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] [
-Dxunit/yunit/zunit/scale/offset/title/remark ] [ -F ] [
-H[nrec] ] [ -L ] [ -Nnodata ] [ -S[zfile] ] [ -V ] [
-Z[flags] ] [ -: ] [ -bi[s][n] ]
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 formats, 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 tri-
plets, 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.
OPTIONS
-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 registra-
tion].
-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 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 indicate 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 ele-
ment 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/output. [Default is
(longitude,latitude)].
-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.
EXAMPLES
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
SEE ALSO
gmt(l), grd2xyz(l), grdedit(l)