Research on magnetic declination in Lithuanian territory

Abstract

Magnetic declination is the angle between the planes of the astronomic and magnetic meridians. Magnetic declination is used in navigation, geophysics, geodesy, cartography, geology, and other fields. Magnetic declination is often computed from the World Magnetic Model (WMM). It is therefore important to be aware of the accuracy of the computed declination and to investigate its changes. For this purpose, magnetic declination was measured and the methodology of its measurement analyzed. Research was performed at six established points in 1999, 2001 and 2004. Magnetic declination was measured at Vilnius, Kaunas and Klaipeda airports in 2006. For magnetic declination measurements, the nonmagnetic Theo 010 B theodolite with Flux D/I magnetometer was used. Astronomical azimuth was determined according to the Sun’s hourly angle. Possibilities of determining astronomical meridian were investigated. The influence of the point and Sun coordinates were estimated. Based on this research, the Belsk Geomagnetic Observatory was selected as the most suitable one for the reduction of Lithuanian observation data. The registration at the Belsk observatory was used to compute annual mean values. The mean error of declination obtained was 0.3'. Based on research results, it was determined that declination values computed from the WMM magnetic model may have errors up to 1.5°. Annual variations in declination reached 7'.

Magnetinės deklinacijos reikšmė navigacijoje dažniausiai apskaičiuojama naudojant pasaulinį magnetinį modelį WMM (World Magnetic Model). Lietuvoje be pakartotinų geomagnetinio lauko matavimų amžių variacijų punktuose magnetinės deklinacijos reikšmė išmatuota ir keturiuose Lietuvos oro uostuose. Straipsnyje į vertintas pasaulinio geomagnetinio lauko modelio WMM tikslumas Lietuvos teritorijoje. Tirta ir įvertinta geomagnetinio lauko parametrų kaita. Išanalizuotas aplinkinių observatorijų tinkamumas Lietuvoje atliktų matavimų rezultatų redukavimui. Remiantis gautais tyrimų rezultatais, galima pasirinkti tinkamiausią laiką krypties astronominiam azimutui, o kartu ir astronominio dienovidinio krypčiai nustatyti, atsižvelgiant į žinomas parametrų paklaidas, punkto platumą ir metų laiką.