3.2.4. Forware Modeling Input File

The forward problem is solved using the executable program dcipoctree_fwd.exe. The lines of input file are as follows:

Line #

Description

Description

1

Data Type

data being modeled: DC|IP|IPL

2

OcTree Mesh

path to octree mesh file

3

Survey File

path to survey file

4

Conductivity Model

conductivity model

5

Chargeability Model

chargeability model

6

Active Topography Cells

topography

../../_images/create_fwd_input.png

Fig. 3.4 Example input file for the inversion program (Download ).

3.2.4.1. Line Descriptions

  • Data Type: This line chooses the data which are modeled by the program:

    • DC: DC resistivity data are modeled. Although the line for the chargeability input file is ignored, something must be put there as a placeholder.

    • IP: DC resistivity data and IP data are modeled. IP data are modeled with a non-linear formulation.

    • IPL: DC resistivity data and IP data are modeled. IP data are modeled with a linear formulation.

  • Survey File: On this line, we enter a flag LOC_XY or LOC_XYZ, followed by the file path to the survey file. The flag tells the program whether the electrodes should be projected to the discrete surface or modeled in their current locations.

    • LOC_XY filepath: The electrodes are all projected to the discrete surface topograpy. If Active Topography Cells line is set to ALL_ACTIVE, the electrodes are placed on the top of the mesh. The predicted data files output by the code will be in ‘general format’; i.e. they will contain the elevations of the electrodes.

    • LOC_XYZ filepath: Electrodes remain at the exact xyz locations defined in the survey file. Necessary for borehole survey. Make sure you have run the surface electrodes executable on your original data file to ensure none of the electrodes are modeled as living above the discrete surface topography. Or you can use the file ‘data_Z.txt’ that is output when generating the octree mesh.

  • Active Topography Cells: Here, the user can choose to specify the cells which lie below the surface topography. To do this, the user may supply the file path to an active cells model file or type ALL_ACTIVE. The active cells model has values 1 for cells lying below the surface topography and values 0 for cells lying above.