In the past few decades the Global Positioning System (GPS) has been the number one positioning tool in a range of Geodesy and Geophysics applications. The emerging Regional and Global Navigation Satellite Systems (RNSSs/GNSSs) can enhance positioning and non-positioning applications. GPS modernisation from dual-frequency to triplefrequency signals has lately also been complemented by global GLObal’ naya NAvigatsionnaya Sputnikovaya Sistema (GLONASS), Galileo and BeiDou Navigation Satellite System (BDS), as well as the regional Quasi-Zenith Satellite system (QZSS) and Navigation with Indian Constellation (NavIC). By 2024 it is expected that we will have access to more than 110 satellites in a multi-GNSS model transmitting their signals on a range of different frequencies. This will significantly improve current dual-frequency GPS positioning as well as non-positioning applications, such as atmospheric modelling and timing applications. Rigorous models and algorithms are however needed so as to link and integrate such multi-frequency, multi-GNSS signals to the estimable parameters of interest. Important topics in this field include singleand multi-frequency, multi-GNSS modelling, while making use of survey-grade and low-cost receiver and antenna equipment, including smartphones. With low-cost we refer to GNSS receivers and antennas having a cost of at most a few hundreds of dollars, whereas survey-grade receivers and antennas typically have a cost of several thousands of dollars. Other important topics include ionospheric and tropospheric delay estimation, and multi-GNSS Precise Point Positioning Real Time Kinematic (PPP-RTK). This Special Feature showcases the latest trends in multi-GNSS modelling. Five papers were accepted, based on their quality and significant contributions to the field. The topics covered are: multi-frequency and multiGNSS for stochastic modelling, single-baseline RTK and PPP-RTK, respectively, ionospheric modelling, and a PPP performance analysis of dual-frequency, multi-GNSS data collected in smartphones.

中文翻译：

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多 GNSS 处理、定位和应用

在过去的几十年中，全球定位系统 (GPS) 一直是一系列大地测量学和地球物理学应用中排名第一的定位工具。新兴的区域和全球导航卫星系统 (RNSS/GNSS) 可以增强定位和非定位应用。GPS 从双频信号到三频信号的现代化最近也得到了全球 GLObal' naya NAvigatsionnaya Sputnikovaya Sistema (GLONASS)、伽利略和北斗导航卫星系统 (BDS) 以及区域准天顶卫星系统 (QZSS) 和使用印度星座 (NavIC) 导航。到 2024 年，预计我们将能够使用多 GNSS 模型中的 110 多颗卫星，在一系列不同的频率上传输它们的信号。这将显着改善当前的双频 GPS 定位以及非定位应用，例如大气建模和授时应用。然而，需要严格的模型和算法，以便将这种多频、多 GNSS 信号与感兴趣的可估计参数联系起来并整合起来。该领域的重要主题包括单频和多频、多 GNSS 建模，同时利用测量级和低成本的接收器和天线设备，包括智能手机。低成本是指 GNSS 接收器和天线的成本至多数百美元，而勘测级接收器和天线的成本通常为数千美元。其他重要主题包括电离层和对流层延迟估计，和多 GNSS 精确点定位实时运动学 (PPP-RTK)。本专题展示了多 GNSS 建模的最新趋势。五篇论文被接受，基于他们的质量和对该领域的重大贡献。涵盖的主题包括：用于随机建模的多频和多 GNSS，分别是单基线 RTK 和 PPP-RTK，电离层建模，以及智能手机中收集的双频、多 GNSS 数据的 PPP 性能分析。