Abstract. The goal of magnetic observatories is to measure and provide a vector magnetic field in a geodetic coordinate system. For that purpose, instrument set-up and calibration are crucial. In particular, the scale factor and orientation of a vector magnetometer may affect the magnetic field measurement. Here, we highlight the baseline concept and demonstrate that it is essential for data quality control. We show how the baselines can highlight a possible calibration error. We also provide a calibration method based on high-frequency "absolute measurements". This method determines a transformation matrix for correcting variometer data suffering from scale factor and orientation errors. We finally present a practical case where recovered data have been successfully compared to those coming from a reference magnetometer.
Abstract. The DI-flux, consisting of a fluxgate magnetometer coupled with a theodolite, is used for the absolute manual measurement of the magnetic field angles in most groundbased observatories worldwide. Commercial solutions for an automated DI-flux have recently been developed by the Royal Meteorological Institute of Belgium (RMI), and are practically restricted to the AutoDIF and its variant, the GyroDIF. In this article, we analyze the pros and cons of both instruments in terms of its suitability for installation at the partially manned geomagnetic observatory of Livingston Island (LIV), Antarctica. We conclude that the GyroDIF, even if it is less accurate and more power demanding, is more suitable than the AutoDIF for harsh conditions due to the simpler infrastructure that is necessary. Power constraints in the Spanish Antarctic Station Juan Carlos I (ASJI) during the unmanned season require an energy-efficient design of the thermally regulated box housing the instrument as well as thorough power management. Our experiences can benefit the geomagnetic community, which often faces similar challenges.
Abstract. Absolute magnetic measurements are of great importance in magnetic observatories. They allow not only instrument calibration but also data quality checking. They require the vertical and the geographic or true north as reference directions, usually determined by means of a level and by pointing an azimuth mark, respectively. We present here a novel system able to measure the direction of the magnetic field and of the vertical and true north. A design of a north seeker is proposed taking into account sensor bias as well as misalignment errors. Different methods are derived from this model and measurement results are presented. A measurement test at high latitude is also shown.
Abstract. The previous release of our automatic DI-flux instrument, called AutoDIF mk2.2, has now been running continuously since June 2012 in the absolute house of Dourbes magnetic observatory performing measurement every 30 min.
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