Corrections and integrity bounds of the ionospheric delay generated at the Satellite-Based Augmentation System (SBAS) for aviation users may confront a wide range of ionospheric conditions over its update interval. Ionospheric irregularities affecting Single Frequency (SF) SBAS can cause the risk of service integrity and a loss of service continuity. The aim of the Ionospheric Anomaly Detection (IAD) scheme is to detect the effect of ionospheric irregularities on the SBAS SF service operational capability over China. It will help in establishing statistical anomaly models and then provides a high level of service for aviation users. The IAD scheme uses a fusion protocol to reach consensus among subdetectors, which monitor different ionospheric features. Moreover, the threshold of every sub-detector is derived based on system availability. We analyze the IAD scheme by practical ionosphere observations recorded at the crustal movement observation network of China in 2015. It successfully identifies ionospheric anomalies affecting SF SBAS and conforming with physical characteristics. Furthermore, it provides sufficient detection reliability. The statistical results illustrate that the difference of 95% residual error for post-ionosphere correction between normal and anomalous zones is between 1.4 m and 3.2 m. The average value is 2.1723 m. Additionally, there exist two types of ionospheric anomalies affecting SBAS SF service over China. The range is mainly at latitude 15 •-35 • N. The occurrence time is mainly at GPS time 4-15 h and 12-19 h, respectively.

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The Satellite-based augmentation system (SBAS) is intended to provide real-time differential global navigation satellite system corrections with the high accuracy, availability, and integrity required for aviation applications. Since the performance of Satellite clock and ephemeris (SCE) corrections and Ionospheric range delay (IRD) corrections can vary dramatically depending on satellites and Ground reference stations (GRSs) geometry, therefore, we present a GRSs distribution optimized criteria and process to improve SBAS corrections performance. The present step-by-step optimized scheme using the average satellite surveillance dilution of precision and relative centroid metric availability of grid points as fitness values to determine the appropriate GRSs distribution to sufficiently meet the corrections requirements. The results show that the statistical mean RCM availability can reach more than 0.5518 for all IGPs and the coverage depth of GRSs in China and its surrounding areas is more than 25, which fully satisfies the requirement for solving SCE and IRD corrections.

The water-level-fluctuating zone (WLFZ) in the Three Gorges Reservoir (TGR) changes seasonally because of the special hydrological characteristics and agriculture practices. Rapid land use changes have taken place in the WLFZ of the TGR, which is affected by the functions and structures of the local environmental system directly or indirectly. Land use change analysis is very important for land planning and environmental management in the TGR area. This paper presents an integrated study of land use change in the WLFZ of the TGR area by using Geographic Information Systems (GIS). The study explored the temporal and spatial characteristics of this area from 2000a to 2005a and the land use/cover changes during this period. Data of viewdata graphics, social statistics and environmental monitor were collected and inputted into ArcGIS for calculating the transition matrix of land use and used to analyze the changes in the landscape. The main purpose of this study was to determine the land use transition rate between land use types in this area over the 5 years from 2000-2005 and to quantify the changes of various land uses. Surprisingly the results show that the arable land has increased by 1466.79ha while the garden land has decreased by 519.71 ha and the water area has decreased by 652.39ha during the past 5 years. The major factors influencing the ecosystem and land use changes of the WLFZ were human-related factors, such as transmigrant, and intensified and unreasonable utilization of land resources.