grdblend - Blend several partially over-lapping grids into one large
grdblend blendfile -Ggrdfile -Ix_inc[m|c][/y_inc[m|c]]
-Rwest/east/south/north[r] [ -Nnodata ] [ -Q ][ -Zscale ] [ -V ] [ -W ]
[ -f[i|o]colinfo ]
grdblend reads a listing of gridded files and blend parameters and cre-
ates a binary grdfile by blending the other grids using cosine-taper
weights. grdblend will report if some of the nodes are not filled in
with data. Such unconstrained nodes are set to a value specified by the
user [Default is NaN]. Nodes with more than one value will be set to
the weighted average value.
ASCII file with one record per grid file to include in the
blend. Each record must contain the gridfile name, the -R-set-
ting for the interior region, and the relative weight wr, sepa-
rated by spaces or tabs. In the combined weighting scheme, this
grid will be given weight = zero outside its domain, weight = wr
inside the interior region, and a 2-D cosine-tapered weight
between those end-members in the boundary strip. If the ASCII
file is not given grdblend will read standard input.
-G grdfile is the name of the binary output grdfile.
-I x_inc [and optionally y_inc] is the grid spacing. Append m to
indicate minutes or c to indicate seconds.
-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[:ss.xxx][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).
-N No data. Set nodes with no input grid to this value [Default is
-Q Create a header-less gridfile suitable for use with grdraster.
Requires that the output gridfile is a native format (i.e., not
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-W Do not blend, just output the weights used for each node. This
option is valid when only one input grid is provided [Default
makes the blend].
-Z Scale output values by scale before writing to file. .
-f Special formatting of input and output columns (time or geo-
graphical data) Specify i(nput) or o(utput) [Default is both
input and output]. Give one or more columns (or column ranges)
separated by commas. Append T (Absolute calendar time), t (time
relative to chosen TIME_EPOCH), x (longitude), y (latitude), g
(geographic coordinate), or f (floating point) to each column or
column range item.
To create a grdfile from the four gridded files piece_?.grd, make the
blendfile like this
piece_1.grd -R<subregion_1> 1
piece_2.grd -R<subregion_2> 1
piece_3.grd -R<subregion_3> 1
piece_4.grd -R<subregion_4> 1
grdblend blend.job -Gblend.grd -R<full_region> -I<dx/dy> -V
gmt(l), grd2xyz(l), grdedit(l)
GMT4.0 1 Oct 2004 GRDBLEND(l)
Man(1) output converted with