High precision GPS can measure position in centimeter order. So, it may be utilized to measure waves at sea. However, there are some problems in high precision GPS measurements. For an example, it is impossible to measure waves at sea far from shore in quasi real time. And amounts of communication between the reference and observation points are quite big, and the communication cost is rather expensive. The author and others have developed a convenient method to measure ocean waves in quasi real time manner. In the present paper, a method to make real time measurements possible is discussed.