RTK Performance Analysis In City Area

The current satellite positioning systems(NAVSTAR/US GPS and GLONASS Russian)and the future European GALILEO,grouped under the generic term GNSS,allow any user to calculate his position in real time.They are based on the principle of spatial multilateration in which the unknown position of the user is determined by measuring the geometric distances separating its receiver from a set of satellites in orbit.BeiDou Navigation Satellite System(BDS)is constructed and operated by China independently.It has important significance in researching the real-time kinematic based on BDS and GPS.The fusion of multi-GNSS in data processing can increase satellites observed,improve the geometric configuration of satellites constellation,enhance the accuracy.The method for determining the geometric distance between receiver and satellite is to use the measure directly phase of the carrier of the received signal.This measure on the phase,which is much more precise than the measure on the pseudo-random code,is unfortunately ambiguous and it is necessary to be able to use it to fix this ambiguity beforehand.The location mode using the real-time phase,called RTK(Real Time Kinematic)is the most interesting mode.It makes it possible to achieve precisions of the order of a few centimeters on the position at a rate that is quite sufficient.This study explores the RTK attainable accuracy and repeatability underneath different satellite configurations and site conditions in a city area.Because at present there are only RTK mode,which is capable of giving us the high accuracy and defines various useful performance characteristics for carrier phase Ambiguity Resolution(AR),these parameters,including base-rover distance,AR reliability,RTK accuracy,availability and integrity,etc.,GNSS and particularly GPS and BeiDou systems are currently used in all geodetic applications to obtain a centimeter-level precise position.Such a level of accuracy is obtained by performing complex processing data on receivers and antennas,and by using precise corrections.Moreover,these applications are typically performed in open area environments and cannot be applied in constrained environmentsResults prove that the accuracy of RTK is more stable for the horizontal coordinates than the height,particularly when we use GPS/BeiDou data latency creates errors of a few millimetres.Positioning precision on the mm level is very precise in RTK which can be habitually attained when observing a sufficient number of satellites.GPS alone may not furnish the necessary geometry to correctly solve the ambiguities in a timely,necessary especially in city areas where satellites ratio decreases.That's why we used the combination system BeiDou and GPS.