.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/forward/point_mass.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Click :ref:`here <sphx_glr_download_gallery_forward_point_mass.py>`
        to download the full example code

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_forward_point_mass.py:


Point Masses in Cartesian Coordinates
=====================================

The simplest geometry used to compute gravitational fields are point masses.
Although modelling geologic structures with point masses can be challenging,
they are very useful for other purposes: creating synthetic models, solving
inverse problems, generating equivalent sources for interpolation, etc. The
gravitational fields generated by point masses can be quickly computed either
in Cartesian or in geocentric spherical coordinate systems. We will compute the
gravitational acceleration generated by a set of point masses on a computation
grid given in Cartesian coordinates using the
:func:`harmonica.point_mass_gravity` function.

.. GENERATED FROM PYTHON SOURCE LINES 21-67



.. image:: /gallery/forward/images/sphx_glr_point_mass_001.png
    :alt: Gravitational acceleration (downward)
    :class: sphx-glr-single-img


.. rst-class:: sphx-glr-script-out

 Out:

 .. code-block:: none

    [[ 0.00181314  0.00190983  0.00200888 ... -0.00328218 -0.0032428
      -0.00320183]
     [ 0.00196785  0.00207626  0.00218766 ... -0.0034324  -0.00338955
      -0.00334507]
     [ 0.0021343   0.00225579  0.00238107 ... -0.00359128 -0.00354465
      -0.00349633]
     ...
     [-0.0014489  -0.00151296 -0.0015806  ... -0.01802268 -0.01727698
      -0.01655213]
     [-0.00144777 -0.00151078 -0.00157723 ... -0.01697132 -0.0162955
      -0.01563681]
     [-0.00144484 -0.00150675 -0.00157197 ... -0.01599028 -0.01537726
      -0.01477824]]
    /home/runner/work/harmonica/harmonica/examples/forward/point_mass.py:62: UserWarning: FixedFormatter should only be used together with FixedLocator
      ax.set_xticklabels(ax.get_xticks() * 1e-3)
    /home/runner/work/harmonica/harmonica/examples/forward/point_mass.py:63: UserWarning: FixedFormatter should only be used together with FixedLocator
      ax.set_yticklabels(ax.get_yticks() * 1e-3)






|

.. code-block:: default

    import harmonica as hm
    import verde as vd
    import matplotlib.pyplot as plt
    import matplotlib.ticker


    # Define the coordinates for two point masses
    easting = [5e3, 15e3]
    northing = [7e3, 13e3]
    # The vertical coordinate is positive upward so negative numbers represent
    # depth
    upward = [-0.5e3, -1e3]
    points = [easting, northing, upward]
    # We're using "negative" masses to represent a "mass deficit" since we assume
    # measurements are gravity disturbances, not actual gravity values.
    masses = [3e11, -10e11]

    # Define computation points on a grid at 500m above the ground
    coordinates = vd.grid_coordinates(
        region=[0, 20e3, 0, 20e3], shape=(100, 100), extra_coords=500
    )

    # Compute the downward component of the gravitational acceleration
    gravity = hm.point_mass_gravity(
        coordinates, points, masses, field="g_z", coordinate_system="cartesian"
    )
    print(gravity)

    # Plot the results on a map
    fig, ax = plt.subplots(figsize=(8, 6))
    ax.set_aspect("equal")
    # Get the maximum absolute value so we can center the colorbar on zero
    maxabs = vd.maxabs(gravity)
    img = ax.contourf(
        *coordinates[:2], gravity, 60, vmin=-maxabs, vmax=maxabs, cmap="seismic"
    )
    plt.colorbar(img, ax=ax, pad=0.04, shrink=0.73, label="mGal")
    # Plot the point mass locations
    ax.plot(easting, northing, "oy")
    ax.set_title("Gravitational acceleration (downward)")
    # Convert axes units to km
    ax.set_xticklabels(ax.get_xticks() * 1e-3)
    ax.set_yticklabels(ax.get_yticks() * 1e-3)
    ax.set_xlabel("km")
    ax.set_ylabel("km")
    plt.show()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** ( 0 minutes  0.755 seconds)


.. _sphx_glr_download_gallery_forward_point_mass.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download sphx-glr-download-python

     :download:`Download Python source code: point_mass.py <point_mass.py>`



  .. container:: sphx-glr-download sphx-glr-download-jupyter

     :download:`Download Jupyter notebook: point_mass.ipynb <point_mass.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_