Data File

The data file format used by EMFEM was largely inspired by MARE2DEM’s data format. It contains the transmitters, receivers and frequencies, and has a table of data types, values and standard errors. Like the model file, lines prefixed by the character # are considered as comments. It consists of four parts.

Part 1 - Frequencies

This block lists the number of frequencies (both MT and CSEM) and the specific values (Hz).

First line: <# of frequencies>
Remaining lines list # of frequencies:
  <frequency>
  ...

Part 2 - Transmitters

This block lists the number of CSEM receivers, each receiver’s x,y,z (meters) position, rotation angles, currents, electric dipole length. For now, we only support point electric dipole, so the dipole length is not used and preserved for future use.

One line: <# of transmitters>
Following lines list # of transmitters:
  <x> <y> <z> <azimuth> <dip> <current> <dipole length>

Part 3 - Receivers

One line: <# of receivers>
Following lines list # of receivers:
  <x> <y> <z>

Part 4 - Data Block

The Data block lists the number of data and has a table with a line for each datum. Each line lists the data parameters, the datum and its standard error. The first four values are data parameters for each datum and the 5th and 6th columns are the data, the 7th and 8th columns are the standard errors. The standard errors are not used for now and are preserved for future use.

One line: <# of datum>
Following lines list # of data:
  <data type> <frequency index> <transmitter index> <receiver index> <real part of data> <imag part of data> <real part of error> <imag part of error>

All the index are starting from 0. For MT datum, the transmitter index must be -3.

CSEM Data types

Code	Description
111	Ex, real and imaginary
121	Ey, real and imaginary
131	Ez, real and imaginary
141	Hx, real and imaginary
151	Hy, real and imaginary
161	Hz, real and imaginary
112	Ex, amplitude and phase
122	Ey, amplitude and phase
132	Ez, amplitude and phase
142	Hx, amplitude and phase
152	Hy, amplitude and phase
162	Hz, amplitude and phase

MT Data types

Code	Description
311	Zxx, real and imaginary
321	Zxy, real and imaginary
331	Zyx, real and imaginary
341	Zyy, real and imaginary
351	Tzx, real and imaginary
361	Tzy, real and imaginary
312	Zxx, amplitude and phase
322	Zxy, amplitude and phase
332	Zyx, amplitude and phase
342	Zyy, amplitude and phase

Here is an example:

# frequencies
5 # number of frequencies
1.0000E-01
5.0000E-01
1.0000E+00
2.0000E+00
5.0000E+00
# transmitters
1
#     X        Y        Y  Azimuth   Dip   Current  Length
    0.0  -4000.0    900.0     90.0   0.0       1.0     0.0
# receivers
121
#        X           Y           Z
0.0000E+00 -6.0000E+03  1.0010E+03
0.0000E+00 -5.9000E+03  1.0010E+03
0.0000E+00 -5.8000E+03  1.0010E+03
...

# observations
3630
#  Type   Freq#     Tx#     Rx#    Real(data)    Imag(data)   Real(error)   Imag(error)
    111       0       0       0  1.000000E+00  1.000000E+00  1.000000E+00  1.000000E+00
    111       0       0       1  1.000000E+00  1.000000E+00  1.000000E+00  1.000000E+00
    111       0       0       2  1.000000E+00  1.000000E+00  1.000000E+00  1.000000E+00
    ...

Response File

The response file is almost identical to the data file, except that the last two columns of the data section are the responses, not the standard errors.