Peuquet, Donna J.

Abstract: Understanding the spatial and temporal characteristics of individual and group behavior in social networks is a critical component of visual tools for intelligence analysis, emergency management, consumer analysis, and human geography. Identification and analysis of patterns of recurring events is an essential feature of such tools. In this paper, we describe an interactive visual tool for exploring the visitation patterns of guests at two hotels in central Pennsylvania from 1894 to 1900. The centerpiece of the tool is a wrapping spreadsheet technique, called reruns, that reveals regular and irregular periodic patterns of events in multiple overlapping artificial and natural calendars. Implemented as a coordinated multiple view visualization in Improvise, the tool is in ongoing development through an iterative process of data collection, transcription, hypothesis, design, discovery, analysis, and evaluation in close collaboration with historical geographers. Numerous discoveries have driven additional data collection from archival newspaper and census sources, as well as plans to enhance analysis of spatial patterns using historic weather records and railroad schedules. Distributed online evaluations of usability and usefulness have resulted in feature and design recommendations that are being incorporated into the tool.

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Abstract: Representations historically used within GIS assume a world that exists only in the present. Information contained within a spatial database may be added-to or modified over time, but a sense of change or dynamics through time is not maintained. This limitation of current GIS capabilities has recently received substantial attention, given the increasingly urgent need to better understand geographical processes and the cause-and-effect interrelationships between human activities and the environment. Models proposed so-far for the representation of spatiotemporal data are extensions of traditional raster and vector representations that can be seen as location- or feature-based, respectively, and are therefore best organized for performing either location-based or feature-based queries. Neither form is as well-suited for analysing overall temporal relationships of events and patterns of events throughout a geographical area as a temporally-based representation. In the current paper, a new spatio-temporal data model is proposed that is based on time as its organizational basis, and is thereby intended to facilitate analysis of temporal relationships and patterns of change through time. This model is named the Event-based Spatio Temporal Data Model (ESTDM). It is shown that temporally-based queries relating to locations can be implemented in an efficient and conceptually straightforward manner using ESTDM by describing algorithms for three fundamental temporally-based retrieval tasks based on this model: (1) retrieving location(s) that changed to a given value at a given time, (2) retrieving location(s) that changed to a given value over a given temporal interval, and (3) calculation of the total area that has changed to a given value over a given temporal interval. An empirical comparison of the space efficiency of ESTDM and compressed and uncompressed forms of the 'snapshot' model is also given, showing that ESTDM is also a compact representation of spatio-temporal information.

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Abstract: The need for greater understanding of regional and global environmental processes and how mans activities are affecting hatural process dynamics is being viewed genreally with increasing urgency. The study of spatiotemporal dynamics is certainly not new, nor is it unique to the field of Geography. Tey, addressing current human and environmental issues requires empirical examination from a much broader and integrated perspective than our current representational techniques will allow. Current geographic data representational techniques are predominantly geared toward representation of static situations. Cartography has traditionally focused on the visible representation of a portion of the world at a specific point in time. Although GIS are intended to provide an integrated and flexible tool for analyzing large volumes of data, representations historically used in GIS are also geared toward a similar static view. Efforts to enhance the temporal capabilities of GIS have served to reveal many problems as a fundamental, conceptual level. This is also true of recent research by cartographers in the areas of scientific visualization and map animation. A representational framework that unifies temporal, as well as spatial and object (i.e., featur-related) aspects is described. This is an extension of the representational framework originally discussed by Peuquet (1988) and incorporates concepts from Perceptual Psychology, Artificial Intelligence and other fields. It is the goal of this research to provide a drawint-together of many concepts and ideas, many of which are well known on an individual basis, so that not only can analytical tools be improved, but also to provide a more common ground among various fields. The inclusion of time is shown to be a natural and obvious extension of the original, Dual framework. The new, Triad framework includes the definition of fundamental types of temporal relationships within this context. Some potential mechanisms for operationalizing the Triad framework are also discussed. These mechanisms include conceptual graphs and non-monotonic reasoning, which allow temporal as well as spatial patterns and cause-and-effect associations to be expressed as assertions, tested against observational data, and stored as information.

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Abstract: The study of spatiotemporal dynamics is certainly not new, nor is it unique to the field of geography. Nevertheless, addressing complex human and environmental issues such as global warming and human impacts on the environment requires empirical examination from a much broader and integrated perspective than can be accomplished with current techniques. Although Geographic Information Systems (GIS) are intended to provide an integrated and flexible tool for analyzing large volumes of data, they are historically geared toward the representation and analysis of situations frozen in time. Efforts to enhance the temporal capabilities of GIS have served to reveal many problems at a fundamental conceptual level. In order to address this problem, this paper presents a new Triad representational approach that unifies temporal-as well as locational-and object-related aspects and that incorporates concepts from perceptual psychology, artifical intelligence, and other fields. The goal of this research is a drawing-together of a range of concepts and ideas not only to improve our representational and analytical capabilities, but also to provide more common ground among the various fields noted above. The discrete yet interrelated time-, location-, and object-based views incorporated within the Triad framework allow for questions to be asked and answered relative to each of those aspects. Fundamental types of temporal relationships are also defined as part of the temporal view.

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Abstract: The need for a conceptually high level, unifying representational scheme for geographic phenomena was recognized long ago. A number of attempts to address this issue have been made in the past, and each has usually been centered around a specific theoretical point of view (Bartels 1982). This topic has reappeared recently within the context of geographical information systems. Recognizing that the representational scheme employed in large part determines the efficiency and ease of use withing a given application context, there has been much activity in developing better methods for representating geographic data in digital form. Nevertheless, porgress has been slow, with shuch activity usually focused on narrowly viewed implementational issues with no clear answers or overall insights toward solving the overall problem. This vaccum suggests that need for a more unified approach to both research in methods of representing geographic data and practical geographic database design based on a common and unified framework. Representational theories for spatial and non-spatial phenomena developed within other fields, particularly cognitive and perceptual psychology, computer vision and database management systems, are examined within the context of the geographic literature. Drawing on and combining these concepts with a top-down approach, I suggest a set of unifying principles and an overall framework for representing geographical phenomena based on these principles. This effor includes an enumeration of basic types of spatial relationships and their characteristics. Although the framework as presented is very general, it seems to represent a complete blending of previous geometric and preceptual appraoches, demonstrating that these appraoches are not only compatible but complementary. The theories developed in other disciplines provide insight into the functional relationship between the image-based and object-based views that have existed implicitly in Geography for many years

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Abstract: The purpose of this paper is to provide a general context for understandin the various software components which are commonly used in Geographci Information Systems (GIS). This is done by describing geographically and with narrative the actual analytic and data processing functions which are commonly performed in GIS systems. These functions are generic in nature and relate to no one system. This paper initially presents a background of why these systems have evolved, the absic data types which are contained within them and a series of concepts associated with spatial information including: map automation and data base creation; analytic manipulation technqiues; data base manipulation techniques; and graphic manipulation techniques. Finally a summary outline of the actual application of this technology is provided

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