In this paper, we present design and evaluation of GNet, a novel peer-to-peer geographic overlay network substrate that is well suited to support wide area location-based service. The GNet protocol uses hierarchical geographic address as identifier of Internet-connected nodes. By combination of incremental domain-based routing mechanism like plaxton mesh with geographical domain hierarchy, this peer-to-peer architecture has the advantages of efficient routing, locality preserving and load balancing etc. In particular, it will benefit location-aware service by supporting position-based, proximity-based and especially geographically scoped operations.