Navigation satellites are one of the most useful inventions since the wheel. They were developed in the late 1950's, when ships needed to know exactly where they were at a given time. You can't just find your accurate position by looking out of the window, in the middle of the ocean. Today, navigation satellites are one of the most helpful tools for sailors, military, secret services and cartographers. They are now more advanced, and have a huge impact on our society.
Before navigation satellites were invented, navigation was not developed. It was impossible to find out your exact coordinates when you were sailing. It was also impossible to find out other ships' coordinates or where coral reefs were. Sailors couldn't navigate at night and often crashed into other ships, which may have caused sea pollution. Without navigation satellites, it was also impossible to monitor the Earth, or use the Global Positioning System.
Navigation satellites helped us solve this problem by developing our navigation. They help us find any existing coordinates on Earth, navigate at night, avoid ship crashes and monitor the Earth. Basically, they help us navigate in a much more comfortable and quicker way.
Today, most of the navigation satellites in the world use time and distance to determine a location. Early on, scientists recognized a formula that, given the velocity and the time required for a radio signal to be transmitted between two points, the distance between the two points can be recorded on a computer. The calculation must be done very accurately, and the clocks in the navigation satellite and in the Earth-based receiver must be synchronized- they must be telling exactly the same time. If they are synchronized, then the time it takes for a signal to travel can be...