The Klobuchar model has been widely used to correct the ionospheric delay in applications. However, the NVTEC(Nighttime Vertical Total Electron Content) of the Klobuchar model employs an empirical constant of 9 TECU(T...The Klobuchar model has been widely used to correct the ionospheric delay in applications. However, the NVTEC(Nighttime Vertical Total Electron Content) of the Klobuchar model employs an empirical constant of 9 TECU(Total Electron Content Unit) at L1 frequency. In this paper, the rationality and reliability of the nighttime constant setting are investigated using the GIM(Global Ionosphere Map) product of the IGS(International GNSS Service) from 1998 to 2015. Our study indicates that the suitable time span of NVTEC average in nighttime should be between 20:00 and 06:00 LT(local time). The NVTEC is highly correlated with seasons, having positive extremes in spring and autumn and negative extremes in summer through the mean values in all latitudes. In addition to seasonal dependence, solar activity in the solar cycle 23 strongly influences NVTEC as well and leads to its variation within a range between 25 and30 TECU in spring and autumn at solar maximum, which is about 1.5 times greater than that in summer and winter. The NVTEC also has a dependence on the latitude at solar maximum, with the mean value from 30 TECU in low latitudinal regions to 15 TECU in high latitudinal regions. Therefore, these results demonstrate that the nighttime VTEC has much greater deviations from the imperial constant in the Klobuchar model, and the newly estimated constant is expected to bring improvement to the predictability of the Klobuchar ionospheric delay model in nighttime.展开更多
电离层延迟是全球卫星导航系统(GNSS)的主要误差源之一。对于装配GNSS单频接收机的航空器,选择简单有效的Klobuchar广播电离层模型来改正电离层延迟误差,其修正率为50%~60%。针对45°(N)纬度带,提出了更高电离层修正需求。考虑到季...电离层延迟是全球卫星导航系统(GNSS)的主要误差源之一。对于装配GNSS单频接收机的航空器,选择简单有效的Klobuchar广播电离层模型来改正电离层延迟误差,其修正率为50%~60%。针对45°(N)纬度带,提出了更高电离层修正需求。考虑到季节因素对中高纬度地区电离层的显著影响,利用GIMs(Global Ionospheric Maps)分析了昼夜中TEC(Total Electron Content)的峰值和谷值随季节(年积日)的变化,建立了一种适用于45°(N)纬度带的Klobuchar-like电离层模型。该模型不增加广播模型系数,新模型的夜间和VTEC高峰时电离层修正率分别达到了82%和80%,表明在穿刺点集中的45°(N)纬度地区使用该模型可以更精确地描述该地区的电离层,帮助航空器实现更高精度的定位。展开更多
基金supported by National Key R&D Program of China (2016YFB0501503-3)the key project of National Natural Science Fund (41730108)the National Natural Science Fund (11103068)
文摘The Klobuchar model has been widely used to correct the ionospheric delay in applications. However, the NVTEC(Nighttime Vertical Total Electron Content) of the Klobuchar model employs an empirical constant of 9 TECU(Total Electron Content Unit) at L1 frequency. In this paper, the rationality and reliability of the nighttime constant setting are investigated using the GIM(Global Ionosphere Map) product of the IGS(International GNSS Service) from 1998 to 2015. Our study indicates that the suitable time span of NVTEC average in nighttime should be between 20:00 and 06:00 LT(local time). The NVTEC is highly correlated with seasons, having positive extremes in spring and autumn and negative extremes in summer through the mean values in all latitudes. In addition to seasonal dependence, solar activity in the solar cycle 23 strongly influences NVTEC as well and leads to its variation within a range between 25 and30 TECU in spring and autumn at solar maximum, which is about 1.5 times greater than that in summer and winter. The NVTEC also has a dependence on the latitude at solar maximum, with the mean value from 30 TECU in low latitudinal regions to 15 TECU in high latitudinal regions. Therefore, these results demonstrate that the nighttime VTEC has much greater deviations from the imperial constant in the Klobuchar model, and the newly estimated constant is expected to bring improvement to the predictability of the Klobuchar ionospheric delay model in nighttime.
文摘电离层延迟是全球卫星导航系统(GNSS)的主要误差源之一。对于装配GNSS单频接收机的航空器,选择简单有效的Klobuchar广播电离层模型来改正电离层延迟误差,其修正率为50%~60%。针对45°(N)纬度带,提出了更高电离层修正需求。考虑到季节因素对中高纬度地区电离层的显著影响,利用GIMs(Global Ionospheric Maps)分析了昼夜中TEC(Total Electron Content)的峰值和谷值随季节(年积日)的变化,建立了一种适用于45°(N)纬度带的Klobuchar-like电离层模型。该模型不增加广播模型系数,新模型的夜间和VTEC高峰时电离层修正率分别达到了82%和80%,表明在穿刺点集中的45°(N)纬度地区使用该模型可以更精确地描述该地区的电离层,帮助航空器实现更高精度的定位。
