# 4.2.1. GGFOR3D¶

This program performs forward modelling. Command line usage:

ggfor3d mesh.msh obs.loc model.den [topo.dat]

and will create the forward modelled data file ggfor3d.gg.

NOTE: The program will ignore values less than -90 g/cc in the model file. Therefore, files with values of -100 (the flag for above topography) from the inversion code will not contribute to the forward modelling.

## 4.2.1.1. Input files¶

All files are in ASCII text format - they can be read with any text editor. Input files can have any name the user specifies. Details for the format of each file can be found in Section [Elements]. The files associated with are:

• mesh.msh: The 3D mesh.
• obs.loc: The observation locations.
• model.den: The density contrast model in g/cc.
• topo.dat: Surface topography (optional). If omitted, the surface will be treated as being flat and the top of the 3D mesh.

## 4.2.1.2. Output file¶

The created file is ggfor3d.gg. The file format is that of the data file without the associated standard deviations. The forward modelled data are in Eotvos.