GPS receiver can receive accurate and precise information to nano second. It can be used to forecast compendium of satellite location in the next few months to predict star calendar, used to calculate coordinates in satellite  positioning, precision is to ten meters (each satellite is different, changed at any time); And GPS system information, such as satellite condition and so on.
GPS receiver to yards of measurement can get satellite receiver distance, due to diversionary receiver satellite clock error and atmospheric transmission error so called the pseudorange. To OA yards of measured pseudorange called UA yards pseudorange, precision is about 20 meters, to P yards of measured pseuorange called p yards pseudorange, precision is about 2meters.
For received signal of satellites, GPS receiver will decode or adopt other technology. After removing the information modeled in carrier, it can return to carrier. Strictly speaking, the carrier phase should be called carrier clap frequency phase. It is received by the Doppler frequency influenced of satellite signal carrier phase and receives this machine oscillations produce signals phase difference. General in the receiver clock determine precessed moment measure, to maintain a satellite signal tracking, can record the phase change value, but when begin to observe the receiver and satellite oscillator initial phase is can not get, starting precessed phase integer is also unknown, namely the whole week fuzzy degrees, only as parameters for calculating in data processing. Phase observation data of high precision to mm, but the premise is to work out a full week fuzzy degrees, so only in relative positioning ,and have a period of continuous observation value can use the phase observation data, and to achieve superior meter scale positioning accuracy of also can adopt phase observations.  
According to the localization way, GPS positioning is divided into single point positioning and relative location (differential positioning). A single point is according to the observation data from receiver to determine the receiver position way, it can use pseudorange observation to measure, which can be used in cars or boats’ outlined navigation and positioning . Relative positioning (differential positioning) is a way based on more than two receiver’s observation data to determine the relative position between receiver points. It can be adopted pseudorange observation to measure, geodesy or engineering measurement shall be made phase observation value to carry out relative positioning.
In GPS observation amount contains the satellite and the receiver’s clock error, atmospheric propagation delay, multipath effect etc, in positioning calculation it will also be affected by satellite radio star calendar error, when carrying out relative positioning most public error was offset or weakened ,therefore positioning accuracy will rise greatly, double-frequency receiver can according to two frequency’s observed quantity to offset the the main error in the atmosphere ionosphere ., when high precision is required ,the distance between receiver is remote ,should choose double-receiver .
In positioning observation, if the receiver move relative to the earth’s surface, it is know as a dynamic positioning, as for transport of navigation and positioning accuracy is 30-100 meters pseudorange single point positioning, or used in city vehicle navigation positioning precision to meter scale pseudorange difference positioning (RTK), real-time differential positioning need data chain to transmit observation data of two or more stations together to calculate. In positioning observation, if the receiver is motionless relative to the earth’s surface, it is known as a stationary positioning, when carrying out controlling network and observing, the average uses this approach: observing by several sets receiver. ,it can exert mostly the GPS’s positioning accuracy, the receiver which specialize in using this purpose is called earth type receiver machine , which is the best kind receivers of performance. At present, the GPS can already enough to reach the crustal deformation observation accuracy requirement, and IGS perennial observation stations can constitute mm level’s global coordinates framework.