D.V. Murzin1, G.V. Ershov2, A.R. Murlaga3, T.A. Mirtalibov4

1-3 JSC “Central Radio-Research Institute named after academician A.I. Berg” (Moscow, Russia)

4 “Almaz-Antey” Corp. (Moscow, Russia)

Nowadays unmanned aerial vehicles are in wide use to obtain coordinates of ground-based radio sources and to transmit them to control centers. At the same time angular coordinates of ground-based radio source are being obtained in local coordinate system of unmanned aerial vehicle, thus, causing difficulties in their usage in control center. Hence, transformation of ground-based radio source angular coordinates in geocentric coordinate system immediately on board of unmanned aerial vehicle is a vital problem.

The purpose of this paper consists in suggesting of an algorithm allowing on board of unmanned aerial vehicle to transform ground-based radio source coordinates in geocentric coordinate system using on-board passive direction finder data.

As a result, this algorithm is elaborated. Its fulcrum is a method based on principles of spherical geometry and allowing to determine differences between geographic latitudes and longitudes of unmanned aerial vehicle and ground-based radio source.

The algorithm includes four main steps. At first step the following parameters are being determined and measured in local coordinate system of unmanned aerial vehicle: height of unmanned aerial vehicle above Earth surface, geographical coordinates of unmanned aerial vehicle, angle between instantaneous direction of unmanned aerial vehicle flight and meridian/parallel crossing projection of unmanned aerial vehicle position onto Earth surface, angular coordinates of ground-based radio source (azimuth and angle of elevation). At second step differences between geographic latitudes and longitudes of unmanned aerial vehicle and ground-based radio source are being determined. At third step geographical coordinates of ground-based radio source are being determined. At fourth step coordinates of ground-based radio source in geocentric coordinate system are being determined.

Transformation of ground-based radio source angular coordinates in geocentric coordinate system immediately on board of unmanned aerial vehicle is necessary to successfully accomplish an entire class of problems when time is a key factor, for example, when ground-based radio source is mobile. In this case it may be important not only to determine coordinates of ground-based radio source at a given point of time but also to update their values during its motion. To accomplish this, in the algorithm must be taken into account Earth rotation. Elaboration of such algorithm is left for further investigations.

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