Software for total electron content of gps ionospheric pierce points

Bu çalışmada Global Positioning System (GPS) ölçüsü yapılan herhangi bir nokta için GPS uyduları iyonosfer geçiş noktalarının (IPP) toplam elektron yoğunluğu (TEC) hesaplama yazılımı MATLAB programlama dilinde yazılmıştır. TEC değerleri, GPS uyduları iyonosfer geçiş noktaları için hem düşey hem de eğik mesafe olarak istenilen uydu yükseklik derecesinde yazılım tarafından hesaplamaktadır. Yazılımın kullanıcı ara yüzü sayesinde kullanımı kolay ve oldukça hızlıdır. Yazılımın girdi verileri, günlük RINEX dosyası, hassas efemeris dosyası (ultra-hızlı, hızlı veya son ürün) ve ionosphere exchange (IONEX) dosyalarıdır (hızlı veya son ürün). Yazılım bu verileri kullanarak GPS ölçümü yapılan noktadan istenilen uydu yükseklik açısına göre zaman içerisinde izlenilen uyduları ve bu uyduların koordinatlarını hesaplamaktadır. Daha sonra hesaplanan uydu koordinatlarına göre bu noktaların düşey ve yatay TEC değerleri IONEX dosyasındaki veriler kullanılarak hesaplanmaktadır. IONEX dosyaları için istenilen herhangi bir kurumun ürettiği dosyalar kullanılabilir. Yazılımın kaynak kodları istenilen şekilde değiştirilerek elde edilen düşey ve eğik TEC değerleri ihtiyaç duyulan analizlerde kolaylıkla kullanılabilir. Yazılım MATLAB’ın hiçbir hazır fonksiyonunu kullanmamaktadır dolayısıyla sadece MATLAB programının yüklü olması yazılımı kullanmak için yeterlidir.In this study, total electron content (TEC) computation software of the GPS satellites’ ionosphere pierce points (IPP) for any test site using Global Positioning System (GPS) survey is written in the MATLAB programming language. TEC values are calculated by the software as both vertical and slant distance for GPS satellites’ IPPs with respect to cutoff angle. Due to the graphical interface of the software, usage of the software is easy and fast. The input data of the software are the daily RINEX file, the precise ephemeris file (ultra-fast, fast or final product) and the ionosphere exchange (IONEX) file (fast or final product). The software distinguishes the tracked satellites and computes their coordinates over time according to the desired satellite elevation cutoff angle from the survey point. Then, according to the calculated satellite coordinates, the vertical and slant TEC values of these points are calculated using the data in the IONEX file. IONEX files from any institution can be used. The vertical and slant TEC values can be extracted by changing the source code of the software and can be easily used in any scientific analysis. The software does not use any built-in function of MATLAB, so only the MATLAB program is required to run the software.

The Mechanism for GNSS-Based Kinematic Positioning Degradation at High-Latitudes Under the March 2015 Great Storm

In this study, we focus on the kinematic precise point positioning (PPP) solutions at high-latitudes during the March 2015 great geomagnetic storm. We aim to discover the mechanism behind the positioning degradation from the perspective of the impacts of the storm-induced ionospheric disturbance on the global navigation satellite system (GNSS) data processing. We observed that the phase scintillation dominated the amplitude scintillation at high-latitudes and the variation pattern of the rate of total electron content index (ROTI) was consistent with that of the phase scintillation during the storm. The kinematic PPP errors at high-latitudes were almost three times larger than those at the middle- and low-latitude, which were accompanied by large ROTI variations. From the perspective of GNSS data processing, the large positioning errors were also found to be related to the large number of satellites experiencing cycle slips (CSs). Based on the lock time from the ionospheric scintillation monitoring receiver, we found that a large amount of the CSs was falsely detected under the conventional threshold of the CS detector. By increasing such threshold, the kinematic positioning accuracy at high-latitudes can be improved to obtain similar magnitude as at middle- and low-latitude. The improved positioning accuracy may suggest that the ionospheric disturbance induced by the geomagnetic storm at high-latitudes has minor effects on triggering the CSs. Therefore, precise positioning can be achieved at high-latitudes under geomagnetic storms, given that the CS problem is well addressed.The study is funded by the National Natural Science Foundation of China (No.42004012, 42004025), the Natural Science Foundation of Shandong Province, China (No.ZR2020QD048), the State Key Laboratory of GeoInformation Engineering (No.SKLGIE2019-Z-2-2), the State Key Laboratory of Geodesy and Earth's Dynamics (No. SKLGED-2021-3-4) and by the project RTI2018-094295-B-I00 funded by the MCIN/AEI 10.13039/501100011033, which is co-funded by the FEDER programme.Peer ReviewedPostprint (published version

An EISCAT UHF/ESR Experiment That Explains How Ionospheric Irregularities Induce GPS Phase Fluctuations at Auroral and Polar Latitudes

A limitation to the use of Global Navigation Satellite System (GNSS) for precise and real-time services is introduced by irregularities in the ionospheric plasma density. An EISCAT UHF/ESR experiment was conducted to characterize the effect of electron density irregularities on temporal fluctuations in TEC along directions transverse to GPS ray paths in the high latitudes ionosphere. Two representative case studies are described: Enhancements in temporal TEC fluctuations originating (a) in the auroral ionosphere following auroral particle precipitation and (b) in the polar ionosphere following the drift of a polar patch as well as particle precipitation. The results indicate that the origin of enhancements in TEC fluctuations is due to the propagation through large-to-medium scale irregularities (i.e., ranging from few kilometres in the E region to few tens of kilometres in the F region) and occurring over spatial distances of up to approximately 400 km in the E region and up to approximately 800 km in the F region with a patchy distribution. Furthermore, the results indicate that enhancements in TEC fluctuations produced by polar plasma patches and particle precipitation occur over similar temporal scales, thus explaining the overall observation of higher phase scintillation indices in the high-latitude ionosphere. The similarity in the temporal scales over which enhancements in TEC fluctuations occur in the presence of both particle precipitation and plasma patches suggests an intrinsic limitation in the monitoring and tracking of plasma patches through ground GNSS observations

Assessing the Performance of GPS Precise Point Positioning Under Different Geomagnetic Storm Conditions during Solar Cycle 24

The geomagnetic storm, which is an abnormal space weather phenomenon, can sometimes severely affect GPS signal propagation, thereby impacting the performance of GPS precise point positioning (PPP). However, the investigation of GPS PPP accuracy over the global scale under different geomagnetic storm conditions is very limited. This paper for the first time presents the performance of GPS dual-frequency (DF) and single-frequency (SF) PPP under moderate, intense, and super storms conditions during solar cycle 24 using a large data set collected from about 500 international GNSS services (IGS) stations. The global root mean square (RMS) maps of GPS PPP results show that stations with degraded performance are mainly distributed at high-latitude, and the degradation level generally depends on the storm intensity. The three-dimensional (3D) RMS of GPS DF PPP for high-latitude during moderate, intense, and super storms are 0.393 m, 0.680 m and 1.051 m, respectively, with respect to only 0.163 m on quiet day. RMS errors of mid- and low-latitudes show less dependence on the storm intensities, with values less than 0.320 m, compared to 0.153 m on quiet day. Compared with DF PPP, the performance of GPS SF PPP is inferior regardless of quiet or disturbed conditions. The degraded performance of GPS positioning during geomagnetic storms is attributed to the increased ionospheric disturbances, which have been confirmed by our global rate of TEC index (ROTI) maps. Ionospheric disturbances not only lead to the deteriorated ionospheric correction but also to the frequent cycle-slip occurrence. Statistical results show that, compared with that on quiet day, the increased cycle-slip occurrence are 13.04%, 56.52%, and 69.57% under moderate, intense, and super storms conditions, respectively