| Distributed CORS has become the main form of ground-based augmentation system because it can overcome the problem of insufficient data processing capacity of a single server.In the face of large-scale distributed deployment of CORS network,the existing RTK service software has some problems,such as high concurrency restriction of users,inability to cross regional service,cross system visualization and so on,which have become the key problems to be solved to hinder the development of popular high-precision location services such as emergency rescue,automatic driving,intelligent logistics and so on.Based on the development of mature virtual reference station positioning technology,this thesis focuses on the spatiotemporal characteristics of atmospheric delay and VRS grid division,designs and implementation of the distributed CORS network differential data service system,it has certain practical value and reference significance in the transformation of CORS network high-precision location service to the popularization and massive user service technology.The main work of this thesis is summarized as follows:1.Aiming at the problem that conventional software can’t guarantee the optimal balance between user positioning accuracy and server data process pressure when setting virtual grid spacing by empirical value,an adaptive virtual grid spacing determination and service accuracy dynamic evaluation method is designed.The grid spacing is determined by setting the influence of space atmospheric error on each component of the baseline between stations both is less than 1 cm.The experiment was carried out using the observation data on December8,2020,and the results show that the grid spacing limits in east-west and south-north directions in Chengdu area are 9.8 km and 2.6 km respectively,the grid spacing limits in eastwest and south-north directions in Hong Kong area are 5 km and 1.6 km respectively.In the dynamic evaluation experiment of service accuracy in Chengdu area,when the grid spacing is taken as the limited value,the component errors between the weakest point and the reference station baseline are basically within 2 cm,and when the grid spacing is taken as the average value of a single day,the component errors of the baseline between the weakest point and the reference station have reached the decimeter level at noon.2.To solve the problem of cross regional service,a distributed CORS network differential data service system is developed.The system separates the business service module of RTK service software from the data processing module,and forms a differential resource pool through virtual grid division,which can provide users with cross regional positioning service.To solve the problem of cross system visualization,the system provides cross system visualization of team developed network RTK service software(Venus),which can be remotely managed on Windows PC and Android mobile terminal.3.The performance of the system,user positioning status,cross regional service related content are tested.The results show that the performance of the system is stable,and compared with the traditional service mode,the fixed rate of user positioning are both 100%,the average differential data delay time is 0.72 seconds slower,the positioning error in N and E directions is equal,basically within 1 cm,and the positioning error in U direction is slightly larger,up to4 cm,and in the distributed deployment of CORS network,the system can provide users with cross regional seamless positioning service. |
