Wireless sensor networks are networks composed of a large number of distributed sensors, connected via wireless links. This paper deals with the problem of localization in wireless sensor networks. Such a problem becomes challenging in indoor environments, where signals of Global Positioning Systems are no more reliable. In this paper, the localization problem is defined using connectivity measurements. The proposed technique consists thus of estimating unknown sensors positions using known position information of neighboring sensors. The estimation is then performed using polar intervals. The estimated positions are thus two-dimensional intervals defined in some polar coordinates system. Using intervals, the proposed approach performs an outer estimation of the solution, leading to estimates covering for sure the actual positions of the sensors.