Virtual 3D city models usually evolved from other geodata sets and were not set up from scratch. As traditional geodata used to be only 2D and 2.5D for a long time, 3D city models started naturally with 3D building models. On the one hand, this has a technical aspect, because buildings, especially when being modelled in a higher level of detail, can neither be described in 2D nor in 2.5D. On the other hand, this is because buildings form the identity of a city. This can clearly be seen when looking at the sights of a city, which are usually historic or modern buildings, such as cathedrals, palaces, skyscrapers, etc. In many cases, the 3D building models themselves were called 3D city model, because they are so essential for a virtual 3D city. A common way to create a 3D city model beyond the buildings is to combine them with 2D (i.e. city map) and 2.5D (i.e. digital terrain model) GIS data sets. In case the models are used for visualization purposes only, the city map is normally used in a raster format as texture on the terrain model. In case semantic 3D models are aimed for in order to use them for analysis, 2D city map vector data are raised, e.g. to a terrain model or a 3D point cloud. Continuative steps to enrich the virtual scene are often adding 3D bridge models or vegetation created by a set of template tree models and point-based tree information with height and tree top diameter as attributes to the point information. Problems usually occur due to temporal incoherence of the data sets. While for visualization purposes, these problems might be neglectable, they have to be tackled in case the resulting 3D city model should serve as basis for a city information model. In this paper, we want to discuss a new strategy in producing the 3D city model as well as other geodata products of Vienna which completely rethinks and reverses the geodata workflows currently in use. The centre of the strategy is to use the existing three-dimensional surveying and mapping data and potentially further input data to directly model a Digital geoTwin—a virtual, semantic 3D replica of all elements and objects of the city. Digital twins are an upcoming concept of digitizing elements, processes and systems of physical entities in order to create living digital simulation models as collaborative platform for many disciplines. We chose to add the prefix geo to our neologism Digital geoTwin to emphasize our focus on the geodetic, geometric aspect of creating semantic geo-objects for a digital twin. This Digital geoTwin should allow to derive other needed GIS data sets from it, which in corollary ensure full temporal coherence for all derived products. By linking the objects of the Digital geoTwin with further data and information, e.g. census data, socio economic data, energy consumption data, maintenance management data, etc., a city information model can be built up to serve as basis for a living digital twin of Vienna.

虚拟3D城市模型通常是从​​其他地理数据集演变而来，而不是从头开始建立的。由于传统地理数据在很长一段时间内仅是2D和2.5D，因此3D城市模型从3D建筑模型自然地开始。一方面，这具有技术方面的问题，因为尤其是在以更高的详细程度建模时，建筑物既不能以2D形式描述也不能以2.5D形式描述。另一方面，这是因为建筑物构成了城市的身份。在查看城市景点时可以清楚地看到这一点，这些景点通常是历史或现代建筑，例如大教堂，宫殿，摩天大楼等。在许多情况下，3D建筑模型本身被称为3D城市模型，因为它们对于虚拟3D城市至关重要。在建筑物之外创建3D城市模型的一种常见方法是将其与2D结合（即 城市地图）和2.5D（即数字地形模型）GIS数据集。如果模型仅用于可视化目的，则通常以栅格格式将城市地图用作地形模型上的纹理。如果要使用语义3D模型进行分析，则可以将2D城市地图矢量数据提升到例如地形模型或3D点云。丰富虚拟场景的连续步骤通常是添加3D桥梁模型或由一组模板树模型和基于点的树信息（以高度和树顶直径作为点信息的属性）创建的植被。问题通常是由于数据集的时间不连贯而发生的。尽管出于可视化目的，这些问题可能是可以忽略的，但必须解决这些问题，以防生成的3D城市模型应作为城市信息模型的基础。在本文中，我们要讨论一种产生3D城市模型以及维也纳其他地理数据产品的新策略，该策略将完全重新考虑和逆转当前使用的地理数据工作流。该策略的中心是使用现有的三维测量和制图数据以及可能的其他输入数据直接对Digital geoTwin（城市的所有元素和对象的虚拟，语义3D副本）进行建模。数字孪生是将物理实体的元素，过程和系统数字化的一种即将出现的概念，目的是创建生动的数字仿真模型作为许多学科的协作平台。我们选择添加前缀 我们想讨论一种产生3D城市模型以及维也纳其他地理数据产品的新策略，该策略将完全重新考虑和逆转当前使用的地理数据工作流程。该策略的中心是使用现有的三维测量和制图数据以及可能的其他输入数据直接对Digital geoTwin（城市的所有元素和对象的虚拟，语义3D副本）进行建模。数字孪生是将物理实体的元素，过程和系统数字化的一种即将出现的概念，目的是创建生动的数字仿真模型作为许多学科的协作平台。我们选择添加前缀 我们想讨论一种产生3D城市模型以及维也纳其他地理数据产品的新策略，该策略将完全重新考虑和逆转当前使用的地理数据工作流程。该策略的中心是使用现有的三维测量和地图数据以及可能的其他输入数据直接对Digital geoTwin（城市的所有元素和对象的虚拟，语义3D副本）进行建模。数字孪生是将物理实体的元素，过程和系统数字化的一种即将出现的概念，目的是创建生动的数字仿真模型作为许多学科的协作平台。我们选择添加前缀 城市所有元素和对象的语义3D复制品。数字孪生是将物理实体的元素，过程和系统数字化的一种即将出现的概念，目的是创建生动的数字仿真模型作为许多学科的协作平台。我们选择添加前缀 城市所有元素和对象的语义3D复制品。数字孪生是将物理实体的元素，过程和系统数字化的一种即将出现的概念，目的是创建生动的数字仿真模型作为许多学科的协作平台。我们选择添加前缀地理到我们的新词新义的数字地理双床强调，我们专注于为数字双创建语义地理对象的大地，几何方面。该数字geoTwin应该允许从中导出其他所需的GIS数据集，从而必然确保所有导出产品的时间一致性。通过将Digital geoTwin的对象与其他数据和信息（例如普查数据，社会经济数据，能源消耗数据，维护管理数据等）链接起来，可以建立城市信息模型，以作为生活中的数字孪生的基础维也纳。