区域NWP动态约束下的GNSS长基线实时大气延迟估计方法研究

The real-time estimation of high precision atmospheric delay for GNSS long-range baseline, speeding up the convergence of ambiguity resolution, is the premise of using long-range Network RTK technology to achieve high-precision positioning in western region without intensive reference stations. To estimate the atmospheric delay based on the triple-frequency observations and the NWP forecast information with high spatial and temporal resolution is one of the most promising technologies. However, the long-range baseline atmospheric delay estimation is still suffering from key issues of low accuracy, slow convergence and unreasonable NWP inversed Zenith Tropospheric Delay (ZTD) constraint information. In this project, the real-time atmospheric delay estimation method for GNSS long-range baseline with regional NWP dynamic constraint is studied: The GNSS triple-frequency optimal geometry-free combination and the ambiguity partial solution mechanism are used to improve and extend the ionospheric delay estimation method in the ambiguity search process; The error characteristics of ZTD inversed by NWP are analyzed, the dynamically adjustable correlation function between ZTD error, relative humidity and precipitation probability is constructed, and the corresponding stochastic model breaks the limitations of traditional single fixed constraint information.The high and low elevation angle satellite constellation mapping function-observation residual mathematical model is established and the real-time tropospheric delay search method for GNSS long-range baseline is developed. The research results of this project can effectively improve the accuracy and convergence speed of GNSS long-range baseline atmospheric delay, which has theoretical significance and application value.

实时估计GNSS长基线高精度的大气延迟，加快模糊度的收敛速度，是利用长距离网络RTK技术在缺少密集参考站网的西部地区实现高精度定位的前提，结合GNSS三频观测值及高时空分辨率的NWP预报资料估计大气延迟是最具潜力的技术之一。目前长基线大气延迟估计还存在精度低、收敛速度慢、NWP反演的天顶对流层延迟（ZTD）约束信息不合理等关键问题。对此本项目研究区域NWP动态约束下的GNSS长基线实时大气延迟估计方法：结合GNSS三频最优几何无关组合和模糊度部分解机制，改进并扩展在模糊度搜索过程中消除电离层延迟的方法；分析NWP反演ZTD的误差特性，构建其和相对湿度、降水概率间可动态调整的相关函数和随机模型，突破传统单一固定约束信息的局限；建立高、低高度角卫星映射函数-观测值残差的数学模型，发展GNSS长基线实时ZTD搜索方法。本项目研究成果有效提高长基线大气延迟的精度和收敛速度，具有理论意义和应用价值。

实时估计GNSS长基线高精度的大气延迟，加快模糊度的收敛速度，是利用长距离网络RTK技术在缺少密集参考站网的西部地区或远海实现高精度定位的前提，结合GNSS三频观测值及高时空分辨率的NWP预报资料估计大气延迟是最具潜力的技术之一。本项目针对长基线大气延迟估计存在的精度低、收敛速度慢、NWP反演的天顶对流层延迟（ZTD）约束信息不合理等关键问题展开研究：结合GNSS三频最优几何无关组合和模糊度部分解机制，改进并扩展了在模糊度搜索过程中消除电离层延迟的方法，并采用了GPS和BDS三频观测值检验了此算法的有效性，实验结果表明，采用此算法，长基线的模糊度可在10分钟内固定；比较了ECMWF和NCEP再分析资料反演ZTD的精度，分析了NWP反演的ZTD应用于网络RTK时存在的问题，分析了精度较高的ECMWF资料反演的ZTD的残差随温度、湿度、纬度、季节等因子变化的规律；提出了一种新的多因子约束下的NWP反演ZTD残差改正模型，一种基于GRNN模型的区域NWP对流层延迟改正方法和一种改进的低纬度地区NWP反演GNSS对流层延迟积分模型，明显提高了NWP反演对流层延迟的精度；提出了一种基于映射函数与残差数学函数模型的单历元高精度ZTD搜索方法，实现了长距离网络RTK的对流层延迟的快速估计及模糊度的快速固定。本项目研究成果有效提高长基线大气延迟的精度和收敛速度，具有理论意义和应用价值。