中文摘要：

在地形可视性分析中,R3视域算法和参考面算法是两种重要的算法。在对两种算法的计算结果进行对比后,可以发现参考面算法的计算结果总要比R3算法的结果偏高。本文在此对比的基础上继续深入分析造成这种结果差异的本质原因,进一步解释了这种差异多表现在山体和沟壑等地形起伏较大的区域原因,并得出结论：这种结果差异不能作为两种算法精度相互评价的依据。

英文摘要：

As we know,R3 and reference plane are important viewshed algorithm in visibility analysis. After compared with two algorithms in this paper,we find that the result computed by reference plane viewshed algorithm is higher than by R3 viewshed algorithm. Based on the contrast of these results,the key reasons caused the results＇ difference will be analyzed in this paper. Finally,there is a conclusions： if evaluating the two algorithms＇ accuracy mutually,the difference can＇t be become the reason,for example R3 algorithm is not more accurate than reference because of the difference.