Gps Application In The Measurement Of Road And Bridge Projects

Some features of the engineering control network demand special applications of GPS in road and bridge engineering, for example, particular requirement of accuracy on some aspect that results in distribution of net points and sometimes bigger height difference of points, consideration of staking out in construction in the design of engineering control network, application of independent engineering coordinate system, and use of engineering mean height surface as the projection surface of computation. According to the features of engineering control network and the requirements of accuracy and convenience of staking out in construction, The main achievements of this paper are as follows:1. Taking the characteristics of road and bridge engineering into account, this paper makes systematic analysis and study on applications of static GPS in data processing of surveying in road and bridge engineering: The feasibility of using single point positioning result as starting point is studied and the influence of it on baseline solution is discussed; On account that the software provided along with instrument by vendors usually does not support coordinates in the independent engineering coordinates system from GPS observations, a simple and effective method is represented for the GPS data processing in the independent engineering coordinates system and is programmed. Through real examples the method and programs are testified; From GPS surveying the WGS-84 coordinates are acquired, while in reality coordinates in local coordinate system are needed, so conversion from WGS-84 coordinates to local coordinates is necessary. During conversion, the conversion models determined by datum transformation and errors from the GPS computation by incorrect coordinates of the reference station under WGS-84 datum will surely have influence on datum transformation. And the influence is studied from practical data in this paper; The applicability of single point conversion is analyzed and studied;2. In field GPS work, errors of receiver's antenna phase center and instrument height measurement are inevitable, so in this paper the influence of the error of instrument height measurement on planar coordinates is studied and it is proved theoretically that the influence of the error of instrument height measurementon planar coordinates can be neglected;3. In road and bridge engineering, GPS can not replace the IPS(Total station Positioning System) completely out of practical needs. In this paper the combination of GPS and TPS is discussed through real examples;4. The height from GPS surveying is geodetic height while normal height is needed in reality. This paper discusses current methods of GPS height processing and proposes a processing method of GPS height within small areas based on real example;...