Introduction The primal interest of GPS (GNSS) is positioning, but we can monitor seismic wave with real-time kinematic processing. "GPS seismometer" based on real-time and high-rate GPS observation is helpful in great earthquake cases which regular seismometer (accelerator) is saturated with huge motions. GPS receivers keep observation data for a while even in blackout or damage of GPS antenna, and we can you such saved data for research of the mechanism of the earthquake. Many GPS (GNSS) networks are now transferring observation data in real-time (GPS Earth Observation Network (GEONET) in Japan, UNAVCO PBO network in the US., for example). We can monitor seismic wave of earthquakes with real-time by processing such data with real-time. Such real-time observation is beneficial for earthquake modeling and then to improve tsunami forecast.