Analysis of the Network Geometry and Station Separation for Network-Based RTK

Dorota A. Grejner-Brzezinska, Israel Kashani, and Pawel Wielgosz

Abstract:	The use of the multi-reference approach in GPS kinematic positioning significantly increases the distance over which kinematic carrier-phase ambiguity resolution can be performed. This can be achieved either by imposing some geometric conditions based on fixed reference locations, and/or through the use of reference network data to estimate the observation errors/corrections. Consequently, if the carrier-phase observable errors are corrected or minimized, it is generally possible to resolve integer ambiguities over longer distances and to increase the accuracy and reliability of the user position. The use of a multiple reference station approach for wide area and regional differential kinematic GPS positioning has been successfully implemented in the Multi Purpose GPS Processing Software (MPGPSTM) developed at The Ohio State University. One of the currently implemented MPGPSTM processing engines uses the weighted free-net (WFN) approach with the distance-dependent weighting scheme to derive optimal estimates of the user coordinates as well as realistic accuracy measures. The WFN approach, combined with the single epoch (instantaneous) ambiguity resolution algorithm (i.e., every epoch is considered independent from the previous epoch solution) will be used to obtain the test solutions described below. While the three-step processing algorithm (float solution, ambiguity fixing, and final WFN solution) was presented by Kashani et al. (2003), this paper presents an extended discussion on the effects of network geometry and station separation on the final quality and reliability of the rover location. A 24-hour data set of August 31, 2003, collected by the Ohio continuously operating reference stations (CORS) network were processed in the instantaneous mode and under different network geometry (a selected sub-network of the Ohio CORS) and reference base separation. The selected number of reference stations and their separation vary, and several independent solutions reflecting the effects of local vs. regional solutions were obtained and analyzed. Various solutions, such as (1) single base solution for varying base-rover separation, (2) multiple reference solution with medium-range base separation, and (3) multiple reference solution with long-range base separation, were obtained and compared for accuracy and consistency. The primary objective of this test is to verify the feasibility of sub-decimeter rover positioning from a network of reference receivers with a 150–200 km separation.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	469 - 474
Cite this article:	Grejner-Brzezinska, Dorota A., Kashani, Israel, Wielgosz, Pawel, "Analysis of the Network Geometry and Station Separation for Network-Based RTK," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 469-474.
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