As the interest in unmanned vehicles increases, much research is under way to improve their accuracy of location estimation. Among them, RTK-GPS is the most used in using GNSS. The RTK-GPS has been widely used for surveying and mapping. So it was usually used in static or low speed conditions. The RTCM message, which is the core of RTK-GPS, is usually provided and used in 1Hz. In this paper, we investigate whether the current transmission rate of RTCM message is good for unmanned vehicle (UV) usage and also analyze whether increase of the RTCM message transmission rate is possible. Then, we examine the effect of UV speed and RTCM message transmission rate on RTK-GPS. Finally, we discuss the challenges and solutions of increasing the RTCM message transmission rate.