利用Helmert转换模型,首先对起算点先验坐标可能存在的粗差进行探测并剔除,其次依据剩余起算点坐标的相似变换构建最小约束条件,最后实现整网坐标框架的确定.选取中国境内及周边IGS站和陆态网GNSS基准站单周观测数据,采用IGS站ITRF2014坐标分别构建参数加权约束、最小约束、顾及IGS站先验坐标误差的Helmert模型约束,然后利用不同的基准约束平差方法获取整网坐标成果.实验结果表明,利用Helmert模型能有效削弱起算点坐标粗差对网形扭曲的影响,在一定程度上可提高区域参考框架的精度和可靠性.

The observation of GNSS monitoring in mountain area is often severely restricted by tropospheric delay, resulting in the reduction of positioning accuracy. In this paper, a constraint method for the prior information of tropospheric delay at ground points is put forward to realize the fast and high-precision double differenced observation of the peak. This method can make full use of the augmentation information of tropospheric delay of long-distance ground station, the observation duration decreased notably, increase the stations range of mountain monitoring, so as to reduce costs of mountain measurement task. In this paper, the applicability is verified by the spatio-temporal characteristics of observation duration, baseline distance and number of ground stations. The experimental results indicate that takes the high-precision tropospheric delay into account as prior constraints, acquired by long-time GNSS observation at ground stations, which can weaken the influence of tropospheric delay residuals efficiently induced by large heights different between different stations and improve success rate of ambiguity fixing, and can achieve tropospheric delay parameter estimation and fast high-precision positioning of peak monitoring points. Compared with the unconstrained method, the accuracy of each coordinate component is improved after the troposphere prior constraints, and the accuracy of the elevation direction is improved significantly.