*Article* **Determination of Navigation System Positioning Accuracy Using the Reliability Method Based on Real Measurements**

**Mariusz Specht**

Department of Transport and Logistics, Gdynia Maritime University, 81-225 Gdynia, Poland; m.specht@wn.umg.edu.pl

**Abstract:** In navigation, the Twice the Distance Root Mean Square (2DRMS) is commonly used as a position accuracy measure. Its determination, based on statistical methods, assumes that the position errors are normally distributed and are often not reflected in actual measurements. As a result of the widespread adoption of this measure, the positioning accuracy of navigation systems is overestimated by 10–15%. In this paper, a new method is presented for determining the navigation system positioning accuracy based on a reliability model where the system's operation and failure statistics are referred to as life and failure times. Based on real measurements, the method proposed in this article will be compared with the classical method (based on the 2DRMS measure). Real (empirical) measurements made by the principal modern navigation positioning systems were used in the analyses: Global Positioning System (GPS) (168'286 fixes), Differential Global Positioning System (DGPS) (900'000 fixes) and European Geostationary Navigation Overlay Service (EGNOS) (900'000 fixes). Research performed on real data, many of which can be considered representative, have shown that the reliability method provides a better (compared to the 2DRMS measure) estimate of navigation system positioning accuracy. Thanks to its application, it is possible to determine the position error distribution of the navigation system more precisely when compared to the classical method, as well as to indicate those applications that can be used by this system, ensuring the safety of the navigation process.

**Keywords:** navigation positioning system; positioning accuracy; reliability method; Global Positioning System (GPS); Differential Global Positioning System (DGPS); European Geostationary Navigation Overlay Service (EGNOS)
