Estimation of code observation-specific biases (OSBs) for the modernized multi-frequency and multi-GNSS signals: an undifferenced and uncombined approach
Estimation of code observation-specific biases (OSBs) for the modernized multi-frequency and multi-GNSS signals: an undifferenced and uncombined approach
复制标题
现代化多频和多 GNSS 信号的代码观测特定偏差 (OSB) 估计：一种无差异且未组合的方法
DOI：
10.1007/s00190-021-01549-x
复制
发表时间：
2021-08-01
影响因子：
4.4
通讯作者：
Zhang, Baocheng
中科院分区：
文献类型：
--
作者：
Liu, Teng;Zhang, Baocheng
长期以来，全球导航卫星系统（GNSS）的码偏一直被参数化，并在差分模式下表示，即通常所说的差分码偏（DCB）。然而，随着现有星座的不断现代化和新系统的快速发展，各种新的频率和类型的GNSS信号不断出现，这使得传统的DCB模式在应对新情况和挑战时变得不那么灵活和有效。近年来，观测特定表示中的代码偏差最终提供了观测特定偏差（OSB），这被证明是一个很好的解决方案，并逐渐被GNSS社区所接受，尽管现有的产品是基于常规程序生成的，并且很少有研究集中在新方法上。有鉴于此，本研究旨在提出一种严格、灵活、高效的现代化多频、多GNSS信号OSB估计方法。为了实现这一点，而不是在现有的文献中基于原始观测值的线性组合，扩展的多频率几何无关模型首先建立基于未差分和未组合的观测值，它可以适应任意频率和类型的观测值，以兼容和灵活的方式，用于提取感兴趣的OSB的各种类型的线性组合。然后，在基于台站的电离层建模后，将得到的线性组合作为虚拟观测量，在一个正规方程中建立和估计OSB参数，并通过引入不同类型的约束条件，对线性系统中的秩亏进行识别和消除.用一个月的真实的数据对该方法进行了验证，生成了GPS、GLONASS、Galileo、BeiDou和QZSS等卫星的32种OSB。估计的OSB与其他机构现有的OSB和DCB产品进行了比较。结果表明，该方法可以作为一种灵活、精确的全星座全类型OSB估计方法。
For a long time, code biases of global navigation satellite system (GNSSs) have been parameterized and presented in the differential mode, namely the commonly-known differential code biases (DCB). However, with the continuous modernization of the existing constellations and rapid developments of the new systems, various new frequencies and types of GNSS signals are emerging, which makes the traditional DCB mode less flexible and efficient to handle the new situations and challenges. Recently, code biases in observation-specific representation, which finally provides observation-specific biases (OSBs), turns out to be a good solution and is gradually accepted by the GNSS community, though existing products are generated based on routine procedures and few studies concentrate on the new methods. In view of it, this study aims to propose a rigorous, flexible and efficient approach of OSB estimation for the modernized multi-frequency and, multi-GNSS signals. To achieve this, instead of being-based on linear combinations of raw observations in the existing literature, an extended multi-frequency geometry-free model is first established based on undifferenced and uncombined observations, which can adapt to observations of arbitrary frequencies and types in a compatible and flexible way and is used to extract the various types of linear combinations of the interested OSBs. Then, regarding the previously-obtained linear combinations as virtual observables after station-based ionosphere modeling, all OSB parameters are setup and estimated in a single normal equation, during which a clear identification and elimination of the rank deficiencies in the linear system is carefully conducted by introducing different types of constraints. The proposed new method is validated with one month of real data to generate totally 32 types of OSBs for GPS, GLONASS, Galileo, BeiDou, and QZSS. The estimated OSBs are compared with existing OSB and DCB products from other agencies. Results indicate that the proposed method can be used as a flexible and precise method for full-constellation and full-type OSB estimation.