Abstract
Global Navigation Satellite Systems (GNSS) are extensively used for location-based services, civil and military applications, precise time reference, atmosphere sensing, and other applications. In surveying and mapping applications, GNSS provides precise three-dimensional positioning all over the globe, day and night, under almost any weather conditions. The visibility of the ground receiver to GNSS satellites constitutes the main driver of accuracy for GNSS positioning. When this visibility is obstructed by buildings, high vegetation, or steep slopes, the accuracy is degraded and alternative techniques have to be assumed. In this study, a novel concept of using an unmanned aerial system (UAS) as an intermediate means for improving the accuracy of ground positioning in GNSS-denied environments is presented. The higher elevation of the UAS provides a clear-sky visibility line towards the GNSS satellites, thus its accuracy is significantly enhanced with respect to the ground GNSS receiver. Thus, the main endeavor is to transfer the order of accuracy of the GNSS on-board the UAS to the ground. The general architecture of the proposed system includes hardware and software components (i.e., camera, gimbal, range finder) for the automation of the procedure. The integration of the coordinate systems for each payload setting is described, while an error budget analysis is carried out to evaluate and identify the system’s critical elements along with the potential of the proposed method.
Highlights
In the last few decades, Global Navigation Satellite System (GNSS) receivers have become the fundamental instruments for a plethora of applications in aviation, civil and surveying engineering, geodesy, geophysics, as well as in time keeping and atmosphere monitoring, to mention a few
Accuracy refers to the deviation of the measured position with respect to the “true” position of any given point on a global coordinate reference system; integrity is the level of confidence and credibility of the observations provided by the GNSS system; continuity corresponds to the system’s ability to work with no failure; and availability indicates the function of time in which the GNSS signal fulfills the previous criteria [2]
GNSS positioning accuracy in urban canyons and under tree canopies becomes degraded, as the satellite signal is obstructed by buildings and/or dense vegetation
Summary
In the last few decades, Global Navigation Satellite System (GNSS) receivers have become the fundamental instruments for a plethora of applications in aviation, civil and surveying engineering, geodesy, geophysics, as well as in time keeping and atmosphere monitoring, to mention a few (https://gssc.esa.int/navipedia/index.php/GNSS_Applications). When global coordinates are required, land surveying is often carried out using GNSS [1], complemented with traditional positioning instruments and methods such as total stations and terrestrial laser scanners, whereas there is a growing utilization of unmanned aerial systems (UAS) to support medium to large scale mapping These techniques are employed to complement GNSS positioning when its performance, as mainly assessed by its accuracy, integrity, continuity, and availability, is degraded. Accuracy refers to the deviation of the measured position with respect to the “true” position of any given point on a global coordinate reference system; integrity is the level of confidence and credibility of the observations provided by the GNSS system; continuity corresponds to the system’s ability to work with no failure (i.e., signal loss); and availability indicates the function of time in which the GNSS signal fulfills the previous criteria [2]. The presence of buildings and trees prohibit the directSystem detection of satellitein signal
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