psmask - To clip or mask areas of no data on a map


       psmask         [xyzfile]        -Idx[m|c][/dy[m|c]]        -Jparameters
       -Rwest/east/south/north[r] [  -Btickinfo  ]  [  -Ddumpfile  ]  [  -Eaz-
       imuth/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 ]


       psmask  reads a (x,y,z) file [or standard input] and uses this informa-
       tion to find out which grid cells are reliable.  Only  gridcells  which
       have one or more data points are considered 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  reli-
       able/not  reliable points, psmask will either paint tiles to mask these
       nodes (with the -T) switch, or use contouring 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.

              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 setting in .gmtdefaults4, but this
              can be overridden on the command line by appending c, i, or m to
              the scale/width value.  For map height, max  dimension,  or  min
              dimension, append h, +, or - to the width, respectively.


              -Jclon0/lat0/scale (Cassini)
              -Jjlon0/scale (Miller)
              -Jmscale (Mercator - Greenwich and Equator as origin)
              -Jmlon0/lat0/scale (Mercator - Give meridian and standard paral-
              -Joalon0/lat0/azimuth/scale  (Oblique  Mercator  -   point   and
              -Joblon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
              -Joclon0/lat0/lonp/latp/scale  (Oblique  Mercator  -  point  and
              -Jqlon0/scale (Equidistant Cylindrical  Projection  (Plate  Car-
              -Jtlon0/scale (TM - Transverse Mercator, with Equator as y = 0)
              -Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
              -Juzone/scale (UTM - Universal Transverse Mercator)
              -Jylon0/lats/scale (Basic Cylindrical Projection)


              -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)


              -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)


              -Jp[a]scale[/origin]  (polar  (theta,r)  coordinates, optional a
              for azimuths and offset theta [0])
              -Jxx-scale[l|ppow][/y-scale[l|ppow]][d] (Linear, log, and  power
              More details can be found in the psbasemap man pages.

       -R     xmin,  xmax,  ymin, and ymax specify the Region of interest. For
              geographic regions,  these  limits  correspond  to  west,  east,
              south,  and north and you may specify them in decimal degrees or
              in [+-]dd:mm[][W|E|S|N] format. Append r  if  lower  left
              and  upper  right map coordinates are given instead of wesn. The
              two shorthands  -Rg  -Rd  stand  for  global  domain  (0/360  or
              -180/+180  in longitude respectively, with -90/+90 in latitude).
              For calendar time coordinates you may either give relative  time
              (relative  to  the  selected  TIME_EPOCH  and  in  the  selected
              TIME_UNIT; append t to -JX|x), or  absolute  time  of  the  form
              [date]T[clock]  (append  T  to  -JX|x). At least one of date and
              clock must be present; the T is always required. The date string
              must  be  of  the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or
              yyyy[-Www[-d]] (ISO week calendar), while the clock string  must
              be  of  the form hh:mm:ss[.xxx]. The use of delimiters and their
              type and positions must be as indicated  (however,  input/output
              and plotting formats are flexible).


       No space between the option flag and the associated arguments

       -B     Sets  map  boundary  annotation  and tickmark intervals; see the
              psbasemap man page for all the details.

       -C     Mark end of existing clip path. No input file is needed. Implic-
              itly 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 perspective plots

       -F     Force pixel registration. [Default is grid registration].

       -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/s/v, with h  in  0-360,  s,  and  v  in  0-1,  and  set
              COLOR_MODEL = hsv, or c/m/y/k, each in 0-100 %).

       -H     Input file(s) has Header record(s). Number of header records can
              be changed by editing your  .gmtdefaults4  file.  If  used,  GMT
              default  is  1  header record. Use -Hi if only input data should
              have header records [Default will write out  header  records  if
              the input data have them].  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  and
              -bo[s]n must set the number of output columns explicitly.

       -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  sys-

       -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
              indicate km, also implying that -R and -I are in degrees.

       -T     Plot  tiles  instead of clip polygons (Only works with -Jx, -Jj,
              -Jm, -Jq, and -Jy).  Use -G to set tile color.

       -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.).  The  GMT parameters
              UNIX_TIME and UNIX_TIME_POS can affect the appearance;  see  the
              gmtdefaults man page for details.

       -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  abso-
              lute  coordinates; the default (r) will reset plot origin.  Give
              c to center plot using current page size.

       -:     Toggles between  (longitude,latitude)  and  (latitude,longitude)
              input  and/or output. [Default is (longitude,latitude)].  Append
              i to select input only or o  to  select  output  only.  [Default
              affects both].

       -bi    Selects  binary input. Append s for single precision [Default is
              double].  Append n for the  number  of  columns  in  the  binary
              [Default is 2 input columns].

       -c     Specifies the number of plot copies. [Default is 1].


       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, use:

       psmask africa_grav.xyg -R20/40/20/40 -I5m -JM10i -O -K >

       The same example but this time we use white tiling:

       psmask africa_grav.xyg -R20/40/20/40 -I5m  -JM10i  -T  -O  -K  -G255  >


       gmt(l), grdmask(l), surface(l), psbasemap(l), psclip(l)

GMT4.0                            1 Oct 2004                         PSMASK(l)

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