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.)

[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

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 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 .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 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/output. [Default is (longitude,latitude)]. Applies to geographic 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)