In Wu et al. (2003), a newly proposed centroid-relative track, with the position weighting based on the steering flow induced by the potential vorticity (PV) anomaly associated with the other storm, is laid out to highlight the binary interaction process. Moreover, based on the piecewise PV inversion, the method provides a means to quantitatively evaluate how the binary tropical cyclones interact with each other. As a follow-up work of Wu et al. (2003), here we study the binary interaction between Typhoons Fengshen (2002) and Fungwong (2002), and the impact of the large-scale flow fields on their motions. The impact of different data and resolutions on the evaluation of the binary interaction based on the PV method is also investigated. The binary interaction between Fengshen and Fungwong is also examined from the meso-scale numerical model simulations. With different initial conditions in bogusing both/either storms, the sensitivity of the vortices characteristics on the binary interaction is demonstrated. Such result sheds lights on the importance of the initial vortex structure in the binary-interaction process.