A prototype temporal GIS for multiple spatio-temporal representations.

Introduction

Is geographic reality changing gradually or rapidly, continuously or discretely? How do human activities interact with the environment? Temporal information is useful in answering these questions and to understand better the dynamic world. After almost forty years of development, current GIS are still static in nature and ineffective at working with spatio-temporal data (Hornsby and Egenhofer 2000; McMaster and Usery 2004; Worboys and Hornsby 2004). Because of the complexity of spatio-temporal data, many spatio-temporal representations have been proposed for different types of data (Yuan 1997; Sengupta and Yan 2004; Worboys 2005). However, only a few, such as the sequential snapshots approach, are supported by existing GIS (Langran 1992; Peuquet and Duan 1995). In order to visuallze spatio-temporal data, the person who proposes a STDM usually has to develop a temporal system to work with that specific model (Wachowicz 1999; Koncz and Adams 2002). As a result, although certain GIS with temporal capabilities have been introduced for specific STDMs, they can only work with data represented in that specific model. In reality, we usually need to work with spatio-temporal data represented in different data models. For example, temporal data of transportation, population, and land use are required for post-analysis of the planning of a highway, and these data may be represented in different data models. Therefore, there is a need for temporal GIS to work with spatio-temporal data represented in different models.

This paper studies temporal GIS capable of working spatio-temporal data represented in different data models and introduces a prototype temporal GIS. The integration of various STDMs is based on common spatial and temporal reference systems. By providing temporal information, this technology will enable many GIS applications to perform spatio-temporal query, visualization, and analysis, thereby contributing to moving traditional static GIS toward temporal GIS.

The remainder of this paper is organized as follows. The following section discusses why temporal GIS should be based on common spatial and temporal reference systems and how to design and develop a temporal GIS capable of working with spatio-temporal data represented in different data models. This is followed by a case study, where I briefly describe three STDMs, and introduce a prototype temporal GIS to work with these data models. The paper concludes with discussion and recommendations.

Temporal Gig

How Does Temporal GIS Work with Multiple Spatio-Temporal Representations?

Before this question is answered, another should be asked--how does traditional GIS work with multiple spatial data models? In Figure 1 there are two graphs showing spatial data represented in different spatial data models--vector and raster. The top layers are transportation data in vector form and the bottom layers are land use/land cover in raster form. All datasets in the figure are correctly registered in one coordinate system. The transportation and land use/land cover data in Figure 1a (left) cover a different area and have no overlap, while those in Figure 1b (right) cover the same area, or at least have some overlap in space dimension. In traditional GIS, the two datasets on the left cannot overlay and work together, while those on the right can. For example, one may overlay transportation and land use data of Atlanta, Georgia, for visualization or spatial analysis, but it will not combine transportation data of Atlanta, Georgia, with the land use data of Las Vegas, Nevada. In other words, a map window of GIS only shows objects and/or fields within one spatial region. Therefore, traditional GIS integrate multiples spatial data models, including fields and objects, based on common spatial reference system.

[FIGURE 1 OMITTED]

Since there are analogies between time and space (Galton 2001; 2004), I propose to integrate multiple spatio-temporal representations based on common spatial and temporal reference systems. In other words, a map window of temporal GIS displays spatio-temporal data valid not only at the same location in space, but also at the same location in time. For example, temporal GIS will put 1990 land use and 1990 population data together; but it does not often put land use data at 1960 together with population data at 2000 for analysis, unless both datasets are valid at a certain time. In the temporal GIS presented in this paper, the map window visually represents geographic objects and/or fields valid at the same location in both space and time.

Figure 2 presents spatio-temporal data covering the same spatial area, and which are valid at a) different and b) common time periods. As in Figure 1, the top layers are transportation data in vector form and the bottom layers are land use data in raster form. These two types of data are represented in different STDMs. All datasets cover the same spatial region. In addition to the XY spatial coordinate system, there is a time axis in Figure 2. On …