In this paper, two methods are proposed, namely the unified processing method and the distributed processing method, to process the global navigation satellite system observation data in integrated navigation simulation which uses the strapdown inertial navigation system as the reference system and the multi-global navigation satellite systems as the sub-systems. The unified processing method takes all the global navigation satellite systems as a whole as one sub-system while the distributed processing method takes each global navigation satellite system as one sub-system. The centralized filter and federated filter are utilized respectively to process the global navigation satellite system observation data in the unified processing method and the distributed processing method. The mathematical models of the unified processing method and the distributed processing method are given in detail. Through theoretical derivation and mathematical simulations, the performances of the unified processing method and the distributed processing method are investigated and compared, showing that while they have the same position (velocity) accuracy, the distributed processing method offers better efficiency than the unified processing method especially when the number of global navigation satellite systems is large (>3).

The availability of advanced receiver autonomous integrity monitoring for vertical guidance down to altitudes of 200 ft (LPV-200) is discussed using real satellite orbit/ephemeris data collected at eight international global navigation satellite system service stations across China. Analyses were conducted for the availability of multi-constellation advanced receiver autonomous integrity monitoring and multi-fault advanced receiver autonomous integrity monitoring, and the sensitivity of availability in response to changes in error model parameters (i.e. user range accuracy, user range error, Bias-Nom and Bias-Max) was used to compute the vertical protection level. The results demonstrated that advanced receiver autonomous integrity monitoring availability based on multiple constellations met the requirements of LPV-200 despite multiple-fault detections that reduced the availability of the advanced receiver autonomous integrity monitoring algorithm; the advanced receiver autonomous integrity monitoring availability thresholds of the user range error and Bias-Nom used for accuracy were more relevant to geographic information than the user range accuracy and Bias-Max used for integrity at the eight international global navigation satellite system service stations. Finally, the possibility of using the advanced receiver autonomous integrity monitoring algorithm for a Category III navigation standard is discussed using two sets of predicted errors, revealing that the algorithm could be used in 79% of China.

Receiver Autonomous Integrity Monitoring (RAIM) method is an effective means to provide integrity monitoring for users in time. In order to solve the misjudgment caused by the interference of gross error to the least squares algorithm, this paper proposes a RAIM method based on M-estimation for multiconstellation GNSS. Based on five programs, BDS, GPS/BDS, and GPS/BDS/GLONASS at the current stage, the future Beidou Global Navigation Satellite System, and the future GPS/BDS/GLONASS/Galileo system, the new RAIM method is compared with the traditional least squares method by simulation. The simulation results show that, with the increase of constellations, RAIM availability, fault detection probability, and fault identification probability will be improved. Under the same simulation conditions, the fault detection and identification probabilities based on M-estimation are higher than those based on least squares estimation, and M-estimation is more sensitive to minor deviation than least squares estimation.

Simulation technologies provide necessary validation tools for the conceptual design of complex products involving multiple disciplines. A variety of simulation models are developed in specific organizations or enterprises to verify the design plan, while they are hard to be shared and to be reused. Based on the analysis of several typical solutions to share and reuse different kinds of resources, a simulation model design method is proposed to provide a simple implementation of simulation model reuse for cloud-based simulation environment. This paper firstly creates the simulation models' metamodel and ontology for their universal description. Secondly, four rules are proposed to design/reprogram a simulation model into service-oriented form for its interoperability, and the ontology of service-oriented simulation model is established. Thirdly, the way to call one simulation model and the way to compose several simulation models into a simulation process are elaborated. Finally, a simple case of using this method to design an aircraft dynamic model is elaborated, and a prototype simulation system is constructed, and then a simple simulation process is composed to verify the practicability of the method. The result shows that the new design/reprogram method has big advantages on the compatibility, expansibility, and reusability despite the decreasing efficiency.

Commonly, the code noise and multipath error is considered to fully obey the Gaussian distribution. While in the cases with different elevation angles and orbit types, the assumption may be inappropriate. Based on an empirical study, by considering both the elevation angle and the orbit type, a new code noise and multipath distribution model is proposed to describe a more accurate code noise and multipath distribution in this paper. Actual code noise and multipath data from 10 observation stations during two months are researched, and the parameters and elevation angle range of code noise and multipath distribution model are determined. The code noise and multipath distribution model is verified to be more accurate than the model presented in the Global Navigation Satellite System Evolutionary Architecture Study report, according to the analysis on the code noise and multipath overbounding, position error overbounding, and the availability of receiver autonomous integrity monitoring. This model provides more accurate prior information for receiver autonomous integrity monitoring, especially its availability.