Safety of air transportation strongly depends on the performance of on-board positioning sensors. Positioning by data from navigational aids is considered by international aviation community as one of the main stand-by positioning approaches onboard of civil airplanes. However, only positioning by pair of distance measuring equipment (DME) meets requirements of Performance-Based Navigation. A DME service volume model based on path loss between a pair of transmitting and receiving antennas has been proposed in the paper. The model takes into account the influence of relief on radio waves propagation and diffraction from high-altitude elements of relief. The proposed model has been used in the analysis of DME global network performance. In particular, performance of a global network is analyzed based on availability area of DME service, area of positioning by pairs of DME/DME support, availability of particular positioning accuracy, and areas of meeting various RNAV requirements. Obtained results indicate that only in 27.76% of global airspace a DME service can be provided. However, only within 15.9% of airspace, a DME/DME positioning can be used. Results of the analysis indicate about the necessity of actions for further development of global navigational aids network in order to guarantee safe airlines connections around the globe.

航空运输的安全在很大程度上取决于机载定位传感器的性能。国际航空界认为，通过助航设备数据进行定位是民用飞机机载的主要备用定位方法之一。但是，只有通过一对测距设备（DME）进行定位才能满足基于性能导航的要求。论文提出了一种基于一对发射和接收天线之间路径损耗的DME服务量模型。该模型考虑了地形对无线电波传播的影响，以及地形高空要素的衍射。所提出的模型已用于分析 DME 全球网络性能。特别是，基于 DME 服务的可用区域来分析全球网络的性能，DME/DME 支持的定位区域、特定定位精度的可用性以及满足各种 RNAV 要求的区域。获得的结果表明，只有 27.76% 的全球空域可以提供 DME 服务。但是，只有在 15.9% 的空域内，才能使用 DME/DME 定位。分析结果表明，有必要采取行动进一步发展全球助航网络，以保证全球航线的安全连接。