  This paper aims at detecting an accurate position of the main entrance of the
buildings. The proposed approach relies on the fact that the GPS signals drop
significantly when the user enters a building. Moreover, as most of the public
buildings provide Wi-Fi services, the Wi-Fi received signal strength (RSS) can
be utilized in order to detect the entrance of the buildings. The rationale
behind this paper is that the GPS signals decrease as the user gets close to
the main entrance and the Wi-Fi signal increases as the user approaches the
main entrance. Several real experiments have been conducted in order to
guarantee the feasibility of the proposed approach. The experiment results have
shown an interesting result and the accuracy of the whole system was one meter
