Analysis of Network RTK with Weighted Ionospheric Corrections Under Severe Ionospheric Storm

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

Abstract:	"The primary objective of the research work presented in this paper is to test the Network RTK technique using weighted ionospheric corrections to assist fast ambiguity resolution (AR) over long baselines (>100 km) in a single-baseline mode and under severe ionospheric conditions (i.e., ionospheric storm). In order to assess the performance of the Network RTK positioning, two 24- hour data sets, representing quiet and disturbed ionospheric conditions, were processed and analyzed. The test data were collected by the Ohio Continuously Operating Reference Stations (CORS) on October 11, 2003, when the Kp index amounted to 1o (i.e., very low value), and on October 29, 2003, when the Kp index reached 9o (i.e., the highest possible value). A subnetwork of three Ohio CORS stations was selected to provide the network-derived ionospheric corrections. The average distance between the CORS stations in the test area was ~200 km. Another CORS station was selected as a simulated rover with a distance to the closest reference station of ~120 km. These distances are representative of the future High Accuracy-Nationwide Differential Global Positioning System (HA-NDGPS), where better than 10 centimeter (95%) accuracy is required over long distances. The Network RTK module in the Multi Purpose GPS Processing Software (MPGPS?) was used in these analyses to evaluate the ionospheric corrections and to test the AR and the positioning performance. In particular, the time required to fix the ambiguities (i.e., time-to-fix), positioning quality and reliability, together with the accuracy of the network-derived ionospheric corrections were studied under quiet and stormy ionospheric conditions. During the quiet period, the doubledifferenced (DD) ionospheric correction accuracies were usually within ±20 cm, assuring fast AR and reliable RTK positioning. However, the ionospheric correction accuracy varied greatly during the ionospheric storm and ranged from ± 5 cm to ±1.5 m, obviously hindering the AR and RTK positioning. During the quiet day, the ambiguities were resolved in 94% of the analyzed sessions and centimeter-level position was obtained; however, only 78% of the sessions were solved during the stormy day. These analyses are a continuation of the research presented in (Wielgosz et al., 2005b)."
Published in:	Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005) June 27 - 29, 2005 Royal Sonesta Hotel Cambridge, MA
Pages:	449 - 456
Cite this article:	Wielgosz, Pawel, Kashani, Israel, Grejner-Brzezinska, Dorota A., "Analysis of Network RTK with Weighted Ionospheric Corrections Under Severe Ionospheric Storm," Proceedings of the 61st Annual Meeting of The Institute of Navigation (2005), Cambridge, MA, June 2005, pp. 449-456.
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