Techniques to determine a position estimate for a wireless terminal. An accurate position estimate for the initially obtained (e.g., based on a first (accurate) position determination sub-system). For each of one or more transmitters (e.g., base stations) in a second (less accurate) position determination sub-system, an “expected” pseudo-range is computed based on the accurate position estimate for the terminal and the base station location, a “measured” pseudo-range is also obtained, and a pseudo-range residual is then determined based on the expected pseudo-range and the measured pseudo-range. Therefore, to determine an updated position estimate for the terminal, measured pseudo-ranges are obtained for a sufficient number of transmitters. The measured pseudo-range for each base station may be corrected based on the associated residual. The updated position estimate is then determined based on the corrected pseudo-ranges for these transmitters.