# 1. MVI Package Overview¶

The magnetic vector inversion (MVI) package is a program library for carrying out 3D forward modelling and inversion of magnetic data for the full magnetization vector. The program library is comprised of the following executables:

1. MVIFWD: Forward modelling of the magnetic anomaly response for a 3D distribution of magnetized volumes.
2. MVIINV: Performs the 3D magnetic vector inversion for magnetic anomaly data. The model is defined on a mesh of rectangular cells and is comprised of the effective susceptibilities in 3 orthogonal directions for each cell.
3. MVISEN: Calculates the sensitivities for the inversion.

Note

• This code recovers the total magnetization vector in terms of effective susceptibility.
• The code models the combined contribution of induced fields (susceptibility), self-demagnetization and remenance.
• Inversion can be carried out in Cartesian (p,s,t) and Spherical (a,t,p) coordinate systems, but sparsity constraints can only be applied on the Spherical (atp) formulation.

## 1.1. Licensing¶

Licensing for an unconstrained academic version is available - see the Licensing policy document.

NOTE: All academic licenses will be time-limited to one year. You can re-apply after that time. This ensures that everyone is using the most recent versions of codes.

Licensing for commercial use is managed by third party distributors. Details are in the Licensing policy document.

## 1.2. Installing¶

There is no automatic installer currently available for this package. Please carry out the following steps in order to use the software:

1. Extract all files provided from the given zip-based archive and place them all together in a new folder
2. Add the path to the new folder to your environment variables.

• Do not store anything in the “bin” directory other than executable applications and Graphical User Interface applications (GUIs).

## 1.3. Highlights of changes from version 2.0¶

• Distance weights are calculated directly from the sensitivity matrix; as a result, the user is no longer required to run the PFWEIGHT program.
• Length scales used in differential operators are set internally based on the mesh cell dimensions. The default values for $$\boldsymbol{\alpha_s}$$ is now 1.
• An approximated sensitivity calculation is now used to speed up the code for the MVI-Spherical formulation.
• Compression of the sensitivities both the MVI-Cartesian and MVI-Spherical formulations is now available. Default threshold tolerances are determined iteratively, and favoring lowest compression error.
 True model Smooth solution MVI v1 Smooth solution MVI v2 Smooth solution MVI v3 Sparse solution MVI v3

Note