Research On The Application Of Global Ionosphere Map In Singlefrequency Precise Point Positioning

The production cost of single-frequency GNSS receivers is low,and there are a large number of users in production and life scenarios such as mobile navigation,transportation,and precision agriculture.However,when single-frequency receivers are used for high-precision positioning,they cannot handle ionospheric delay as efficiently as dual-frequency receivers,resulting in low positioning accuracy and long convergence time,which limits its wider application,especially the application of realtime high-precision positioning.The method of estimating ionospheric delay parameters and adding high-precision constraints to deal with ionospheric delay can speed up positioning convergence.With the development of the high-precision grid ionospheric model,it plays an increasingly important role in correcting the ionospheric delay error in single-frequency positioning,but its performance needs to be comprehensively evaluated.This paper based on the the ionospheric constrained single-frequency precise point positioning principle,has perfected the ionospheric constrained single-frequency PPP software,and realized the use of GIM products from multiple centers to constrain single-frequency precise point positioning.Based on this,comprehensively evaluated the effect and applicability of correcting ionospheric delay the of multiple final and rapid GIM product.According to the geomagnetic 3h-Kp index,select the most active and calmest month of the ionosphere in the recent solar cycle,and screen the IGS observatories that did not participate in the calculation of GIM products during the experimental period as the validation station,the use of the GIM final products and rapid products of the seven centers as constraint to process observation data from validation station was carried out in two periods when the ionospheric activity was different.And kinematic experiment was designed to collect kinematic data and use GIM products as the constraint to process.The results of static and imitation kinematic positioning show that GIM products can speed up positioning convergence as constraints in most areas of mid-high latitudes;relatively dense IGS tracking stations are evenly distributed in some low-latitude areas,and the effect of GIM products in correcting ionospheric delay errors in this area even better than some mid-to-high latitude regions;the use of GIM final products and rapid product constraints can shorten the positioning convergence time by about 10%?43% and 12%?25% respectively;the area where GIM final products used as constraints can speed up the positioning convergence are wider than rapid products,and the effect of accelerating positioning convergence is better than that of rapid products.In kinematic positioning,additional ionospheric constraints can speed up the initial convergence of the positioning and improve the positioning accuracy to a certain extent,and the positioning results of the final product and the rapid product constraints have little difference.This article recommends the GIM final products of the CAS and CODE analysis centers,and the rapid products of the CAS,CODE and UPC centers for singlefrequency precise point positioning to constrain the ionospheric delay parameter estimation,provides a reference for the use of low-cost receivers for high-precision positioning,which helps low-cost receivers to be more widely used.