The positioning of a target with radar measurements could be inaccurate because of the atmospheric refraction effects. We present a technique for determining the refractivity parameters using known position information of cooperative targets. The estimated refractivity parameters are then used to find the position of a noncooperative target, along with its radar range and angle measurements. The performance of the proposed algorithm is assessed by comparing the mean squared error (MSE) of the estimate with the Cramer-Rao lower bound (CRLB) as well as by testing the algorithm with real field data. Ground-based military surveillance radar can adopt the proposed algorithm and benefit when there are some cooperative flying aircraft while there is no external refractivity information such as radiosonde data.