Kalman filter is widely taken as an optimal fusion algorithm in GNSS/INS integration, and GNSS positioning error is often simply modeled as white noise in a loosely-coupled system. But many research results have shown that GNSS positioning error has the characteristic of temporal correlation. Correct error model of Kalman filter can ensure that the level of estimated accuracy is equal to that of actual accuracy. Inaccurate model will influence the consistency between estimated accuracy and actual integrated accuracy. Moreover, quality control method based on variance-covariance with inconsistency is not reliable and not utilized to detect gross errors. So, this paper mainly researches on GNSS positioning and velocity error model and its impact on quality control in GNSS/INS integration. In this paper, state-augmentation method is applied to solve the problems of GNSS colored noise to ensure the navigation accuracy consistency, and the rationality of the improved model is verified by the effect of quality control. Simulation and field test results show that state-augmentation method can improve the consistency between actual error and estimation standard deviation, and satisfy the requirement of quality control based on variance-covariance to improve the integration reliability.

The paper presents a multiloop system for noncoherent tracking of the radionavigation parameters of global navigation satellite system (GNSS) signals in autonomous satellite navigation system. Comparative analysis of accuracies of traditional tracking system with discriminators and filter in the tracking loop and the proposed system without discriminators is conducted. RMS errors of estimates, pull-in range and the probability of signal acquisition are studied under various SNR values. Experimental tests of derived noncoherent tracking loop are performed.

The performance of a Global Positioning System (GPS) receiver usually depends on the racking loops, so they can be considered the heart of the GPS receivers. It has been proven that the carrier tracking loop is more sensitive to noise and interference than the code tracking loop. Therefore, the carrier tracking loop can be used as a means for investigating the GPS receiver performance in presence of interference. In this paper, closed form analytical expressions for the carrier tracking loop phase error are derived in presence of different types of interference signals such as continuous wave interference, narrowband interference, partial band interference, broadband interference, match spectrum interference, and pulse interference. Also the carrier-to-noise ratio threshold is analytically derived. The derived analytical expressions have been validated with the aid of simulation experiments.

Integration of a multiantenna GNSS receiver and inertial sensors (gyroscopes) is proposed to determine attitude parameters using GNSS phase measurements, containing integer ambiguity, and measurements of the absolute rotation rate of a moving vehicle. The potential accuracy of the proposed technology is estimated based on the simulation and full-scale tests. The implementation of the proposed approach is considered.

The motion of aerodynamically stabilized nanosatellites of the CubeSat design is studied. The features of the nanosatellites behavior in low orbits are conditioned both by the atmospheric effects and their own mass and inertial characteristics: the lifetime of nanosatellites is shorter, while the angular acceleration generated by the aerodynamic moment is much higher as compared with big satellites having large mass. CubeSats may experience resonance modes of motion caused by the shape factor of a rectangular parallelepiped. In addition, the existing commercial CubeSat deployers often generate large initial angular velocities that are random in nature. The conditions that cause the specific features of the CubeSat motion are considered and analyzed. A probabilistic approach to choosing their mass and inertial characteristics is proposed. The problems of motion stabilization are studied, and recommendations are formulated on the design of aerodynamically stabilized CubeSats with a passive/active magnetic damping system.

Since its initial operation in 1982, GLONASS has completed 35 years of service and has passed through eventful journey. Being the first global alternative to GPS, it generated interest among users worldwide. After initiation, the system declined to a period of unstable constellation status; the system has been revitalized and modernized since the end of 2012. This paper presents a concise discussion on initiation, development, decline and revitalization phases of the system and a review on the available research reports which presented the development and advantages of GLONASS as a stand-alone system and as a multi-GNSS component. The paper reviews the experiences of using the advantages of GLONASS from India during its complete service period based on real-time, long-term systematic analysis over the Indian region both for the initial and the revitalized and modernized phases. Finally, considering the long-term experience of using GLONASS, the paper presents a few issues towards popularization and quality enhancement of GLONASS services from India. This review may be useful in understanding the need, advantages and challenges of using GLONASS from the region.

A methodology has been developed to form SBAS ionospheric grid points, based on the data from ionosphere radio occultation monitoring systems such as COSMIC. This methodology facilitates calculation of vertical delay of SRNS signals on frequency L1 for any geographical location. The corrections are used by a singlefrequency consumer for improving the accuracy of its position estimation in solving the navigation problem. Using the combination of ionosphere model and the data from radio occultation monitoring systems, it is possible to form real-time corrections in global scale, and to make their short-term forecasts. The proposed method testing results showed good conformance with the data from vertical probing stations, and the magnitudes of vertical delays of signal on frequency L1, represented by EGNOS system as differential corrections for consumers.

The paper presents a new engineering solution which considerably reduces costs for the development and operation of sonar sensor networks (SSN), while retaining small size and high level of energy saving for each of the network nodes (modems functioning as e.g. communication network devices, long-baseline bottom antenna units, etc.). The SSN performance parameters are shown for the mode being of interest, in particular, for positioning and navigation of autonomous unmanned underwater vehicles; delays in forwarding small datasets from the SSN, as well as probabilities of small datasets delivery from source for finite user are studied (e.g. control commands, sensor data, data on positions of long baseline units, and timing sequences). The solution is based on the design and introduction of special-purpose software framework EviNS (EvoLogics Intelligent Networking Software Framework) into the soft- and hardware platform of underwater acoustic modem (UAM). Results of experimental studies of digital SSN performance are demonstrated, where the SSN employs part of EviNS framework protocols, namely the combination of uncoordinated medium access protocol and routing protocol based on the network «flooding» algorithm with sequence number control (control of numbers of data packets and network forwarding nodes). The experimentally obtained values of probabilities and delays of data delivery from source to finite recipient provide the network user with the information necessary for planning the tasks of group interaction and online coordination of the SSN nodes, such as mobile nodes on underwater vehicles (at least in the SSN having the configuration and size similar to those described in the paper. 

The paper addresses the history of marine gyrocompasses development in the USSR and Russia. It is noted that despite the development and implementation of attitude and heading reference systems (AHRS), strapdown inertial navigation systems, and satellite compasses (SNS-compasses), the classical gyrocompass of both pendulum and adjustable types is and will be still in demand due to its simple operation and low cost along with the accuracy sufficient for safe navigation; therefore, it will require further development and improvement.