GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 15, Page 6
GRADIENT ARRAY NOTES
The objective of this resistivity calculation scheme is to make it easy to input grid coordinates for
gradient surveys.
CAUTION: The LINE number in Menu 2 has been changed to Ay in this program as the Y-
coordinate of the AB transmitter dipole. Carefully read the following definitions:
a = [A-SP] = a-spacing (size of receiver dipole) in meters
V = Received voltage in volts [Measured].
I = 4/π * [Tx Curr] = 4/π * Transmitter current in amperes.
The 4/π factor is included in the software.
Ax, Bx = Transmitter current electrode locations, A and B. Ax and Bx are input in
Menu 1, in meters, and are coordinate locations.
Ay = By = Y-coordinate of the transmitter dipole in meters, which is input in Menu 2.
Set to 0 if Tx dipole runs along the baseline.
AB = |Ax - Bx| = Transmitter dipole length in meters.
Rx and Ry are the coordinates of the first electrode in a receiver setup.
Rx = [Rx] = Coordinate parallel to the transmitter dipole of the first potential electrode.
It will be the western-most electrode if running west-to-east; eastern-most
if running east to west. If Ax is set to zero, Rx will be equal to Dx and
will be the distance from Ax.
Ry = [Ry] = Coordinate perpendicular to the transmitter dipole of the first potential
electrode. If LINE is set to zero, Ry will be the distance from the AB
dipole and will be equal to Dy.
N = Electrode location (in multiples of a) with respect to Rx. This value is
positive (+) if running in the direction of increasing coordinates, negative
(-) if running in direction of decreasing coordinates. (This value is used as
N-spacing in other programs.)
Summary of input parameters for resistivity calculations:
Ax, Bx : Menu 1, in meters. "X" Coordinates of the transmitter dipole.
Ay : Menu 2, in meters. "Y" coordinate of the transmitter dipole.
A-SP : Menu 2, in meters. Receiver dipole spacing.
Rx, Ry : Menu 4, in meters. Coordinates of the first receiver electrode.
Tx Curr : Menu 4, in amperes. Transmitter current.
N : Menus 3, 4. The product of a * N = potential electrode position with respect to Rx.
To Next Page
