The Forward Modelling GUI

The wizard makes it easier for the user to select the correct modelling parameters.

1. In the first wizard panel, you can choose the name of your forward model and check the components that you would like to compute. It is also possible to "clone" a case, i.e. reuse the parameters from a previous modelling run.
2. The second panel lets you choose an observed grid for the component you want to calculate and determines the surface where you want to calculate the model. The "field" under the "From External Resource" box lets you choose a band if your input grids has multiple bands. You can safely ignore it if your just working with a regular grid.
   You can calculate the model response on a constant elevation (this is a real elevation, not a clearance from the highest topographic point or similar) or you can use a drape surface. By setting "Drape->Terrain clearance" to 0, you will calculate the forward response at the height of the terrain. If you set it to, say, 100 m you will calculate it at a clearance of 100 m above the terrain. With the third option "Drape -> Load from dataset" you can load any drape surface that is used to calculate the forward response.
3. The next panel lets you set the resolution and extent of the voxet. Here you can also choose to do a spatial or FFT forward model.
   • For spatial forward modelling, the z-resolution of the DTM (if any) will be adjusted to the value given in "Vertical sampling interval", e.g. if you set it to 50 m, the resampled DTM will only have values that are equal to the lowest elevation plus integer multiples of 50 m.
   • For the 3d FFT method, the vertical expansion is crucial. The larger this expansion factor (in percent) is, the better the result. However, depending on the voxet resolution, this can require huge amounts of memory. For your reference, the estimated memory requirements are displayed in the bottom row. There is also a "signal light" that gives you an idea how accurate the result will be. The accuracy is only a crude estimate of the real error though, and is only representative for the centre of your grid. The accuracy will deteriorate towards the grid edges.
4. The second-to-last panel lets you set the geophysical properties, if you haven't already done so in Geomodeller.
5. The last panel lets you run the forward model. The "Number of Cores" is only relevant for spatial forward modelling. If you have a computer with multiple CPUs/Cores, you can set the number of cores that Geomodeller should use to speed up the forward modelling.
6. The results window shows the following:
   • Bottom row, left - regional field that you can set or let Geomodeller solve for the best fit to the observed data
   • Bottom row, right - the calculated model response
   • Upper row, left - the observed field
   • Upper row, centre - the final model = sum of computed response and regional
   • Upper row, right - misfit between observed and model