With the rapid development of spatial satellite-based infrastructure in US, Europe, Japan, China and India, there is no doubt that the next generation Global Navigation Satellite Systems (GNSS) will significantly improve the integrity, accuracy, reliability and availability of the position solution. GNSS is becoming an essential element of personal, commercial and public infrastructure and consequently part of our daily lives. However, the applicability of GNSS in supporting a range of location-sensitive applications such as location based services in an urban environment is severely curtailed by the interference of the three-dimensional urban settings. To characterize and gain in-depth understanding of such interferences and to be able to provide location-based optimization alternatives, a high-fidelity three-dimensional urban model is built with large scale high-resolution spatial data sets. The model is then used to support a comprehensive simulation study of current and future GNSS performance, in terms of availability, strength, geometry, positioning accuracy and reliability based on a number of scenarios. Useful time-stamped spatial patterns of the signal performance over the experimental area have been revealed which are very valuable for supporting location based services applications, such as emergency responses, the optimisation of wireless communication infrastructures and car navigation services.