中文摘要：

为 3D 城市建模的 OGC 标准广泛地在越来越多的应用被使用。它定义详细(到有增加精确性和结构的复杂性的 LoD4 的 LoD0 ) 的五个连续层次，在哪个 LoD3 包括所有外面的外观和几何细节并且随后要求许多存储空间。新 LoD 与象窗户，门以及更小的 fa 一样的 LoD3 模型和开的目标的外面的壳作为壳模型被介绍 ? 果汁饮料目标被投射到墙上。在这份报纸，用户调查被介绍。这的结果调查壳模型能几乎给用户的表演象 LoD3 模型的一样的视觉印象。Furthermroe，算法被开发从 LoD3 提取壳模型模型。实验证明这个壳模型能减少原来的 LoD3 模型的多达 90% 存储。因此，一方面，它能为一个 LoD3 模型被用作一个代用品为小显示上的可视化。在另一方面，它能在 CityGML 被当作详细(SLoD3 ) 的分段，自从它几乎保留信息的一样的数量，但是要求少得多存储空间。

英文摘要：

The OGC standard for 3D city modeling is widely used in an increasing number of applications. It defines five consecutive Levels of Detail （LoD0 to LoD4 with increasing accuracy and structural complexity）, in which LoD3 includes all exterior appearances and geometrical details and subsequently requires much storage space. A new LoD is introduced as shell model with the exterior shell of the LoD3 model and the opening objects like windows, doors as well as smaller facade objects are projected onto walls. In this paper, a user survey is presented. The results of this survey show that the shell model can give users almost the same visual impression as the LoD3 model. Furthermroe, algorithms are developed to extract the shell model from LoD3 model. Experiments show that this shell model can reduce up to 90% storage of the original LoD3 model. Therefore, on one hand it can be used as a substitute for a LoD3 model for the visualization on small displays. On the other hand, it can be treated as a sub-level of detail （SLoD3） in CityGML, since it retains almost the same amount of information but requires much less storage space.