Title: Modified Kriging Based Double-Difference Tropospheric Correction Interpolation Method for Network RTK User
Author(s): Donguk Kim, Junesol Song, Deokhwa Han, Sunkyoung Yu, and Changdon Kee, Seungwoo Seo and Junpyo Park
Published in: Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017)
September 25 - 29, 2017
Oregon Convention Center
Portland, Oregon
Pages: 4090 - 4102
Cite this article: Kim, Donguk, Song, Junesol, Han, Deokhwa, Yu, Sunkyoung, Kee, Changdon, Seo, Seungwoo, Park, Junpyo, "Modified Kriging Based Double-Difference Tropospheric Correction Interpolation Method for Network RTK User," Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 4090-4102.
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Abstract: A Network RTK (Real-Time Kinematic) is a double-difference carrier phase based navigation system which can obtain cm-level position accuracy. One of the important research issue in the Network RTK is how to combine Network RTK corrections appropriately for user location. The conventional interpolation methods such as the DIM (Distance-Based Linear Interpolation Method), the LIM (Linear Interpolation Method), the LCM (Linear Combination Model), and the LSM (Low-Order Surface Model) have shown the performance degradation when interpolating low-elevation corrections. In this paper, we propose a new optimal interpolation method that is appropriate for Network RTK corrections especially at low-elevation satellites. We are not only considering the location geometry of reference stations but also adopting function of satellite elevation angle for optimal interpolation on each satellite. Moreover, we make use of the Kriging interpolation method in order to consider spatial characteristics of GPS error sources. This paper specifically focuses on the characteristics of a tropospheric delay error. The tropospheric delay error depends on the GPS signal path through the atmosphere, and then, it can be modeled as a zenith tropospheric delay and a mapping function represented of the satellite elevation angle. We modified the conventional Ordinary Kriging method using the relationship between the zenith tropospheric delay and double-difference tropospheric delay with function of elevation angle for optimal interpolation of each satellite, and conducted feasibility tests using realistic simulation data. In conclusion, through applying the new interpolation method, the maximum range residual error of user is reduced about 15% and 31% for GUMC and SOUL location with compare to the conventional LSM method. The 95% horizontal and vertical position error is also improved at both RTK user locations. Since our proposed method is effective when interpolating low-elevation corrections outstandingly, we expect that this new optimal method can contribute to performance improvement for Network RTK user by using low-elevation satellites.