There is evidence that shows that the majority of all vehicle accidents are caused by human error. This has been the major motivation for advancements in Advanced Driving Assistance Systems (ADAS). A driver's gaze can provide valuable information about the focus and intention of a driver. Therefore, determining the degree of driver awareness and scene perception, and predicting driver intentions can be valuable in the next generation of ADAS. To this end, we have instrumented a vehicle with a front-facing stereoscopic vision system on the roof of the vehicle and a camera gaze tracking system pointing toward the driver's face. These are two completely different systems with dissimilar sensing modalities. Data is collected separately from these systems and when calibrated can be used to estimate the Point-of-Gaze (PoG) of the driver. We present an efficient approach for the cross-calibration of the gaze tracker with the stereoscopic vision system. The experimental results show that our proposed cross-calibration technique obtains promising results for estimating Point-of-Gaze (PoG).