Research on Observer Sitting Problem in Terrain Visiblilty Analysis

Abstract

观察点设置问题是地形可视性分析中的一类重要问题，对该问题的研究可以在空间信息辅助决策、通信、旅游、野生动物保护等领域发挥重大作用。本文在对地形可视性分析中观察点设置问题现有研究成果总结和分析基础上对该问题展开深入研究。 首先，针对现有解决方法只从智能算法或地形数据表示方法单一角度进行分析和研究的局限性，提出了一种问题相关的智能算法和数据表示方法相结合的解决问题新框架。该框架考虑了解决观察点设置问题时智能算法的优点和数据表示方式的特点相互配合问题，目的是充分发挥二者各自的优势以提高观察点设置问题解决的准确度与效率。 其次，在深入分析观察点设置问题本身特点的基础上，结合隶属云理论的基本理论和方法，对经典模拟退火算法从退温函数设计、温度产生过程、状态生成过程三方面进行了问题相关的改进，提出了一种适于观察点设置问题的改进模拟退火算法(Improved Simulated Annealing algorithm, ISA)。该算法一方面保持了经典模拟退火算法的稳定倾向特性，保证了算法满足伴随退火温度的不断下降，对恶化的新状态越来越难于接受这一模拟退火算法的最基本特征；另一方面其退火温度的连续性随机变化特性和隐含的“回火升温”过程，则有利于算法有效拒绝恶化解，加速算法收敛，能够更好地满足观察点设置问题对于算法收敛速度的要求。 再次，在分析地形数据的精度、误差等因素对观察点设置问题的解决准确性和解决效率影响程度的基础上，提出了一种基于离散余弦变换的地形数据内插方法(Discrete Cosine Transformation Interpolation method, DCTI)。新方法将传统空域上的地形内插转换到变换域上进行，同时充分利用了离散余弦变换的熵保持特性和能量压缩特性，简化了变换域上的内插过程，提高了地形数据内插的效率和精度。DCTI方法与其他现有典型地形数据内插方法相比，对地形可视性信息获取的准确性和效率影响最小，为平衡观察点设置问题解决过程中时间效率和准确度之间的关系，最终有效地解决观察点设置问题提供了数据基础。 最后，从智能算法和地形数据相结合的角度出发，提出了一种基于ISA和DCTI相结合的观察点设置问题多分辨率处理方法(Multi-Resolution Processing method, MRP)。新方法将模拟退火算法的逐次退火特点和地形数据的多分辨率表示充分结合，达到了发挥算法数据相结合的综合优势的目的。与现有单纯基于模拟退火算法的解决方法相比，在问题解决准确度保持不变的前提下，基于MRP方法的观察点设置问题解决的平均耗时减少85%~95%，为实际工程应用问题的解决提供了一条重要途径。The observer sitting problem is an important problem in terrain visibility analysis. The research on this problem can play an important role in many fields such as spatial information aid decision, communication, tourism, wild animal protection, and so on. The research work in this dissertation is based on the conclusion and the analysis of existed research outcome for this problem. Firstly, aiming to solve the disadvantage that is the existed methods almost analyze this problem only from intelligent algorithm aspect or only from terrain data representation aspect, a new problem related solution framework is developed, which combines the algorithm’s and data’s analysis. This framework is to consider the cooperation of intelligence algorithm and data representation in the solving process for observer problem, and the aim is to improve the solving process’ accuracy and efficiency. Secondly, based on the characteristic of observer sitting problem itself and combining with the basic theory and method of subjected cloud theoretic, a problem related improved simulated annealing algorithm (ISA) has been proposed, whose improvements concludes the new annealing function, a new temperature generating process and a new status producing process. The ISA holds the same characteristics of traditional SA such as stable orientation and the acceptation of bad solution being harder and harder as the annealing temperature descending from one side, and has the specialties that are annealing temperature’s continuous and random variety and implied “Re-Annealing” process which can refuse the bad solution and accelerate the ISA’s conferencing speed from the other side. Thirdly, based on the influence degree of the factors such as the terrain data’s resolution and errors for the observer sitting problem’s solving accuracy, a discrete cosine transformation based terrain data interpolation method (DCTI) has been provided. The DCTI makes the interpolation process from traditional spatial domain to frequency domain and utilizes the “entropy preservation characteristic” and “energy compression characteristic”, which improve the interpolation’s efficiency and accuracy. Compared with other existed terrain data interpolation methods, DCTI has the smallest influence for the visibility information, which lays the foundation for the making balance between the efficiency and accuracy of observer sitting problem and solving this problem finally. Finally, from the combination of algorithm and data aspects, an ISA and DCTI based multi-resolution processing method (MRP) for observer sitting problem has been illustrated, which combining the simulated annealing algorithm’s characteristics and the terrain data’s multi-resolution representation, in order to get the aim that exerting the power of algorithm’s and data’s advantage. Compared with the existed method which is only based on the traditional simulated algorithm, the time cost of the MRP method reduces 85%~95% under the condition that the precision does not deteriorate, which provides an important approach to solve the actual engineering application problem