建立了进线档导线相间距离的三维精确校验模型，根据斜抛物线理论和三维坐标转换技术，提出了三维计算机辅助设计（computer aided design, CAD)交互式相间距离计算软件的实现方法，并结合工程计算实例验证了该方案的可行性和可靠性。

This paper established a three-dimensional (3D) precise calibration model for the phase distance of approach span. Based on the oblique parabola theory and 3D coordinate conversion technology, the implementation method of the 3D-CAD interactive software was suggested. Finally, the feasibility and the reliability of this method were verified by a project example.