The ionospheric anomalies are often responsible for compromising the accuracy and performance of Global Navigation Satellite System (GNSS). GPS Aided Geo Augmented Navigation (GAGAN) is the autonomous Space Based Augmentation System of India which serves to provide timely error detection and correction for the corrupted GNSS signals in aircrafts. This paper discusses a Maximum Minimum Eigen (MME) detector to identify the ionosphere induced errors in the GNSS signals. Data has been collected from 24 different GAGAN receivers spread over the length and breadth of India from January to December, 2015. The climatology of ionospheric anomaly over India, has been established using the MME detector. This paper discusses the spatio-temporal dependence of ionospheric anomalies over India. The observations indicate an increased ionospheric activity in the course of equinoxes and a comparitively quiet ionosphere in the course of solstices. A higher number of ionospheric disturbance incidents have been noticed closer to the anomaly crest. The results from the MME detector have been verified against the Rate of Total Electron Content (TEC) Index (ROTI) values and S4 observations for the year 2015 at the 24 GAGAN TEC stations. The disturbance climatology obtained from MME detector, ROTI and S4 exhibit a high correlation. However, the outcome of the MME detector clearly shows that it is capable of picking up even small irregularities in the ionospheric TEC.

中文翻译：

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GAGAN接收器的电离层异常检测和印度电离层气候

电离层异常通常是损害全球导航卫星系统（GNSS）的准确性和性能的原因。GPS辅助地理增强导航（GAGAN）是印度自主的基于空间的增强系统，用于为飞机中受损的GNSS信号提供及时的错误检测和纠正。本文讨论了一个最大最小本征（MME）检测器，用于识别GNSS信号中电离层引起的误差。2015年1月至2015年12月，从24个不同的GAGAN接收器收集了分布在印度各地的数据。使用MME探测器建立了印度电离层异常的气候学。本文讨论了印度电离层异常的时空依赖性。观测结果表明，在春分期间电离层活动增加，而在溶蚀期间电离层活动相对安静。在离异常波峰较近的地方发现了更多的电离层扰动事件。MME检测器的结果已针对24个GAGAN TEC站的总电子含量比率（TEC）指数（ROTI）值和2015年的S4观测值进行了验证。从MME检测器，ROTI和S4获得的干扰气候表现出高度相关性。但是，MME检测器的结果清楚地表明，它能够拾取电离层TEC中甚至很小的不规则性。MME检测器的结果已经针对24个GAGAN TEC站的2015年总电子含量率（TEC）指数（ROTI）值和S4观测值进行了验证。从MME检测器，ROTI和S4获得的干扰气候表现出高度相关性。但是，MME检测器的结果清楚地表明，它能够拾取电离层TEC中甚至很小的不规则性。MME检测器的结果已针对24个GAGAN TEC站的总电子含量比率（TEC）指数（ROTI）值和2015年的S4观测值进行了验证。从MME检测器，ROTI和S4获得的干扰气候表现出高度相关性。但是，MME检测器的结果清楚地表明，它能够拾取电离层TEC中甚至很小的不规则性。