Online global positioning system (GPS) processing services have provided users with the opportunity to obtain freely high precision coordinates in a recognized datum. However, all services are dependent on the quality of the data and the length of data span supplied to them by the user. This study aims to assess the four globally available online GPS processing services from the point of view of a user wishing to take advantage of such a service for datum realization. Data from eight selected international GNSS service stations have been processed by each service and the results have allowed a statistically significant comparison analysis to be performed. Although users can expect a variability of results from different services when processing identical data, solutions with 24 h data are generally repeatable at the 1–2 cm level and accurate in terms of international terrestrial reference frame coordinate recovery at the 3–4 cm level. Such differences are accentuated as observation time decreases. Finally...

International Journal of Metrology and Quality Engineering (IJMQE),an international journal for the rapid publication of articles dealing with applied metrology and quality tools for process improvement in industry and in research

The emergence of low-cost, navigation-type receivers capable to provide carrier-phase data (the so-called high-sensitivity carrier-phase positioning) has been steadily growing over the recent years. The aim of this study was to evaluate the positioning performance of a high-sensitivity receiver in a network real-time kinematic environment for mapping surveying applications. Specifically, using as rover receiver the u-blox NEO-7P module and the low-cost antenna Tallysman TW2410, sets of data were collected for the purpose of mapping surveying. The external accuracy of the obtained solutions is considered using different positioning techniques and the internal indicators of the system during real-time kinematic (RTK) positioning are assessed. The assessment indicates that in benign environments this type of receivers produce results that are comparable to RTK positioning using geodetic receivers and with a significantly lower cost.

Network-based real-time kinematic (NRTK) positioning in local or regional reference networks has been proven to be an efficient technology for high precision global positioning systems (GPS) positioning over the last few years. With a view to GPS modernization and the development of the European Galileo system, considerable improvements are expected, enabling high reliability of real-time kinematic (RTK) rover positioning on distances larger than the typical ones of current RTK networks. This paper evaluates the expected performance of a GPS/Galileo NRTK by assessing the spatial variability of specific quality indicators; namely, the success rates of correct integer ambiguity resolution and the network internal reliability. This approach provides a useful tool for design analysis of RTK networks. The Greek GPS-RTK network is used to simulate different geometric configurations to demonstrate in a practical sense whether or not a particular configuration can meet the user specified requirements. As a result...