Conservation and planning in a 4D world

Three-dimensional models allow efficiently storing, analyzing and monitoring the geographical space around us by means of proper threedimensional objects which can be manipulated and queried. During the past decade or so, the collection of three-dimensional data has been facilitated and the data itself has been improved significantly, both qualitatively and quantitatively, using new geospatial methodologies such as 3D laser scanning and mobile mapping. Three-dimensional models have shown to be fruitful for a wide range of application fields concerning the urban environment (e.g., urban planning, ventilation, distribution of sunlight, noise pollution etc.). This paper takes these models one step further by the consideration of an additional fourth dimension viz. the temporal dimension. While in recent years significant progress in the development of 4D models has been made, the development of a fully integrated 4D model (3D + time) that can store, manage, visualize and analyze three-dimensional objects over time is still in its early stages. Drawing on recent studies, we will discuss potential urban applications of such integrated fourdimensional models, and, more specifically, their usefulness to simulate future and reconstruct past spatial configuration of urban environments and their implications for conservation and planning.