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  • 1
    Electronic Resource
    Electronic Resource
    Toward a model for airflow on the lee side of aeolian dunes (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 43 (1996), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The interaction between dunes and the primary wind results in a complex pattern of secondary airflow on the lee side of dunes. From 15 dunes studied during transverse flow conditions at Padre Island in Texas, White Sands in New Mexico, and the Algodones in California, distinct flow regions can generally be recognized, with the overall flow structure comparing favourably to that proposed for subaqueous bedforms. Downwind of dunes with flow separation is a back-flow eddy that extends about four dune-brink heights downwind from the brink of the dune. Beyond the separation cell, the velocity profiles can be divided into regions based upon segments separated by ‘kinks’ in the velocity profiles. The interior is an area above the dunes of relative high wind speed but low velocity gradient. Beneath the interior is the wake, which consists of two layers. The upper wake exhibits an uppermost portion where the flow decelerates while the remainder exhibits accelerating flow, so that the overall velocity gradient decreases downwind. The lower wake exhibits low velocity gradients and wind speeds that accelerate downwind at all heights, but primarily near the top of the layer, thereby causing the velocity gradient to increase downwind. At about eight dune heights downwind, the upper and lower wakes equilibrate to a single profile with the kink between them no longer apparent. The lowest recognizable region is the internal boundary layer. It is recognized by a relatively steep velocity gradient below the wake, and never exceeds a few tens of centimetres in height for our data set. Because of acceleration and increasing shear stress within this layer, interdune flats are at least potentially erosional. Overall, the wake and internal boundary layer show a downward transfer of momentum from upper regions so that the flow recovers. Where flow separation does not occur, simple flow expansion down the lee-face causes flow deceleration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.1996.d01-20.x
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  • 2
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    Built in Destabilization: A. O. Hirschman's Strategy of Economic Development (Book Review) (1960)
    Chicago : Periodicals Archive Online (PAO)
    Economic development and cultural change. 8:4 (1960:July) 433 
    Details
    ISSN: 0013-0079
    Topics: Geography , Economics
    Notes: REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5112-1960-008-04-000007
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  • 3
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    Human Capital and Economic Growth (1960)
    Chicago : Periodicals Archive Online (PAO)
    Economic development and cultural change. 8:2 (1960:Jan.) 170 
    Details
    ISSN: 0013-0079
    Topics: Geography , Economics
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5112-1960-008-02-000004
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  • 4
    Electronic Resource
    Electronic Resource
    Part 4 Technology and the future of GIS and spatial analysis (2000)
    Springer
    Journal of geographical systems 2 (2000), S. 99-105 
    Details
    ISSN: 1435-5949
    Keywords: Key words: Multi-agent systems, computational geography, field-computing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract. Geographical Information Science is essentially computational geography and has its own research program, namely all aspects of formal models for spatial natural processes and the interaction of humans with the environment in space and time. This is not a question of technology and technology-related research; but technology influences what questions can be researched effectively. Collection of data in the field and the simulation of field experience through Virtual Reality are just two questions of how spatial reality and human experience are linked. The focus on human spatial cognition is similarly found in software engineering for interoperable Geographic Information Systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101090050036
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  • 5
    Electronic Resource
    Electronic Resource
    Formal specification of image schemata -- a step towards interoperability in geographic information systems (1999)
    Springer
    Spatial cognition and computation 1 (1999), S. 67-101 
    Details
    ISSN: 1542-7633
    Keywords: image schemata ; formal specifications ; spatial cognition ; spatial relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Psychology
    Notes: Abstract The formal specification of spatial objects and spatial relations is at the core of geographic data exchange and interoperability for geographic information systems (GIS). It is necessary that the representation of such objects and relations comes close to how people use them in their everyday lives, i.e., that these specifications are built upon elements of human spatial cognition. Image schemata have been suggested as highly abstract and structured mental patterns to capture spatial and similar physical as well as metaphorical relations between objects in the experiential world. We assume that image-schematic details for large-scale (geographic) space are potentially different from image-schematic details for small-scale (table-top) space. This paper reviews methods for the formal description of spatial relations, integrates them in a categorical view, and applies the methods arrived at to formally specify image schemata for large-scale (LOCATION, PATH, REGION, and BOUNDARY) as well as small-scale (CONTAINER, SURFACE, and LINK) space. These specifications should provide a foundation for further research on formalizing elements of human spatial cognition for interoperability in GIS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010004718073
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of estimation errors on wayfinding-decisions in unknown street networks – analyzing the least-angle strategy (2000)
    Springer
    Spatial cognition and computation 2 (2000), S. 283-313 
    Details
    ISSN: 1542-7633
    Keywords: decision making ; error classification ; least-angle strategy ; wayfinding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Psychology
    Notes: Abstract The least-angle strategy is a common wayfinding method that can be applied in unknown environments if the target direction is known. The strategy is based on the navigator's heuristic to select the street segment at an intersection which is most in line with the target direction. To use this strategy, the navigator needs to know the angles between the target direction and the street segments leading out from the intersection. If the direct view to the target is blocked and the target vector cannot be perceived, the target direction that is needed for the decision process is based on the agent's believed position and orientation (estimated through path integration). The agent's believed position and target direction are distorted by human errors in estimation of distances and directions, mainly affecting the path integration process. In this paper we examine how human estimation errors of distance and rotation influence the decision behavior in the wayfinding process in an unknown street environment. To demonstrate the geometrical consequences for a specific test case, we use a simulated software agent which navigates in a simulated street environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015566423907
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  • 7
    Electronic Resource
    Electronic Resource
    Editorial (1997)
    Springer
    Geoinformatica 1 (1997), S. 215-217 
    Details
    ISSN: 1573-7624
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009754529532
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  • 8
    Electronic Resource
    Electronic Resource
    Finite-Resolution Simplicial Complexes (1998)
    Springer
    Geoinformatica 2 (1998), S. 281-298 
    Details
    ISSN: 1573-7624
    Keywords: Geographic Information Systems ; finite resolution ; line intersection ; topological data models ; discrete simplicial complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract Simplicial complexes are used to model topology in Geographic Information Systems (GIS). Line intersection is an essential operation to update them. We introduce a finite-resolution line intersection method, called Zero Order Intersection, and apply it to simplicial complexes. Any reliable implementation of a line intersection algorithm has to address the limitations of a discrete computational environment. If handled improperly, finite representation can cause drifting lines and similar effects in otherwise topologically consistent data. The Zero Order Intersection method is designed to avoid such inconsistencies. Its application to simplicial complexes results in the Discrete Simplicial Data Model which guarantees consistency and reliability of topological queries within a GIS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009773822002
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  • 9
    Electronic Resource
    Electronic Resource
    On the design of formal theories of geographic space (1999)
    Springer
    Journal of geographical systems 1 (1999), S. 237-275 
    Details
    ISSN: 1435-5949
    Keywords: Key words: Abstraction ; formal systems ; GIS ; spatial reasoning ; JEL classification: C60 ; C63 ; C88
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract. This paper discusses the design of formal theories of geographic space for the application in Geographic Information Systems. GIS software is an implementation of formal theories of geographic space. The notions of formal theories are introduced and discussed in the context of examples from the GIS field.  Our approach is an application of the general framework of formal theories to the special class of theories of geographic space, in particular to the geometry of geographic space. A framework is introduced for characterizing and evaluating formal theories of geographic space and the process of their design. This is used to provide (1) a classification of formal theories of geographic space, (2) criteria of their adequacy, and (3) an evaluation of design decisions in the process of formalization.  The paper demonstrates the choices in the design of GIS and the dependencies between these choices. Considering the design space for theories underlying a GIS, we can see that current GIS are based on one choice: analytical geometry. Other designs are possible and a systematic exploration of alternative types of GIS, for example, based on constraints or based on stored spatial relations, becomes necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101090050014
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  • 10
    Electronic Resource
    Electronic Resource
    IGU commission on the coastal environment no. 32, August 1992 (1992)
    Springer
    GeoJournal 27 (1992), S. 392-396 
    Details
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185103
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