Global navigation satellite system (GNSS) networks with multi-frequency data can be used to monitor the activity of the Earth's ionosphere and to generate global maps of the vertical total electron content (VTEC). This article introduces and evaluates operational GFZ VTEC maps. The processing is based on a rigorous least squares approach using uncombined code and phase observations, and does not entail leveling techniques. A single-layer model with a spherical harmonic VTEC representation is used. The solutions are generated in a daily post-processing mode with GPS, GLONASS, and Galileo data, and are provided for the period since the beginning of 2000. A comparison of the GFZ VTEC maps with the final combined International GNSS Service (IGS) product shows a high consistency with the solutions of the IGS analysis centers. A validation with about four years of Jason-3 altimetry-derived VTEC data is provided, in which the GFZ solution has the smallest bias of 1.2 TEC units compared to the solutions of the IGS analysis centers, and with 3.0 TEC units one of the smallest standard deviations.

中文翻译：

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GFZ 的操作性多 GNSS 全球电离层地图源自未组合的代码和相位观测

具有多频数据的全球导航卫星系统 (GNSS) 网络可用于监测地球电离层的活动并生成垂直总电子含量 (VTEC) 的全球地图。本文介绍并评估了可操作的 GFZ VTEC 地图。处理基于严格的最小二乘法，使用未组合的代码和相位观察，不需要调平技术。使用具有球谐函数 VTEC 表示的单层模型。这些解是在每日后处理模式下生成的，使用 GPS、GLONASS 和伽利略数据，并提供自 2000 年初以来的时期。 GFZ VTEC 地图与最终组合国际 GNSS 服务 (IGS) 产品的比较与 IGS 分析中心的解决方案高度一致。