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Geoscientific Instrumentation, Methods and Data Systems An interactive open-access journal of the European Geosciences Union

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Geosci. Instrum. Method. Data Syst., 6, 257-261, 2017
https://doi.org/10.5194/gi-6-257-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
13 Jul 2017
Semiautomatic sun shots with the WIDIF DIflux
Jean L. Rasson, Olivier Hendrickx, and Jean-Luc Marin 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.

Citation: Rasson, J. L., Hendrickx, O., and Marin, J.-L.: Semiautomatic sun shots with the WIDIF DIflux, Geosci. Instrum. Method. Data Syst., 6, 257-261, https://doi.org/10.5194/gi-6-257-2017, 2017.
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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.
In geomagnetism, geodesy and in general disciplines requiring orientation on Earth, accurately...
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