gprMax/gprMax

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This section provides example models of some of the more advanced features of gprMax. Each example comes with an input file which you can download and run.

Building a heterogeneous soil

This example demonstrates how to build a more realistic soil model using a stochastic distribution of dielectric properties. A mixing model for soils proposed by Peplinski (http://dx.doi.org/10.1109/36.387598) is used to define a series of dispersive material properties for the soil.

```.. literalinclude:: ../../user_models/heterogeneous_soil.in
:language: none
:linenos:

```

FDTD geometry mesh showing a heterogeneous soil model with a rough surface.

Line 10 defines a series of dispersive materials to represent a soil with sand fraction 0.5, clay fraction 0.5, bulk density 2~g/cm^3, sand particle density of 2.66~g/cm^3, and a volumetric water fraction range of 0.001 - 0.25. The volumetric water fraction is given as a range which is what defines a series of dispersive materials.

These materials can then be distributed stochastically over a volume using the `#fractal_box` command. Line 11 defines a volume, a fractal dimension, a number of materials, and a mixing model to use. The fractal dimension, 1.5, controls how the materials are stochastically distributed. The fractal weightings, 1, 1, 1, weight the fractal in the x, y, and z directions. The number of materials, 50, specifies how many dispersive materials to create using the mixing model (`my_soil`).

A rough surface can be added to any side of `#fractal_box` using,
```#add_surface_roughness: 0 0 0.070 0.15 0.15 0.070 1.5 1 1 0.065 0.080 my_soil_box
which defines one of the surfaces of the `#fractal_box`, a fractal dimension, and minimum and maximum values for the height of the roughness (relative to the original `#fractal_box` volume). In this example the roughness will be stochastically distributed with troughs up to 5mm deep, and peaks up to 10mm high.