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Absolute magnetic measurements, methods and instrumentation |
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Domján, Á. (1) |
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(1) MinGeo Ltd., Budapest, Hungary |
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Absolute geomagnetic measurement is an accurate determination of magnetic declination D and inclination I at a given location and time on the Earth. These quantities are essential to monitor the long-term baseline changes and calibration parameters of variometers in observatories and repeat station surveys.
Methods and the instrumentation are tightly coupled to this kind of measurement. Since all the relevant methods based on the usage of a classical theodolite equipped with flux-gate magnetometer known as declination inclination magnetometer (DIM). The most commonly used method in the magnetic community is the null method. In the null method procedure we need to find the close to zero magnetic output of the magnetometer in a predefined sequence. Then the processing is not more than additions subtraction and mean calculation.
In the article of (Brunke and Matzka, Numerical evaluation of magnetic absolute measurements with arbitrarily distributed DI-fluxgate theodolite orientations, 2018) a new method was proposed, where the determination of D and I is a search for global minimum of the non-linear inverse problem of the DIM instrument model. This method more general than null method. There is no rigorous constrain about the measurement protocol and it can process the null method data too.
DIMs have several difficulties. Measurement procedure is carried out manually. Difficult to use DIM for I observation in equatorial region because the telescope cannot be read in nearly vertical position even with diagonal eyepiece. The computation of magnetic meridian is calculated by the operator during the measurements.
To overcome this problem at MinGeo company we developed a cable-less, digital, non-magnetic DIM instrument, known as the FluxSet Declination Inclination Digital Station 1 (DS-1), which was designed to facilitate the absolute magnetic measurements.
The aim of this presentation to asses the accuracy and precision of the absolute magnetic measurements, which were measured by a reference DIM and DS-1 instrument using null and this new proposed method. |
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Instrumentation |
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oral |
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