Recently, utilization of position information by global navigation satellite system (GNSS) is expected in various fields. However, positioning accuracy is dependent on the measurement environment. Therefore, it is difficult to show uniquely the positioning accuracy. We apply the Sky View Factor (SVF) for estimation of positioning accuracy with GPS/BeiDou system. In particular, positioning accuracy is measured and evaluated at a place with SVF of 39.0%. By evaluating the influence of multipath for position accuracy, the number of visible satellites and multipath are trade-off. Also, we evaluate about the optimal elevation mask settings. And, we evaluate about the cause of positioning accuracy lowering. As a result, it can be said that the lowering in positioning accuracy can be divided into 3 cases. The first case is greatly affected by the number of visible satellites. The second is the case where the influence of the number of visible satellites is large or equivalent to multipath. The third is the case where the influence of multipath is large.