Estimation of Distance Measurement Equipment accuracy

Determination of the location of the aircraft is one of the important tasks of navigation. The accuracy of air-craft positioning in the airspace is directly related to the safety of aviation. Modern trends in the development of aircraft positioning systems gradually increase the role of DME in the modern air navigation system, which sets cer-tain requirements for the accuracy of navigation measurements. Measurement of DME distance is considered under the influence of additive measurement error characterized by Gaussian probability distribution with zero mathematical expectation and a certain value of dispersion. In accordance with regulative documents, DME error is considered as the sum of errors such as an error connected with signal propagation in space and airborne interagetor error. However, different regulative documents set up different requirements for the maximum permissible dispersion value. In particular, FAA AC90-100A and ICAO DOC-9613, consider the error of on-board equipment as a function of distance between an interrogator and DME, while the RTCA DO-189 limits it to a certain value. In the general case, the components of error of signal propagation in space are the following: an error of signal arrival detection at the ground part of equipment; an error of delay of navigation signal at the ground part of DME; an error associated with the propagation of radio waves in the airspace. Computer simulation shows that error of modern DME systems is much more smaller then associated requirements of regulative documents. An article analyzes the approaches used to estimate accuracy of DME measurements, proposes a generalized model for estimating accuracy, and analyzes the ways to improve accuracy of DME measurements. One of the effective means of DME accuracy increasing is the introduction of new forms of interrogating signal that is completely compatible with existing equipment, which, in contrast to the change of navigation signal, does not require the change of ground infrastructure.