Provided by: gmt-common_5.4.3+dfsg-1_all 
NAME
splitxyz - Split xyz[dh] data tables into individual segments
SYNOPSIS
splitxyz [ table ] [ -Aazimuth/tolerance ] [ -Ccourse_change] [ -Dminimum_distance ] [
-Fxy_filter/z_filter ] [ -Ntemplate ] [ -Qflags ] [ -S ] [ -V[level] ] [ -bbinary ] [ -dnodata ] [
-eregexp ] [ -fflags ] [ -ggaps ] [ -hheaders ] [ -iflags ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated arguments.
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.
REQUIRED ARGUMENTS
none.
OPTIONAL ARGUMENTS
table One or more ASCII [or binary, see -bi] files with 2, 3, or 5 columns 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 files are specified, splitxyz will read from standard input.
-Aazimuth/tolerance
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].
-Ccourse_change
Terminate a segment when a course change exceeding course_change degrees of heading is detected
[ignore course changes].
-Dminimum_distance
Do not write a segment out unless it is at least minimum_distance units long [0]
-Fxy_filter/z_filter
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].
-Ntemplate
Write each segment to a separate output file [Default writes a multiple segment file to stdout].
Append a format template for the individual file names; this template must contain a C format
specifier that can format an integer argument (the running segment number across all tables); this
is usually %d but could be %08d which gives leading zeros, etc. [Default is
splitxyz_segment_%d.{txt|bin}, depending on -bo]. Alternatively, give a template with two C format
specifiers and we will supply the table number and the segment number within the table to build
the file name.
-Qflags
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 only 2 input columns)].
-S Both d and h are 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. Use -fg to indicate map data; then x,y are
assumed to be in degrees of longitude, latitude, distances are considered to be in kilometers, and
angles are actually azimuths. Otherwise, distances are Cartesian in same units as x,y and angles
are counter-clockwise from horizontal].
-V[level] (more …)
Select verbosity level [c].
-bi[ncols][t] (more …)
Select native binary input. [Default is 2, 3, or 5 input columns as set by -S].
-bo[ncols][type] (more …)
Select native binary output. [Default is 1-5 output columns as set by -Q].
-d[i|o]nodata (more …)
Replace input columns that equal nodata with NaN and do the reverse on output.
-e[~]”pattern” | -e[~]/regexp/[i] (more …)
Only accept data records that match the given pattern.
-f[i|o]colinfo (more …)
Specify data types of input and/or output columns.
-g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more …)
Determine data gaps and line breaks. Do not let a segment have a gap exceeding gap; instead, split
it into two segments. [Default ignores gaps].
-h[i|o][n][+c][+d][+rremark][+rtitle] (more …)
Skip or produce header record(s).
-icols[+l][+sscale][+ooffset][,…] (more …)
Select input columns and transformations (0 is first column).
-:[i|o] (more …)
Swap 1st and 2nd column on input and/or output.
-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explanation of any module-specific option
(but not the GMT common options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
ASCII FORMAT PRECISION
The ASCII output formats of numerical data are controlled by parameters in your gmt.conf file. Longitude
and latitude are formatted according to FORMAT_GEO_OUT, absolute time is under the control of
FORMAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point values are formatted according to
FORMAT_FLOAT_OUT. Be aware that the format in effect can lead to loss of precision in ASCII 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
FORMAT_FLOAT_OUT setting.
DISTANCE CALCULATIONS
The type of input data is dictated by the -f option. If -fg is given then x,y are in degrees of
longitude, latitude, distances are in kilometers, and angles are azimuths. Otherwise, distances are
Cartesian in same units as x,y and angles are counter-clockwise from horizontal.
EXAMPLES
Suppose you want to make a wiggle plot of magnetic anomalies on segments oriented approximately east-west
from a NGDC-supplied cruise called JA020015 in the region -R300/315/12/20. You want to use a 100 km
low-pass filter to smooth the tracks and a 500km high-pass filter to detrend the magnetic anomalies. Try
this:
gmt mgd77list JA020015 -R300/315/12/20 -Flon,lat,mag,dist,azim | gmt splitxyz -A90/15 -F100/-500 \
-D100 -S -V -fg | gmt pswiggle -R300/315/12/20 -Jm0.6i -Baf -B+tJA020015 -T1 \
-W0.75p -Ggray -Z200 > JA020015_wiggles.ps
MGD-77 users: For this application we recommend that you extract dist,azim 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_###.txt (when gap exceeds 100 km). Try this:
gmt splitxyz survey.bin -Nsurvey_%03d.txt -V -gd100k -D100 -: -fg -bi3d
SEE ALSO
gmt, filter1d, mgd77list, pswiggle
COPYRIGHT
2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe