Abstract: Transition curve is a constituent element of highway or railway horizontal alignment. A drawing method of transition curve in GIS is presented. Based on the fundamental of curve drawing method in Computer Graphics and geometrical feature of clothoid, a polylines approach is used to plot transition curve. A precise formula for determining segments number of the polylines is ratiocinated by Compound Trapezia numerical integral method. Further more, conversion method of arc length and point coordinate in transition curve is delivered. This drawing method of transition curve has been programmed in Supermap GIS and is found that the precision and efficiency can fill the requirements of application.

Key words: computer application, drawing transition curve, polylines approach, GIS