Study On Data Processing Methods And Software Development Of GPS Engineering Control Network

To overcome the limitations that the current data processing methods in GPS engineering control network can not meet the accuracy requirement under the condition of large range, this thesis presents the discussion and investigation on the adjustment methods, coordinate transformation model and projection distortion caused by GPS control network.First, it is illustrated that five methods and their fundamentals for GPS data adjustment and coordinate transformation model. These methods include 3D constrained adjustment with rectangular space coordinates as unknowns, 3D constrained adjustment with geodetic coordinates as unknowns, 2D constrained adjustment with plane baseline vectors as observations, 2D constrained adjustment with plane coordinates' differences as virtual observations and GPS data adjustment with one point and one direction constrained. The GPS engineering control network in a certain intercity passenger-dedicated line is selected as data source to validate these methods.Secondly, by analyzing the distortion caused by GPS projection, several projection methods of GPS control network applied to high-speed railway are discussed. These methods include Gauss projection based on arbitrary central meridian with given height datum and oblique Mercator projection with transverse cylinder and normal cylinder derived from oblique cylindrical projection. Also the two methods are applied to the CP I GPS control network in a certain High-speed Railway. The testing result using the two methods is further compared and analyzed in the thesis.Based on the above discussion and experimental result analysis, two major conclusions can be drawn in the thesis. The first is that the rigorous 3D constrained adjustment methods are necessary to meet the accuracy requirement in large range GPS engineering control network. The second is that the oblique Mercator projection is preferable to Gauss projection in the consistency between the projected baseline length and that of real ground. The former is more applicable especially in GPS control network of route-shaped high-speed railway. Finally, according to the derived algorithms and conclusions, the software, GPS network adjustment (GPSNAS) with the function of coordinate transformation and projection distortion processing is developed utilizing Visual C#.NET tool to meet the needs in various projects.