This paper demonstrates the concept of very long duration coherent integration to estimate the trajectory of a moving object using Global Navigation Satellite System (GNSS) passive radar. The theoretical framework of the concept is presented followed by a practical demonstration. The purpose of this experiment is to replicate the scenario where a GPS signal is scattered by a low earth orbit object and due to the multipath, the indirect signal has different properties in comparison to the direct signal such as Doppler and phase. A proper estimation of the indirect signal can remove most of the modulation from the indirect signal and thereby observe the phase difference over time between the replica and the actual signal. The processing method and the predicted accuracy for the proposed system are shown. One of the two GPS receivers used in this experiment is kept stationary. The other is moving at a constant speed keeping a fixed distance from the reference receiver. The experiment was performed outdoors as well as indoors to confirm the utilization of GPS signal in this purpose and at the same time to prove the potential use of phase tracking for target localization. The complete estimation method is theoretically derived and then experimentally confirmed using experimental data collected from both outdoor and indoor tests.