Study Of Differential Correction Method Of Long Wave Ground-wave Propagation Delay

The ground-based long wave navigation/timing system is an important part of the modern PNT(Positioning Navigation and Timing)system,which has good application value in the environment of star-based navigation/timing system rejection.High prediction/correction accuracy of the long wave ground-wave propagation delay is one of the key factors to ensure its performance.The propagation delay is not only related to the path distance from the long wave transmitting station to the receiving point,but also to factors such as weather and geoelectric parameters on the path,which will vary with these factors.The differential correction method can uniformly package the errors caused by these factors into the differential correction amount and broadcast it to users,achieving high-precision correction of propagation delay.Based on the problem of high-precision correction of long wave ground-wave propagation delay,this paper focuses on the differential correction method of the propagation delay of long wave ground-wave.The specific contents are as follows:(1)Based on the Integral equation method,the spatial variation of the propagation delay of long wave ground waves under different ground conditions is analyzed;Through research on measurement principles,system composition,measurement software,measurement strategies,etc.,a long wave ground wave propagation delay measurement system was established.Based on long-term measurement data,the time-varying characteristics and spatial correlation of propagation delay were analyzed.The results indicate that the propagation delay of different ground types varies with distance,and the propagation delay of the same receiving point exhibits daily and seasonal variation characteristics.The propagation delay between similar propagation environments and different receiving positions has strong spatial and geographical correlation,thus clarifying the feasibility of differential correction and laying the foundation for subsequent research on differential correction methods for different ground types.(2)A differential correction method based on theoretical extension is proposed for different types of local smooth paths,starting from the spatial geographical correlation and time-varying law and degree consistency of propagation delay in the same region.This method is based on the approximation of electrical parameters of propagation paths in the same region:a method for short distance propagation downward continuation based on the same ground type on the propagation path,and a long distance propagation downward continuation based on complex multi segment ground types.The validity of the continuation method is verified through experiments:compared with the Integral equation method,the theoretical continuation method can effectively improve the correction accuracy of time delay.(3)The differential correction method based on theoretical extension cannot fully consider the differences in terrain,features,and ground media in the differential correction area,resulting in significant differences between the predicted and measured results.In response to this issue,a differential correction method for propagation delay considering local non smooth paths is proposed based on the pan Kriging method.The time component of user point delay is compensated using the differential station as the reference point,and a time delay spatial component correction model that varies with latitude and longitude is established using the Universal Kriging method,thereby achieving the fitting of user point delay.Experiments have shown that the differential correction method based on Universal Kriging can effectively correct the delay prediction error caused by actual ground differences.The study on the correction method of the delay difference of long-wave ground wave propagation can provide some reference value for further improving the performance of the navigation/time-service system of long waveguide on the foundation.