IP geolocation determines geographic location by the IP address of Internet hosts. The physical location of Internet hosts is critical for many location-aware applications. Most geolocation methods are based on linear assumption of correlation between network latency and geographic distance on a large scale. In this paper, a lightweight geolocation approach is proposed to accurately determine the location of Internet hosts. This approach takes advantage of relative delay measurement and common routers. We studied localized delay- distance correlation in small region. We proposed an approach of discovering the accurate positions of common routers and converted common routers as secondary landmarks on a small scale and evaluated the efficiency of our method in the city level. The evaluation results show that the proposed algorithm improves the accuracy of IP geolocation by about 9.5% compared to Street-level Geolocation (SLG), one of the latest methods.