GNSS Antenna Orientation and Detection of Multipath Signals from Direction of Arrival

D.E. Grimm, L. Steiner, R. Mautz

Abstract:	This paper presents a concept to determine the directions of arrival (DOA) of GNSS satellite signals using a normal GNSS antenna. The DOA is determined by modifying the directional antenna pattern by applying specific signal attenuation. Knowing the DOA with regard to the antenna has two advantages. First, the absolute orientation of the antenna can be determined without the need for a second antenna or auxiliary orientation sensors such as magnetic or gyro-compasses. The standard measurement uncertainty of the orientation is between 1 degree to 3 degrees, dependent on the measuring time and the conditions. Secondly, the DOA of signals from individual satellites can be used to detect indirect signals resulting from multipath. The orientation of the antenna is essential for many navigation applications. When a mobile GNSS antenna is already in motion, its orientation can be derived from the position track, but for efficient navigation it is also necessary to provide the navigation direction at an initial static position. Therefore, this approach is useful in situations where • no position history is available, • the movement is too irregular for proper determination of the orientation and • a baseline of two or more antennas is impractical. When the orientation of the antenna is known, the DOA of the satellite signals can be further exploited for quality control of the received signals. The observed DOAs are therefore compared to the expected DOAs from the almanac. This allows the detection of signals reaching the antenna from wrong directions. Even a distinction between signals arriving only from a single, wrong direction and signals reaching the antenna from several directions can be achieved. This is of particular importance for the detection of reflected signals or signals affected by multipath. Excluding such signals from the position calculation can remove systematic biases and therefore improve the accuracy of the position. Additionally, the knowledge of the antenna orientation can be used to implement correction models of the antenna phase center variation (PCV) for static high precision GNSS applications.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1179 - 1185
Cite this article:	Grimm, D.E., Steiner, L., Mautz, R., "GNSS Antenna Orientation and Detection of Multipath Signals from Direction of Arrival," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 1179-1185.
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