In GPS kinematics measurements, the baseline length has significant effect especially on the determination of the initial phase ambiguities. In VD (Variance Detection) method, the ambiguities are not required. In the present paper, the Effects of baseline length in VD method is discussed. The effects seem to be small RTK (Real Time Kinematics) and VD (Variation Detection) methods are combined, and measurements in very wide frequency range from the direct component to very high frequency component become possible. RTK and VD are used at long and short epoch, and they measure low and high frequency components respectively. The results by RTK and VD are then synthesized. This method has been applied to analyze motions of a buoy installing a GPS antenna and floating on sea surface. The results obtained in this way seem to give quite reasonable ones.