xyz2grd - Converting an ASCII or binary table to grd file format
xyz2grd xyzfile -Ggrdfile -Ix_inc[m|c][/y_inc[m|c]] -Rwest/east/south/north[r] [ -A[n|z] ] [ -Dxunit/yunit/zunit/scale/offset/title/remark
] [ -F ] [ -H[nrec] ] [ -L ] [ -Nnodata ] [ -S[zfile] ] [ -V ] [ -Z[flags] ] [ -: ] [ -bi[s][n] ]
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
formats, see -Z below.)
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 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.
-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. [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
-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 .gmtdefaults file. If used, GMT default
is 1 header record. Not used with binary data.
-L Indicates that the x column contains longitudes, which may differ from the regions in -R by [multiples of] 360 degrees [Default
assumes no periodicity].
-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 con-
vention 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 indicate that first element is at left or right end of row. Likewise for column for-
mats: start with L or R to position first column, and then append T or B to position first element in a row. For gridline regis-
tered 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/output. [Default is (longitude,latitude)]. Applies to geo-
graphic coordinates only.
-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.
To create a grdfile from the ASCII data in hawaii_grv.xyz, try
xyz2grd hawaii_grv.xyz -Ddegree/degree/mGal/1/0/"Hawaiian Gravity"/"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, try
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) scanline-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), try
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
gmt(1gmt), grd2xyz(1gmt), grdedit(1gmt)
1 Jan 2004 XYZ2GRD(l)