"></a>
<h2>EXAMPLES</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>
<a name="SEE ALSO"></a>
<h2>SEE ALSO</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="GMT.html">GMT</A></i>(1),
<i><A HREF="mgd77list.html">mgd77list</A></i>(1), <i><A HREF="pswiggle.html">pswiggle</A></i>(1)</p>
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