地磁导航是利用地球上任意一点的磁场大小和方向进行匹配定位以实现导航的技术,与卫星、惯性、地形和无线电等导航手段相比,具有隐蔽性好、使用便捷、实用范围广等优点,在水下、室内和地下等空间具有广阔的应用前景。随着我国经济的快速发展,高速铁路深入到国家的各个角落,高铁为经济发展和人民出行带来便利的同时,却对地磁匹配导航区的地磁背景场测量带来了不利影响。高铁及其附属设施（如铁轨、电线杆、输电线、路灯、路栏等）,会对磁力测量带来非常大的干扰,为了得到比较纯净的地磁背景场数据,需要测量获取高铁对于磁场环境的影响数据,从而对干扰磁场进行补偿。本文设计野外试验,在距离高速铁路100m内的不同位置设置测点,利用Overhauser高精度磁力仪,首次获得了高铁这种新型的交通工具在运行时对地磁背景场的影响数据;同时,勘选地磁环境变化平稳地区,架设地磁日变站,测量获得地磁日变数据;提出采用低通数字滤波技术来计算地磁日变站基值,可以更好地消除日变数据中的十分之几秒到几小时不等的各种短周期变化,获得更加精确的地磁日变改正值;对试验数据进行日变改正,分析测量数据的变化规律,从而获得高铁运营对地磁背景场的影响结果。本文的研究成果,不仅可以为地磁匹配导航区中地磁背景场图的构制提供参考,而且可以为磁力测量设备试验鉴定、磁力测量仪器定标场地选取及后期建设、新建地磁台站站址勘选及后期建设、磁力测量生产作业中干扰磁场补偿等提供技术支撑。

为实现航磁标量和矢量数据的向下延拓,提高延拓结果的应用效果,本文在传统插值-迭代法的基础上,增加了延拓数据滤波处理环节,进而提出了改进插值-迭代法,并利用模拟和实测数据验证了新方法的有效性,实验结果表明:（1）传统插值-迭代法存在明显的高频噪声放大特点,迭代计算导致误差快速累积,观测数据中无噪声时标量和矢量数据延拓误差小于0.25nT,观测数据中含有噪声时标量和矢量数据的延拓误差约为添加噪声的4倍;（2）改进插值-迭代法在迭代过程中能够有效抑制高频噪声影响,减少迭代误差,提高向下延拓结果的精度,观测数据中含有噪声时标量和矢量数据的延拓误差略小于添加噪声,其中标量数据延拓精度优于2nT,矢量数据延拓精度优于13nT;（3）将改进插值-迭代法应用于内蒙古某实验区的实测数据向下延拓,取得了有益成果,其中航磁标量数据延拓精度优于7.6nT,东向分量数据延拓精度优于12.5nT,北向分量数据延拓精度为33nT,垂直分量数据延拓精度优于17.3nT。

A virtual geomagnetic diurnal station has been used to calculate the diurnal variation correction data in the regions where the ground magnetic surveying is difficult to be implemented, and this will provide diurnal variation correction data for the airborne geomagnetic measurement. The weight factors of reverse distance weighting (RDW) method usually use the empirical values, which have limitation in the application of different testing areas. The correlation coefficients are proposed and introduced to calculate the weight factors iteratively, which are more practical. The numerical experimental results show that the diurnal variation correction data, whose weight factors are calculated by correlation coefficients, have a higher precision. The precision of northern component X and horizontal component H are superior to 2.2 nT, eastern component Y and geomagnetic total intensity F are superior to 1.0 nT, vertical component Z is superior to 0.3 nT, and geomagnetic declination D and geomagnetic inclination I are superior to 10″. Therefore, the diurnal variation correction data in higher precision can be provided for the airborne scalar and vector geomagnetic measurement in the regions where the ground magnetic surveying is difficult. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

At present, China’s BDS-3 basic system has been completed and started to provide global services. However, the accuracy of satellite clock difference seriously restricts the service performance of BDS, and the performance of satellite atomic clock directly determines the accuracy of satellite clock difference. To solve this problem, this paper studies and evaluates the performance of BDS-3 spaceborne atomic clock in detail. Based on the precision satellite clock data of BDS from August to October 2019, using the median method, this paper pre-processed the BDS-2 and BDS-3 data, and obtained the fitting residuals of the spaceborne atomic clock by using the polynomial fitting method. In addition, in the frequency domain, this paper studied and compared the periodic characteristics of spaceborne atomic clock of BDS-3 and BDS-2. The experimental results show that all the clock difference of BDS show significant periodic characteristics, and the main period of BDS satellite clock difference is 12 h and 24 h respectively, corresponding to 0.5 times, 1 times and 2 times of each satellite orbit period. Compared with BDS-2, the main period term of BDS-3 is clearer, more accurate and more stable. In addition, the experiment also shows that the period of satellite clock difference is different in different orbits and in the same orbit the periodic term of satellite clock difference is also different. The period term of BDS-3 is consistent with that of other MEO satellites. Finally, the performance analysis of BDS atomic clock shows that the performance of BDS-3 hydrogen atomic clock is better than that of BDS-2 atomic clock.
© 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

目前,航空磁力测量是快速获取陆地和近海区域高精度高分辨率地磁场信息的非常有效的技术手段。利用航空磁力矢量仪试样机在200m和700m相对飞行高度的东西、南北各20条交叉测线的400个交叉点不符值,完成了对航空磁力矢量仪试样机的飞行测线数据的精度评估。结果表明,试样机在飞行测线上地磁场总强度的测量精度在200m高度和700m高度为1nT,连续飞行的三分量精度在10nT以内,非连续飞行的三分量精度在20nT以内。

The prediction accuracy of satellite clock bias (SCB) directly affects the performance of navigation system. According to the spectrum analysis method, the periodic characteristics of satellite clocks are analyzed, and using precise SCB data of BDS/GPS satellite the prediction tests are conducted, and then we build the forecast model considering periodic items. Based on this, the influence of the number of periodic items on the result of SCB prediction is analyzed. The effect of SCB prediction between periodic term model and quadratic polynomial model is compared, and the SCB prediction performance of different types of satellites is summarized. Experimental results show that the periodic variation of satellites are significant. The periodic items of BDS are 24, 12 and 8 h, and the periodic items of GPS are 24, 12 and 6 h. The number of periodic items affects the prediction results. The prediction accuracy of BDS using 2–3 main periodic items is the best, and the prediction accuracy of GPS using 3–4 main periodic items is the best. Compared with the quadratic polynomial prediction model, the prediction accuracy of the proposed model with additional periodic items can be improved by 1–6 ns.
© 2018, Springer Nature Singapore Pte Ltd.