Viewshed analysis based on the regular grid digital elevation model (DEM) is one of the basic functions of geographic information systems. Traditional viewshed analysis algorithms are mainly carried out in a geospatial coordinate system, that create complexities when it is necessary to accurately express a perspective relationship. Moreover, it can only reduce the amount of calculation by using approximation methods, which result in decreased accuracy. We found that the error ratio of approximation algorithms is low but uneven and thereby highly likely to result in continuous area visibility errors. Despite the quality of DEM data having improved significantly in the last decade, traditional approximation algorithms have been unable to take full advantage of the improved data. Finding a fast and accurate algorithm has therefore become an urgent task. This study takes a new perspective to solve this problem by establishing a ‘proximity-direction-elevation’ (PDE) coordinate system and proposing a PDE spatial reference line (PDERL) algorithm within it. Many experiments prove that the accuracy of PDERL is the same as the R3 algorithm and its speed is about half that of the XDraw and reference plane algorithms, but much faster than R3. Due to the speed of PDERL, it is now possible and practical to do an accurate large-area DEM-based viewshed analysis.

基于常规网格数字高程模型（DEM）的视域分析是地理信息系统的基本功能之一。传统的视域分析算法主要在地理空间坐标系中执行，当需要准确表达视点关系时会产生复杂性。而且，它只能通过使用近似方法来减少计算量，从而导致精度降低。我们发现，近似算法的错误率低但不均匀，因此极有可能导致连续的区域可见性错误。尽管近十年来DEM数据的质量有了显着提高，但是传统的近似算法仍无法充分利用改进后的数据。因此，找到一种快速，准确的算法已成为当务之急。这项研究通过建立“接近方向-高程”（PDE）坐标系并在其中提出PDE空间参考线（PDERL）算法，以解决该问题的新观点。许多实验证明PDERL的精度与R3算法相同，并且其速度约为XDraw和参考平面算法的一半，但比R3快得多。由于PDERL的速度，现在可以进行精确的基于DEM的大面积视域分析。许多实验证明PDERL的精度与R3算法相同，并且速度约为XDraw和参考平面算法的一半，但比R3快得多。由于PDERL的速度，现在可以进行精确的基于DEM的大面积视域分析。许多实验证明PDERL的精度与R3算法相同，并且其速度约为XDraw和参考平面算法的一半，但比R3快得多。由于PDERL的速度，现在可以进行精确的基于DEM的大面积视域分析。