Towards Instantaneous Network-Based RTK GPS Over 100 km Distance

Israel Kashani, Dorota Grejner-Brzezinska and Pawel Wielgosz

Abstract:	A network-based approach to instantaneous (singleepoch) long-range real-time kinematic (RTK) GPS positioning has been implemented and tested in the Multi Purpose GPS Processing Software (MPGPSTM), developed at The Ohio State University. The use of this approach, in GPS kinematic positioning, significantly increases the distance, over which carrier-phase ambiguities can be recovered to their integer values. However, especially with long baselines, the instantaneous ambiguity resolution may not always be possible, due to the increasing noise and lack of sufficient redundancy to verify the integer selection. The algorithm proposed here is based on a single baseline solution aided by double difference (DD) ionospheric delay from the previous epoch (up to 60-second latency in DD ionospheric delay may be accepted), which supports the ambiguity resolution and provides a quality instantaneous kinematic position over long distances. However, obtaining the initial DD ionospheric delay requires atmospheric corrections provided by the reference network and some accumulation at the beginning of the session — i.e., on-the-fly (OTF) initialization is needed. Afterwards, instantaneous RTK positioning is assured. In this contribution, a feasibility test of instantaneous realtime rover positioning is performed, and the effect of the DD ionospheric corrections latency on the instantaneous ambiguity resolution in the long-range RTK is investigated. The positioning accuracy achieved in the tests, expressed as the differences between the resulted coordinates and the known “true” coordinates, is at millimeter-level accuracy for the horizontal components and centimeter-level for the vertical one, for baselines over 100 km long.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	679 - 686
Cite this article:	Kashani, Israel, Grejner-Brzezinska, Dorota, Wielgosz, Pawel, "Towards Instantaneous Network-Based RTK GPS Over 100 km Distance," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 679-686.
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