Articles | Volume 6, issue 2
Geosci. Instrum. Method. Data Syst., 6, 257–261, 2017
https://doi.org/10.5194/gi-6-257-2017

Special issue: The Earth’s magnetic field: measurements, data, and applications...

Geosci. Instrum. Method. Data Syst., 6, 257–261, 2017
https://doi.org/10.5194/gi-6-257-2017

Research article 13 Jul 2017

Research article | 13 Jul 2017

Semiautomatic sun shots with the WIDIF DIflux

Jean L. Rasson, Olivier Hendrickx, and Jean-Luc Marin Jean L. Rasson et al.
  • Royal Meteorological Institute, Centre de Physique du Globe, Dourbes, 5670, Belgium

Abstract. The determination of magnetic declination angle entails finding two directions: geographic north and magnetic north. This paper deals with the former. The known way to do it by using the sun's calculable orientation in the sky is improved by using a device based on a WIDIF DIflux theodolite and split photocells positioned on its telescope ocular. Given the WIDIF accurate timing and location provided by the onboard GPS receiver, an astronomical computation can be effected to accurately and quickly determine the sun's azimuth and an auxiliary mark's azimuth. The precise sun's crossing of the split photocell, amplified by the telescope's magnification, allows azimuth accuracies of a few seconds of arc.

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Short summary
In geomagnetism, geodesy and in general disciplines requiring orientation on Earth, accurately finding the direction of true north is a challenge. This paper describes a method to do so using a traditional theodolite and the proposed apparatus: an electro-optical add-on. The details of the concepts, design and operation of the add-on are explained.