Methods of radio tomography (RT) based on the low-and high-orbital navigational systems and radio occultation data are considered. Examples of RT imaging of the ionosphere in different regions of the world illustrate the use of low-orbital and high-orbital radio tomography (LORT and HORT, respectively) separately and in combination with each other. RT methods allow studying of various ionospheric structures: troughs, travelling ionospheric disturbances (TIDs), spots of enhanced ionizations, patches, blobs, wavelike structures, manifestations of particle precipitation. The possibilities for the application of RT systems together with other methods of UV and radio sounding are discussed.

В статье показаны возможности использования онлайн-сервисов при обработке измерений глобальных навигационных спутниковых систем (ГНСС-измерений), описаны их достоинства и недостатки. Приведены результаты оценки точности высокоточного местоопределения пунктов сети ПДБС НСО различными онлайн-сервисами. Выполнено сравнение результатов обработки ГНСС-измерений онлайн-сервисами с методом классической обработки и методом отдельной обработки в программном обеспечении Trimble Business Centre v.4.0. Показано, что результаты четырех из шести сервисов согласуются с эталонными значениями координат на уровне, не превышающем 2,5 см, а также превосходят по точности результаты, полученные методом отдельной обработки ГНСС-измерений. Полученные в результате эксперимента скорости смещений пунктов сети ПДБС НСО сопоставлены с общемировыми моделями движения точек земной поверхности. Также онлайн-сервисы оценены по результатам ГНСС-измерений, выполненных в других частях земного шара.Ключевые слова: ГНСС-измерения, онлайн-сервис, постобработка, Trimble Business Centre, метод PPP, высокоточное местоопределение. ВведениеДля определения местоположения пунктов в общеземной системе координат можно использовать следующие методы с применением технологий глобальных навигационных спутниковых систем (ГНСС): абсолютный, относительный и дифференциальный [1]. С развитием ГНСС-технологий повышается уровень точности определения координат пункта, который зависит не только от методов определения местоположения, но и от режима обработки ГНССизмерений [2]. Наиболее точным режимом измерений является постобработка, поскольку здесь может использоваться большое количество дополнительной информации (вычисленные точные эфемериды спутников, применение моделей тропосферной и ионосферной задержек, параметры вращения Земли и пр.) [1, 2].Программное обеспечение (ПО) для обработки ГНСС-измерений может реализовывать различные методы обработки, среди них: вычисление базовых линий (относительный) [3];Получено 30.03.2019The advantages of usage of free online GNSS post-processing services are shown. Advantages and disadvantages are described. The results of assessing the accuracy of high-precision positioning by free online services are given on the example of observations of Novosibirsk region reference stations network. The results obtained with using free online post-processing services were compared with the results obtained with using conventional and other positioning methods processed with TBC v.4.0 software. It is shown that the results of 4 out of 6 services are consistent with the reference values of the coordinates at the 2.5 centimeters level and have advantages over the method of separate measurement processing. As a result of the experiment the reference stations network velocities of Novosibirsk region, that after were compared with the results of global models of the earth's surface movement are revealed. These online services are estimated by the results of GNSS measurements performed in other parts of the globe.

The measurements of Global Navigation Satellite System (GNSS) obtained from different reference stations: Novosibirsk Region reference stations network, Russian state reference stations network ‒ Fundamental Astronomical and Geodetic Networks (FAGN) and stations of International GNSS service (IGS) are checked and analyzed. The relevance of the usage of regional (commercial or industrial) reference stations in state foundation geodetic framework for formation of a unified system of coordinate-time and navigation support is shown. The article describes quality analysis results of the GNSS measurements by the main criteria: number of rejected measurements, ionospheric delay, multipath effect, signal-to-noise ratio, receiver clock slips. The main errors affecting satellite measurements are estimated. The conclusions about the possibility of including the Novosibirsk Region reference stations network into one of the levels of the state foundation geodetic framework are drawn. The comparison of quality of the GNSS measurements showed that according to all criteria of quality the GNSS measurements of the Novosibirsk Region reference stations network are not worse than GNSS measurements of FAGN. According to all criteria the GNSS measurements of the Novosibirsk Region reference stations network approximately corresponds to GNSS measurements of IGS stations, except the signal-to-noise ratio criterion.

The article highlights the issue of interpreting reference stations networks as a local realization of the global reference system. The substantiation of the proposed approach is given and its advantages are shown. The rationale for the proposed approach is given and its advantages are shown. In particular, the top block in the structure of the formation of the Russian state coordinate system (GSK‑2011) is the fundamental astronomical and geodetic network. It is a regional realization of a global reference system. The creation of GSK‑2011 was carried out with a focus on the global International Terrestrial Reference System (ITRS) however geodynamic processes affecting the displacement of reference points relative to the center of the Earth's masses play a different role in the time evolution of systems. Such processes in GSK‑2011 are not subject to accounting, since the system was created to conduct various types of applied geodetic and cartographic activities in it. In this case, taking into account the constant change in the coordinates of reference points is almost never implied. In this regard, the asynchronous movement of the Russian state coordinate system (GSK‑2011) with the global reference system (ITRS) began to lead to inconsistencies in the results of high-precision positioning performed at different times, by different methods. Based on this, the necessity to find a way of matching GSK‑2011 to ITRS is urgent. The article presents the rates of change of the match parameters of the above-mentioned systems. These parameters make it possible to match the results of high-precision positioning performed in different reference systems using different methods of positioning for different epochs of the GNSS observations. The experiment carried out in the second part of the article confirms this.

The article suggests a technique for relation global kinematic reference system and local static realization of global reference system by regional continuously operated reference stations (CORS) network. On the example of regional CORS network located in the Novosibirsk Region (CORS NSO) the relation parameters of the global reference system WGS-84 and its local static realization by CORS NSO network at the epoch of fixing stations coordinates in catalog are calculated. With the realization of this technique, the main parameters to be determined are the speed of displacement one system center relativly to another and the speeds of rotation the coordinate axes of one system relatively to another, since the time evolution of most stations in the Russian Federation is not currently provided. The article shows the scale factor for relation determination of coordinate systems is not always necessary to consider. The technique described in the article also allows detecting the errors in determining the coordinates of CORS network in global coordinate system and compensate for them. A systematic error of determining and fixing the CORS NSO coordinates in global coordinate system was detected. It is noted that the main part of the error falls on the altitude component and reaches 12 cm. The proposed technique creates conditions for practical use of the advanced method Precise Point Positioning (PPP) in some regions of the Russian Federation. Also the technique will ensure consistent PPP method results with the results of the most commonly used in the Russian Federation other post-processing methods of high-precision positioning.