RINEX Files Research Articles

Open Access GNSS Data for Studies of the Lithosphere

AbstractVarious types of Global Navigation Satellite System (GNSS) data are used for a wide range of applications. When modeled correctly, millimeter precision daily GNSS position time‐series yield velocities and other derived products that can be used for investigations of lithospheric processes and properties. In this review paper, we describe the specific types of GNSS data and data products that are valuable for studies of the lithosphere, such as coseismic offsets, post‐seismic decay in time‐series, seasonal signals, secular velocities, and strain rates, and how those data are derived. We also discuss the applications of several types of GNSS data and data products. We provide open access resources for precision GNSS daily position time‐series, quality secular velocity solutions, and daily GNSS RINEX files for researchers interested in processing their own data.

Analyzing Rinex Data Files Using the Python Programming Language

Abstract The techniques and tools developed for geodetic determinations have made it possible, over the past half century, to carry out measurements using global navigation satellite systems. As the accuracy and precision of positioning solutions, such as Fast Static and RTK, improve through technological advances, more applications will become available that can provide users with positioning information over time, autonomously verify the integrity of transmitted data, and ensure sufficient accuracy for their intended purposes. In our study for the interpretation, analysis, and visualization of raw and/or processed RINEX GNSS data recorded over time at a geodetic point using the information available from the Fast Static technique, we used the GeoRinex library from the Python programming language. This library converts data to xarray.data set, for easy use in processing parameter sets, from Rinex files: of ROMPOS reference stations and of the new B10 point resulting from measurements using the Fast Static technique: pseudorange (C1, C2, P1, P2....), carrier phase (L1, L2,…), doppler (D1, D2....) and signal strength (S1, S2....). All this information will help us to analyse and interpret the degradation of the parameters associated with Rinex version 2.11 epoch positioning files 12.02.2023, time interval 12:00-14:00 (fast static) and to understand their accuracy and behavior in different environments. Based on this study, our aim was to evaluate the error in determining the positioning accuracy of the B10 point located in a crowded and heavily trafficked area, which allows sufficient coverage of the GNSS satellites.

PyRINEX: a new multi-purpose Python package for GNSS RINEX data.

Since the first receiver independent exchange format (RINEX) version was released in 1989, it has gone through several versions, making the existing software, such as TEQC, incompatible with certain later versions. This study proposes a new Python package named PyRINEX, which is developed to batch process the most generally used versions of RINEX files, namely 2.0 and 3.0. The proposed package can be used to manage and edit numerous RINEX files as well as perform a data quality check function. PyRINEX can be easily imported into any Python IDE similar to any other open-source Python package, it also makes secondary development easy for users.

Нові виклики для функціонування активних перманентних ГНСС-станцій під час бойових дій на прикладі України

The study presents the current state of GNSS Continuously Operating Reference Stations (CORS) networks and their operational characteristics during the ongoing hostilities in Ukraine. Stable GNSS CORS network operation is crucial not only for agricultural, geodetic, and land management tasks but also for military navigation and topography. The aim of this work is to analyze the impact of hostilities in Ukraine's GNSS network, considering factors like temporary occupation of certain territories, power outages due to missile strikes on energy infrastructure, and GNSS signal jamming using radio-electronic methods in front-line regions. Another objective of this study is to highlight examples of incorrect RTK or VRS operation due to potential errors from radio-electronic jamming or GPS spoofing as well as to provide practical recommendations for surveyors. As a result, the research has analyzed changes in the number of properly functioning GNSS stations from 2021 to 2023 using the GeoTerrace and System.NET networks. These networks cover all regions of Ukraine except the temporarily occupied territories by russia. Daily processing of RINEX files with a sampling interval of 30 seconds from CORS GNSS stations was conducted using the Bernese GNSS v.5.2 software package over three years. It was noted that following the large-scale invasion in February 2022 and through the spring of that year, there was a sharp reduction of about 10% in the number of properly functioning active GNSS stations. Scientific novelty and practical importance. The article presents practical recommendations for users, such as surveyors and land managers, performing GNSS measurements in RTK or VRS modes using permanent stations, to assess the influence of radio-electronic jamming or GPS spoofing on observations. CORS network assessment and daily calculated coordinates of GNSS stations from 2021 to 2023 can be used for future geodynamic research in the region.

QUALITY ANALYSIS OF SMARTPHONE GNSS OBSERVATIONS AND IMPACT ON PRECISE POSITIONING

Abstract. The use of low-cost and ultra-low-cost receivers such as smartphones and wearables has been raising these days due to their affordability and widespread availability. Along with the release of Android Version 7 in 2016, the raw GNSS measurements became accessible through the location API, which includes the GNSSMeasurement class and GNSSClock class. However, the users are required to extract the typical GNSS observations, such as pseudorange, carrier-phase, and Doppler observations, from the raw data coming from these two classes. It should be mentioned some quality concerns may arise during the conversion process from the raw GNSS measurements to the typical GNSS measurements. These quality concerns would subsequently affect GNSS data processing such as cycle slip detection, code smoothing and ultimately positioning performance. In this paper, we first analyse the quality of GNSS observations logged from smartphones. Furthermore, we address potential issues that can arise during the generation of GNSS observations. We also introduce our developed in-house software, UofC CSV2RINEX, which is designed to convert CSV files into RINEX files.

DATA INTEGRITY AND QUALITY ANALYSIS OF LOW COST ZED-F9P U-BLOX GNSS RECEIVER

Thanks to the rapidly emerging low-cost dual-frequency GNSS receivers, a feasible alternative for geodetic-grade GNSS receivers became available for some GNSS applications. In this study, the performance of data integrity and quality of a low-cost ZED-F9P u-blox GNSS receiver was investigated by comparing it with a geodetic-grade GNSS receiver. Availability of the epoch and phase/code signal channels, signal-to-noise ratio (SNR), code multipath, and cycle slips were analyzed for the geodetic-grade and low-cost ZED-F9P u-blox GNSS receivers. One month’s data of GPS, GLONASS, and Galileo constellations were analysed using the RINEX files of the receivers. The results showed that the epoch availability of the geodetic-grade and u-blox GNSS receiver is comparable to each other, while the availability of phase/code signal channels of the geodetic-grade receiver is higher than the u-blox receiver. In terms of data quality, SNR values from both receivers are comparable, while the multipath level of the u-blox GNSS receiver is significantly higher than the geodetic-grade one. The results also showed that the number of cycle slips of the u-blox receiver is significantly higher than the geodetic-one.

Development of a System for Detecting Traveling Ionospheric Disturbances Based on GNSS Data

The large amount of data that are available for ionospheric studies using the GPS TEC method, as well as the need to take into account complex atmospheric dynamics, create certain difficulties in automating the process of searching and recognizing traveling ionospheric disturbances generated by different sources. To automate the process of detecting wave disturbances, numerical criteria for assessing the level of the wave disturbance signal were proposed. The signal-to-noise ratio calculated by the proposed method was used as one of such criteria. This work contains a description of the developed software system that implements the proposed methodology and allows the loading of RINEX files and processing, analyzing, and visualizing total electron content data.

Real-Time Precise GPS Orbit and Clock Estimation With a Quasi-Orbit-Fixed Solar Radiation Pressure Model

<h3>Abstract</h3> Real-time precise global navigation satellite system (GNSS) orbit and clock products play a key role for real-time GNSS-based applications, both in the scientific and industrial communities. Different from the typical two-step procedure to generate orbit and clock solutions separately, we estimate the real-time orbit and clock products simultaneously using a Kalman filter. For this purpose, we developed a GNSS data processing software that can run in pseudo-real-time mode with RINEX files and is ready to run in real-time mode once given the real-time observation stream. Meanwhile, a quasi-orbit-fixed solar radiation pressure (SRP) model is developed. In order to verify the performance of the software and the new SRP model, several experiments with a global network of 60 tracking stations over a time span of three months were conducted to generate real-time Global Positioning System (GPS) orbit and clock products. Then, the results were assessed in terms of accuracy and efficiency, both critical for real-time precise GNSS applications. Compared to the International GNSS Service (IGS) final orbits, the real-time GPS orbit accuracy was 2.82 cm, 5.45 cm, and 5.47 cm in the radial, along-track, and cross-track components, respectively. The precision of the clock product in terms of standard deviation (STD) value was about 0.1 ns. Moreover, the average execution time per epoch was usually less than 1.0 s, which ensures the high efficiency of the processing.

Impact of Approximate Implementation manner in Klobuchar Model

This paper focuses on the approximations that John A. Klobuchar made in mid 70s in his famous algorithm of ionospheric correction model for single frequency GPS receiver. At that time Klobuchar used a system of fixed geomagnetic north pole coordinates which are not accurate nowadays according to the International Geomagnetic Reference Field and to the World Magnetic Model because the geomagnetic poles move slowly. In addition, Klobuchar had to do other trigonometry simplifications in his implementation to avoid sophisticated computations. In order to evaluate this approximate implementation in a single frequency GPS receiver, ionospheric time and range delay are estimated on the entire day of January 1st 2010, using a different implementation in MATLAB. The required GPS data is obtained from recorded RINEX files at UDMC near DAMASCUS, SYRIA. In this comparative study, we reformulated the standard equations of Klobuchar model and examined the influence of its approximations on the ionospheric range delay and found a non- negligible bias in order of ten centimeters, whereas the influence of the movement of the geomagnetic poles was in order of few centimeters.

First Results of Time Series Analysis of the Permanent GNSS Observations at Polish EPN Stations Using GipsyX Software

Abstract The aim of this work is to explore, for the first time in Poland, the possibility of determining Earth’s crust movements from permanent observations at selected permanent stations using the GipsyX software for a period of 8 years (2011–2018) in the ITRF2014 reference frame. The data used in this work are from 15 Aktywna Sieć Geodezyjna (ASG)-EUPOS stations from 2011 to 2018, which are also European Permanent Network (EPN) stations. The stations Borowa Góra, Borowiec, Józefosław, Lamkówko, and Wroclaw are also International Global Navigation Satellite Systems (GNSS) Service (IGS) stations. Daily data, rinex files, for these stations have been made available for this work by the Main Office of Surveying and Cartography. The calculations were made using the GipsyX software in the ITRF14 reference frame. The tests performed have shown that daily solutions from 8-year-long time series give secular trends with an accuracy of 0.01 mm/yr. Our results suggest that there are small differences in horizontal and vertical velocities and in the accuracy estimated between our and EPN solutions. At some stations, for example, Łódź, the differences are much larger. The impact of additional GNSS observations on the accuracy of determination of horizontal and vertical movements of the Earth’s crust shows a submillimeter accuracy in computed coordinates of stations even at a relatively small time interval. It means that multi-GNSS Precise Point Positioning (PPP) processing can be used in the future for the estimation of geodynamic processes.

Sampling Rate Impact on Precise Point Positioning with a Low-Cost GNSS Receiver

Nowadays, with the incursion of low-cost GNSS receivers with modern characteristics, it is common to investigate and apply new methodologies and solutions with different receivers of this nature. Based on this fact, the performance of the solution obtained from the low-cost GNSS receiver is evaluated compared to a geodetic grade GNSS receiver at different sampling frequencies for the PPP-static and PPP-kinematic modes. For this, the original RINEX observation files were analyzed and decimated into different sampling rates as 0.1, 0.2, 1, 5, 15 and 30 s with TEQC software. All RINEX files were submitted to the Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP) online service for processing with static and kinematic modes. The PPP-derived coordinates from the low-cost GNSS receiver were compared with the geodetic receiver to evaluate the obtained solution. The results reveal that the behavior of all studied sampling rates from the low-cost GNSS receiver are constant in achieved positioning. In addition, the achieved precision shows that it is recommendable to use a high sampling rate to obtain a cm level in PPP-static mode by using a low-cost GNSS receiver, this mode being the most accurate and potential alternative for structural health monitoring studies, mapping and positioning in urban areas.

Regional Assimilation of GPS-Derived TEC into GIMs

Global ionosphere models may not be accurate enough in regions where there are insufficient observations. Therefore, there is strong interest in regional ionosphere modeling using observations from dual-frequency Global Navigation Satellite System (GNSS) receivers in such regions. This paper presents a data assimilation method for hourly total electron content (TEC) modeling along with estimation of the receivers’ differential code biases (DCBs). For this purpose, first, initial values for slant TEC (STEC) and the receivers’ DCBs are estimated utilizing global ionosphere maps (GIMs). Second, STEC is expanded to a linear combination of spherical radial basis functions with time-dependent coefficients to reduce the number of unknowns, and a constrained least-squares adjustment is applied to resolve the corrected STEC and DCB values in the study area using observations from dual-frequency GNSS receivers. Third, the resolved STEC at ionospheric pierce points (IPPs) are converted to vertical TEC (VTEC) using a mapping function and assimilated into the background provided by spatial and temporal interpolation of GIM. Retrieved VTECs are weighted according to the satellites’ elevation angles, and an objective function is defined to determine the background’s covariance matrix. In this study, the Iranian permanent Global Positioning System (GPS) network is used to construct the regional hourly VTEC model and calculate hourly DCB variations. The proposed method is validated in two ways. First, some of the VTEC values are excluded from the dataset for use as test data and compared with modeling results. The root mean square (RMS) of the constructed regional assimilative model on test data is significantly better than GIM. Second, the RINEX file of Tehran station, whose observations did not play a role in modeling, is corrected using the regional model. The single-frequency positioning results with corrected observations show much better accuracy than GIMs.

Examination of seismo-ionospheric anomalies before earthquakes of Mw ≥ 5.1 for the period 2008–2015 in Oaxaca, Mexico using GPS-TEC

Earthquakes are a major danger in a constantly growing society due to their imminent impact and power of destruction. Therefore, the idea of successfully forecasting an earthquake continues to motivate the multidisciplinary study of phenomena proposed as possible earthquake precursors such as ionospheric anomalies. In that sense, total electron content (TEC) has demonstrated to be an efficient parameter for investigating the state of the ionosphere by making use of the Global Positioning System receivers. In the present study, raw vertical TEC data obtained from the standard RINEX files of the GPS constellation are used to examine the state of the ionosphere during the occurrence of light to moderate earthquakes in Mexico from years 2008 to 2015 with the aim of search for possible ionospheric anomalies related to seismic activity. In order to evaluate the impact at the geomagnetic and ionospheric environments, the Geomagnetic Equatorial Dst index, which is considered to have a great influence on TEC during geomagnetic storm period, and solar activity parameters, have been considered. The results indicated that 17 (74%) of the studied events presented not quiet geomagnetic conditions for the days before the earthquake. Thus, the changes in VTEC are most likely related to geomagnetic anomalies which rules out its possible seismic origin. Contrariwise, 3 (13%) of the events presented geomagnetic anomalies the days after the earthquake. For the remaining 3 (13%) events, these presented particular characteristics, such as: not quiet geomagnetic condition for the earthquake day, geomagnetic anomalies throughout the period and the opposite.

IMPACT OF USING THE NEW THIRD FREQUENCY ON GPS AMBIGUITY RESOLUTION

The new GPS L5 signal, is a part of the U.S. efforts to modernize its global positioning system (GPS). It was designed to support safety of life applications such as civil aviation navigation. Its structure designed to provide higher performance in terms of measurement accuracy. Till now, the GPS system cannot transmit L5 from all satellites. So, in this paper a GPS simulator software in MATLAB environment was implemented to simulate RINEX observations files with the three frequencies. MATLAB: GPSDP (GPS Differential Processing) program was used to process static and kinematic data from all three frequencies . RINEX files for both base and rover stations had been generated for different baselines lengths 5, 50 and 100 km approximately in different day times. These data are used to study the impact of the third frequency on rate of resolving integer ambiguities and the time needed to fix the integer ambiguities correctly. Also, the positioning accuracy after adding the third frequency to dual frequencies data. All parameters are studied under variation of ionosphere intensities. The results of experiments have been illustrated and they show efficiency of using the third frequency over dual frequencies.

Calculation of the Ephemeris and Clock Corrections of GLONASS and GPS Navigation Space Vehicles in Ultra-Rapid Regime on the Basis of Measurement Data

An algorithm and program for calculation in ultra-rapid regime of the ephemeris and time information of GLONASS and GPS navigation space vehicles are developed. The results presented here were obtained at the Main Metrological Center of the State Time and Frequency Service and Determination of the Parameters of the Earth’s Rotation at the All-Russia Research Institute of Physicotechnical and Radio Measurements (VNIIFTRI). Calculations of the ephemeris and time information are performed on the basis of the data of code and phase measurements at two carrier frequencies. The measurement data are presented in the form of hourly RINEX files of observations and files of navigation messages from tracking stations in the network of the IGS international service of global navigation satellite systems (International GNSS Service). Results of test calculations of the ephemeris and clock corrections of GLONASS and GPS navigation satellites in ultra-rapid regime are presented. An analysis of the precision of the results as compared to a posteriori (final) data from other data processing and analysis centers is presented.

PANG-NAV: a tool for processing GNSS measurements in SPP, including RAIM functionality

Global Navigation Satellite Systems (GNSSs) are theoretically able to provide accurate, three-dimensional, and continuous positioning to an unlimited number of users. An important shortcoming of GNSS is the lack of integrity, defined as the ability of a system to provide timely warnings in case of malfunction; this problem is especially felt in safety-of-life applications such as aviation. A common way to fill this gap is the use of Receiver Autonomous Integrity Monitoring (RAIM) techniques, which are able to provide integrity information by analyzing redundant measurements. A possible RAIM functionality is the ability to identify, and so discard, anomalous measurements; this functionality has made RAIM very useful also in case of severe signal degradation, such as in urban or dense vegetation areas, where blunders are common. PANG-NAV is a tool, developed by the PArthenope Navigation Group, able to process GNSS measurements (from RINEX files) in order to obtain a position solution. The core of PANG-NAV is the single point positioning (SPP) technique, including a RAIM functionality. A multi-constellation solution, with GPS and Galileo, can be provided. Both static processing and kinematic processing are possible, and in cases where ground truth is available, error analysis can be carried out.

Variation of ionospheric range errors for L1 frequency GPS users during the 23rd solar cycle over BAHR IGS station

Errors induced by the ionosphere on global navigation satellite systems (GNSS) signal propagation significantly affect the positioning calculation done by ground receivers. These ionospheric errors may end up reaching tens of meters in the final positioning calculation. In this study, the ionospheric range error (IRE) was monitored over the local ionosphere of BAHR, Bahrain (26.209N, 50.608E) during the period of the 23rd solar cycle. IRE values were obtained through observation data derived from RINEX files and compared with NeQuick 2 (NQ2) model calculations. It was found that, for the region of study, NQ2 overestimated the total electron content (TEC) values as compared to observation data, resulting in higher IRE values of up to 12 m. However, IRE derived using GNSS observations and NQ2 follow similar trends over the course of the solar cycle. IRE values were also compared to the smoothed sunspot number (SSN) and F10.7 indexes which resulted in significant correlation between the seasonal calculation of IRE and solar activity. Throughout the 23rd solar cycle, the highest IRE values were found during the equinoxes and the lowest during solstices. The largest IRE value was observed in the vernal equinox of 2000 (19.13 m), while the lowest IRE value was observed in the winter solstice of 1998 (0.276 m).

Una metodología de posicionamiento cooperativo diferencial para el posicionamiento de dispositivos múltiples

Introducción: esta publicación es el producto de una investigación del grupo de investigación de computación avanzada y en gran escala (Cage) de la Universidad Industrial de Santander, a lo largo de 2018. Objetivo: Se propone un algoritmo de posicionamiento cooperativo en el que un conjunto de dispositivos intercambia observables satelitales, y estimaciones de distancia entre dispositivos GPS cercanos, con el objetivo de aumentar su precisión de posicionamiento. Metodología: se establecen escenarios donde los receptores de GPS intercambian información satelital, y utilizan diferentes modelos de corrección ionosférica con el fin de evaluar las condiciones en que es posible mejorar la precisión en posicionamiento. Conclusiones: El algoritmo propuesto produce una mayor precisión cuando todos los receptores emplean el mismo modelo de corrección ionosférica. Además, el nivel de incertidumbre en la medida de distancia entre dispositivos no presenta mayor influencia sobre la mejora de la precisión, cuando la separación entre receptores es muy grande. Originalidad: el algoritmo propuesto permite explotar la naturaleza del problema sin aumentar la complejidad a nivel de hardware y software, y se ofrece como una alternativa de solución de posicionamiento cooperativo de bajo costo. Limitación: Los resultados exponen la ejecución del algoritmo cooperativo utilizando archivos Rinex de estaciones de referencia gnss. Por lo tanto, para los escenarios en que la distancia de separación entre estaciones es muy alta, los niveles de error en posicionamiento pueden ser elevados.

Análisis de los residuales en el calculo de velocidades geocentricas a partir de series de tiempo diarias PPP

El procesamiento de observaciones GNSS en línea ha venido en aumento en los útlimos años. Diferentes servicios como el ofrecido por el Canadian Space Reference System (CSRS), bajo la modalidad de Posicionamiento Puntal Preciso (PPP), brinda la posibilidad de conocer de una manera rápida y efectiva la posición tridimensional a partir de un archivo rinex. Aprovechando estos resultados, se procesaron archivos diarios por un periodo de 2,5 años y para 10 estaciones GNSS de Costa Rica integradas al Sistema de Referencia Geocéntrico para las Américas (SIRGAS). Las coordenadas geocéntricas derivadas del procesamiento PPP en línea, se consideraron como vectores de observaciones para la estimación de sus velocidades (Moya et al, 2017). No obstante, previamente se programó e implementó una prueba estadística denominada test de errores groseros (Pelzer, 1985) para la estimación de potenciales observaciones atípicas. Esta prueba es usada frecuentemente en el análisis de redes geodésicas (Knight et al, 2010), sin embargo, ahora se aplicó en el modelo lineal de cálculo de velocidades. El proceso de ajuste para el cálculo de las velociadades se hizo de manera iterativa por estación y por coordenada, excluyendo las observaciones groseras marcadas por el test en cada proceso. En promedio esta prueba detectó una serie de observaciones con residuos que variaron entre los -50 mm y los 40 mm en sus tres componentes. Finalmente con las velocidades depuradas de errores groseros se validaron respecto a la solución multianual SIR15P01 de SIRGAS, tomando como a la época de referencia 2017,0. Las diferencias promedio entre ambas determinaciones fueron de _15 mm.

Precision of PPP as a Function of the Observing-Session Duration

Over the past decade, precise point positioning (PPP) has become a tool widely used in many Global Navigation Satellite Syste applications and the performance levels of the method are often close to those that can be achieved through a differenced approach. The aim of this paper is to analyze the dependency of the precision of a PPP solution output from the GIPSY-OASIS II software on the observing-session durations. In detail, starting from real data acquisitions spanning 24, 12, 6, 3 h, 1 h, and ½ an hour, all processed through the PPP, a continuous function has been defined and the related coefficients have been estimated. The original dataset consists of daily RINEX files provided from 44 sites of both International GNSS Service (IGS) and European Permanent Network (EPN) permanent networks acquired over one year. Each RINEX file was split into several shorter files according to the above listed time spans and processed by using GIPSY-OASIS II together with jet propulsion laboratory (JPL) precise post-processed products. The uncertainty of the proposed function was also estimated and a complete analysis of its compliance with the data sample has been provided. The estimated model is demonstrated to reach a millimeter accuracy level within a statistical confidence level of 99% using the experimental data.