Abstract— Localization is an important aspect in the field of wireless sensor networks that has attracted significant research interest recently. The interest in wireless sensor network localization is expected to grow further with the advances in the wireless communication techniques and the sensing techniques, and the consequent proliferation of wireless sensor network applications. This paper presents an improved localization algorithm with high accuracy in large-scale Sensor networks with a large number of sensor nodes based on the Graham’s scan, called Slsng. the Graham's scan adapted here for our approximation technique to determining the convex hull of a set of sensors used instead of the Grid-Scan method, to take into account the requirements in memory, to make it scalable and rapidly convergent with small location estimation error. We verify our algorithm in various scenarios and compare it with AT-Dist method. Simulation results show that our proposal is superior to the state-of-the-art localization algorithms for Wireless sensor networks in largescale.