High-Accuracy DGPS and Precise Point Positioning Based on Ohio CORS Network

Pawel Wielgosz, Dorota Grejner-Brzezinska and Israel Kashani

Abstract:	Differential GPS (DGPS) positioning is an important technique used in many GPS applications. DGPS method reduces the impact of several error sources that occur in absolute GPS positioning, and allows usually a meter level real-time navigation. Reference network-derived DGPS corrections may improve the positioning accuracy comparing to a single base solution (i.e. using corrections from the closest reference station only) due to the additional information collected from the network. However, the problem of the errors affecting absolute GPS positioning may be addressed not only by differential positioning, but also by absolute precise point positioning (PPP) with the use of the currently available mature GPS products, such as precise satellite orbits and clocks and atmospheric models. In the PPP module of the Multi Purpose GPS Processing Software (MPGPSTM), developed at the Ohio State University, International GPS Service (IGS) products are used along with the MPGPSTM-derived ionosphere models to provide instantaneous (single- epoch), kinematic and static positioning obtained from code and phase observables using a single GPS receiver In this contribution, we present the analysis of the accuracy of PPP in the instantaneous, kinematic and static modes, when one hour of GPS data, either single or dualfrequency, is available. In addition, an applicability of local and global ionosphere models in PPP is evaluated and analyzed. All GPS measurements used in this study were collected by the Ohio Continuously Operating Reference Stations (CORS) network. GPS data were processed in two one-hour sessions. In the first session, the data were collected during the local night (low ionospheric total electron content — TEC), and the second session includes the data collected just after the local noon (high TEC) in order to assess the impact of varying ionospheric conditions on the absolute GPS positioning. The primary objectives of the tests are to verify the feasibility of decimeter-level absolute GPS positioning in kinematic and static modes using the PPP approach, and the sub-meter positioning of the instantaneous PPP and DGPS. Since currently there are no data links between the Ohio CORS stations and the rover, the multi-station DGPS solution is simulated in post-processing, using algorithms that can be applied in real-time. Static observations were used in the kinematic processing mode in order to evaluate the positioning accuracy in both DGPS and PPP.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	754 - 759
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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