Accuracy of Geopotential Models Used in Smartphone Positioning in the Territory of Poland

Abstract

Effective realisation of both land and sea transport has always required the determination of safe and fast routes. In the era of technological progress and modern technologies, the classic methods of navigation and paper maps have been practically replaced by satellite positioning and marine electronic maps. The degree of occurring changes is evident in the widespread use of mobile phones and tablets in car navigation and recreation. Among the determined geolocation data in these fields, only the ellipsoidal longitude and latitude of the receiver are most commonly used. Knowledge of these coordinates is sufficient to present the position on the maps available online or offline. The third of the coordinates, ellipsoidal height, finds particular application in some areas of recreation, such as mountain climbing or cycling to present the differences in elevation along the track. However, the ellipsoidal heights related to the reference ellipsoid, excluding some regions of the Earth, are not identical to the normal heights used widely in many European countries. The conversion of ellipsoidal heights into normal heights takes place through the use of geopotential models that are currently commonly implemented in the GNSS modules of smartphones. Geopotential models, which are discrete sets of quasigeoid spacing values from the reference ellipsoid, allow interpolation of the local undulation value added later on to the determined ellipsoidal height of the receiver. The publication will present the results of the conducted comparative analysis of geopotential models of selected telephones with the EGM2008 model developed by The National Geospatial- Intelligence Agency (NGA). The analysis will concern the results of measurements carried out in selected regions of Poland. The cohesion of both geopotential models will be shown, which directly translates into the correctness of the heights computed by the phone receiver. The conducted research proves the occurrence of significant distortions in the calculated values of undulations. The examined issue, in the perspective of the rapid development of personal navigation and the increasing accuracy of the receivers of mobile phones, is an important factor affecting the credibility of the positioning results.