关键词: 铁轨, 曲率半径, 区域生长, 曲线拟合

Abstract: When railway train running on sections of small radius，its speeding will make great hidden trouble for security.Through analyzing the onboard video image，this paper constructs detection templates of rail，uses region growing，curve fitting，and other means to achieve calculation of the rail curvature.Automatically detect the smallest radius of curvature in front of the train.The driver acquires early warning，and ensures safe operation of trains.

Key words: rail, curvature radius, region growing, curve fitting