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```gmtgravmag3d(1)                       GMT                      gmtgravmag3d(1)

```

## NAME

```       gmtgravmag3d  -  Compute  the  gravity/magnetic effect of a body by the
method of Okabe

```

## SYNOPSIS

```       gmtgravmag3d  -Tpxyz_file[+m]  -Tvvert_file OR  -Tr|sraw_file [  -Cden-
sity  ]  [   -D  ]  [  -Ethickness ] [  -Fxy_file ] [  -Goutputgrid ] [
-Hf_dec/f_dip/m_int/m_dec/m_dip ] [  -Lz_observation ] [  -Sradius ]  [
-Zlevel ] [  -V[level] ] [ -fg]

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

```

## DESCRIPTION

```       gmtgravmag3d will compute the gravity or magnetic  anomaly  of  a  body
described by a set of triangles. The output can either be along a given
set of xy locations or on a grid. This method is not particularly  fast
but allows computing the anomaly of arbitrarily complex shapes.

```

## REQUIRED ARGUMENTS

```       -Cdensity
Sets  body density in SI. This option is mutually exclusive with
-H.

-Hf_dec/f_dip/m_int/m_dec/m_dip
Sets  parameters  for  computing   a   magnetic   anomaly.   Use
f_dec/f_dip  to  set  the geomagnetic declination/inclination in
degrees. m_int/m_dec/m_dip are the body magnetic intensity  dec-
lination and inclination.

-Fxy_file
Provide  locations where the anomaly will be computed. Note this
option is mutually exclusive with -G.

-Goutgrid
Output the gravity or magnetic anomaly at  nodes  of  this  grid
file.

-Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
Specify the region of interest.

-Tpxyz_file[+m] -Tvvert_file OR Tr|sraw_file
Gives  names  of xyz (-Tpxyz_file[+m]) and vertex (-Tvvert_file)
files defining a close surface.  The file formats correspond  to
the  output of the triangulate program.  The optional +m flag to
-Tp instructs the program that the xyzm file  has  four  columns
and  that the fourth column contains the magnetization intensity
(plus signal), which needs not to be constant. In this case  the
third  argument  of  the  -H  option  is  ignored.  A raw format
(selected by the -Tr option) is a file with N rows (one per tri-
angle)  and  9 columns corresponding to the x,y,x coordinates of
each of the three vertex of each triangle.   Alternatively,  the
-Ts  option  indicates that the surface file is in the ASCII STL
(Stereo Lithographic) format.  These two type of files are  used
to provide a closed surface.

```

## OPTIONAL ARGUMENTS

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

-E[thickness]
give  layer thickness in m [Default = 0 m]. Use this option only
when the triangles describe a non-closed surface  and  you  want
the anomaly of a constant thickness layer.

-L[z_observation]
sets  level of observation [Default = 0]. That is the height (z)
at which anomalies are computed.

search radius in km. Triangle centroids that  are  further  away
than  radius  from  current  output point will not be taken into
account.  Use this option to speed up computation at expenses of
a less accurate result.

-Z[level]
level of reference plane [Default = 0]. Use this option when the
triangles describe  a  non-closed  surface  and  the  volume  is
defined  from each triangle and this reference level. An example
will be the hater depth to compute a Bouguer anomaly.

-fg    Geographic grids (dimensions of  longitude,  latitude)  will  be
converted  to  meters via a aFlat Eartha approximation using the
current ellipsoid parameters.

-^ 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.

```

## GRID DISTANCE UNITS

```       If the grid does not have meter as the horizontal unit,  append  +uunit
to the input file name to convert from the specified unit to meter.  If
your grid is geographic, convert distances to meters by  supplying  -fg

```

## EXAMPLES

```       Suppose you a|

gmt gmtgravmag3d ...

```

```       gmt(1), grdgravmag3d(1), talwani2d(1), talwani3d(1)

```

## REFERENCE

```       Okabe,  M., Analytical expressions for gravity anomalies due to polyhe-
dral bodies and translation into magnetic  anomalies,  Geophysics,  44,
(1979), p 730-741.

```

```       2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
```© manpagez.com 2000-2021