NAME
psmask - To clip or mask areas of no data on a map
SYNOPSIS
psmask [xyzfile] -Idx[m|c][/dy[m|c]] -Jparameters
-Rwest/east/south/north[r] [ -Btickinfo ] [ -Ddumpfile ] [
-Eazimuth/elevation ] [ -F ] [ -Gfill ] [ -H[nrec] ] [ -K ]
[ -M[flag] ] [ -N ] [ -O ] [ -P ] [ -Sradius[k] ] [ -T ] [
-U[/dx/dy/][label] ] [ -V ] [ -Xx-shift ] [ -Yy-shift ] [
-ccopies ] [ -: ] [ -bi[s][n] ]
psmask -C [ -K ] [ -O ]
DESCRIPTION
psmask reads a (x,y,z) file [or standard input] and uses
this information to find out which grid cells are reliable.
Only gridcells which have one or more data points are con-
sidered reliable. As an option, you may specify a radius of
influence. Then, all gridcells that are within radius of a
data point are considered reliable. Furthermore, an option
is provided to reverse the sense of the test. Having found
the reliable/not reliable points, psmask will either paint
tiles to mask these nodes (with the -T) switch, or use con-
touring to create polygons that will clip out regions of no
interest. When clipping is initiated, it will stay in
effect until turned off by a second call to psmask using the
-C option.
xyzfile
File with (x,y,z) values (e.g., that was used to run
surface). If no file is given, standard input is read.
For binary files, see -b.
-I x_inc [and optionally y_inc] is the grid spacing.
Append m to indicate minutes or c to indicate seconds.
-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 MEASURE_UNIT set-
ting 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 origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and stan-
dard 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 Equator
as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set ori-
gin)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/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:
-Jpscale[/origin] (polar (theta,r) coordinates, option-
ally offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and
power scaling)
More details can be found in the psbasemap manpages.
-R west, east, south, and north specify the Region of
interest. To specify boundaries in degrees and minutes
[and seconds], use the dd:mm[:ss] format. Append r if
lower left and upper right map coordinates are given
instead of wesn.
OPTIONS
No space between the option flag and the associated argu-
ments
-B Sets map boundary tickmark intervals. See psbasemap for
details.
-C Mark end of existing clip path. No input file is
needed. Implicitly sets -O.
-D Dumps out the resulting clipping polygons to disk.
Ignored if -T is set. If no dumpprefix is given we use
mask (Files will be called mask_*.d).
-E Sets the viewpoint's azimuth and elevation for perspec-
tive plots [180/90]
-F Force pixel registration. [Default is grid registra-
tion].
-G Paint the clip polygons [or tiles] with selected fill
[Default is no fill]. Specify the shade (0-255) or
color (r/g/b, each in 0-255).
-H Input file(s) has Header record(s). Number of header
records can be changed by editing your .gmtdefaults
file. If used, GMT default is 1 header record. Not
used with binary data.
-K More PostScript code will be appended later [Default
terminates the plot system].
-M Multiple segment file(s). Segments are separated by a
special record. For ASCII files the first character
must be flag [Default is '>']. For binary files all
fields must be NaN.
-N Invert the sense of the test, i.e. clip regions where
there is data coverage.
-O Selects Overlay plot mode [Default initializes a new
plot system].
-P Selects Portrait plotting mode [GMT Default is
Landscape, see gmtdefaults to change this].
-S Sets radius of influence. Grid nodes within radius of a
data point are considered reliable. [Default is 0,
which means that only grid cells with data in them are
reliable]. Append k to indicated km, also implying
that -R -I are in degrees.
-T Plot tiles instead of clip polygons (Only works with
-Jx, -Jj, -Jm, -Jq, and -Jy).
-U Draw Unix System time stamp on plot. User may specify
where the lower left corner of the stamp should fall on
the page relative to lower left corner of plot.
Optionally, append a label, or c (which will plot the
command string.)
-V Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].
-X -Y
Shift origin of plot by (x-shift,y-shift). Prepend a
for absolute coordinates; the default (r) will reset
plot origin.
-: Toggles between (longitude,latitude) and
(latitude,longitude) input/output. [Default is
(longitude,latitude)].
-c Specifies the number of plot copies. [Default is 1]
-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].
EXAMPLES
To make an overlay PostScript file that will mask out the
regions of a contour map where there is no control data
using clip polygons, try:
psmask africa_grav.xyg -R20/40/20/40 -I5m -JM10i -O -K >
mask.ps
The same example but this time we use tiling:
psmask africa_grav.xyg -R20/40/20/40 -I5m -JM10i -T -O -K >
mask.ps
SEE ALSO
gmt(l), grdmask(l), surface(l), psbasemap(l), psclip(l)