Provided by: gmt-common_5.4.3+dfsg-1_all 
NAME
grdrotater - Finite rotation reconstruction of geographic grid
SYNOPSIS
grdrotater ingrdfile -Erot_file|lon/lat/angle
-Goutgrdfile [ -Drotoutline ] [ -Fpolygonfile ] [ -N ] [ -Rregion ] [ -S ] [ -Tages ] [ -V[level]
] [ -bbinary ] [ -dnodata ] [ -hheaders ] [ -nflags ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated arguments.
DESCRIPTION
grdrotater reads a geographical grid and reconstructs it given total reconstruction rotations.
Optionally, the user may supply a clipping polygon in multiple-segment format; then, only the part of the
grid inside the polygon is used to determine the reconstructed region. The outlines of the reconstructed
region is also returned provided the rotated region is not the entire globe.
REQUIRED ARGUMENTS
ingrdfile
Name of a grid file in geographical (lon, lat) coordinates.
-Erotfile
Give file with rotation parameters. This file must contain one record for each rotation; each
record must be of the following format:
lon lat tstart [tstop] angle [ khat a b c d e f g df ]
where tstart and tstop are in Myr and lon lat angle are in degrees. tstart and tstop are the ages
of the old and young ends of a stage. If tstop is not present in the record then a total
reconstruction rotation is expected and tstop is implicitly set to 0 and should not be specified
for any of the records in the file. If a covariance matrix C for the rotation is available it must
be specified in a format using the nine optional terms listed in brackets. Here, C = (g/khat)*[ a
b d; b c e; d e f ] which shows C made up of three row vectors. If the degrees of freedom (df) in
fitting the rotation is 0 or not given it is set to 10000. Blank lines and records whose first
column contains # will be ignored. You may prepend a leading + to the filename to indicate you
wish to invert the rotations. Alternative 1: Give the filename composed of two plate IDs
separated by a hyphen (e.g., PAC-MBL) and we will instead extract that rotation from the GPlates
rotation database. We return an error if the rotation cannot be found. Alternative 2: Specify
lon/lat/angle, i.e., the longitude, latitude, and opening angle (all in degrees and separated by
/) for a single total reconstruction rotation.
-Goutgrdfile
Name of output grid. This is the grid with the data reconstructed according to the specified
rotation. If more than one reconstruction time is implied then outgrdfile must contain a C-format
specifier to format a floating point number (reconstruction time) to text.
OPTIONAL ARGUMENTS
-Drotoutline
Name of the grid polygon outline file. This represents the outline of the grid reconstructed to
the specified time. If more than one reconstruction time is implied then rotoutline must contain a
C-format specifier to format a floating point number (reconstruction time) to text. If only one
time is implied and -D is not set then we write the polygon to stdout (but see -N).
-Fpolygonfile
Specify a multisegment closed polygon file that describes the inside area of the grid that should
be projected [Default projects entire grid].
-N Do Not output the rotated polygon outline [Default will write it to stdout, or to a file via -D].
-Rwest/east/south/north[/zmin/zmax][+r][+uunit]
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). Alternatively for grid
creation, give Rcodelon/lat/nx/ny, where code is a 2-character combination of L, C, R (for left,
center, or right) and T, M, B for top, middle, or bottom. e.g., BL for lower left. This indicates
which point on a rectangular region the lon/lat coordinate refers to, and the grid dimensions nx
and ny with grid spacings via -I is used to create the corresponding region. Alternatively,
specify the name of an existing grid file and the -R settings (and grid spacing, if applicable)
are copied from the grid. Appending +uunit expects projected (Cartesian) coordinates compatible
with chosen -J and we inversely project to determine actual rectangular geographic region. For
perspective view (-p), optionally append /zmin/zmax. In case of perspective view (-p), a z-range
(zmin, zmax) can be appended to indicate the third dimension. This needs to be done only when
using the -Jz option, not when using only the -p option. In the latter case a perspective view of
the plane is plotted, with no third dimension.
-S Skip the rotation of the grid, just rotate the polygon outline (requires -F if no grid is
provided).
-Tages Sets the desired reconstruction times. For a single time append the desired time. For an
equidistant range of reconstruction times give -Tstart/stop/inc or -Tstart/stop/npoints+. For an
non-equidistant set of reconstruction times please pass them via the first column in a file, e.g.,
-Tagefile. If no -T option is given and -E specified a rotation file then we equate the rotation
file times with the reconstruction times.
-V[level] (more …)
Select verbosity level [c].
-bi[ncols][t] (more …)
Select native binary input. [Default is 2 input columns].
-bo[ncols][type] (more …)
Select native binary output. [Default is same as input].
-d[i|o]nodata (more …)
Replace input columns that equal nodata with NaN and do the reverse on output.
-h[i|o][n][+c][+d][+rremark][+rtitle] (more …)
Skip or produce header record(s).
-:[i|o] (more …)
Swap 1st and 2nd column on input and/or output.
-n[b|c|l|n][+a][+bBC][+c][+tthreshold] (more …)
Select interpolation mode for grids.
-^ 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.
CONSEQUENCES OF GRID RESAMPLING
Resample or sampling of grids will use various algorithms (see -n) that may lead to possible distortions
or unexpected results in the resampled values. One expected effect of resampling with splines is the
tendency for the new resampled values to slightly exceed the global min/max limits of the original grid.
If this is unacceptable, you can impose clipping of the resampled values values so they do not exceed the
input min/max values by adding +c to your -n option.
GEODETIC VERSUS GEOCENTRIC COORDIINATES
All spherical rotations are applied to geocentric coordinates. This means that incoming data points and
grids are considered to represent geodetic coordinates and must first be converted to geocentric
coordinates. Rotations are then applied, and the final reconstructed points are converted back to
geodetic coordinates. This default behavior can be bypassed if the ellipsoid setting PROJ_ELLIPSOID is
changed to Sphere.
EXAMPLES
To rotate the data defined by grid topo.nc and the polygon outline clip_path.d, using a total
reconstruction rotation with pole at (135.5, -33.0) and a rotation angle of 37.3 degrees and bicubic
interpolation, try
gmt grdrotater topo.nc -E135.5/-33/37.3 -V -Fclip_path.d -Grot_topo.nc > rot_clip_path.d
To rotate the entire grid faa.nc back to 32 Ma using the rotation file rotations.txt and a bilinear
interpolation, try
gmt grdrotater faa.nc -Erotations.txt -T32 -V -Grot_faa.nc -nl > rot_faa_path.d
To just see how the outline of the grid large.nc will plot after the same rotation, try
gmt grdrotater large.nc -Erotations.txt -T32 -V -S \| psxy -Rg -JH180/6i -B30 -W0.5p \| gv -
To rotate the grid topo.nc back to 100 Ma using the rotation file rotations.txt and request a
reconstruction every 10 Myr, saving both grids and outlines to filenames that derive from templates, try
gmt grdrotater topo.nc -Erotations.txt -T10/100/10 -V -Grot_topo_%g.nc -Drot_topo_path_%g.d
Let say you have rotated gridA.nc and gridB.nc, restricting each rotation to nodes inside polygons
polyA.d and polyB.d, respectively, using rotation A = (123W,22S,16,4) and rotation B = (108W, 16S,
-14.5), yielding rotated grids rot_gridA.nc and rot_gridB.nc. To determine the region of overlap between
the rotated grids, we use grdmath:
gmt grdmath 1 rot_gridA.nc ISNAN SUB 1 rot_gridB.nc ISNAN SUB 2 EQ = overlap.nc
The grid overlap.nc now has 1s in the regions of overlap and 0 elsewhere. You can use it as a mask or use
grdcontour -D to extract a polygon (i.e., a contour).
NOTES
GMT distributes the EarthByte rotation model Global_EarthByte_230-0Ma_GK07_AREPS.rot. To use an
alternate rotation file, create an environmental parameters named GPLATES_ROTATIONS that points to an
alternate rotation file.
SEE ALSO
backtracker, grdcontour, gmtpmodeler, grdmath, grdpmodeler, grdspotter, hotspotter, originator,
rotconverter
COPYRIGHT
2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe