3D Gravity Inversion

Use the 3D Gravity Inversion option to perform density inversion on a GM-SYS 3D model.

Inversion surface	Drop down list of the model’s surface grids. The chosen surface defines the top of the inversion layer. With structural inversion, this grid will be altered. With density inversion, the layer's corresponding lateral density distribution grid will be altered.
Max # of Inversion Iterations	Inversion process will stop after this many iterations, even if the convergence target has not been reached.
Convergence limit (mGal)	Inversion will stop when either the mean error or the standard deviation of the error is less than this limit. Note that under certain conditions, the calculations may not converge at all. The algorithm attempts to detect this and terminate accordingly.
Lower High-Cut limit	A cosine tapered high cut filter is applied to the error before inverting. This is the beginning point of the cosine taper.
Upper High-Cut limit	… and this is it’s end. If these numbers are <= 1.0, they are a fraction of the Nyquist - 0.5 and 0.7 are the defaults. If the limits are > 1.0, they are treated as ground unit wavelengths.
Regional Offset	This constant will be subtracted from the observed gravity before inverting.
Constraints Grid	Grid to control where the inversion surface may change. Values of 0 indicate no change; 1 indicates maximum change.
[Limits]	Brings up a dialog that limits the amount of change possible during inversion.

Gravity Inversions and 3D Gravity Inversion use this same dialog.

Gravity Inversions performs the gravity structural inversion on the selected layer surface.

3D Gravity Inversion performs the lateral density inversion on the material below the "Inversion surface".

In order for 3D Gravity Inversion to work, the density of the layer must be defined by a lateral density grid.

Before inverting, the model is checked to assure that the calculated model response is up to date with respect to the other model files.

Inversion is not supported if the density distribution of the layer to be inverted or of the layer above is a 3D distribution defined by a voxel.