pswiggle - Plot z = f(x,y) anomalies along tracks


pswiggle [ table ] -Jparameters -Rwest/east/south/north[/zmin/zmax][r] -Zscale[units] [ |-A|[*azimuth] ] [ -B[p|s]parameters ] [ -Ccenter ] [ -G[+|-|=]fill ] [ -Ifix_az ] [ -K ] [ -O ] [ -P ] [ -S[x]lon0/lat0/length[/units] ] [ -Tpen ] [ -U[stamp] ] [ -V[level] ] [ -Wpen ] [ -Xx_offset ] [ -Yy_offset ] [ -bibinary ] [ -ccopies ] [ -dinodata ] [ -fflags ] [ -ggaps ] [ -hheaders ] [ -iflags ] [ -pflags ] [ -ttransp ] [ -:[i|o] ]

Note: No space is allowed between the option flag and the associated arguments.


pswiggle reads (x,y,z) triplets from files [or standard input] and plots z as a function of distance along track. This means that two consecutive (x,y) points define the local distance axis, and the local z axis is then perpendicular to the distance axis, forming a right-handed coordinate system. The user may set a preferred positive anomaly plot direction, and if the positive normal is outside the plus/minus 90 degree window around the preferred direction, then 180 degrees are added to the direction. Either the positive or the negative wiggle may be shaded. The resulting PostScript code is written to standard output.

Required Arguments

-Jparameters (more ...)
Select map projection.
-R[unit]xmin/xmax/ymin/ymax[r] (more ...)
Specify the region of interest.

For perspective view p, optionally append /zmin/zmax. (more ...)

Gives anomaly scale in data-units/distance-unit, where distance-unit is the currently chosen unit specified by PROJ_LENGTH_UNIT. Alternatively, append a distance-unit among the other choices (c|i|p).

Optional Arguments

One or more ASCII (or binary, see -bi[ncols][type]) data table file(s) holding a number of data columns. If no tables are given then we read from standard input.
Sets the preferred positive azimuth. Positive wiggles will “gravitate” towards that direction, i.e., azimuths of the normal direction to the track will be flipped into the -90/+90 degree window centered on azimuth and that defines the positive wiggle side. If no azimuth is given the no preferred azimuth is enforced. Default is -A0.
-B[p|s]parameters (more ...)
Set map boundary frame and axes attributes.
Subtract center from the data set before plotting [0].
Set fill shade, color or pattern for positive and/or negative wiggles [Default is no fill]. Optionally, prepend + to fill positive areas (this is the default behavior). Prepend - to fill negative areas. Prepend = to fill both positive and negative areas with the same fill.
Set a fixed azimuth projection for wiggles [Default uses track azimuth, but see -A]. With this option, the calculated track-normal azimuths are overridden by fixed_az.
-Jz|Zparameters (more ...)
Set z-axis scaling; same syntax as -Jx.
-K (more ...)
Do not finalize the PostScript plot.
-O (more ...)
Append to existing PostScript plot.
-P (more ...)
Select “Portrait” plot orientation.
Draws a simple vertical scale centered on lon0/lat0. Use -Sx to specify cartesian coordinates instead. length is in z units, append unit name for labeling. FONT_ANNOT_PRIMARY is used as font.
Draw track [Default is no track]. Append pen attributes to use [Defaults: width = 0.25p, color = black, style = solid].
-U[[just]/dx/dy/][c|label] (more ...)
Draw GMT time stamp logo on plot.
-V[level] (more ...)
Select verbosity level [c].


-bi[ncols][t] (more ...)
Select native binary input. [Default is 3 input columns].
-ccopies (more ...)
Specify number of plot copies [Default is 1].
-dinodata (more ...)
Replace input columns that equal nodata with NaN.
-f[i|o]colinfo (more ...)
Specify data types of input and/or output columns.
-g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more ...)
Determine data gaps and line breaks.
-h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
Skip or produce header record(s).
-icols[l][sscale][ooffset][,...] (more ...)
Select input columns (0 is first column).
-p[x|y|z]azim/elev[/zlevel][+wlon0/lat0[/z0]][+vx0/y0] (more ...)
Select perspective view.
-t[transp] (more ...)
Set PDF transparency level in percent.
-:[i|o] (more ...)
Swap 1st and 2nd column on input and/or output.
-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explanation of any module-specific option (but not the GMT common options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.


To plot the magnetic anomaly stored in the file track.xym along track @ 1000 nTesla/cm (after removing a mean value of 32000 nTesla), using a 15-cm-wide Polar Stereographic map ticked every 5 degrees in Portrait mode, with positive anomalies in red on a blue track of width 0.25 points, use

gmt pswiggle track.xym -R-20/10/-80/-60 -JS0/90/15c -Z1000 -B5 \
             -C32000 -P -Gred -T0.25p,blue -S1000 -V >

and the positive anomalies will in general point in the north direction. To instead enforce a fixed azimuth of 45 for the positive wiggles, we add -I and obtain

gmt pswiggle track.xym -R-20/10/-80/-60 -JS0/90/15c -Z1000 -B5 \
          -C32000 -P -Gred -I45 -T0.25p,blue -S1000 -V >


Sometimes the (x,y) coordinates are not printed with enough significant digits, so the local perpendicular to the track swings around a lot. To see if this is the problem, you should do this:

awk '{ if (NR > 1) print atan2(y-$1, x-$2); y=$1; x=$2; }' | more

(note that output is in radians; on some machines you need “nawk” to do this). Then if these numbers jump around a lot, you may do this:

awk '{ print NR, $0 }' | filter1d -Fb5 -N4/0 \

which performs a 5-point boxcar filter, and plot this data set instead.