NAME GMT − The Generic Mapping Tools data processing and display ...

[Pages:263]GMT(1)

Generic Mapping Tools

GMT(1)

NAME GMT - The Generic Mapping Tools data processing and display software package

INTRODUCTION GMT is a collection of public-domain Unix tools that allows you to manipulate x,y and x,y,z data sets (filtering, trend fitting, gridding, projecting, etc.) and produce PostScript illustrations ranging from simple x-y plots, via contour maps, to artificially illuminated surfaces and 3-D perspective views in black/white or full color. Linear, log10, and power scaling is supported in addition to 25 common map projections. The processing and display routines within GMT are completely general and will handle any (x,y) or (x,y,z) data as input.

SYNOPSIS GMT is also a wrapper script that can start any of the programs:

GMT module module-options

where module is the name of a GMT program and the options are those that pertain to that particular program.

GMT OVERVIEW The following is a summary of all the programs supplied with GMT and a very short description of their purpose. Detailed information about each program can be found in the separate manual pages.

blockmean blockmedian blockmode filter1d fitcircle gmt2rgb gmtconvert gmtdefaults gmtmath gmtset gmtselect grdfilter grd2cpt grd2xyz grdblend grdclip grdcontour grdcut grdedit grdfft grdgradient grdhisteq grdimage grdinfo grdlandmask grdmask grdmath grdpaste grdproject grdreformat grdsample grdtrend grdtrack

L2 (x,y,z) data filter/decimator L1 (x,y,z) data filter/decimator

Mode (x,y,z) data filter/decimator Filter 1-D data sets (time series) Finds the best-fitting great circle to a set of points

Convert Sun rasterfile or grid to r, g, b grids Convert between ASCII and binary 1-D tables List the current default settings

Mathematical operations on data tables Set individual default parameters

Extract data subsets based on spatial criteria Filter 2-D data sets in the space domain Make a color palette table from grid files Conversion from 2-D grid file to table data

Blend several partially over-lapping grid files onto one grid Limit the z-range in gridded data Contouring of 2-D gridded data Cut a sub-region from a grid file Modify header information in a 2-D grid file Operate on grid files in the wavenumber (or frequency) domain Compute directional gradient from grid files

Histogram equalization for grid files Produce images from 2-D gridded data Get information about grid files Create mask grid file from shoreline data base Reset nodes outside a clip path to a constant Mathematical operations on grid files Paste together grid files along a common edge Project gridded data onto a new coordinate system Converting between different grid file formats Resample a 2-D gridded data set onto a new grid Fits polynomial trends to grid files Sampling of 2-D data set along 1-D track

GMT 4.5.18

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GMT(1)

Generic Mapping Tools

GMT(1)

grdvector grdview grdvolume greenspline makecpt mapproject minmax nearneighbor project ps2raster psbasemap psclip pscoast pscontour pshistogram psimage pslegend psmask psrose psscale pstext pswiggle psxy psxyz sample1d spectrum1d splitxyz surface trend1d trend2d triangulate xyz2grd

Plot vector fields from grid files 3-D perspective imaging of 2-D gridded data

Volume calculations from 2-D gridded data Interpolation using Green's functions for splines in 1-3 dimensions

Make color palette tables Forward or inverse map projections of table data Find extreme values in data tables Nearest-neighbor gridding scheme Project data onto lines/great circles

Crop and convert PostScript files to raster images, EPS, and PDF Create a basemap plot Use polygon files to define clipping paths Plot coastlines and filled continents on maps Contour xyz-data by triangulation Plot a histogram Plot images (EPS or Sun raster files) on maps Plot legend on maps Create overlay to mask out regions on maps Plot sector or rose diagrams Plot gray scale or color scale on maps Plot text strings on maps Draw time-series along track on maps Plot symbols, polygons, and lines on maps Plot symbols, polygons, and lines in 3-D Resampling of 1-D table data sets Compute various spectral estimates from time-series Split xyz-files into several segments A continuous curvature gridding algorithm Fits polynomial or Fourier trends to y = f(x) data Fits polynomial trends to z = f(x,y) data Perform optimal Delaunay triangulation and gridding Convert equidistant xyz data to a 2-D grid file

SEE ALSO Look up the individual man pages for more details and full syntax. Run GMT without options to list all GMT programs and to show all installation directories. Information is also available on the GMT home page gmt.soest.hawaii.edu

REFERENCES Wessel, P., and W. H. F. Smith, 2018, The Generic Mapping Tools (GMT) version 4.5.18 Technical Reference & Cookbook, SOEST/NOAA. Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579. Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Mapping Tools Released, EOS Trans., AGU, 76 (33), p. 329. Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Mapping Tools Released, , Copyright 1995 by the American Geophysical Union. Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Display Data, EOS Trans., AGU, 72 (41), p. 441.

GMT 4.5.18

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BLOCKMEAN(1)

Generic Mapping Tools

BLOCKMEAN(1)

NAME blockmean - filter to block average (x,y,z) data by L2 norm

SYNOPSIS blockmean [ xyz[w]file(s) ] -Ixinc[unit][=|+][/yinc[unit][=|+]] -Rxmin/xmax/ymin/ymax[r] [ -C ] [ -E ] [ -F ] [ -H[i][nrec] ] [ -S[w|z] ] [ -V ] [ -W[io] ] [ -:[i|o] ] [ -b[i|o][s|S|d|D[ncol]|c[var1/...]] ] [ -f[i|o]colinfo ]

DESCRIPTION blockmean 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 mean 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 .gmtdefaults4 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, blockmean will read from standard input.

-I

x_inc [and optionally y_inc] is the grid spacing. Optionally, append a suffix modifier. Geographi-

cal (degrees) coordinates: Append m to indicate arc minutes or c to indicate arc seconds. If one

of the units e, k, i, or n is appended instead, the increment is assumed to be given in meter, km,

miles, or nautical miles, respectively, and will be converted to the equivalent degrees longitude at

the middle latitude of the region (the conversion depends on ELLIPSOID). If /y_inc is given but

set to 0 it will be reset equal to x_inc; otherwise it will be converted to degrees latitude. All coor-

dinates: If = is appended then the corresponding max x (east) or y (north) may be slightly adjusted

to fit exactly the given increment [by default the increment may be adjusted slightly to fit the given

domain]. Finally, instead of giving an increment you may specify the number of nodes desired by

appending + to the supplied integer argument; the increment is then recalculated from the number

of nodes and the domain. The resulting increment value depends on whether you have selected a

gridline-registered or pixel-registered grid; see Appendix B for details. Note: if -Rgrdfile is used

then grid spacing has already been initialized; use -I to override the values.

-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 w/e/s/n. The two shorthands -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude respectively, with -90/+90 in latitude). Alternatively, specify the name of an existing grid file and the -R settings (and grid spacing, if applicable) are copied from the grid. For calendar time coordinates you may either give (a) relative time (relative to the selected TIME_EPOCH and in the selected TIME_UNIT; append t to -JX|x), or (b) 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 exactly as indicated (however, input, output and plot formats are customizable; see gmtdefaults).

OPTIONS -C

Use the center of the block as the output location [Default uses the mean location].

-E Provide Extended report which includes s (the standard deviation of the mean), l, the lowest value, and h, the high value for each block. Output order becomes x,y,z,s,l,h[,w]. [Default outputs x,y,z[,w]. See -W for w output.

-F Force pixel node registration [Default is gridline registration]. (Node 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 -R 10/15/10/15 and and -I 1: with the -F option 10 ................
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