Experimental Research Of GPS Height Error Based On Central Difference System

Because of its real-time,fast,high-precision,GPS is widely used in Measurement field,an experimental platform based on the central differential system is designed,which can realize the real-time location solution and the post-processing of the observed data.Through the platform,the experiment can analyze the factors and the influence results of the GPS elevation error.And proposed a new joint solution to meet the positioning accuracy requirements,has important theoretical significance and engineering application value.Firstly,this paper introduces the function and experimental platform of the center differential system,and clarifies its working flow and technical index.I determine the factors that may affect the GPS elevation positioning error as a baseline change and a delay factor.Based on the reason of error formation,a new solution of elevation error is proposed,which is the joint method formed by ionospheric model improvement and GPS height fitting.Secondly,the mathematic model of space error(satellite ephemeris error,tropospheric error,ionospheric error)caused by baseline change is simulated.The results show that the spatial error also increases with the increase of baseline length.Setting up the experimental platform for experimental verification,which collects datas of the active station and the base station taken at different distances.The calculation results indicate the size of the positioning error in the actual situation.The improving experiment results show that the effect of the elevation fitting in the joint solution is obvious in connection with the elevation positioning error causing by the baseline changes.Then,this paper analyzes the tropospheric and ionospheric error caused by delay,and uses the experiment platform analyze the positioning error for two different scenarios(Single-station delay,Double station delay).The results show that the influence of base station delay is longer than that of active station in the case of single station delay,and the station delay has a certain offsetting effect on the positioning solution,and the positioning error is lower than that of single station The improving experiment results show that the effect of the ionospheric model in the joint solution is obvious in connection with the elevation positioning error causing by the delay.Finally,in order to comprehensively analyze the relationship between the two influencing factors,we carry on the joint experiment of the baseline change and the delay,the experiment is divided into three parts(the base station delay time with the baseline length change,the active station delay time with the baseline length changes As well as the Double station delay and the change of the baseline length),the experimental results show that there is a certain coupling between the two influencing factors.The improved elevation error is reduced from 2.2-4.1m to 1.2-1.9m by using the combination solution of plane height fitting and ionospheric model correction.The results show that the system can meet the positioning accuracy needs of the system,getting a good practical effect.