# HydroGeoSphere/Finite-Difference Options

## Finite difference modeEdit

Causes **HydroGeoSphere** to use the finite difference approach instead of the default finite element method.

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The following instructions affect the transport simulation in a general way when finite difference method is being used:

## Compute fd cross termsEdit

Causes **HydroGeoSphere** to compute cross terms explicitly when a finite difference representation is chosen, which, by default, are ignored.

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## Control volumeEdit

Causes the control-volume finite difference approach to be used instead of the default standard finite difference approach. This instruction has no effect when the finite element approach is being used because the control volume approach is always used in that case.

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