Study Of The Positioning Of Vehicle-borne 3d Surveying System Based On Cors

GPS Continuous Operational Reference System(CORS) based on network RTK technology, as one of the development aspect of GPS applications has become the indispensable infrastructure of urban and rural areas information construction. Vehicle-borne 3D surveying system (3Dsurs) is a system which collects three-dimensional information of urban environment and various project objectives rapidly from the ground to satisfy the need of current "digital city" and various construction projects. The system uses relative positioning mode, therefore it needs to lay reference stations. With the distance between 3Dsurs and the base station increasing, the errors about distance (satellite orbit errors, ionospheric delay and tropospheric delay error) are growing, so that positioning accuracy rapidly declining; Furthermore, taking into account the initialization time,the correct model and so on, the system consumes both resources and manpower. The data that the system needs for positioning not only the original GPS data, also reference stations' original data. This situation makes the low efficiency of data collection and a great limitation to high-efficient city operations.In response, this paper makes a study of the positioning of the 3Dsurs based on the CORS: It discusses the basic principles of the CORS, its ingredient and their effect; For getting the integrated error correction of the 3Dsurs,the article discusses the principles and formula of the three algorithms: interpolation method,linear combination method,GPS virtual reference station method and compares the features,applicability and merits of these algorithms; Also, it discusses how to set out the errors equations using the integrated error corrections of the 3Dsurs and calculate coordinate corrections and get the precise positioning coordinates finally. The author has programmed a set of data processing procedure of the positioning of the 3Dsurs based on the CORS. This data-processing procedure can process the 3Dsurs's data based on the original data provided by the CORS stations, then it can get the error correction of each successive epoch and calculate the corrected coordinates using approximate coordinate of the 3Dsurs. Finally, the article gives us an example using the Qingdao Continuous Operational Reference System (QDCORS) which has been built, and verifies the positioning accuracy according to the precision analysis.