grdseamountgmt - Online in the Cloud

PROGRAM:

NAME

grdseamount - Compute synthetic seamount (Gaussian or cone, circular or elliptical)
bathymetry

SYNOPSIS

grdseamount [ intable ] increment region [ [out/in] ] [ c|d|g|p ] [ [unit] ] [ ] [
[flattening] ] [ grdfile ] [ [cut] ] [ list ] [ norm ] [ bmode/qmode ] [ scale ] [
t0[u][/t1[u]/dt[u]|n][+l] ] [ level ] [ [level] ] [ -bi<binary> ] [ -fg ] [ -i<flags> ] [
-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, parabolic, 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 complicated 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][=|+][/yinc[unit][=|+]]
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, nautical
mile or US survey foot, respectively, and will be converted to the equivalent
degrees longitude at the middle latitude 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 coordinates: 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 App-file-formats for details.
Note: if -Rgrdfile is used then the grid spacing has already been initialized; use
-I to override the values.

-R[unit]xmin/xmax/ymin/ymax[r] (more ...)
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 (Gaussian) 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 [Default is Circular]. Read lon, lat, azimuth, major, minor,
height (m) for each seamount.

-F[flattening]
Seamounts are to be truncated to guyots. Append flattening, otherwise we expect to
find it in last input column [no truncation]. 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 filename template also contains either %s (for unit name) or %c
(for unit letter) then we use the corresponding time (in units specified 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 surface. Specify c for cumulative volume
through time, or i for incremental volume added for each time slice. The qmode
determines 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 calculations [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. Alternatively, 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 ...)
Select native binary input. [Default is 4 input columns].

-fg Geographic grids (dimensions of longitude, latitude) will be converted to km via a
"Flat Earth" approximation using the current ellipsoid parameters.

-h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
Skip or produce header record(s). Not used with binary data.

-icols[l][sscale][ooffset][,...] (more ...)
Select input columns (0 is first column).

-V[level] (more ...)
Select verbosity level [c].

-r (more ...)
Set pixel node registration [gridline].

-:[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
use just -).

-+ 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 options, then
exits.

--version
Print GMT version and exit.

--show-datadir
Print full path to GMT share directory and exit.

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 "Flat Earth" 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 Gaussian 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

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