Bañadores de suelo empotrados

The central points of conclusion drawn from the literature review and the initial research investigation can be summarised as follows:

 The most crucial component in the navigation system for visually impaired people is the positioning technology. Important information about when and

where the services are delivered is derived from the positioning technology.

GPS is the most commonly deployed positioning technology.

Nevertheless, the performance is influenced by numerous error sources that is degrading the accuracy of the position solutions accuracy, and also restraining its service integrity and availability. Even though several GPS augmentation techniques have been presented and employed in different applications, yet, the attained positioning performance was based on the availability of up-to-date and dependable correction information. This is affected by the data transmission means, measurement scenarios and navigation environments.

Moreover, a deep deliberation of visually impaired people navigation system applications architecture and positioning needs is required when utilising NRTK GNSS and its augmentation systems.

 A set of preliminary performance experiments of different mobile wireless technologies were conducted, such as UMTS and HSDPA, for utilisation in the system. The performance assessment was focused on the following link features: delay, jitter and packet loss of the GPS data and the live voice and video streaming. These features were chosen to be assessed because they have a significant impact on the overall performance of the navigation system. The outcome of these preliminary experimental studies have confirmed that the HSDPA is the only technology that matches the ITU standards in navigation environments, such as urban, suburban, rural and indoor. Therefore, these contextual factors were considered in the developed positioning model for sustainable and efficient performance.

The applied strategy to address the conclusions above and enhance the positioning performance of GPS for visually impaired people navigation system applications, was presented in this thesis in two different steps as explained below:

1. A new precise positioning model that raises the positioning accuracy and service reliability of the applications for visually impaired people was suggested and developed. The establishment of an efficient positioning model that incorporates NRTK GNSS and its augmentation position

solutions. The positioning model was applied as client-server architecture comprising two main components, the Navigation Service Centre (NSC) and the Mobile Navigation Unit (MNU). The new model has incorporated both components for the purpose of switching the MNU from position determination to server-based positioning mode grounded on the NSC, in case of positioning and augmentation data unavailability. The MNU utilises WADGNSS sources supplying networked-DGNSS correction data with the aim of efficiently augmenting the GPS and GLONASS measurements accumulated at the MNU, and compute an advanced position solution.

In order to explore the positioning model performance in terms of the achieved position solutions accuracy, precision, and service availability and reliability, a comprehensive evaluation methodology was illustrated and utilised. The evaluation process entailed experimental and simulation studies which were carried out while taking into account several contextual aspects identified within the adaptive framework. This embraces the navigation environment, measurements scenarios and available position sensing resources. The central conclusions drawn from the evaluation process are summarised as follows:

 The results from the experiments have shown and thus confirmed that the positioning model‟s position computation methods NRTK GNSS, applied at the MNU, were capable of delivering position solutions with enhanced accuracy levels in contrast to the existing GPS positioning service, throughout all navigation environments and measurement scenarios. The NRTK positioning method has satisfied the performance requirements for high accuracy demanding applications. Therefore, the positioning model is capable of delivering precise positioning in real-time using GPS-RTK Signal for visually impaired people.

 The average of position accuracy achieved from NRTK GNSS within the urban environment and during a dynamic measurement scenario was below 85

cm. In the same concern, the corresponding NRTK availability values computed using NRTK GNSS data at the MNU was 73.68% comparing to 88.44% computed at the rural/suburban environment. During the best measurement conditions in rural area, the average of the position accuracy achieved from NRTK GNSS was below 2 cm for the static measurement, in comparison to below 35 cm and below 80 cm achieved using static measurements in suburban and urban areas respectively. Hence, the NRTK GNSS positioning methods at MNU have outperformed the existing GPS services in worst and best conditions for accuracy measurements. This can be explained due to the high precision dual frequency receiver and the assured high availability of up-to-date and reliable augmentation data at the MNU alongside with the effectiveness of the functional lines in processing and correcting navigation data.

 The conclusions from the simulation results showed that appropriately accurate and reliable position samples can be obtained from the combination of future Galileo OS with GPS standard positioning services. The hybrid positioning service outperformed by the NRTK GNSS positioning model at MNU in terms of the positions service accuracy in all scenario and navigation environments. Furthermore, the hybrid system of Galileo and GPS could not be verified in a “real” experimentation because Galileo system is yet not fully functional, therefore a simulation study was conducted. However, the satellite availability in all scenarios and navigation environments was higher than the positioning model at MNU using NRTK GNSS. This recognises the need for further work on development of the positioning model and the exploration of the possibility of incorporating the future services within the same platform including the positioning model.

 In this research the experiments of NRTK GNSS at MNU and the quality of service (QoS) of the transmission of video, voice and positioning data over

various wireless mobile networks (Chapter 5, Section 5.3.1) were not conducted in a combined system. As it is outside the scope of this thesis.

However, HSDPA technology is sufficient to transmit video streams of micro environment of the visually impaired person with sufficient resolution to the NSC. With improved accuracy with NRTK, the system will be able to guide the blind to avoid obstacles with better accuracy.