GRDCUT

grdcut − Extract a subregion out of a .grd file

grdcut input_file.grd −Goutput_file.grd −Rwest/east/south/north[r] [ −V ] [ −f[i|o]colinfo ]

grdcut will produce a new output_file.grd file which is a subregion of input_file.grd. The subregion is specified with −R as in other programs; the specified range must not exceed the range of input_file.grd. If in doubt, run grdinfo to check range. Complementary to grdcut there is grdpaste, which will join together two grdfiles along a common edge.

input_file.grd

this is the input .grd format file.

−Goutput_file.grd

this is the output .grd format file.

−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). This defines the subregion to be cut out.

−V

Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].

−f

Special formatting of input and output columns (time or geographical 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), or f (floating point) to each column or column range item. Shorthand −f[i|o]g means −f[i|o]0x,1y (geographic coordinates).

Suppose you have used surface to grid ship gravity in the region between 148E - 162E and 8N - 32N, and you do not trust the gridding near the edges, so you want to keep only the area between 150E - 160E and 10N - 30N, then:

grdcut grav_148_162_8_32.grd −Ggrav_150_160_10_30.grd −R150/160/10/30 −V

grdpaste(l), grdinfo(l), GMT(l)