Hi, As Sean notes, one possible way is to define a starting model with susceptibility 0 everywhere except inside your region of interest and then to use the Active Model constraint. There is another way that is less of a "firm" constraint if you'd like to explore another range of possible solutions.
If you've created a 3D wireframe or closed geosurface from your drilling geostring you can define a Parameter Reference Model and a Parameter Weighting Model using the tools in VOXI. Export your Mesh from VOXI by RMB the Mesh and selecting Export Click the Constraints Menu in VOXI and Choose Create > Build a Model Enter your exported Mesh as your input voxel Select Parameter Reference Model for the Constraint Type Enter a name for your output voxel Select Geosurface as your contact definition Browse for the Geosurface file and select the correct surface Outside the contact define your chosen susceptibility as a "constant value" Inside the contact define your chosen susceptibility as a "constant value" NB: It is important to choose your constraint susceptibilities relative to any background that you've removed - inversion always returns property values relative to the input or observed data after all trend removal or for density after all Bouguer corrections. Click OK. To define a Parameter Weighting, you can either choose a constant or a voxel distribution. High parameter weights (e.g. 1, 10, etc.) mean that you are confident in your Parameter Reference model. Low parameter weights (e.g. 0.001, 0.1) mean that you are less confident in your Parameter Reference model. Create either a voxel (using the same method as above or voxel math) with a distribution of weights, or choose a constant. Do this by click Constraints > Add > Parameter Weights... NB: The default weighting is low because the default parameter reference model is 0 everywhere. You can find out more about constraining your VOXI models by visiting the VOXI Learning Paths: https://my.geosoft.com/elearning/step/475#/step_475 Or watching this episode of the Top 5 Inversion Best Practice Series: https://my.geosoft.com/supportcentre#video/414 --- Forum archives can be accessed here: http://lyris.geosoft.com/read/?forum=geonet You are currently subscribed to geonet as: [email protected]. To subscribe or unsubscribe from any of our forums, select the User Forum selection on the Geosoft Community page: http://www.geosoft.com/support/community/forums/register/
