1SPLITXYZ(1) GMT SPLITXYZ(1)
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6 splitxyz - Split xyz[dh] data tables into individual segments
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9 splitxyz [ table ] [ -Aazimuth/tolerance ] [ -Ccourse_change] [
10 -Dminimum_distance ] [ -Fxy_filter/z_filter ] [ -Ntemplate ] [
11 -Qflags ] [ -S ] [ -V[level] ] [ -bbinary ] [ -dnodata ] [ -eregexp ]
12 [ -fflags ] [ -ggaps ] [ -hheaders ] [ -iflags ] [ -:[i|o] ]
13 Note: No space is allowed between the option flag and the associated
15 arguments.
16
18 splitxyz reads a series of (x,y[,z]) records [or optionally
19 (x,y,z,d,h); see -S option] from standard input [or xyz[dh]file] and
20 splits this into separate lists of (x,y[,z]) series, such that each
21 series has a nearly constant azimuth through the x,y plane. There are
22 options to choose only those series which have a certain orientation,
23 to set a minimum length for series, and to high- or low-pass filter the
24 z values and/or the x,y values. splitxyz is a useful filter between
25 data extraction and pswiggle plotting, and can also be used to divide a
26 large x,y[,z] dataset into segments.
27
29 none.
30
32 table One or more ASCII [or binary, see -bi] files with 2, 3, or 5
33 columns holding (x,y,[z[,d,h]]) data values. To use (x,y,z,d,h)
34 input, sorted so that d is non-decreasing, specify the -S
35 option; default expects (x,y,z) only. If no files are specified,
36 splitxyz will read from standard input.
37 -Aazimuth/tolerance
39 Write out only those segments which are within +/- tolerance
40 degrees of azimuth in heading, measured clockwise from North, [0
41 - 360]. [Default writes all acceptable segments, regardless of
42 orientation].
43 -Ccourse_change
45 Terminate a segment when a course change exceeding course_change
46 degrees of heading is detected [ignore course changes].
47 -Dminimum_distance
49 Do not write a segment out unless it is at least minimum_dis‐
50 tance units long [0]
51 -Fxy_filter/z_filter
53 Filter the z values and/or the x,y values, assuming these are
54 functions of d coordinate. xy_filter and z_filter are filter
55 widths in distance units. If a filter width is zero, the filter‐
56 ing is not performed. The absolute value of the width is the
57 full width of a cosine-arch low-pass filter. If the width is
58 positive, the data are low-pass filtered; if negative, the data
59 are high-pass filtered by subtracting the low-pass value from
60 the observed value. If z_filter is non-zero, the entire series
61 of input z values is filtered before any segmentation is per‐
62 formed, so that the only edge effects in the filtering will hap‐
63 pen at the beginning and end of the complete data stream. If
64 xy_filter is non-zero, the data is first divided into segments
65 and then the x,y values of each segment are filtered separately.
66 This may introduce edge effects at the ends of each segment, but
67 prevents a low-pass x,y filter from rounding off the corners of
68 track segments. [Default = no filtering].
69 -Ntemplate
71 Write each segment to a separate output file [Default writes a
72 multiple segment file to stdout]. Append a format template for
73 the individual file names; this template must contain a C format
74 specifier that can format an integer argument (the running seg‐
75 ment number across all tables); this is usually %d but could be
76 %08d which gives leading zeros, etc. [Default is splitxyz_seg‐
77 ment_%d.{txt|bin}, depending on -bo]. Alternatively, give a tem‐
78 plate with two C format specifiers and we will supply the table
79 number and the segment number within the table to build the file
80 name.
81 -Qflags
83 Specify your desired output using any combination of xyzdh, in
84 any order. Do not space between the letters. Use lower case. The
85 output will be ASCII (or binary, see -bo) columns of values cor‐
86 responding to xyzdh [Default is -Qxyzdh (-Qxydh if only 2 input
87 columns)].
88 -S Both d and h are supplied. In this case, input contains
90 x,y,z,d,h. [Default expects (x,y,z) input, and d,h are computed
91 from delta x, delta y. Use -fg to indicate map data; then x,y
92 are assumed to be in degrees of longitude, latitude, distances
93 are considered to be in kilometers, and angles are actually
94 azimuths. Otherwise, distances are Cartesian in same units as
95 x,y and angles are counter-clockwise from horizontal].
96 -V[level] (more ...)
98 Select verbosity level [c].
99 -bi[ncols][t] (more ...)
101 Select native binary input. [Default is 2, 3, or 5 input columns
102 as set by -S].
103 -bo[ncols][type] (more ...)
105 Select native binary output. [Default is 1-5 output columns as
106 set by -Q].
107 -d[i|o]nodata (more ...)
109 Replace input columns that equal nodata with NaN and do the
110 reverse on output.
111 -e[~]"pattern" | -e[~]/regexp/[i] (more ...)
113 Only accept data records that match the given pattern.
114 -f[i|o]colinfo (more ...)
116 Specify data types of input and/or output columns.
117 -g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more ...)
119 Determine data gaps and line breaks. Do not let a segment have a
120 gap exceeding gap; instead, split it into two segments. [Default
121 ignores gaps].
122 -h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
124 Skip or produce header record(s).
125 -icols[+l][+sscale][+ooffset][,...] (more ...)
127 Select input columns and transformations (0 is first column).
128 -:[i|o] (more ...)
130 Swap 1st and 2nd column on input and/or output.
131 -^ or just -
133 Print a short message about the syntax of the command, then
134 exits (NOTE: on Windows just use -).
135 -+ or just +
137 Print an extensive usage (help) message, including the explana‐
138 tion of any module-specific option (but not the GMT common
139 options), then exits.
140 -? or no arguments
142 Print a complete usage (help) message, including the explanation
143 of all options, then exits.
144
146 The ASCII output formats of numerical data are controlled by parameters
147 in your gmt.conf file. Longitude and latitude are formatted according
148 to FORMAT_GEO_OUT, absolute time is under the control of FOR‐
149 MAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point val‐
150 ues are formatted according to FORMAT_FLOAT_OUT. Be aware that the for‐
151 mat in effect can lead to loss of precision in ASCII output, which can
152 lead to various problems downstream. If you find the output is not
153 written with enough precision, consider switching to binary output (-bo
154 if available) or specify more decimals using the FORMAT_FLOAT_OUT set‐
155 ting.
156
158 The type of input data is dictated by the -f option. If -fg is given
159 then x,y are in degrees of longitude, latitude, distances are in kilo‐
160 meters, and angles are azimuths. Otherwise, distances are Cartesian in
161 same units as x,y and angles are counter-clockwise from horizontal.
162
164 Suppose you want to make a wiggle plot of magnetic anomalies on seg‐
165 ments oriented approximately east-west from a NGDC-supplied cruise
166 called JA020015 in the region -R300/315/12/20. You want to use a 100 km
167 low-pass filter to smooth the tracks and a 500km high-pass filter to
168 detrend the magnetic anomalies. Try this:
169 gmt mgd77list JA020015 -R300/315/12/20 -Flon,lat,mag,dist,azim | gmt splitxyz -A90/15 -F100/-500 \
171 -D100 -S -V -fg | gmt pswiggle -R300/315/12/20 -Jm0.6i -Baf -B+tJA020015 -T1 \
172 -W0.75p -Ggray -Z200 > JA020015_wiggles.ps
173 MGD-77 users: For this application we recommend that you extract
175 dist,azim from mgd77list rather than have splitxyz compute them sepa‐
176 rately.
177 Suppose you have been given a binary, double-precision file containing
179 lat, lon, gravity values from a survey, and you want to split it into
180 profiles named survey_###.txt (when gap exceeds 100 km). Try this:
181 gmt splitxyz survey.bin -Nsurvey_%03d.txt -V -gd100k -D100 -: -fg -bi3d
183
185 gmt, filter1d, mgd77list, pswiggle
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188 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
1895.4.5 Feb 24, 2019 SPLITXYZ(1)