Consciousness of the importance of accurate weather forecasts and climate modeling to manage our daily activities or to better understand physical processes of the atmosphere, many efforts have been made. Among the activity is monitoring and data collection, especially measurements of water vapor in the atmosphere, which was previously using conventional technology. One technology currently being developed and widely used in communications is Global Positioning System (GPS). The new GPS technology can be implemented in the field of meteorology in the early 1990s, where scientists have successfully developed a technique for determining the water vapor by exploiting the signal delays during the propagation from satellite to a receiver, which has significantly improve weather forecasting accuracy. The result of these efforts created a new science, namely GPS Meteorology.