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In this paper, TDOA (time difference of arrival) measurements from pilot signals of a wireless communication network is proposed to solve the navigation problem in the case that under the environments that each BS(base station) have NLOS(non-line-of-sight) error. TDOA measurements are known to have poor accuracy due to technical limitations of a communication system and propagation environments. The major error source of TDOA is the NLOS. NLOS propagation error occurs when a direct LOS(line-of-sight) path between an MS(mobile station) and a BS(base station) is blocked by some obstacles. To mitigate the NLOS error in a cellular network, TDOA error modeling is used for each BS channel. And then, remove NLOS error from each measurement. Some simulations and real tests are conducted to evaluate the performance of the proposed methods. Real experiments are conducted at the city center of Seoul. A commercial GPS cellular phone and a QXDM program are used. And then, TDOA measurements are measured. Test results show that the proposed methods continuously provide subscribers a reasonably accurate location under the NLOS environments.