ycugv

Author: joa-quim

documentation/modules/grdgravmag3d.md

@@ -26,3 +26,111 @@ If two grids are provided then the gravity/magnetic effect of the volume between
 - **F** or **track** : -- *track=xy_loc*\
     Provide *xy_loc* (file name or GMTdataset) locations where the anomaly will be computed. Note,
     this option is mutually exclusive with the **save** option.
+
+
+Optional Arguments
+------------------
+
+- **E** or **thickness** : -- *thickness=??*\
+    To provide the layer thickness in m [Default = 500 m].
+
+- **H** or **mag_params** : -- *mag_params=f_dec/f_dip/m_int/m_dec/m_dip* **|** *mag_params="magfile"|maggrid* **|**  *mag_params="x|X|y|Y|z|Z|h|H|t|T|f|F" **|** *mag_params="+i|+n"*\
+    Sets parameters for computation of magnetic anomaly (Can be used multiple times).
+
+      - *f_dec/f_dip* -> geomagnetic declination/inclination
+
+      - *m_int/m_dec/m_dip* -> body magnetic intensity/declination/inclination
+
+    OR for a grid mode
+
+      - *maggrid*, a GMTgrid  grid, or *magfile*, where *magfile* is the name of the magnetic intensity file.
+
+    To compute a component, specify any of:
+
+      - **x**|**X**|**e**|**E**  to compute the E-W component.
+
+      - **y**|**Y**|**n**|**N**  to compute the N-S component.
+
+      - **z**|**Z**      to compute the Vertical component.
+
+      - **h**|**H**      to compute the Horizontal component.
+
+      - **t**|**T**|**f**|**F**  to compute the total field.
+
+    If we want to compute the magnetic anomalies over a large region where the ambient magnetic field
+    can no longer be assumed to be constant we can set variable inclinations and declinations via IGRF.
+    Set any of **mag_params="+i|+n"** to do that.
+
+\textinput{common_opts/opt_I}
+
+- **L** or **z_obs** or **observation_level** : -- *z_obs=0*\
+    Sets level of observation [Default = 0]. That is the height (z) at which anomalies are computed.
+
+- **Q** or **pad** : -- *pad="nn_pad" **|** *pad="pad_dist"* **|** *pad="region"*\
+    Extend the domain of computation with respect to output **region** region.
+      - *pad="nn_pad"* artificially extends the width of the outer rim of cells to have a fake width of *n_pad* * dx[/dy].
+
+      - *pad="pad_dist"* extend the region by west-pad, east+pad, etc.
+
+      - *pad="west/east/south/north"* Same syntax as **region**.
+
+\textinput{common_opts/opt_R}
+
+- **S** or **radius** : -- *radius=30*\
+    Set search radius in km (valid only in the two grids mode OR when **thickness**) [Default = 30 km].
+    This option serves to speed up the computation by not computing the effect of prisms that
+    are further away than *radius* from the current node.
+
+\textinput{common_opts/opt_V}
+
+- **Z** or **level** or **reference_level** : -- *level="b|t"* **|** *level=(bottom=true | top=true)*\
+    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 water depth to compute a Bouguer anomaly. Use **level=:b** or **level=:t** to close the body
+    at its bottom (for example, to compute the effect of a dome) or at its top (to compute the effect of a *spoon*).
+
+\textinput{common_opts/opt_f}
+
+\textinput{common_opts/opt__x}
+
+Grid Distance Units
+-------------------
+
+If the grid does not have meter as the horizontal unit, append **+u**_unit_ to the input file name to convert from the
+specified unit to meter. If your grid is geographic, convert distances to meters by supplying **f=:g** instead.
+
+Examples
+--------
+
+To compute the vertical component due to a magnetization stored in *mag.grd* over a zone defined by
+the surface *bat.grd*, using variable declination and inclination provided the IGRF and using 4
+processors, do:
+
+```julia
+G = grdgravmag3d("bat.grd", thickness=10000, H="z -H+n -H+mmag.grd", x=4, radius=50);
+```
+
+Suppose you want to compute the gravity effect of the Gorringe bank.
+
+\begin{examplefig}{}
+```julia
+using GMT
+
+G = grdgravmag3d("@earth_relief_10m", region=(-12.5,-10,35.5,37.5),
+                 density=2700, inc=0.05, pad=0.5, z_level=:bottom, f=:g);
+viz(G, title="Gorringe FAA", colorbar=true)
+```
+\end{examplefig}
+
+
+See Also
+--------
+
+gravmag3d, gravprism, talwani2d, talwani3d
+
+Reference
+---------
+
+Okabe, M., 1979, Analytical expressions for gravity anomalies due to
+polyhedral bodies and translation into magnetic anomalies, *Geophysics*,
+44, 730-741.