Research On Measurement Error Of Automated Geomagnetic Declination And Inclination Absolute Measuring Instrument

The magnetic field,as an extremely important field on the earth,is one of the basic characteristics of matter.Geomagnetic field detection is an important means of geophysical basic field measurement.It can provide data basis for Geo-scientific research,resource exploration,space weather prediction,aerospace,national defense mapping,geo-navigation and seismic monitoring.Geomagnetic observation is a combination of absolute observation and relative recording.At present,all geomagnetic reference stations in China have set up absolute geomagnetic observation system,which consists of proton precession magnetometer and fluxgate theodolite.However,the development of absolute geomagnetic observation technology is restricted by the capacity limitation of non-magnetic theodolites,the observation mode of human beings and the severe natural environment limitation.Therefore,the research and development of automatic absolute observation technology of geomagnetic declination and dip angle and instrument have become the research hotspot in the field of international geomagnetic measurement.Till now,only Germany and Belgium have developed experimental prototypes of automatic absolute geomagnetic measurement systems,such as Gauss and Auto DIF.So far,no commercial instruments have been formed,and the technology is still being tested at observation stations.In 2017,the Institute of Geophysics,China Earthquake Administration,developed the first experimental prototype of automatic absolute geomagnetic declination and inclination measuring instrument in China,and made tests at several observation stations.In this paper,through the domestic and abroad literature review of absolute geomagnetic observation technology,the author summarizes the history of absolute geomagnetic observation instrument development and the research progress of the international leading automatic absolute geomagnetic observation system.Based on the development experience and practical measurement problems of the automatic absolute geomagnetic declination and inclination measuring instrument,the author has carried out the analysis and research on the measurement errors caused by environmental changes.The main innovative achievements are as follows:1.Through the experiments of calibration at different distances,the optimum laser calibration distance of the automatic absolute measuring instrument of geomagnetic declination and inclination under the existing observation conditions is given.By optimizing the structure of the marker of the filter and the super-long shade,the author can effectively suppress the interference of other light sources,thus ensuring the calibration accuracy in second level;the author have successfully introduced the azimuth of the north of geography to the laser markers in the absolute observation room.The measured results and the baseline values of the stations are fixed system differences.2.Through the displacement experiment,the author verify that the deviation of the instrument in millimeter level will result in the second level deviation of the observation results at a shorter calibration distance.Therefore,the automatic absolute measurement of geomagnetic declination and inclination must ensure that the position in the position is strictly unchanged.3.Through the experiment of steel block with constant magnetism,the author verify the influence of constant magnetic interference source on the measurement results of automation instrument at different distances,and draw the attenuation curve of influence with distance;the automatic measurement frequency(two groups per hour),can obtain the geomagnetic diurnal variation signal.But it is not enough to measure continuous absolute data of geomagnetic declination and inclination;the larger disturbances such as high voltage direct current have a great impact on the accuracy of continuous measurement of automated instruments.It is necessary to discriminate and select the measured data.4.Through the test of temperature drop experiment,the author verify the stability of the automatic instrument designed by fluxgate probe with good temperature characteristics and symmetrical mechanism of uniform material.It also shows that there is no need for strict thermal insulation in the future absolute observation room.The research has acquired a new understanding of the measurement errors of the automatic absolute geomagnetic declination and inclination measurement instrument,which lays a certain theoretical and experimental foundation for the future of the optimization design of the instrument,the exploration of automatic correction of the error of the absolute geomagnetic observation data,the actual erection and daily observation of the automatic instrument,and the construction of the National Automatic Absolute Geomagnetic Observation Network.The research results in this paper have important reference value for the realization of wider application and practicality of the automated absolute observation system in the future.