55、已知某交点JD的桩号K5+119.99,右角为136°24′,半径R=300m,试计算圆曲线元素和主点里程,并且叙述圆曲线主点的测设步骤。( )计算得圆心角α=180°-136°24′=43°36′,R=300m的圆曲线元素得:切线长T=119.99(m).曲线长L=228.29(m),外矢距E=23.11(m),切曲差D=11.69(m)(2)主点里程:ZY里程=K5+119.99-119.99=K5+000,YZ里程=K5+000+228.29=K5+228.29,QZ里程=K5+228.29-114.15=K5+114.14.(3)从交点(JD)向后导线推量119.99m得ZY点,从交点(JD)向前导线丈量119.99m得YZ点,从交点(JD)向分角线方向丈量23.11m得QZ点。