Original sentence: GPS has become a common-place aid to navigation around the world, and an useful tool for map-making and land surveying.Utlizing a constellation of at least 24 medium Earth orbit satellites that transmit precise radio signals, the system enables a GPS receiver to determine it's location, speed and direction
Edited sentence: More than 24 GPS satellites are in medium Earth orbit, transmitting signals allowing GPS receivers to determine the receiver's location, speed and direction.Since the first experimental satellite was launched in 1978, GPS has become an indispensable aid to navigation around the world, and an important tool for map-making and land surveying