Multi-sensor system for airborne geophysical prospecting and method
A multi-sensor electromagnetic (EM) system and method for measuring gradients of EM signals. The multi-sensor EM system includes a frame; a transmitter device attached to the frame and configured to generate a primary EM field; a receiver device attached to the frame and configured to record a secondary EM field generated by the earth after being excited by the primary EM field; and a gradient sensor device attached to the frame and configured to record a gradient of the secondary EM field.
1. A multi-sensor electromagnetic (EM) system for measuring EM signals, the multi-sensor EM system comprising:
a frame;
a transmitter device attached to the frame and configured to generate a primary EM field;
a receiver device attached to the frame and configured to record an EM measurement, which is indicative of a secondary EM field generated by the earth after being excited by the primary EM field;
a gradient sensor device attached to the frame and configured to record a gradient of the secondary EM field, the gradient sensor device including two parallel coils that sandwich a transmitter coil of the transmitter device, the two parallel coils being placed symmetrically about the transmitter coil; and
a peripheral sensor attached to the frame and configured to determine a position or an orientation or a state of the EM measurement.
2. The system of claim 1 , wherein the peripheral sensor includes a global positioning system.
3. The system of claim 1 , wherein the peripheral sensor includes at least one of a radar, laser altimeter, gyroscope, or inclinometer.
4. The system of claim 1 , wherein the peripheral sensor measures the position of the EM measurement.
5. The system of claim 1 , wherein the peripheral sensor measures a position of coils belonging to the transmitter device, or the receiver device or the gradient sensor device.
6. The system of claim 1 , further comprising:
a controller attached to the frame and electrically connected to the transmitter device, the receiver device, and the gradient sensor device,
wherein the controller instructs each of three transmitter coils of the transmitter device to generate a magnetic field with a given pulse repetition frequency.
7. The system of claim 1 , wherein the transmitter device includes three transmitter coils perpendicular to each other, the receiver device includes three receiver coils perpendicular to each other, and the gradient sensor device includes three gradient coils perpendicular to each other, at least one of the three gradient coils including the two parallel coils that sandwich the transmitter coil, which is one of the three transmitter coils.
8. The system of claim 7 , wherein each three gradient coils includes two respective parallel coils that sandwich a corresponding one of the three transmitter coils.
9. The system of claim 1 , wherein the two parallel coils are electrically connected to each other so that currents flowing through the two coils have opposite directions.