In wireless sensor networks, localization systems use data from sensors which receive signals from moving targets, measure RSSI, and translate RSSI into the distance between sensor and target. We consider a localization system that gives an error measurement model of distance and introduce a relationship between the number of data and accuracy. Extending the lifetime of a system is needed to save the energy of sensors and collect the necessary data. In this paper, we propose an efficient data collecting technique to get the accuracy required for the applications while saving energy. We verify that our proposal can efficiently collect necessary data to get accuracy in cases of random sensor placement.