Department of Surveying and Mapping, China University of Petroleum (East China), Qingdao 266580, China.
Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China.
Sensors (Basel). 2018 Oct 19;18(10):3546. doi: 10.3390/s18103546.
The Chinese BeiDou Navigation Satellite System (BDS) has been an important constitute of the Global Navigation Satellite System (GNSS), and the combination of GPS and BDS shows significant improvements when compared with single GPS system for real-time kinematic (RTK) positioning, and improves on availability and fixing rates, especially in the East Asian area. While network RTK might have different types of receivers, both for global and regional networks, different types of receiver may adopt different internal multipath mitigation methods and other techniques that result in different pseudorange characteristics, especially for a multipath. Then, the performance of wide-lane ambiguity resolution (WL AR) is affected. In this study, we first analyze and compare the characteristics of BDS dual-frequency observations for different types of receivers, including Trimble, Leica, Javad, and Septentrio, based on multipath (MP) observables, and then we assess their influence on double-differenced (DD) WL AR. The numerical results show that an obvious low-frequency component exists in MP observables of BDS geostationary earth-orbit satellites (GEOs) for Leica receivers, while its high-frequency measurement noise is very small. For geosynchronous orbit satellites (IGSOs) and medium earth-orbit satellites (MEOs), a slight fluctuation can also be observed that is similar to that of GPS satellites, except for the satellite-included code bias. In Trimble, Javad, and Septentrio receivers, the MP series are dominated by high-frequency measurement noise, both for GEOs and non-GEOs, except for satellite-included code bias. Furthermore, the characteristic of Leica receivers for BDS GEOs seriously affects WL AR and, even for a short baseline, it takes a long time for WL ambiguities to converge, or not converge for many GEO-related DD WL ambiguities, while Trimble, Javad, and Septentrio receivers perform well for short and medium baselines. Then, a time-difference method is proposed to mitigate the multipath of BDS GEOs for a Leica receiver. After applying the proposed method, WL ambiguity fixing rates of GEO-related satellite pairs are improved significantly and the convergence time is shortened from several hours to ten minutes.
中国北斗导航卫星系统（BDS）是全球导航卫星系统（GNSS）的重要组成部分，GPS 和 BDS 的组合在实时动态（RTK）定位方面与单一 GPS 系统相比有显著的改进，提高了可用性和固定率，特别是在东亚地区。虽然网络 RTK 可能有不同类型的接收器，无论是全球网络还是区域网络，不同类型的接收器可能采用不同的内部多径缓解方法和其他技术，从而导致不同的伪距特征，特别是对于多径。然后，宽巷模糊度分辨率（WL AR）的性能会受到影响。在这项研究中，我们首先基于多径（MP）观测值，分析和比较了不同类型接收器（包括 Trimble、Leica、Javad 和 Septentrio）的 BDS 双频观测值的特征，然后评估了它们对双差（DD）WL AR 的影响。数值结果表明，Leica 接收器的 BDS 地球静止轨道卫星（GEOs）的 MP 观测值存在明显的低频分量，而其高频测量噪声非常小。对于地球同步轨道卫星（IGSOs）和中地球轨道卫星（MEOs），也可以观察到类似于 GPS 卫星的轻微波动，除了卫星内码偏差。在 Trimble、Javad 和 Septentrio 接收器中，MP 系列主要由高频测量噪声主导，无论是 GEOs 还是非 GEOs，除了卫星内码偏差。此外，Leica 接收器的 BDS GEO 特征严重影响 WL AR，即使对于短基线，WL 模糊度也需要很长时间才能收敛，或者对于许多与 GEO 相关的 DD WL 模糊度，根本无法收敛，而 Trimble、Javad 和 Septentrio 接收器在短基线和中基线时表现良好。然后，提出了一种时差法来缓解 Leica 接收器的 BDS GEO 多径。应用所提出的方法后，与 GEO 相关的卫星对的 WL 模糊度固定率显著提高，收敛时间从几个小时缩短到十分钟。
