Provided by: gmt-common_5.2.1+dfsg-3build1_all 
NAME
grdview - Create 3-D perspective image or surface mesh from a grid
SYNOPSIS
grdview relief_file parameters [ [p|s]parameters ] [ [cpt]] [ drapefile | grd_r,grd_g,grd_b ] [
intensfile|intensity ] [ -Jz|Zparameters ] [ -K ] [ level[+gfill] ] [ -O ] [ -P ] [ args[+m] ] [
west/east/south/north[/zmin/zmax][r] ] [ smooth ] [ [s][o[pen]] ] [ [just/dx/dy/][c|label] ] [ typepen ]
[ x_offset ] [ y_offset ] [ -ccopies ] [ -n<flags> ] [ -p<flags> ] [ -t<transp> ]
Note: No space is allowed between the option flag and the associated arguments.
DESCRIPTION
grdview reads a 2-D grid file and produces a 3-D perspective plot by drawing a mesh, painting a
colored/grayshaded surface made up of polygons, or by scanline conversion of these polygons to a raster
image. Options include draping a data set on top of a surface, plotting of contours on top of the
surface, and apply artificial illumination based on intensities provided in a separate grid file.
REQUIRED ARGUMENTS
relief_file
2-D gridded data set to be imaged (the relief of the surface). (See GRID FILE FORMAT below.)
-Jparameters (more ...)
Select map projection.
-Jz|Zparameters (more ...)
Set z-axis scaling; same syntax as -Jx.
OPTIONAL ARGUMENTS
-B[p|s]parameters (more ...)
Set map boundary intervals.
-C[cpt]
name of the CPT file. Must be present if you want (1) mesh plot with contours (-Qm), or (2)
shaded/colored perspective image (-Qs or -Qi). For -Qs: You can specify that you want to skip a
z-slice by setting red = -; to use a pattern give red = P|pdpi/pattern[:Fcolor[Bcolor]].
Alternatively, supply the name of a GMT color master CPT [rainbow] and let grdview automatically
determine a 16-level continuous CPT from the grid's z-range.
-Gdrapefile | -Ggrd_r,grd_g,grd_b
Drape the image in drapefile on top of the relief provided by relief_file. [Default is
relief_file]. Note that -Jz and -N always refers to the relief_file. The drapefile only provides
the information pertaining to colors, which is looked-up via the CPT file (see -C). Alternatively,
give three grid files separated by commas. These files must contain the red, green, and blue
colors directly (in 0-255 range) and no CPT file is needed. The drapefile may be of higher
resolution than the relief_file.
-Iintensfile|intensity
Gives the name of a grid file with intensities in the (-1,+1) range, or a constant intensity to
apply everywhere. [Default is no illumination].
-K (more ...)
Do not finalize the PostScript plot.
-Nlevel[+gfill]
Draws a plane at this z-level. If the optional color is provided via the +g modifier, the frontal
facade between the plane and the data perimeter is colored. See -Wf for setting the pen used for
the outline.
-O (more ...)
Append to existing PostScript plot.
-P (more ...)
Select "Portrait" plot orientation.
-Qargs[+m]
Select one of following settings. For any of these choices, you may force a monochrome image by
appending the modifier +m. Colors are then converted to shades of gray using the (monochrome
television) YIQ transformation
1. Specify m for mesh plot [Default], and optionally append color for a different mesh paint
[white].
2. Specify mx or my for waterfall plots (row or column profiles). Specify color as for plain m
3. Specify s for surface plot, and optionally append m to have mesh lines drawn on top of surface.
4. Specify i for image plot, and optionally append the effective dpi resolution for the
rasterization [100].
5. Specify c. Same as -Qi but will make nodes with z = NaN transparent, using the colormasking
feature in PostScript Level 3 (the PS device must support PS Level 3). .
-R[unit]xmin/xmax/ymin/ymax[r] (more ...)
Specify the region of interest.
For perspective view p, optionally append /zmin/zmax. (more ...) This option may be used to indicate the
range used for the 3-D axes [Default is region given by the relief_file]. You may ask for a larger
w/e/s/n region to have more room between the image and the axes. A smaller region than specified in the
relief_file will result in a subset of the grid.
-Ssmooth
Smooth the contours before plotting (see grdcontour) [Default is no smoothing].
-T[s][o[pen]]
Plot image without any interpolation. This involves converting each node-centered bin into a
polygon which is then painted separately. Append s to skip nodes with z = NaN. This option is
useful for categorical data where interpolating between values is meaningless. Optionally, append
o to draw the tile outlines, and specify a custom pen if the default pen is not to your liking. As
this option produces a flat surface it cannot be combined with -JZ or -Jz.
-U[just/dx/dy/][c|label] (more ...)
Draw GMT time stamp logo on plot.
-V[level] (more ...)
Select verbosity level [c].
-Wtypepen
-Wc Draw contour lines on top of surface or mesh (not image). Append pen attributes used for the
contours. [Default: width = 0.75p, color = black, style = solid].
-Wm Sets the pen attributes used for the mesh. [Default: width = 0.25p, color = black, style =
solid]. You must also select -Qm or -Qsm for meshlines to be drawn.
-Wf Sets the pen attributes used for the facade. [Default: width = 0.25p, color = black, style =
solid]. You must also select -N for the facade outline to be drawn.
-X[a|c|f|r][x-shift[u]]
-Y[a|c|f|r][y-shift[u]] (more ...)
Shift plot origin.
-ccopies (more ...)
Specify number of plot copies [Default is 1].
-n[b|c|l|n][+a][+bBC][+c][+tthreshold] (more ...)
Select interpolation mode for grids.
-p[x|y|z]azim/elev[/zlevel][+wlon0/lat0[/z0]][+vx0/y0] (more ...)
Select perspective view.
-t[transp] (more ...)
Set PDF transparency level in percent.
-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows use just -).
-+ or just +
Print an extensive usage (help) message, including the explanation of any module-specific option
(but not the GMT common options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation of options, then exits.
--version
Print GMT version and exit.
--show-datadir
Print full path to GMT share directory and exit.
GRID FILE FORMATS
By default GMT writes out grid as single precision floats in a COARDS-complaint netCDF file format.
However, GMT is able to produce grid files in many other commonly used grid file formats and also
facilitates so called "packing" of grids, writing out floating point data as 1- or 2-byte integers. To
specify the precision, scale and offset, the user should add the suffix =id[/scale/offset[/nan]], where
id is a two-letter identifier of the grid type and precision, and scale and offset are optional scale
factor and offset to be applied to all grid values, and nan is the value used to indicate missing data.
In case the two characters id is not provided, as in =/scale than a id=nf is assumed. When reading
grids, the format is generally automatically recognized. If not, the same suffix can be added to input
grid file names. See grdconvert and Section grid-file-format of the GMT Technical Reference and Cookbook
for more information.
When reading a netCDF file that contains multiple grids, GMT will read, by default, the first
2-dimensional grid that can find in that file. To coax GMT into reading another multi-dimensional
variable in the grid file, append ?varname to the file name, where varname is the name of the variable.
Note that you may need to escape the special meaning of ? in your shell program by putting a backslash in
front of it, or by placing the filename and suffix between quotes or double quotes. The ?varname suffix
can also be used for output grids to specify a variable name different from the default: "z". See
grdconvert and Sections modifiers-for-CF and grid-file-format of the GMT Technical Reference and Cookbook
for more information, particularly on how to read splices of 3-, 4-, or 5-dimensional grids.
CONSEQUENCES OF GRID RESAMPLING
Except for Cartesian cases, we need to resample your geographic grid onto an equidistant projected grid.
In doing so various algorithms come into play that projects data from one lattice to another while
avoiding anti-aliasing, leading to possible distortions. One expected effect of resampling with splines
is the tendency for the new resampled grid to slightly exceed the global min/max limits of the original
grid. If this is coupled with tight CPT file limits you may find that some map areas may show up with
fore- or background color due to the resampling. In that case you have two options: (1) Modify your CPT
file to fit the resampled extrema (reported with -V) or (2) Impose clipping of resampled values so they
do not exceed the input min/max values (add +c to your -n option).
EXAMPLES
To make a mesh plot from the file hawaii_grav.nc and drawing the contours given in the CPT file
hawaii.cpt on a Lambert map at 1.5 cm/degree along the standard parallels 18 and 24, with vertical scale
20 mgal/cm, and looking at the surface from SW at 30 degree elevation, run
gmt grdview hawaii_grav.nc -Jl18/24/1.5c -Chawaii.cpt \
-Jz0.05c -Qm -N-100 -p225/30 -Wc > hawaii_grav_image.ps
To create a illuminated color perspective plot of the gridded data set image.nc, using the CPT file
color.rgb, with linear scaling at 10 cm/x-unit and tickmarks every 5 units, with intensities provided by
the file intens.nc, and looking from the SE, use
gmt grdview image.nc -Jx10.0c -Ccolor.rgb -Qs -p135/30 -Iintens.nc > image3D.ps
To make the same plot using the rastering option with dpi = 50, use
gmt grdview image.nc -Jx10.0c -Ccolor.rgb -Qi50 -p135/30 -Iintens.nc > image3D.ps
To create a color PostScript perspective plot of the gridded data set magnetics.nc, using the CPT file
mag_intens.cpt, draped over the relief given by the file topography.nc, with Mercator map width of 6 inch
and tickmarks every 1 degree, with intensities provided by the file topo_intens.nc, and looking from the
SE, run
gmt grdview topography.nc -JM6i -Gmagnetics.nc -Cmag_intens.cpt \
-Qs -p140/30 -Itopo_intens.nc > draped3D.ps
Given topo.nc and the Landsat image veggies.ras, first run grd2rgb to get the red, green, and blue grids,
and then drape this image over the topography and shade the result for good measure. The commands are
gmt grd2rgb veggies.ras -Glayer_%c.nc
gmt grdview topo.nc -JM6i -Qi -p140/30 -Itopo_intens.nc \
-Glayer_r.nc,layer_g.nc,layer_b.nc > image.ps
REMARKS
For the -Qs option: PostScript provides no way of smoothly varying colors within a polygon, so colors can
only vary from polygon to polygon. To obtain smooth images this way you may resample the grid file(s)
using grdsample or use a finer grid size when running gridding programs like surface or nearneighbor.
Unfortunately, this produces huge PostScript files. The alternative is to use the -Qi option, which
computes bilinear or bicubic continuous color variations within polygons by using scanline conversion to
image the polygons.
SEE ALSO
gmt, grd2rgb, gmtcolors, grdcontour, grdimage, nearneighbor, psbasemap, pscontour, pstext, surface
COPYRIGHT
2015, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.2.1 January 28, 2016 GRDVIEW(1gmt)