grd2xyz(1) [debian man page]
GRD2XYZ(l) GRD2XYZ(l) NAME
grd2xyz - Converting a grdfile to an ASCII or binary table SYNOPSIS
grd2xyz grdfile [ -H[nrec] ] [ -L ] [ -Rwest/east/south/north[r] [ -S[r ] [ -V ] [ -Z[flags] ] [ -bo[s][n] ] DESCRIPTION
grd2xyz reads a binary 2-D grdfile and writes out xyz-triplets in ASCII [or binary] format to standard output. Modify the precision of the ASCII output format by editing the D_FORMAT parameter in your .gmtdefaults file, or choose binary output using single or double precision storage. As an option you may output z-values without the (x,y) in a number of formats, see -Z below. grdfile The 2-D binary file to be converted. OPTIONS
-H Output 1 header record based on information in the grdfile header. Ignored if binary output is selected. [Default is no header]. -L Indicates that the x values are longitudes (necessary for -: to work). -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. -S Suppress output for nodes whose z-value equals NaN [Default outputs all nodes]. Append r to reverse the suppression, i.e., only output the nodes whose z-value equals NaN. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. -Z Write a 1-column ASCII [or binary] table. Output will be organized according to the specified ordering convention contained in flags. If data should be written by 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 should start 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 grid is periodic in x but the outcoming data should not contain the (redundant) column at x = xmax, append x. For grid periodic in y, skip writing the redundant row at y = ymax by appending y. 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 output. -bo Selects binary output. Append s for single precision [Default is double]. This option only applies to xyz output; see -Z for z ta- ble output. EXAMPLES
To edit individual values in the 5' by 5' hawaii_grv.grd file, try grd2xyz hawaii_grv.grd > hawaii_grv.xyz To write a single precision binary file without the x,y positions from the file raw_data.grd file, using scanline orientation, try grd2xyz raw_data.grd -ZTLf > hawaii_grv.b SEE ALSO
gmtdefaults(1gmt), gmt(1gmt), grdedit(1gmt), xyz2grd(1gmt) 1 Jan 2004 GRD2XYZ(l)
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BLOCKMEDIAN(l) BLOCKMEDIAN(l) NAME
blockmedian - filter to block average (x,y,z) data by L1 norm. SYNOPSIS
blockmedian [ xyz[w]file(s) ] -Ix_inc[m|c][/y_inc[m|c]] -Rwest/east/south/north[r] [ -C ] [ -F ] [ -H[nrec] ] [ -L ] [ -Q ] [ -V ] [ -W[io] ] [ -: ] [ -bi[s][n] ] [ -bo[s][n] ] DESCRIPTION
blockmedian reads arbitrarily located (x,y,z) triples [or optionally weighted quadruples (x,y,z,w)] from standard input [or xyz[w]file(s)] and writes to standard output a median position and value for every non-empty block in a grid region defined by the -R and -I arguments. Either blockmean, blockmedian, or blockmode should be used as a pre-processor before running surface to avoid aliasing short wavelengths. These routines are also generally useful for decimating or averaging (x,y,z) data. You can modify the precision of the output format by editing the D_FORMAT parameter in your .gmtdefaults file, or you may choose binary input and/or output using single or double precision storage. xyz[w]file(s) 3 [or 4] column ASCII file(s) [or binary, see -b] holding (x,y,z[,w]) data values. [w] is an optional weight for the data. If no file is specified, blockmedian will read from standard input. -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
-C Use the center of the block as the output location [Default uses the median location (but see -Q)]. -C overrides -Q. -F Block centers have pixel registration. [Default: grid registration.] (Registrations are defined in GMT Cookbook Appendix B on grid file formats.) Each block is the locus of points nearest the grid value location. For example, with -R10/15/10/15 and and -I1: with the -F option 10 <= (x,y) < 11 is one of 25 blocks; without it 9.5 <= (x,y) < 10.5 is one of 36 blocks. -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 region in -R by [multiples of] 360 degrees [Default assumes no periodicity]. -Q (Quicker) Finds median z and (x, y) at that z [Default finds median x, median y, median z]. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. -W Weighted modifier[s]. Unweighted input and output has 3 columns x,y,z; Weighted i/o has 4 columns x,y,z,w. Weights can be used in input to construct weighted median values in blocks. Weight sums can be reported in output for later combining several runs, etc. Use -W for weighted i/o, -Wi for weighted input only, -Wo for weighted output only. [Default uses unweighted i/o] -: 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 (or 4 if -W is set) columns]. -bo Selects binary output. Append s for single precision [Default is double]. EXAMPLES
To find 5 by 5 minute block medians from the double precision binary data in hawaii_b.xyg and output an ASCII table, try blockmedian hawaii_b.xyg -R198/208/18/25 -I5m -bi3 > hawaii_5x5.xyg SEE ALSO
blockmean(1gmt), blockmode(1gmt), gmt(1gmt), gmtdefaults(1gmt), nearneighbor(1gmt), surface(1gmt), triangulate(1gmt) 1 Jan 2004 BLOCKMEDIAN(l)