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Wang C.,Collaborative Innovation Center for Geospatial Information Technology | Wang C.,Wuhan University | Shi C.,Collaborative Innovation Center for Geospatial Information Technology | Shi C.,Wuhan University | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2016

The Ionosphere total electron content (TEC) active broadcasting technique using location and cloud computing as well as a platform is proposed in this article. Consisting of physical and virtual servers, the scientific computing and user interface are separated in this technique. Thus, physical servers bring computational efficiency into full play so as to improve the platform's performance. The platform configuration can be adjusted to the number of users for cost savings. With multiple virtual server backups, it maintains the stability and security of the platform. Also, the platform has effective control over the precision of TEC in specific space-times. It can serve regional or global users according to different demands. Users can request TEC by internet, mobile internet, and application programming interfaces to correct ionospheric delay for precise positioning. The ionosphere modeling methodology and users can be separated by this pattern of broadcasting. So users just receive ionosphere TEC broadcasted by the platform, not the ionospheric model's coefficients. It mitigates complexity of receiver data processing, and promotes uniformity. © 2016, Wuhan University All right reserved. Source

Liu Y.,Hubei University | Liu Y.,Key Laboratory of Geographic Information System | Liu Y.,Collaborative Innovation Center for Geospatial Information Technology | He Q.,Hubei University | And 4 more authors.
Journal of Urban Planning and Development | Year: 2016

Urban systems are complicated systems where land-use changes may significantly affect the environment and the ecosystem. Therefore, modeling urban growth is crucial for urban planners and administrators to support sustainable development. This paper provides a spatially disaggregated model for urban growth simulation that is characterized by the innovative idea that considers the behavior of residents and couples the explorations of the game between farmers and governments in the land development process. Three kinds of agents, namely, residents, farmers, and governments, make their decisions according to their land use-conversion preferences. Through the use of different strategies that are abstracted from actual land transactions in China, the payoffs to farmers and governments in the game of land expropriation are quantified and then the Nash equilibrium solution of the game is worked out. Those cells with mixed strategy Nash equilibrium solutions that include a probability of greater than 0.5 that either governments will expropriate land legally or that farmers will accept the land acquisition of the governments are referred to as "candidate regions for urban expansion." Based on how they evaluate the "candidate region" condition according to the surrounding environment and land price, residents determine the final land-use transition of each cell in the candidate region that is formed in the previous step. Jiangxia, a suburban area in Wuhan, is used as a case study area to simulate the spatial and temporal dynamics of urban growth. The proposed model, which couples game theory and human decision making in the land-development process, can effectively represent and simulate the spatiotemporal dynamics and patterns of urban growth as well as explain the driving mechanism of urban expansion. © 2015 American Society of Civil Engineers. Source

Wang C.,Collaborative Innovation Center for Geospatial Information Technology | Wang C.,Wuhan University | Shi C.,Collaborative Innovation Center for Geospatial Information Technology | Shi C.,Wuhan University | And 2 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2016

In this study, vertical total electron content values derived from an ionospheric empirical model (IRI 2012) are applied to global ionospheric modeling. Firstly, a comparison of VTEC maps between IRI 2012 and IGS GIMs during the year 2014 is investigated. The comparison shows that IRI 2012 is capable of representing the TEC at middle and high latitudes. Furthermore, IRI 2012 is applied to provide priori VTEC values as virtual measurements for global ionospheric modeling during the year 2014. The results show that the new approach not only eliminates the non-physical negative VTEC values but also improves the accuracy of VTEC maps. The VTEC RMS maps are improved by 3.67%, 2.95% and 22.16% in the Northern Band, Middle Band and Southern Band of the global ionosphere, respectively. This work also investigates the consistency between VTEC maps from different solutions, IGS final products and GIMs of Ionosphere Associate Analysis Centers (IAACs). The comparisons suggest that there is a slightly better consistency between the improved VTEC maps and the IGS final products. The consistencies of the VTEC maps are improved by 4.58%, 2.76% and 4.77% in the Northern Band, Middle Band and Southern Band, respectively. The annual mean values of the root mean square (RMS) of the differences between the improved VTEC maps and GIMs of IAACs are approximately 4~6 TECU. The results indicate that the new VTEC maps using the IRI 2012 model have better agreement with the IGS final GIMs. © 2016 Elsevier Ltd. Source

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