Application Of GPS Techniques In The Cadastral Surveying

Land information is always obtained through the cadastral surveying. The general cadastral surveying works include the cadastral control survey, the boundary mark survey, the property boundary survey, the cadastral detail survey and the cadastral inventory. The commencement and development of Global Positioning System (GPS) largely accelerates the methodology revolution of the cadastral surveying so that its efficiency has been rapidly improved and the service area has been widely expanded.In the thesis, the GPS techniques of the static positioning and the kinematic positioning, which are suitable for the cadastral surveying, are firstly introduced, based on the requirements and characteristics of the cadastral surveying. Tens of GPS positioning modes have been developed in the past ten years but these ways are not accepted and used widely in the current cadastral surveying, Therefore, about 8 operational modes, which can be used in the cadastral surveying, are detailed introduced in the thesis. There are Conventional Static Positioning (CSP), Rapid Static Positioning (RSP), Conventional Differential GPS (CDGPS), Wide Area Differential GPS (WADGPS), Post-Positioning Kinematic (PPK), Real-lime Kinematic (RTK), Precise Point Positioning (PPP) and Virtual Reference Station (VRS, also named as Network RTK). Especially, the last two methods are the latest techniques in the past few years.In order to understanding the characteristic and performance of the above different modes, all these modes are compared from four aspects: the system requirement, available accuracy, output information and application. Then, these modes are separated into different groups according to their accuracy, coverage and observable used.Each positioning mode only satisfies the individual requirement of the cadastral surveying. To achieve the accuracy requirement of the cadastral control surveying, CSP, RSP and RTK can be used here. But these three ways are optimally adopted in different cases. For example, it isbest to used CSP when baseline is longer than 15km, but we can use RSP and RTK when the baseline is shorter than 10 km. In the cadastral detail surveying, only RTK is available for the large-scale map, but various DGPS techniques can be used for the small-scale map, such as 1:5000. All kinds of DGPS techniques, such as CDGPS, WADGPS, PPK, are suitable for the cadastral inventory. Particularly, the single point positioning can also be used if the accuracy is less than 50 meters. In the case of precise land boundary surveying, the RTK is supposed to be used.VRS and PPP are still in the phase of experiment and development. However, their accuracy potential and operational convenience show that the two kinds of new GPS techniques will change the existing GPS positioning modes and finally make the cadastral investigation become the real individuation work. Based on the analysis of research results of VRS and PPP, we can expect that they will become the crucial methods in the coming future in the field of the cadastral surveying.