gmtselect
gmtselect - Select data subsets based on multiple spatial
criteria
SYNOPSIS
gmtselect [ infiles ] [ -Amin_area[/min_level/max_level] ]
[ -C[f]dist/ptfile ] [ -Dresolution ] [ -Fpolygonfile ] [
-H[nrec] ] [ -I[cflrs] ] [ -Jparameters ] [ -L[dist/line
file] ] [ -M[flag] ] [ -Nmaskvalues[o] ] [
-Rwest/east/south/north[r] ] [ -V ] [ -: ] [ -bi[s][n] ] [
-bo[s] ]
DESCRIPTION
gmtselect is a filter that reads (longitude, latitude)
positions from the first 2 columns of infiles [or standard
input] and uses a combination of 1-5 criteria to pass or
reject the records. Records can be selected based on
whether or not they are 1) inside a rectangular region (-R
[and -J]), 2) within dist km of any point in ptfile, 3)
within dist km of any line in linefile, 4) inside one of
the polygons in the polygonfile, and 5) inside geographi
cal features (based on coastlines). The sense of the
tests can be reversed for each of these 5 criteria by
using the -I option. See option -: on how to read (lati
tude,longitude) files.
No space between the option flag and the associ
ated arguments. Use upper case for the option flags and
lower case for modifiers.
infiles
ASCII (or binary, see-b) data file(s) to be oper
ated on. If not given, standard input is read.
OPTIONS
-A Ignored unless -N is set. Geographical features
with an area smaller than min_area in km^2 or of
hierarchical level that is lower than min_level or
higher than max_level will be ignored [Default is
0/4 (all features)]. See DATABASE INFORMATION in
the pscoast man-pages for more details.
-C Pass all records whose location is within dist km
of any of the points in ptfile. If dist is zero
then the 3rd column of ptfile must have each
point's individual radius of influence. Prepend f
to indicate you want approximate flat' earth dis
tance calculations (faster) than exact great circle
calculations (slower).
-D Ignored unless -N is set. Selects the resolution of
the coastline data set to use ((f)ull, (h)igh,
(i)ntermediate, (l)ow, or (c)rude). The resolution
drops off by ~80% between data sets. [Default is
inside [or outside] when a different resolution is
selected.
-F Pass all records whose location is within one of
the closed polygons in the multiple-segment file
polygonfile.
-H Input file(s) has Header record(s). Number of
header records can be changed by editing your .gmt
defaults file. If used, GMT default is 1 header
record.
-I Reverses the sense of the test for each of the cri
teria specified:
c select records NOT inside any point's
circle of influence.'
f select records NOT inside any of the
polygons.
l select records NOT within the specified
distance of any line.
r select records NOT inside the specified
rectangular region.
s select records NOT considered inside as
specified by -A, -D, -N.
-J Selects the map projection. Scale is UNIT/degree,
1:xxxxx, or width in UNIT (upper case modifier).
UNIT is cm, inch, or m, depending on the MEA
SURE_UNIT setting in .gmtdefaults, but this can be
overridden on the command line by appending the c,
i, or m to the scale/width value.
CYLINDRICAL PROJECTIONS:
-Jclon0/lat0/scale (Cassini)
-Jjlon0/scale (Miller)
-Jmscale (Mercator - Greenwich and Equator as ori
gin)
-Jmlon0/lat0/scale (Mercator - Give meridian and
standard parallel)
-Joalon0/lat0/azimuth/scale (Oblique Mercator -
point and azimuth)
-Joblon0/lat0/lon1/lat1/scale (Oblique Mercator -
two points)
-Joclon0/lat0/lonp/latp/scale (Oblique Mercator -
point and pole)
-Jqlon0/scale (Equidistant Cylindrical Projection
(Plate Carree))
-Jtlon0/scale (TM - Transverse Mercator, with Equa
tor as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set
origin)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/[slat/]scale (General Stereographic)
CONIC PROJECTIONS:
-Jblon0/lat0/lat1/lat2/scale (Albers)
-Jdlon0/lat0/lat1/lat2/scale (Equidistant)
-Jllon0/lat0/lat1/lat2/scale (Lambert)
MISCELLANEOUS PROJECTIONS:
-Jhlon0/scale (Hammer)
-Jilon0/scale (Sinusoidal)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jnlon0/scale (Robinson)
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jwlon0/scale (Mollweide)
NON-GEOGRAPHICAL PROJECTIONS:
-Jp[a]scale[/origin] (polar (theta,r) coordinates,
optional a for azimuths and offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log,
and power scaling)
More details can be found in the psbasemap man
pages.
-L Pass all records whose location is within dist km
of any of the line segments in the multiple-segment
file linefile. If dist is zero then the 2nd column
of each sub-header in the ptfile must have each
lines's individual distance value.' If no argu
ments are given, it means instead that the x column
contains longitudes, which may differ from the
region in -R by [multiples of] 360 degrees [Default
assumes no periodicity]
-M Multiple segment file. Segments are separated by a
record whose first character is flag. [Default is
'>'].
-N Pass all records whose location is inside specified
geographical features. Specify if records should
be skipped or kkept using 1 of 2 formats:
-Nwet/dry.
aries be considered outside the feature [Default is
inside]. [Default is s/k/s/k/s (i.e., s/k), which
passes all points on dry land].
-R west, east, south, and north specify the Region of
interest. To specify boundaries in degrees and min
utes [and seconds], use the dd:mm[:ss] format.
Append r if lower left and upper right map coordi
nates are given instead of wesn. If no map projec
tion is supplied we implicitly set -Jx1.
-V Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
-: Toggles between (longitude,latitude) and (lati
tude,longitude) input/output. [Default is (longi
tude,latitude)]. Applies to geographic coordinates
only.
-bi Selects binary input. Append s for single precision
[Default is double]. Append n for the number of
columns in the binary file(s). [Default is 2 input
columns].
-bo Selects binary output. Append s for single preci
sion [Default is double].
EXAMPLES
To extract the subset of data set that is within 300 km of
any of the points in pts.d but more than 100 km away from
the lines in lines.d, try
gmtselect lonlatfile -Jd1d -C300/pts.d -L100/lines.d -Il >
subset
Here, you must specify a mapprojection so that knows you
are giving it geographical data (otherwise 300 would be
interpreted as Cartesian distance in x-y units instead of
km). To keep all points in data.d except those on land,
as determined by the high-resolution coastlines, try
gmtselect data.d -R120/121/22/24 -Dh -Ns/k > subset
SEE ALSO
gmtdefaults(l), gmt(l), grdlandmask(l), pscoast(l)
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