Data Processing About Initial Values Of Old Highway Planar Linear Fitting Parameter

The related study on how to fit the old highway plane linear with the measurement data is still not enough. The initial value of old highway planar linear parameter is very important in reconstruction project about the adjustment of old highway plane linear and improving the accuracy of old highway planar linear fitting.This article was based on "old highway plane linear fitting technology computer aided" which was proposed by professor LiuSu of Changsha University of Science and Technology. It combined G321 extension project for further study about the initial value of old highway planar linear parameter. Old highway planar linear parameter includes linear parameter and curve parameter. Linear parameter was calculated by the unary linear regression equation which was obtained by least square method. Curve parameter includes circle curve radius and center coordinates. Easement curve length was calculated by the corresponding function based on the curve radius and center coordinates. The key to calculate planar linear parameter is to calculate curve parameter which includes circular curve radius and center coordinates.This article mainly analysis the situation that the highway midpoint’s number involved in the fitting is greater than 3. Put forward the multiple combination average value method which is a new method of round curve fitting. Using multiple combination average value method can improve the accuracy of circular curve parameters. After the circular curve fitting points are determined, using different combination method to calculate the circular curve parameters. Each combination has a corresponding circle curve fitting error. The combination of the smallest circle curve fitting error is the best combination and its circular curve parameter has the highest precision. This paper compared multiple combination average value method with other methods to verify its applicability. The multiple combination average value method has a large amount of calculation, this paper use VB program to realize the multiple combination average value method in the application of planar linear fitting. It was demonstrated by CAD graphics that the circular curve fitting error was depended on the size of the circle curve fitting of discrete degree. The influence factors of discrete degree were analyzed. The main reason of discrete degree is pavement midpoint error. Appropriate methods can be used to improve accuracy of pavement midpoint.The research was based on the G321 old highway reconstruction project. Linear regression theory and multiple combination average value method were combined by VB program to calculate planar linear parameter in all sections. Finally, getting the fitting parameter initial values of old highway planar linear which were adjusted according to specification and the principle of symmetrical easement curve.