Scholarly record

DETERMINING THE DECLINATION IN ROMANIAN AIRPORTS

Natalia-Silvia Asimopolos, Laurentiu Asimopolos, Adrian-Aristide Asimopolos, LUMINITA DINU, EUGEN LAURENTIU NICULICI

Abstract

Civil aircraft navigation uses specific procedures for the continuous determination of the aircraft position using the path and distance traveled in the considered time interval as calculation elements. Throughout the route, errors must be estimated that are generated by a series of parameters such as: hydrometeorological conditions, air current direction, declination, geoid parameters, the ship's nautical qualities and the response mode of the navigation equipment. The indications of the magnetic compass must be constantly compared with those of the gyrocompass to immediately determine any errors and correct them. Declination has a particularly important role because it can differ depending on the variations of the magnetic field. Considering that takeoff and landing are the most sensitive operations of aircraft, the declination values in airport areas must be known very precisely. The measurements of declination, inclination and total field that we performed were based on the measuring station in the vicinity of the airport, which was selected as a magnetic field area without anomalies, at a sufficiently large distance from sources of major industrial disturbances, high-voltage lines, roads and urban spaces. The determination of the declination was made using a Bartington unidirectional fluxgate magnetometer mounted on a Zeiss amagnetic theodolite. To determine the magnetic declination, 4 determinations of the direction of the magnetic field vector and 20 measurements of the Sun's position at the meridian were performed. Following these determinations, the position of the geographic and magnetic meridians of the measuring station can be established. The declination represents the hour angle obtained from the equation of time, the declination of the Sun at the exact time of determining the Sun's position, expressed in sexagesimal degrees. The values of the mean declination of the Sun and the equation of time can be found in the astronomical yearbook, being calculated based on the ephemeris equations. The values thus measured were corrected for diurnal variation and then reduced to the mid-year level, based on the values from the National Geomagnetic Observatory Surlari. To obtain the updated declination value, the annual average value given by the international geomagnetic field reference model – IGRF was used. In this way, the declinations of the airport areas in Romania were calculated and the respective data were represented in ArcGIS.

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