What is a gradiometer?
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By utilising two magnetometers GoSubsea have produced an extremely sensitive and light weight gradiometer. The hard anodised frame has been found to be extremely stable and noise free. It can be configured to for either horizontal or vertical operation. Optional ballast weights are also available.
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While a magnetometer measures the Earth's total magnetic field, a gradiometer measures the first spatial derivative of the Earth's magnetic field. This is the rate of change of total magnetic field as you move through space. The simplest gradiometer measures magnetic gradient in one dimension by subtracting the difference between two independent magnetometer sensors. Since the Earth's magnetic field is three dimensional, up to three independent gradient directions can be measured; vertical, horizontal-transverse, and horizontal-longitudinal.
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Why and when do I need gradiometer data?
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When the sensor is relatively close to the source, both the gradient and total field influences will be strong. As the sensor moves away, the gradient will disappear more quickly than the total field influence. This relationship becomes very useful when trying to distinguish between magnetic bodies of different sizes. A large magnetic body's total field influence may extend for a large distance, obscuring smaller anomalies within it. The same body's magnetic gradient will extend for a significantly smaller distance, allowing better resolution of the smaller anomalies.
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