Estimating Geometric Parameters of Highways and Railways Using Least-Squares Adjustment

Abstract

This paper introduces a least-squares based approach that is developed for the estimation of horizontal geometric parameters of highways and railways. Curve recovery forms an important procedure in the establishment of the spatial database of a Geographic Information System for Transportation (GIS-T), which is especially essential nowadays when different mobile mapping systems such as those using Global Positioning System (GPS) are widely employed for data acquisition. Comparing with the existing methods that estimate the geometric parameters of highway and railway alignments such as straight-lines, circular curves or spiral curves individually, this study discusses how to extract the entire set of parameters of combined alignments simultaneously with an integrated estimation method. Two case studies were used to show the feasibility of the developed technique. The first example investigates the possibility for recovering the geometric parameters of expressway curves whilst the second experiment entails realignment of existing railway curves. The results show that the proposed method has the advantages of high accuracy in the estimation of highway and railway curve parameters, and of less track lining work comparing with the traditional method in railway track realignment.