The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The research presented in this paper introduces a graph-based and computational modelling approach that derives a social network and computes its emerging spatial and thematic properties from the semantics embedded in a series of Web pages. We apply several local and global graph-based operators, and complement them with thematic, spatial and similarity operators. This allows us to infer the degree...
This paper presents a model for positional relations among bodies of arbitrary shape in three dimensions. It is based on an existing model for projective relations among regions in two dimensions. The motivation is to provide a formal qualitative spatial relations model for emerging 3D applications. Two sets of relations are defined: ternary projective relations based on the concept of collinearity...
Mesh-based terrain representations provide accurate descriptions of a terrain, but fail in capturing its morphological structure. The morphology of a terrain is defined by its critical points and by the critical lines joining them, which form a so-called surface network. Because of the large size of current terrain data sets, a multi-resolution representation of the terrain morphology is crucial....
Safeguarding location privacy is becoming a critical issue in location-based services and location-aware computing generally. Two drawbacks of many previous models of location privacy are: 1) the models only consider a person’s location privacy protection, but not the invasion of location privacy by external agents; and 2) the models are static and do not consider the spatiotemporal aspects of movement...
In this paper we present an approach to providing landmark-based routes using a shortest-path algorithm. We start from the assumption, that at one junction there can be several landmarks to choose among, in order to find an optimal description of a route. The landmark selection used for describing the route is optimized taking the quality measures for the landmarks into account. Therefore, it is necessary...
There are many situations in GIScience where it would be useful to be able to assign a region to characterize the space occupied by a set of points. Such a region should represent the location or configuration of the points as an aggregate, abstracting away from the individual points themselves. In this paper, we call such a region a ‘footprint’ for the points. We investigate and compare a number...
Voronoi diagrams are widely used to represent geographical distributions of information, but they are not readily stacked in a hierarchical fashion. We propose a simple mechanism whereby each index Voronoi cell contains the generators of several Voronoi cells in the next lower level. This allows various processes of indexing, paging, visualization and generalization to be performed on various types...
In this paper, a qualitative shape representation is described for the purpose of characterising linear geographical and artificial objects. In particular, we focus on the curve progression telling us how objects spread across the landscape. For instance, sinuosities of rivers provide important information about imperilled locations in the case of flood waters. However, precise geometrical descriptions...
Landmarks support the structuring of environmental information into cognitive conceptual units, they have the potential to identify uniquely pertinent intersections for route following, and they disambiguate spatial situations at complex intersections. Not using them in automatically generated route directions is a violation of cognitive ergonomics. While we have made great progress on the one hand...
A GIS coordinator for a U.S. city complains about data sharing metadata with a single word: “headaches.” He underscores the function of metadata in supporting the process of finding a collective understanding of what the data can be reliably used for. In John Searle’s philosophical work on social reality, this coordinator articulates the struggle to create and maintain the status functions and collective...
The paper will introduce into the subject of recognition of typical patterns in road networks. Especially we will describe the search for ring structures and its implementation in detail. Applications to detect these patterns and to use them for eliciting additional implicit knowledge in vector data are shown. We will familiarise the reader with different methods and approaches for the automatic detection...
In an earlier paper we introduced Anchoring, a new approach for handling indeterminate location in a spatial information system. Here we develop it further, showing how Anchoring can be made to work in real systems. In particular, we specify a new kind of locational component for a spatial data model. We then show how that component can be implemented into an object-relational database with extensions...
It is difficult to generate raster Digital Elevation Models (DEMs) from terrain mass point data sets too large to fit into memory, such as those obtained by LIDAR. We describe prototype tools for streaming DEM generation that use memory and disk I/O very efficiently. From 500 million bare-earth LIDAR double precision points (11.2 GB) our tool can, in just over an hour on a standard laptop with two...
Acquisition and semantic annotation of data are fundamental tasks within the domain of cultural heritage. With the increasing amount of available data and ad hoc cross linking between their providers and users (e.g. through web services), data integration and knowledge refinement becomes even more important. To integrate information from several sources it has to be guaranteed that objects of discourse...
Complex systems theory and Cellular Automata (CA) are widely used in geospatial modeling. However, existing models have been limited by challenges such as handling of multiple datasets, parameter definition and the calibration procedures in the modeling process. Bayesian network (BN) formalisms provide an alternative method to address the drawbacks of these existing models. This study proposes a hybrid...
We are aiming for semantic representations of route descriptions for dialogues between a driver and the Bremen intelligent wheelchair Spatial Cognition Rolland, integrating qualitative orientation calculi with RouteGraphs. Relative orientations, and the algebraic properties of the inverse and full complement operations, are the basis for specifying properties of orientations between directed edges...
The query for retrieving the rank of all neighbors of a moving object at any given time, a continuous rank query, is an important case of continuous nearest neighbor (CNN) queries. An application for ranking queries is given by an ambulance driver who needs to keep track of the closest hospitals at all times. We present a set of incremental algorithms that facilitate efficient rank updates for some...
Directed line segments are fundamental geometric elements used to model through their spatial relations such concepts as divergence, confluence, and interference. A new model is developed that captures spatial relations between pairs of directed line segments through the intersections of the segments’ heads, bodies, and tails. This head-body-tail intersection identifies 68 classes of topological relations...
Urban multi-criteria optimized route guidance by considering unspecified site satisfaction, an extended type of urban multi-objective optimized route selection, called as both NP-Hard problems and one of the branches of multi-criteria shortest path problems (MSPP). It is not only suggests a route based on route guidance principles and optimized due to routing criteria but also passes through all unspecified...
Geographic information is based on observations or measurements. The Open Geospatial Consortium (OGC) has developed an implementation specification for observations and measurements (O&M). It specifies precisely how to encode information. Yet, the O&M conceptual model does not specify precisely which real-world entities are denoted by the specified information objects. We provide formal semantics...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.