xenial (1) grdseamount.1gmt.gz

Provided by: gmt-common_5.2.1+dfsg-3build1_all bug

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

SEE ALSO

       gmt.conf, gmt, grdmath, gravfft, gmtflexure

       2015, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe