Two methods of unsupported distance measurement were discussed when the target nadir could not be reached.The measurement principles, the calculation equations and the measurement error were analyzed.

• 摘要结合工作实践探讨了在目标点天底无法到达时，高压输电线路的两种悬高测量方法，并对其测量原理、计算公式及测量误差进行了分析；