segy2grd(1gmt) [debian man page]
SEGY2GRD(1gmt) Generic Mapping Tools SEGY2GRD(1gmt) NAME
segy2grd - Converting SEGY file to grid file format SYNOPSIS
segy2grd segyfile -Ggrdfile -Ixinc[unit][=|+][/yinc[unit][=|+]] -Rwest/east/south/north[r] [ -A[n|z] ] [ -Dxname/yname/zname/scale/off- set/title/remark ] [ -F ] [ -Nnodata ] [ -S[zfile] ] [ -V ] [ -Z[flags] ] [ -:[i|o] ] [ -bi[s|S|d|D[ncol]|c[var1/...]] ] DESCRIPTION
segy2grd reads an IEEE SEGY file and creates a binary grid file. Either a simple mapping (equivalent to xyz2grd -Z) or a more complicated averaging where a particular grid cell includes values from more than one sample in the SEGY file can be done. segy2grd 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. segyfile is an IEEE floating point SEGY file. Traces are all assumed to start at 0 time/depth. -G grdfile is the name of the binary output grid file. -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, 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). Alterna- tively, specify the name of an existing grid file and the -R settings (and grid spacing, if applicable) are copied from the grid. OPTIONS
-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]. Not used for simple mapping. -D Give values for xname, yname, zname, scale, offset, title, and remark. To leave some of these values untouched, specify = as the value. -F Force pixel registration [Default is grid registration]. -N No data. Set nodes with no input sample to this value [Default is NaN]. -S set variable spacing header is c for cdp, o for offset, b<number> for 4-byte float starting at byte number If -S not set, assumes even spacing of samples at the dx, dy supplied with -I -L Override number of samples in each trace -X applies scalar x-scale to coordinates in trace header to match the coordinates specified in -R -Y Specifies sample interval as s_int if incorrect in the SEGY file -M Fix number of traces to read in. Default tries to read 10000 traces. -M0 will read number in binary header, -Mn will attempt to read only n traces. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. EXAMPLES To create a grid file from an even spaced SEGY file test.segy, try segy2grd test.segy -I0.1/0.1 -Gtest.grd -R198/208/18/25 -V Note that this will read in 18-25s (or km) on each trace, but the first trace will be assumed to be at X=198 To create a grid file from the SEGY file test.segy, locating traces according to the CDP number, where there are 10 CDPs per km and the sample interval is 0.1, try segy2grd test.segy -Gtest.grd -R0/100/0/10 -I0.5/0.2 -V -X0.1 -Y0.1 Because the grid interval is larger than the SEGY file sampling, the individual samples will be averaged in bins SEE ALSO
GMT(1), grd2xyz(1), grdedit(1), pssegy(1) GMT 4.5.7 15 Jul 2011 SEGY2GRD(1gmt)
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PSSEGY(1gmt) Generic Mapping Tools PSSEGY(1gmt) NAME
pssegy - Create imagemasked postscript from SEGY file SYNOPSIS
pssegy SEGYfile -Jparameters -Rwest/east/south/north[r] -Ddeviation -F[rgb|gray]|-W [ -Bbias ] [ -Cclip ] [ -Eerror ] [ -I ] [ -K ] [ -Lnsamp ] [ -Mntrace ] [ -N ] [ -O ] [ -P ] [ -Sheader ] [ -Tfilename ] [ -Uredvel ] [ -V ] [ -Xscale ] [ -Ysample int ] [ -Z ] DESCRIPTION
pssegy reads a native (IEEE) format SEGY file and produces a PostScript image of the seismic data. The imagemask operator is used so that the seismic data are plotted as a 1-bit deep bitmap in a single (user-specified) color or gray shade, with a transparent background. The bitmap resolution is taken from the current GMT defaults. The seismic traces may be plotted at their true locations using information in the trace headers (in which case order of the traces in the file is not significant). Standard GMT geometry routines are used so that in principle any map projection may be used, however it is likely that the geographic projections will lead to unexpected results. Beware also that some parameters have non-standard meanings. Note that the order of operations before the seismic data are plotted is devia- tion*[clip]([bias]+[normalize](sample value)). Deviation determines how far in the plot coordinates a [normalized][biased][clipped] sample value of 1 plots from the trace location. The SEGY file should be a disk image of the tape format (ie 3200 byte text header, which is ignored, 400 byte binary reel header, and 240 byte header for each trace) with samples as native real*4 (IEEE real on all the platforms to which I have access) SEGYfile Seismic data set to be imaged -J Selects the map projection. Scale is UNIT/degree, 1:xxxxx, or width in UNIT (upper case modifier). UNIT is cm, inch, or m, depend- ing on the MEASURE_UNIT setting in .gmtdefaults4, but this can be overridden on the command line by appending c, i, or m to the scale/width value. When central meridian is optional, default is center of longitude range on -R option. Default standard parallel is the equator. For map height, max dimension, or min dimension, append h, +, or - to the width, respectively. More details can be found in the psbasemap man pages. CYLINDRICAL PROJECTIONS: -Jclon0/lat0/scale (Cassini) -Jcyl_stere/[lon0/[lat0/]]scale (Cylindrical Stereographic) -Jj[lon0/]scale (Miller) -Jm[lon0/[lat0/]]scale (Mercator) -Jmlon0/lat0/scale (Mercator - Give meridian and standard parallel) -Jo[a]lon0/lat0/azimuth/scale (Oblique Mercator - point and azimuth) -Jo[b]lon0/lat0/lon1/lat1/scale (Oblique Mercator - two points) -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole) -Jq[lon0/[lat0/]]scale (Cylindrical Equidistant) -Jtlon0/[lat0/]scale (TM - Transverse Mercator) -Juzone/scale (UTM - Universal Transverse Mercator) -Jy[lon0/[lat0/]]scale (Cylindrical Equal-Area) CONIC PROJECTIONS: -Jblon0/lat0/lat1/lat2/scale (Albers) -Jdlon0/lat0/lat1/lat2/scale (Conic Equidistant) -Jllon0/lat0/lat1/lat2/scale (Lambert Conic Conformal) -Jpoly/[lon0/[lat0/]]scale ((American) Polyconic) AZIMUTHAL PROJECTIONS: -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area) -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant) -Jflon0/lat0[/horizon]/scale (Gnomonic) -Jglon0/lat0[/horizon]/scale (Orthographic) -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale (General Perspective). -Jslon0/lat0[/horizon]/scale (General Stereographic) MISCELLANEOUS PROJECTIONS: -Jh[lon0/]scale (Hammer) -Ji[lon0/]scale (Sinusoidal) -Jkf[lon0/]scale (Eckert IV) -Jk[s][lon0/]scale (Eckert VI) -Jn[lon0/]scale (Robinson) -Jr[lon0/]scale (Winkel Tripel) -Jv[lon0/]scale (Van der Grinten) -Jw[lon0/]scale (Mollweide) NON-GEOGRAPHICAL PROJECTIONS: -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r)) -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log, and power scaling) -R west, east, south, and north specify the Region of interest, 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). Alterna- tively, specify the name of an existing grid file and the -R settings (and grid spacing, if applicable) are copied from the grid. -D gives the deviation in X units of the plot for 1.0 on the scaled trace. -F[rgb|gray] Fill trace (variable area, defaults to filling positive). rgb or gray gives the color with which the imagemask is filled. -W Draw wiggle trace. You must specify at least one of -W and -F. OPTIONS
No space between the option flag and the associated arguments. -A Flip the default byte-swap state (default assumes data have a bigendian byte-order). -B Bias to apply to data (added to sample values). -C Sample value at which to clip data (clipping is applied to both positive and negative values). -E Allow error difference between requested and actual trace locations when using -T option. -I Fill negative rather than positive excursions. -K More PostScript code will be appended later [Default terminates the plot system]. -L Override number of samples per trace in reel header (program attempts to determine number of samples from each trace header if pos- sible to allow for variable length traces). -M Override number of traces specified in reel header. Program detects end of file (relatively) gracefully, but this parameter limits number of traces that the program attempts to read. -N Normalize trace by dividing by rms amplitude over full trace length. -O Selects Overlay plot mode [Default initializes a new plot system]. -P Selects Portrait plotting mode [Default is Landscape, see gmtdefaults to change this]. -S Read trace locations from trace headers: header is either c for CDP, o for offset, or b<num> to read a long starting at byte <num> in the header (first byte corresponds to num=0). Default has location given by trace number. -T Plot only traces whose location corresponds to a list given in filename. Order in which traces are listed is not significant - the entire space is checked for each trace. -U Apply reduction velocity by shifting traces upwards by redvel/|offset|. Negative velocity removes existing reduction. Units should be consistent with offset in trace header and sample interval. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. -X Multiply trace locations by scale before plotting. -Y Override sample interval in reel header. -Z Do not plot traces with zero rms amplitude. EXAMPLES
To plot the SEGY file wa1.segy with normalized traces plotted at true offset locations, clipped at +-3 and with wiggle trace and positive variable area shading in black, use pssegy wa1.segy -JX5/-5 -R0/100/0/10 -D1 -C3 -N -So -W -Fblack > segy.ps To plot the SEGY file wa1.segy with traces plotted at true cdp*0.1, clipped at +-3, with bias -1 and negative variable area shaded red, use pssegy wa1.segy -JX5/-5 -R0/100/0/10 -D1 -C3 -Sc -X0.1 -Fred -B-1 -I > segy.ps SEE ALSO
GMT(1), pssegyz(1) GMT 4.5.7 15 Jul 2011 PSSEGY(1gmt)