3. Getting Started

3.1. General workflow

Using SeidarT follows a relatively simple workflow.

  1. You need two or three files to start:

  • A 2D image saved in png format.

  • A csv file listing the X,Y,Z coordinates of receivers for your survey

  • If your material is anisotropic, you need a file in the format delimited file specifying the

Euler angles for a number of crystals, with one triplet per line. See an example orientation file and/or generate one using the orientation_tensor function.

  1. Generate a project file (using prjbuild) and edit that text file to set up your survey.

  2. Create files describing the radar or seismic source (sourcefunction).

  3. Choose the style of survey you want to do [single shot, common offset, common midpoint, or (in development) polarimetric] and run the calculations.

  4. For single shot, you can create an animation of the wave propagation (im2anim for 2D or vtkbuild for 2.5D).

  5. Display your results as radar- or seismograms, or wiggle plots. You can also save the timeseries-receiver data in a csv file for further processing in different software.

Output from the seismic model is m/s and from the radar model is

3.2. Files to generate or edit

  • PNG image (.png)

    This defines the geometry of your model system. A good starting size is 50 to 500 pixels for each direction. Each RGB color represents a different material, so the file must be saved with no antialiasing. Typically each pixel represents the same distance in x and z (in meters). To get started on a new project create a new folder and save the image to the folder. From the command line, change directories to the project folder then enter the following:

    prjbuild -i /path/to/geometry/image.png -p project_filename.prj

    Below, we describe the prj file structure and how to edit it.

  • receiver locations (text file, commonly receivers.xyz)

    A comma separated list of X,Y,Z coordinates (one set per line, with X,Y,Z as the first line) for receiver locations. Can use pixels, but more typically meters as the units.

  • project file (.prj)

    This file is the heart of the software. It defines domain values, material properties, and survey conditions for electromagnetic and seismic runs. Here, we identify what each line means and which to edit. All lines with # are comments. Bold text indicates a line the user should edit.

Table: .prj File lines and their meanings

Line

Description

I,fill2.png

The image file associated with this .prj file.

D,dim,2
Choose either 2D or 2.5D.
2.5D is the 2D image extruded in the y-direction.

D,nx,240

Read from the image file. Do not change.

D,ny,1

Number of pixels in the extruded direction if using 2.5D.

D,nz,50

Read from the image file. Do not change.

D,dx,1

Number of meters each pixel represents in the x direction.

D,dy,1

Number of meters each pixel represents in the y direction.

D,dz,1

Number of meters each pixel represents in the z direction.

D,cpml,20

Thickness of absorbing boundary layer. A typical value is 20.

D,nmats,3

Read from the image file. Do not change.

D,tfile,

An attenuation processing value that is not yet implemented.
M,1,ice1h,98/197/178,
-10,2,910,0,0,TRUE,
test.ang
One comma-separated-values line per material
(per color in the model image).
User should change/add the material name (see list),
temperature (in degrees Celsius), density, porosity, water content,
whether the material is anisotropic (TRUE or FALSE),
and if anistropic, the name of the anisotropy file.
Use a dummy value of 2 for attenuation, recognizing that
attenuation is not yet incorporated in the calculations.
User should not change the material ID or R/G/B values.
Note: Since large density gradients cause numerical instabilities,
the density for air must be increased.
A value of 400.0 works until a better formulation
of the air-rock interface is implemented.

S,dt,

Timestep will be calculated automatically.

S,time_steps,500

Decide how many timesteps you want the model to run.

S,x,100

x-coordinate of the seismic source

S,y,0

y-coordinate of the seismic source

S,z,0

z-coordinate of the seismic source

S,f0,60

Frequency of the seismic source

S,theta,0

Inclination of the seismic source (+ is down)

S,phi,0
Angle of seismic source from x-axis in the x-y plane
(+ is counterclockwise when viewed from above)

C,0.0,
Stiffness tensor for each material. User can
enter or change this manually if desired. If blank,
calculated from materials information in the earlier section.

E,dt,

Timestep will be calculated automatically.

E,time_steps,500

Number of timesteps to run the model.

E,x,100

x-coordinate of the radar source

E,y,0

y-coordinate of the radar source

E,z,0

z-coordinate of the radar source

E,f0,1e8
Frequency of the radar source.
10-100MHz is a good range to start.

E,theta,0

Inclination of the radar source (+ is down)

E,phi,0
Angle of radar source from x-axis in the x-y plane
(+ is counterclockwise when viewed from above)

P,0.0,
Permittivity tensor for each material.
User can enter or change this manually if desired.
If blank, calculated from materials information in the
earlier section.

  • orientation file

    A delimited file of one entry of Bunge notation Euler angles per line. A typical number of entries is 500 to ensure a smooth data field.