@@ -21,144 +21,3 @@ Required Arguments (not all)
2121 are assumed constant (controlled by ** density** or ** mag_params** ). Following cases are: 4 columns -> 4rth col
2222 magnetization intensity; 5 columns: mag, mag dip; 6 columns: mag, mag dec, mag dip; 8 columns: field dec, field dip,
2323 mag, mag dec, mag dip. When n columns > 3 the third argument of the ** mag_params** option is ignored.
24-
25- - ** arg1** : In alternative to ` fname ` pass in a Mx3 matrix or a \myreflink{GMTdataset} with at least 3 columns.
26- ` arg1 ` can also be a \myreflink{GMTfv} type like those produced by the _ solids_ functions (\myreflink{sphere}, etc)
27- but it must be one made of triangles. That is, the output of \myreflink{cube} wont work because the body is
28- made out of quadrangles. Note, if the ** body** option is used neither this option nor ** fname** are used.
29-
30- - ** C** or ** density** : -- * density=??* \
31- Sets body density in _ SI_ . Append either a constant, the name of a grid file or a \myreflink{GMTgrid}
32- grid with variable densities. This option is mutually exclusive with ** mag_params**
33-
34- - ** H** or ** mag_params** : -- * mag_params=f_dec/f_dip/m_int/m_dec/m_dip* \
35- Sets parameters for computing a magnetic anomaly. Use * f_dec* /* f_dip* to set the geomagnetic
36- declination/inclination in degrees. * m_int* /* m_dec* /* m_dip* are the body magnetic intensity
37- declination and inclination.
38-
39- - ** F** or ** track** : -- * track=xy_loc* \
40- Provide * xy_loc* (file name or GMTdataset) locations where the anomaly will be computed. Note,
41- this option is mutually exclusive with the ** save** option.
42-
43- \textinput{common_opts/opt_save_grd}
44-
45- - ** M** or ** body** : -- * body=shape,params* ** |** * body=(shape=name, params=...)* \
46- (An alternative to ** raw_triang** and ** stl** ). Create geometric bodies and compute their grav/mag effect.
47- Select among one or more of the following bodies, where * x0* & * y0* represent the horizontal coordinates
48- of the body center [ default to 0,0 positive up] , * npts* is the number of points that a circle is discretized
49- and * n_slices* apply when bodies are made by a pile of slices. For example Spheres and Ellipsoids are made of
50- * 2 x n_slices* and Bells have * n_slices* [ Default 5] . It is also possible to select more than one body.
51- For example ** body** =* ((shape=: prism , params="1/1/1/-5/-10/1"), (shape=: sphere , params="1/-5"))* computes
52- the effect of a prism and a sphere. Unfortunately there is no current way of selecting distinct densities
53- or magnetic parameters for each body.
54-
55- - *bell,height/sx/sy/z0[/x0/y0/n_sig/npts/n_slices]* Gaussian of height *height* with characteristic
56- STDs *sx* and *sy*. The base width (at depth *z0*) is controlled by the number of sigmas (*n_sig*) [Default = 2]
57-
58- - *cylinder,rad/height/z0[/x0/y0/npts/n_slices]* Cylinder of radius *rad* and height *height* and base at depth *z0*
59-
60- - *cone,semi_x/semi_y/height/z0[/x0/y0/npts]* Cone of semi axes *semi_x/semi_y* height *height* and base at depth *z0*
61-
62- - *ellipsoid,semi_x/semi_y/semi_z/z_center[/x0/y0/npts/n_slices]* Ellipsoid of semi axes *semi_x/semi_y/semi_z*
63- and center depth *z_center*
64-
65- - *prism,side_x/side_y/side_z/z0[/x0/y0]* Prism of sides *x/y/z* and base at depth *z0*
66-
67- - *pyramid,side_x/side_y/height/z0[/x0/y0]* Pyramid of sides *x/y* height *height* and base at depth *z0*
68-
69- - *sphere,rad/z_center[/x0/y0/npts/n_slices]* Sphere of radius *rad* and center at depth *z_center*
70-
71- \textinput{common_opts/opt_R}
72-
73- - ** Tv** or ** index** : -- * index=vert_file* ** |** * index=D* \
74- Gives name of a vertex file defining a closed surface. The file formats correspond to the output
75- of the \myreflink{triangulate} module. The form * raw_triang=D* means that we can also
76- pass the data as a \myreflink{GMTdataset}
77-
78- - ** Tr** or ** raw_triang** : -- * raw_triang=raw_file* ** |** * raw_triang=D* \
79- A * raw* format is a file with N rows (one per triangle) and 9 columns corresponding to the * x, y, z*
80- coordinates of each of the three vertex of each triangle. The form * raw_triang=D* means that we can also
81- pass the data as a \myreflink{GMTdataset}
82-
83- - ** Ts** or ** stl** or ** STL** : -- * stl=raw_file* \
84- Alternatively, the ** stl** option indicates that the surface file is in the ASCII STL
85- (Stereo Lithographic) format. These two type of files are used to provide a closed surface.
86-
87- - ** noswap** or ** no_swap** : -- * noswap=true* \
88- The closed surface formats (_ STL_ or _ raw_ ) are assumed to be provided with the facets (triangles)
89- following the counter-clockwise order. If that is not the case, _ i.e._ they are clockwise oriented,
90- use this option to bring them to the expected order. However, this order may not be easy to check.
91- In case of doubt, compute the gravity anomaly caused by the body and see if it has the expected signal.
92-
93- Optional Arguments
94- ------------------
95-
96- - ** E** or ** thickness** : -- * thickness=??* \
97- Give layer thickness in m [ Default = 0 m] . Use this option only when the triangles describe a non-closed
98- surface and you want the anomaly of a constant thickness layer.
99-
100- - ** L** or ** z_obs** or ** observation_level** : -- -- * z_obs=0* \
101- sets level of observation [ Default = 0] . That is the height (z) at which anomalies are computed.
102-
103- - ** S** or ** radius** : -- * radius=30* \
104- Set search radius in km (valid only in the two grids mode OR when ** thickness** ) [ Default = 30 km] .
105- This option serves to speed up the computation by not computing the effect of prisms that
106- are further away than * radius* from the current node.
107-
108- \textinput{common_opts/opt_V}
109-
110- ** Z** or ** level** or ** reference_level** : -- * level=0* \
111- level of reference plane [ Default = 0] . Use this option when the triangles describe a non-closed
112- surface and the volume is defined from each triangle and this reference level. An example will
113- be the water depth to compute a Bouguer anomaly.
114-
115- ** Q** or ** onebased** or ** one_based** : -- * onebased=true* \
116- Use this option if the indices in file (** index** ) is 1-based instead of the default (C) 0-based.
117- This option is needed when indices are 1-based, as likely is the case when bodies may have been
118- created in Julia.
119-
120- \textinput{common_opts/opt_f}
121- Geographic grids (dimensions of longitude, latitude) will be converted to
122- meters via a "Flat Earth" approximation using the current ellipsoid parameters.
123-
124- \textinput{common_opts/opt_h}
125-
126- \textinput{common_opts/opt__ i}
127-
128- \textinput{common_opts/opt_o}
129-
130- \textinput{common_opts/opt__ r}
131-
132- Grid Distance Units
133- -------------------
134-
135- If the grid does not have meter as the horizontal unit, append ** +u** \ * unit* to the input file name to convert from the
136- specified unit to meter. If your grid is geographic, convert distances to meters by supplying ** f=: g ** instead.
137-
138- Example
139- -------
140-
141- To compute the magnetic anomaly of a cube of unit sides located at 5 meters depth and centered at -10,1 in a domain
142- * R="-15/15/-15/15"* with a magnetization of 10 Am with a declination of 10 degrees, inclination of 60 in a magnetic field
143- with -10 deg of declination and 40 deg of inclination, do:
144-
145- \begin{examplefig}{}
146- ``` julia
147- using GMT
148-
149- G = gravmag3d (region= " -15/15/-15/15" = 0.1 , mag_params= " 10/60/10/-10/40" = (shape= :prism , params= " 1/1/1/-5/-10/1"
150- viz (G, colorbar= true )
151- ```
152- \end{examplefig}
153-
154- See Also
155- --------
156-
157- \myreflink{grdgravmag3d}, \myreflink{gravprisms}, talwani2d, talwani3d, \myreflink{triangulate}
158-
159- Reference
160- ---------
161-
162- Okabe, M., 1979, Analytical expressions for gravity anomalies due to
163- polyhedral bodies and translation into magnetic anomalies, * Geophysics* ,
164- 44, 730-741.
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