Monitoring And Study On Temporal Variation Properties Of Long-wave Ground Wave Propagation Delay

The land-based long-wave navigation timing system is an important part of the national positioning,navigation and timing system,and is also an important backup system for the satellite-based navigation timing system such as GPS and BeiDou in electromagnetic interference and physical occlusion environments.High-precision prediction of propagation delay is one of the key factors to improve its navigation timing accuracy.Based on the long-term monitoring of Pucheng long-wave timing station signal in Shaanxi province,we analyzed temporal variation properties of long-wave signals propagating along the surface,studied the correlation between propagation delay and meteorological factors,and established the prediction model for the variation of long-wave ground wave propagation delay with meteorological factors in this paper.The specific work is as follows:(1)According to the basic theoretical knowledge of long-wave ground wave propagation,the main factors affecting propagation delay are analyzed,and temporal variation properties of long-wave ground wave propagation delay are studied from the perspectives of meteorological factors such as temperature,humidity and vapor pressure.(2)The long-term monitoring system for long-wave ground wave propagation delay is built.According to the measurement principle of propagation delay,the hardware of the propagation delay monitoring system is built.According to requirements of the research content,the data acquisition software of propagation delay is designed and developed,and the measured data of propagation delay is processed.(3)Temporal variation properties of long-wave ground wave propagation delay are analyzed and the prediction model of propagation delay is established.Temporal variation properties of propagation delay are analyzed from three aspects:the diurnal variation of propagation delay,the seasonal variation of propagation delay and the correlation between propagation delay and five meteorological factors including temperature,humidity,vapor pressure,visibility and wind velocity.In addition,the prediction model of propagation delay considering only the temperature and considering comprehensive effects of multiple meteorological factors is established by using the least squares method and BP neural network method,respectively.By comparing measured values with predicted values of propagation delay,it is concluded that the prediction effect of the propagation delay prediction model established by considering comprehensive effects of multiple meteorological factors is better.The monitoring and study on temporal variation properties of long-wave ground wave propagation delay in this paper can provide some reference value for the further study of high-precision land-based long-wave navigation timing system.