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
       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  reliable/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.

       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 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 origin)
              -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 Equator as y = 0)
              -Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
              -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/[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 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 arguments

       -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 perspective plots [180/90]'

       -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     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.

       -bo    Selects binary output. Append s for single precision [Default is double].

       -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.). 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 absolute coordinates; the
              default (r) will reset plot origin.

       -:     Toggles   between   (longitude,latitude)   and  (latitude,longitude)  input/output.
              [Default is (longitude,latitude)].  Applies to geographic coordinates only.

       -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(1gmt), grdmask(1gmt), surface(1gmt), psbasemap(1gmt), psclip(1gmt)

                                            1 Jan 2004                                  PSMASK(l)