Magnetic surveys affected by changes of the magnetic field with time.

What is it about?

Magnetic surveys help in making geologic maps, but when the magnetic field changes with time errors occur in magnetic surveys. Understanding basic patterns in how Earth's magnetic field changes with time can help to minimize and even avoid such errors. For example, there are regions of latitude around the Earth where the magnetic daily variation (called Sq) will have minimal effect on magnetic surveys - these latitude bands are called "magnetic doldrums". Similarly there are coastal regions where magnetic storms will have minimal effect on magnetic surveys - an excellent example is provided by the south coast of Australia.

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Why is it important?

Modern magnetic surveys, especially from low-flying aircraft (and increasingly from unmanned drones) has totally revolutionised geologic mapping. Increasing the accuracy of such surveys is a frontier of interest to all involved. Understanding the physics helps realistic assessment of geologic interpretations of magnetic maps, in the search for mineral and hydrocarbon resources.

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