grdseamount(1) GMT grdseamount(1)
NAME
grdseamount - Compute synthetic seamount (Gaussian or cone, circular or
elliptical) bathymetry
SYNOPSIS
grdseamount [ intable ]
-Iincrement
-Rregion [ -A[out/in] ] [ -Cc|d|g|p ] [ -D[unit] ] [ -E ] [
-F[flattening] ] [ -Ggrdfile ] [ -L[cut] ] [ -Mlist ] [ -Nnorm ] [
-Qbmode/qmode ] [ -Sscale ] [ -Tt0[u][/t1[u]/dt[u]|n][+l] ] [
-Zlevel ] [ -V[level] ] [ -bibinary ] [ -eregexp ] [ -fg ] [ -iflags ]
[ -r ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
grdseamount will compute the combined shape of multiple synthetic
seamounts given their individual shape parameters. We read a list with
seamount locations and sizes and can evaluate either Gaussian, parabol-
ic, conical, or disc shapes, which may be circular or elliptical, and
optionally truncated. Various scaling options are available to modify
the result, including an option to add in a background depth (more com-
plicated backgrounds may be added via grdmath). The input must contain
lon, lat, radius, height for each seamount. For elliptical features
(-E) we expect lon, lat, azimuth, semi-major, semi-minor, height
instead. If flattening is specified (-F) with no value appended then a
final column with flattening is expected (cannot be used for plateaus).
For temporal evolution of topography the -T option may be used, in
which case the data file must have two final columns with the start and
stop time of seamount construction. In this case you may choose to
write out a cumulative shape or just the increments produced by each
time step (see -Q).
REQUIRED ARGUMENTS
-Ixinc[unit][+e|n][/yinc[unit][+e|n]]
x_inc [and optionally y_inc] is the grid spacing. Optionally,
append a suffix modifier. Geographical (degrees) coordinates:
Append m to indicate arc minutes or s to indicate arc seconds.
If one of the units e, f, k, M, n or u is appended instead, the
increment is assumed to be given in meter, foot, km, Mile, nau-
tical mile or US survey foot, respectively, and will be con-
verted to the equivalent degrees longitude at the middle lati-
tude of the region (the conversion depends on PROJ_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 coordi-
nates: If +e 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 +n to
the supplied integer argument; the increment is then recalcu-
lated from the number of nodes and the domain. The resulting
increment value depends on whether you have selected a grid-
line-registered or pixel-registered grid; see App-file-formats
for details. Note: if -Rgrdfile is used then the grid spacing
has already been initialized; use -I to override the values.
-Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
Specify the region of interest.
OPTIONAL ARGUMENTS
-A[out/in]
Build a mask grid, append outside/inside values [1/NaN]. Here,
height is ignored and -L, -N and -Z are disallowed.
-C Select shape function: choose among c (cone), d (disc), g (Gaus-
sian) and p (parabolic) shape [Default is Gaussian].
-Dunit Append the unit used for horizontal distances in the input file
(see UNITS). Does not apply for geographic data (-fg) which we
convert to km.
-E Elliptical data format. We expect the input records to contain
lon, lat, azimuth, major, minor, height (with the latter in m)
for each seamount. [Default is Circular data format, expecting
lon, lat, radius, height].
-F[flattening]
Seamounts are to be truncated to guyots. Append flattening,
otherwise we expect to find it in last input column [no trunca-
tion]. Ignored if used with -Cd.
-Ggrdfile
Specify the name of the output grid file; see GRID FILE FORMATS
below). If -T is set then grdfile must be a filename template
that contains a floating point format (C syntax). If the file-
name template also contains either %s (for unit name) or %c (for
unit letter) then we use the corresponding time (in units speci-
fied in -T) to generate the individual file names, otherwise we
use time in years with no unit.
-L[cut]
List area, volume, and mean height for each seamount; No grid is
created. Optionally, append the noise-floor cutoff level below
which we ignore area and volume [0].
-Mlist Write the names of all grids that were created to the text file
list. Requires -T.
-Nnorm Normalize grid so maximum grid height equals norm.
-Qbmode/qmode
Only to be used in conjunction with -T. Append two different
modes settings: The bmode determines how we construct the sur-
face. Specify c for cumulative volume through time, or i for
incremental volume added for each time slice. The qmode deter-
mines the volume flux curve. Give g for a Gaussian volume flux
history or l for a linear volume flux history between the start
and stop times of each feature.
-Sscale
Sets optional scale factor for radii [1].
-Tt0[u][/t1[u]/dt[u]|n][+l]
Specify t0, t1, and time increment (dt) for sequence of calcula-
tions [Default is one step, with no time dependency]. For a
single specific time, just give start time t0. The unit is
years; append k for kyr and M for Myr. For a logarithmic time
scale, append +l and specify n steps instead of dt. Alterna-
tively, give a file with the desired times in the first column
(these times may have individual units appended, otherwise we
assume year). Note that the grid for t0 (if a range is given)
is not written as it is zero and marks the start of the building
history.
-Zlevel
Set the background depth [0].
-bi[ncols][t] (more a|)
Select native binary input. [Default is 4 input columns].
-e[~]^<i>apattern^<i>a | -e[~]/regexp/[i] (more a|)
Only accept data records that match the given pattern.
-fg Geographic grids (dimensions of longitude, latitude) will be
converted to km via a aFlat Eartha approximation using the cur-
rent ellipsoid parameters.
-h[i|o][n][+c][+d][+rremark][+rtitle] (more a|)
Skip or produce header record(s). Not used with binary data.
-icols[+l][+sscale][+ooffset][,^<i>a|] (more a|)
Select input columns and transformations (0 is first column).
-V[level] (more a|)
Select verbosity level [c].
-r (more a|)
Set pixel node registration [gridline].
-:[i|o] (more a|)
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 explana-
tion 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.
UNITS
For map distance unit, append unit d for arc degree, m for arc minute,
and s for arc second, or e for meter [Default], f for foot, k for km, M
for statute mile, n for nautical mile, and u for US survey foot. By
default we compute such distances using a spherical approximation with
great circles. Prepend - to a distance (or the unit is no distance is
given) to perform aFlat Eartha calculations (quicker but less accurate)
or prepend + to perform exact geodesic calculations (slower but more
accurate).
EXAMPLES
To compute the incremental loads from two elliptical, truncated Gaus-
sian seamounts being constructed from 3 Ma to 2 Ma and 2.8 M to 1.9 Ma
using a linear volumetric production rate, and output an incremental
grid every 0.1 Myr from 3 Ma to 1.9 Ma, we can try:
cat << EOF > t.txt
#lon lat azimuth, semi-major, semi-minor, height tstart tend
0 0 -20 120 60 5000 3.0M 2M
50 80 -40 110 50 4000 2.8M 21.9M
EOF
gmt grdseamount -Rk-1024/1022/-1122/924 -I2000 -Gsmt_%3.1f_%s.nc t.txt -T3M/1.9M/0.1M -Qi/l -Dk -E -F0.2 -Cg -Ml.lis
SEE ALSO
gmt.conf(5), gmt(1), grdmath(1), gravfft(1), gmtflexure(1)
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 grdseamount(1)
gmt5 5.4.2 - Generated Thu Jun 29 08:09:29 CDT 2017