The sporadic E (Es) layer has been known to introduce long-range propagation of aeronautical very high frequency (VHF) navigation beyond the radio horizon and cause potential interference on the navigation system. This study utilizes a rate of total electron content (TEC) index (ROTI) map with dense Global Navigation Satellite System (GNSS) observations for effective Es layer detection. The daytime Es layer shows a well-defined frontal structure when ROTI values are mapped at the typical Es layer height (100 km). A methodology of detecting and characterizing the Es layer frontal structure without manual operation is developed by utilizing the Hough transform. The front direction and drift velocity are successfully derived. Sub-structures in the Es layer front are revealed by analysis using the characteristics of the frontal structure and TEC variation. The developed method is suitable for an automated real-time Es-layer monitoring system in a wide area.

中文翻译：

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利用密集 GNSS 网络观测研究零星 E 层的结构

众所周知，零星的 E (Es) 层会在无线电地平线之外引入航空甚高频 (VHF) 导航的远程传播，并对导航系统造成潜在干扰。本研究利用具有密集全球导航卫星系统 (GNSS) 观测的总电子含量 (TEC) 指数 (ROTI) 地图来进行有效的 Es 层检测。当 ROTI 值映射在典型的 Es 层高度（100 公里）时，白天的 Es 层显示出明确的锋面结构。利用霍夫变换开发了一种无需人工操作即可检测和表征Es层额叶结构的方法。成功导出了锋面方向和漂移速度。利用锋面结构特征和TEC变化特征分析揭示了Es层锋面的亚结构。所开发的方法适用于大范围的自动化实时Es层监测系统。