GPS stands for Global Positioning System. There is a system of satellites and receivers, allowing the people and institutions to learn how their exact position on earth. The heart of the system is based on 24 satellites into orbit, around the Earth twice a day. The devices are equipped with GPS receivers from at least some of the satellites and are in a position to the position very carefully. The first GPS satellite was launched in 1974 and the 24th was founded in 1994. The system is used by the US-defense and the use of the system is free for all people. New satellites are launched regularly replace the aging. As the technology has improved, the cost of GPS devices went, while the accuracy increases. The small portable GPS receivers have become very affordable, and the accuracy is amazing. Accuracy depends on several factors, but it may well be that a few meters! Additional land-based facilities can be used for improving the accuracy, if high accuracy is required.