E=R(sec?2?1)?200?(sec?2?1)=570.98m
J=2T-L=966.27m （2）计算JD3主点桩号
ZY(桩号)= JD(桩号) – T =( K8+099.51)- 744.68 = K7+354.83 QZ(桩号)= ZY(桩号) +
L = (K7+354.83) + 523.09/2= K7+616.38 2YZ(桩号)= ZY(桩号) + L = (K7+354.83) +523.09= K7+877.92 检验式：QZ(桩号) + 计算正确
J = （K7+616.38）+ 966.27/2= K8+099.51 = JD(桩号) 2