城市峡谷环境下GNSS卫星可见性快速预测方法

城市峡谷环境下全球导航卫星系统（GNSS）性能显著下降，通过建立三维城市模型来预测卫星的可见性是该环境下进行GNSS性能分析最为常见的方法之一.为解决三维城市模型数据量大，使得卫星可见性预测计算消耗大量时间的问题，提出了一种快速预测城市中建筑是否遮挡卫星信号的方法.该方法通过分析三角面元的法向量方向、三角面元与用户的相对位置关系以及历史遮挡关系，减少了计算量并缩短了计算时间.仿真结果表明，该方法的相交判断计算次数为传统方法的7.21%，消耗的总计算时间为传统方法的22.38%，平均相对误差为1.89%.该方法具备计算效率高、准确性高的优点. 

Fast Prediction Method for GNSS Satellite Visibility Determination in Urban Canyons

Urban canyons always negatively affect the performance of global navigation satellite system (GNSS). Using 3D city models to predict GNSS satellite visibility is one of the most common methods concerning urban canyons. However, due to the extremely huge data of 3D city models, calculations involved in the prediction of GNSS visibility can be very time-consuming. To solve this problem, a method was proposed that was capable of quickly predicting the existence of urban buildings blocking GNSS satellite signals. This method reduced the burden of calculation and shortened the time for calculating by analyzing the direction of normal vector of the triangular patch, the relative positions of the triangular patch and the user, and the occlusion relation between two adjacent moments. A simulation of this method was conducted. The results show that the intersection calculation counts is only 7.21% of the traditional method, and the computing time 22.38%, while the average relative error is just 1.89%. In conclusion, this new method has a higher computing efficiency and higher accuracy.