In this paper, we present an accurate method to localize an object on a 2D plan using the 1 chipless technology. This method requires a single antenna and a chipless tag. Phase difference 2 between a reference position and an unknown position is used to estimate the distances between each 3 resonator and the antenna. Then, multi-lateration is used to determine the position of the chipless tag 4 in the plan. This method provides a better accuracy compared to classical ones based on received 5 signal strength indicator (RSSI) or round-trip time-of-flight. In a square of 10 cm side above the 6 antenna, error over distance determination between each resonators and the antenna is less than 7 2 mm and localization error on the tag coordinates in the 2D plan is lower than 1 cm. To increase 8 the robustness of this method, we propose also a selection of a subset of the resonators used by the 9 multi-lateration process. This method permits to increase the localization area by more than 20%. All 10 the results have been obtained in real environment, and at different heights to show the robustness 11 of the proposed approach. Finally, localization sensors based on this method can also be used as 12 classical chipless RFID tag for identification with the same coding capacity.