Deducing from a gradient matrix by non-linear least square residual localization, we formulate the errors of located nodes caused by ranging error or location error of anchors. We evaluate the error under various network topology, ranging error, location error and number of anchors, and analyze its performance. The performance shows that more anchors and less noises will help to improve the localization results. We then propose an error control method based upon Gaussian measurements to obtain the location of the free nodes and demonstrate the high efficiency of our proposed algorithm in terms of location estimation error under different conditions.