Workshop 2018
Zhigui Kang - GNSS-based precise troposphere zenith path delay determination with high temporal resolution - October 29, 2018 • 256 Views
The Global Navigation Satellite System (GNSS)-based precise troposphere Zenith Pass Delay (ZPD) determination with high temporal resolution needs precise positioning for ground stations. Current methods for precise positioning using GNSS technology are Differential GNSS (DGNSS) and Precise Point Positioning (PPP). The DGNSS is or will be replaced by PPP in some application areas of GNSS due to the PPP flexibility. Therefore, we study the PPP application for GNSS-based precise troposphere ZPD determination with high temporal resolution. There are two main approaches to estimate the ZPD parameters using PPP: first one is modeled the zenith path delay parameter as random walk for each observation epoch with process noise; second one is modeled the parameter as piecewise linear or piecewise constant for a certain time interval. The characteristics of estimated ZPD parameters are dependent on the approach used in the data processing. If the estimated parameters are used for the supported application, it is better to provide an independent and unconstrained solution for the parameters. The independent and unconstrained solution can not only provide the real solvability, but also keep the real signals. To get independent parameters and unconstrained solutions for ZPD, the piecewise constant parameterization under no or loose constraints are needed. In addition, temporal resolution for ZPD is also important. The question is how to select the interval for the ZPD parameters to get higher temporal resolution . Currently for estimating troposphere ZPD parameters, batch estimation is used for the piecewise linear or constant parameters; sequential estimation is used for the random walk parameters, which can compensate the stochastic model errors by adding process noise. But when the interval is shorter and shorter, the results from both approaches should be closer and closer. However, the estimated some troposphere ZPD parameters are not stable and have jump problems between the parameters during decreasing the interval for piecewise constant parameterization. To solve for such problems, adding process noise for ZPD parameters in batch estimation is proposed. The main goal of this study is to obtain an nearly independent and unconstrained as well as stable solution under no significant loss of signals for ZPD. The preliminary result shows such a solution for ZPD parameter can be obtained with the proposed approach.

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