Free Net Adjustment in Multi Reference Stations Approach for Instantaneous RTK

I. Kashani, P. Wielgosz, D. Grejner-Brzezinska

Abstract:	This paper presents an algorithm based on multi-reference station processing and weighted free-net (WFN) adjustment concepts, suitable for providing more reliable coordinates and realistic accuracy measures in the instantaneous real time kinematic (RTK) mode. The use of multiple reference station approach in a wide area (and regional) differential GPS network to improve kinematic positioning has been successfully applied in the MPGPSTM (Multi Purpose GPS Processing Software) software, currently under development at OSU. About 13 hours of GPS observations collected at the State of Ohio Continuously Operating Reference System (CORS) were processed and analyzed in the instantaneous mode (one epoch solution). The distances between the reference stations varied from 98 to 121 km, and the distances to the rover receiver ranged from 40 to 100 km. A WFN approach was applied in the instantaneous RTK software module, and made it possible to get an optimal estimate of the rover coordinates, reflecting the accuracies of the observations and the coordinates of the CORS stations. The effect of using the distance-dependent weighting scheme for the WFN approach on the final rover solution is analyzed. The influence of the different weights was studied by introducing the distance-dependent weights as a function of the CORS station separation L to the rover (1/L2). The results show that almost 100% of the differences between the computed horizontal rover coordinates and the known coordinates are below a decimeter, and 95% of the differences in the vertical coordinate are below 20cm, when using the WFN approach with distance-dependent weighting scheme. The following methods related to datum definition: minimum constraints (MC), over-constrained (OC) and the WFN, were tested, and the comparison between the three models was carried out. The results show improvements with respect to the mean and STD between 20-50 percent in the estimated rover coordinates while using the suggested approach.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	1390 - 1396
Cite this article:	Kashani, I., Wielgosz, P., Grejner-Brzezinska, D., "Free Net Adjustment in Multi Reference Stations Approach for Instantaneous RTK," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 1390-1396.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In