When we measure the rolling and pitching such as fishing boats by GPS, it is necessary to set up at least 4 antennas. However, in most cases, around the antennas there are structures cut off the radio wave from the satellites. Therefore, we experiment the double use of GPS and GLONASS. The analysis was set up in an angle of elevation which cuts off the radio wave. As a result, when GLONASS was used together, the measurement result shows high accuracy even the elevation mask 25°. Consequently, it proves this method effective.