A mobile device in a cellular communication network collects three or more round-trip time (RTT) measurements for a single active cell. The collected RTT measurements are transmitted to a location server. The location server uses the transmitted RTT measurements to calculate a GNSS position of the single active cell. One or more of the transmitted RTT measurements are taken by the mobile device, and/or are collected from other mobile devices in the single active cell. The transmitted RTT measurements are collected at different GNSS fixes in the same single active cell. The mobile device location stamps the collected RTT measurements using corresponding GNSS fixes, and transmits to the location server using a NML. The location server calculates the GNSS position of the single active cell using location stamped RTT measurements in the received NMLR to refine an associated reference database periodically or aperiodically.