Fine grained indoor localization is attractive for its wide usage in indoor navigation system, infrastructure management, and blooming augmented reality applications. In this paper, we propose a smartphone based indoor localization system called Plotter, providing a centimeter-grade localization service without any prior knowledge or additional devices. Leveraging the simultaneous localization and mapping (SLAM) technology, Plotter not only learns its relative position among surroundings, but also simultaneously constructs and updates the map of unknown area. We take advantage of a modified Kalman Filter algorithm in the system in order to eliminate unacceptable errors produced by motion sensors on smartphones. Evaluation result shows that Plotter achieves centimeter-grade accuracy, which is competitive comparing with prior works assisted by additional devices.