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Inversion

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The inversion parameters are set by selecting Inverse Solver set up from the Explorer menu.

A series of 3 tabbed  windows is presented. In the numerical core we set the Maximum number of Inverse iterations. A value of 15 is typical for Rho (resistivity) and 10 for IP. These are sometimes referred to as the outer iterations. We also set the Maximum internal inverse PCG iterations, which are sometimes called the inner iterations. A value of 12 is typical for Rho (resistivity) and 20 for IP. Finally we set the Tolerance for the Inverse PCG iterations. Larger numbers result in faster inversion.


The roughness parameters are the initial roughness factor, the multiplier for changing the roughness factor and the factor for choosing the optimal roughness  factor. Roughness factor controls that amount of roughness that can be imposed from one iteration to the next. ERTLab employs roughness trials to determine the optimal roughness factor and the initial value is of modest importance. If Simple inversion is used then the multiplier for changing the roughness factor becomes important. If the value is too larger then the roughness factor will become very small before the inversion is complete.

Inverse 2

We also set the Reweight constants in X, Y and Z. Reweight constants less than 1 generate layering, reweight constants greater than 1 generate smoother models.

The Noise parameters are set on the last tab.

Inverse 3

The inversion is launched by returning to the DI workspace page and selecting Run Data inversion from the menu. After clicking the Run Inversion button, ERTLab asks to save a progress file (.prg extension) where the progress of inversion is written. Diagrams describing the behaviour of the inversion are automatically displayed in the inversion progress graphics window that appears after saving the progress file.

Inverse Run

 



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