NAME
xyz2grd - Converting an ASCII or binary table to grd file format
SYNOPSIS
xyz2grd xyzfile -Ggrdfile -Ix_inc[m|c][/y_inc[m|c]]
-Rwest/east/south/north[r] [ -A[n|z|u|l] ] [ -Dxu-
nit/yunit/zunit/scale/offset/title/remark ] [ -F ] [ -H[nrec] ] [ -Nno-
data ] [ -S[zfile] ] [ -V ] [ -Z[flags] ] [ -: ] [ -bi[s][n] ] [
-f[i|o]colinfo ]
DESCRIPTION
xyz2grd reads a z or xyz table and creates a binary grdfile. xyz2grd
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 average
value. As an option (using -Z), a 1-column z-table may be read assuming
all nodes are present (z-tables can be in organized in a number of for-
mats, see -Z below.)
[xy]zfile
ASCII [or binary] file holding z or (x,y,z) values. xyz triplets
do not have to be sorted (for binary triplets, see -b). 1-column
z tables must be sorted and the -Z must be set).
-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).
OPTIONS
-A Add up multiple values that belong to the same node (same as
-Az). Append n to simply count the number of data points that
were assigned to each node. Append l or u to find the lowest
(minimum) or upper (maximum) value at each node, respectively.
[Default (no -A option) will calculate mean value]. Ignored if
-Z is given.
-D Give values for xunit, yunit, zunit, scale, offset, title, and
remark. To leave some of these values untouched, specify = as
the value.
-F Force pixel registration [Default is grid registration].
-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.
-N No data. Set nodes with no input xyz triplet to this value
[Default is NaN]. For z-tables, this option is used to replace
z-values that equal nodata with NaN.
-S Swap the byte-order of the input only. No grid file is produced.
You must also supply the -Z option. The output is written to
zfile (or stdout if not supplied).
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-Z Read a 1-column ASCII [or binary] table. This assumes that all
the nodes are present and sorted according to specified ordering
convention contained in flags. If incoming data represents
rows, make flags start with T(op) if first row is y = ymax or
B(ottom) if first row is y = ymin. Then, append L or R to indi-
cate that first element is at left or right end of row. Likewise
for column formats: start with L or R to position first column,
and then append T or B to position first element in a row. For
gridline registered grids: If data are periodic in x but the
incoming data do not contain the (redundant) column at x = xmax,
append x. For data periodic in y without redundant row at y =
ymax, append y. Append sn to skip the first n number of bytes
(probably a header). If the byte-order needs to be swapped,
append w. Select one of several data types (all binary except
a):
a ASCII representation
c signed 1-byte character
u unsigned 1-byte character
h short 2-byte integer
i 4-byte integer
l long (4- or 8-byte) integer
f 4-byte floating point single precision
d 8-byte floating point double precision
Default format is scanline orientation of ASCII numbers: -ZTLa.
Note that -Z only applies to 1-column input.
-: 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
file(s).
[Default is 3 input columns]. This option only applies to xyz
input files; see -Z for z tables.
-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.
EXAMPLES
To create a grdfile from the ASCII data in hawaii_grv.xyz, use
xyz2grd hawaii_grv.xyz -Ddegree/degree/mGal/1/0/"Hawaiian Grav-
ity"/"GRS-80 Ellipsoid used" -Ghawaii_grv_new.grd -R198/208/18/25 -I5m
-V
To create a grdfile from the raw binary (3-column, single-precision)
scanline-oriented data raw.b, use
xyz2grd raw.b -Dm/m/m/1/0/=/= -Graw.grd -R0/100/0/100 -I1 -V -Z -b3
To make a grdfile from the raw binary USGS DEM (short integer) scan-
line-oriented data topo30. on the NGDC global relief Data CD-ROM, with
values of -9999 indicate missing data, one must on some machine reverse
the byte-order. On such machines (like Sun), use
xyz2grd topo30. -Dm/m/m/1/0/=/= -Gustopo.grd -R234/294/24/50 -I30c
-N-9999 -V -ZTLhw
Say you have received a binary file with 4-byte floating points that
were written on a machine of different byte-order than yours. You can
swap the byte-order with
xyz2grd floats.bin -Snew_floats.bin -V -Zf
SEE ALSO
gmt(l), grd2xyz(l), grdedit(l)
GMT4.0 1 Oct 2004 XYZ2GRD(l)
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