The double-ended measurement-based approach has been widely incorporated in the underground fault localization domain due to high localization accuracy. However, this approach generally requires costly GPS time receivers to synchronize the data at both ends, while the GPS would face satellite invisibility, atmospheric condition problems, and the installation constraint for deep underground cables. This paper proposes a zero-crossing point-based approach, where the zero-crossing point before the fault time from both ends of the cable is identified and calibrated to synchronize the measurements. With the proposed method, the measurements could be synchronized at a low cost without a GPS device. The performance of the proposed technique is evaluated via simulations of an underground cable system modeled in PSCAD, followed by a discussion on results.