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. Santrauka 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 įvertintas 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.
Highlights
The determination of the parameters of the Earth’s geomagnetic field and research of their variation are actual and complex problems in natural science
It is necessary to know the astronomical azimuth of ground objects, which is often determined according to observations of the Sun and the magnetic azimuth of the same object, which is by Flux D/I magnetometers
Errors in the World Magnetic Model (WMM) were determined by using two methods: firstly, by comparing declination values computed from the model with those obtained at the repeat stations and airports, and secondly, by comparing model values with those of an updated map from the 1940.5 epoch [6]
Summary
The determination of the parameters of the Earth’s geomagnetic field and research of their variation are actual and complex problems in natural science. This topic is related to our knowledge of the state of natural physical system outer parameters of present geophysical and geodynamical processes. A compass or director is used in geodesy for orientation when an instrument arrow points along the lines of the geomagnetic field. In this case, information on geomagnetic declination is necessary to determine direction.
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