The most common technology which supports outdoor locating services is the global positioning system, GPS. It mainly receives the positioning satellite signals from over three satellites, and uses triangulation technique to compute the position. The satellite signals are easily interfered by non-line-of-sight (NLOS) wave and climate; thus, create significant positioning errors. The positioning technology based on wireless local area networks (or WiFi) has matured gradually in recent years. The pattern matching method that takes the received signal strength indicator (RSSI) at the receiving end as the fingerprinting is one of the key technologies. In order to improve the precision of positioning under unfavorable weather conditions or in NLOS outdoor environment, this study proposed a positioning technology based on a portable mobile device with GPS and WiFi-based pattern matching method, to design a selective weighting scheme. The experiments validated that the proposed technology is effective with an average positioning error of 3.8 m less than that of GPS.