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Summary India has developed its own regional navigation satellite system called the Indian Regional Navigation Satellite System (IRNSS), also known as Navigation with Indian Constellation (NavIC). IRNSS/NavIC provides standard positioning and timing services for civilians and restricted services for authorized users. In this paper, single point positioning is implemented on the NavIC receiver data. Estimation techniques of the least squares method and extended Kalman filter are implemented after applying broadcast‐based clock corrections, orbit computation, relative time correction, and ionosphere delay correction for single and dual frequency. A data extraction and storage module is developed to store computed parameters at every intermediate stage in separate files. This is followed by an error plotter module to plot the extracted parameters for each satellite and to separately analyze their performance and the obtained errors. The estimated receiver position is visualized on Google Earth. The absolute error in both estimation techniques ranges between 5 and 15 m throughout the period. [ABSTRACT FROM AUTHOR]

We have developed a new multi-GNSS data pre-processing software "RINGO" that provides various features including editing, quality checking, clock jump correction, higher order ionosphere correction, conversion of BINEX and RTCM files, and an interactive viewer for RINEX files. The recent increase in number of GNSS satellites has made GNSS data more complex; however, the software available to pre-process them is very limited. RINGO is a command line tool capable of handling multi-GNSS data, including GPS, QZSS, GLONASS, Galileo, and other systems in RINEX 2.xx, 3.0x, and 4.00 formats, which allows users to easily manage the multi-GNSS data observed at continuously operating reference stations. We present algorithms and applications for each RINGO feature. The results of the quality check feature were compared with results estimated by other existing software packages. Our results agreed well with those of the TEQC software. With RINGO, users can easily pre-process multi-GNSS data without combining multiple tools, and the software will contribute to the popularization of the latest RINEX format. [ABSTRACT FROM AUTHOR]

Map matching is the process which work for location measurement and also find out appropriate route for smooth traveling on the road network, but map matching accuracy fully depends on GPS trajectory data and electronic map of the road network. Unfortunately, GPS data is not accurate because, it's through weak GPS signaling and low quality GPS devices. So, it is difficult to calculate accurate location of movements.This work provides, a map mapping algorithm for simplifying appropriate path, including curves on road network and also, we proposed Frechet distance computing algorithm with road Preliminaries for network simplification. [ABSTRACT FROM AUTHOR]

Within the frame of the International DORIS Service (IDS), the CNES/CLS Analysis Center contributes to the geodetic and geophysical research activity through DORIS data analysis. A strategy was developed for the processing of the measurements of the DGXX instruments in RINEX/DORIS format, as it will be the only type of DORIS format made available by CNES, starting with the Jason-3 and Sentinel-3A missions launched at the beginning of the year 2016. The purpose of this paper is to describe the method implemented in the CNES/CLS Analysis Center orbit computation software GINS to process RINEX/DORIS data files. Phase measurements are converted into Doppler counts and then into relative satellite-to-beacon velocities. In this approach, the iono-free phase centers have to be used as the end points of the measurement instead of the 2 GHz phase centers. Given that, the processing results with RINEX/DORIS data are similar to the ones obtained with the usual doris2.2 data, except the scale factor of the Terrestrial Reference Frame in the 7-parameter transform of the network solution. We also address the issue of the scale factor increase from 2012 observed by all the IDS Analysis Centers in their solutions for the ITRF2014 combination. We show that the scale increase in 2012 is dependent on the type of DORIS data used. This scale increase is also enhanced by a bias due to the inclusion of HY-2A data, but which can be eliminated by adopting different coordinates of the onboard DORIS antenna phase center. [ABSTRACT FROM AUTHOR]

RINEX format is a result of an effort to standardize exchanging GNSS related data in human readable receiver independent format. Besides observation data, RINEX is also de facto standard for exchanging navigation message or meteorological data. The paper describes simple compression methods for navigation messages and meteorological data files. Both formats have their specific features, therefore different methods were used. Followed by standard compression the algorithms reduce the file size by more than 20 percent compared to standard compression. Thanks to the properties of weather and regular parameter observations it allows to reduce the file size of meteorological RINEX to a mere fraction of its original size. [ABSTRACT FROM AUTHOR]

Local Area Augmentation System (LAAS) is an augmentation to GPS, for providing aircraft precision approach and landing. LAAS relies on Hatch filter for code smoothing but its filtered range is affected by code-carrier divergence occurring during ionospheric storms. Substituting traditional Hatch filter by optimized filter reduces this effect to a considerable extent. The objective of this paper is to estimate code-carrier divergence and mitigate it using the optimized filter. The performance of both Hatch and optimized filters is analyzed for different ionosphere conditions such as the geomagnetic storm of October 2003 over a low latitude station. Investigations showed that the optimized filter outperforms Hatch Filter for disturbed day data, whereas for quiet day data, it does not provide any additional advantage. The results obtained are agreeing with the results published elsewhere and are encouraging. [ABSTRACT FROM AUTHOR]

Abstract: The boarding of the first DGXX DORIS instrument on Jason-2 mission gives us the opportunity to present the improvements that have been implemented on the DORIS system. The goal of this paper is to present information about the new capacities of the DORIS system and to give the current status of its components. An overview of the DORIS system, the International DORIS Service and the Jason-2 satellite mission are first presented. Then the new characteristics of the on-board instrument are detailed. The capacity to track up to seven ground beacons simultaneously dramatically increases the number of measurements performed: a factor of three increase over Jason-1 is observed at the altitude of 1330km. It also increases the diversity of directions of observation and allows low elevation measurements from 0°. The new phase measurements capability allows now phase processing. The instability of the Jason-1 USOs (Ultra-Stable Oven-controlled quartz oscillator) while crossing the South Atlantic Anomaly has been solved by decreasing the sensitivity to radiation by a factor of 10. New features of the on-board software enhance the coastal and inland water altimetry and increase the robustness of the data. The new software also improves the real time orbit accuracy for operational altimetry. The improvements introduced concurrently on the ground segment have also significantly enhanced capability. The new RINEX exchange formats provide simultaneous phase and pseudo-range measurements. The maintenance of the DORIS Beacons Network and the work done by the DORIS Signal Integrity monitoring team lead to an increased availability of the Network from 75% to 90% and so to a more homogenous orbit coverage. All these improvements including the lessons learned during the past 20years of operations have pushed the DORIS system forward to a New Age. [Copyright &y& Elsevier]

Presently, the global positioning system (GPS) satellite constellation consists of 40% older Block IIA and IIR space vehicles and 60% newer IIR-M and IIF satellites. Only newer GPS satellites are capable of transmitting the L2C signal which is in quadrature to the legacy L2P(Y) signal being broadcast by all satellites. The data format RINEX-2 is not prepared to contain carrier phase observations of both L2 signals, but should contain either one or the other. If a mix of unaligned L2P(Y) and L2C carrier phase observations are stored in a RINEX-2 file, the quarter cycle bias causes the file to be defective and not usable for precise positioning purposes. Algorithms that detect such files are presented in this study. They are mainly based on the analysis of widelane fractional ambiguities and were applied to RINEX-2 files of 2624 reference stations. Seventy-two station files (2.7%) were found to be defective since they contained mixed and unaligned L2P(Y) and L2C carrier phase observations. If such files are used for precise positioning with ambiguities being fixed to integer values, resulting coordinate errors in long baselines can reach centimeter levels. Unaligned L2 observations often prevent ambiguity fixing, especially in short baselines. [ABSTRACT FROM AUTHOR]