220.127.116.11. EM Data Classes¶
There are two main types of EM data that can be created in GIFtools.
EMdata class, the receivers are assumed to be point measurements of EM fields (E, H) collected along
the Cartesian directions. Only the transmitter type can be defined as
- TRX_LOOP: Simple loop
Radius of the transmitter
\(\theta\) angle from vertical (0=planar loop)
\(\alpha\) (azimuthal) angle from North
- TRX_ORIG: Defined by vertices
For purely inductive source, the first and last entry must be the same in order to close the wire path.
EMdata class is used for:
EMsounding class, parameters describing both the transmitter and receiver are
required and used in the forward and inverse problems. This is the most
general format. It allows to easily store airborne data collected from
transmitters and receivers of arbitrary shapes and orientations. The
EMsounding is further divided into two sub-classes:
EM1Dsounding objects, receiver can either be defined as a
loop source. The position of the receiver is set relative to the
transmitter locations. The following parameters are required:
Along-line offset: The along-line position of receivers, relative to transmitter locations
Cross-line offset: The cross-line position of receivers, relative to transmitter locations
Vertical offset: The vertical location of the receivers relative to the surface
Dipole Moment: Uses a right-handed positive down coordinate system
EM1Dsouding data class used for:
EM3Dsounding objects, information about the position and orientation of
the system are stored directly by the transmitter and receiver objects.
Loop transmitter/receiver: Loop transmitters and receivers must be defined in a left-handed (clockwise) manner. For example, a horizontal loop must be defined in a clockwise manner for its dipole moment to be in the vertical direction. For N loop segments, you will need to define N+1 nodes; e.g. you must close the loop. If a closed loop is used to define a receiver, the corresponding data are the magnetic field in units A/m.
Wire transmitter/receiver: Wire transmitters and receivers are defined using node locations without repetition of the first node.
For display purposes, the averaged receiver node locations are used to plot the data.
This data class is use for: