《公路工程技术标准》规定:三级和三级以上公路的平曲线,当半径R小于规范规定不设超高的最小半径时,要设置缓和曲线。在路线勘测中,测设缓和曲线和测设圆曲线一样,常用偏角法进行测量。所谓偏角法,实际上是一种极坐标法,它借助经纬仪控制偏角,用弦长控制曲线上的点到坐标原点的距离,确定曲线上各点在地面的位置。实地测量中,由于地形地物影响经常遇到经纬仪不通视的情况,为了克服不通视的问题,唯一 “Highway Engineering Standards” provides: the level of three and above the road flat curve, when the radius R is less than the specification does not set the minimum height of the minimum radius, to set the easing curve. In the course of surveying, surveying and setting the easing curve and setting the same as the circular curve, commonly used declination method to measure. The so-called declination method, in fact, is a polar coordinate method, which uses the theodolite control declination, with the chord length control curve point to the origin of the coordinate distance, to determine the point on the curve in the ground position. In the field survey, the theodolite often encounters the situation that the theodolite is not visible due to the influence of topography. In order to overcome the problem of not seeing, the only