Space-time prisms are physically impossible since they assume infinite acceleration and deceleration. This paper is a first step in resolving this issue. A theoretical description of kinetic prism geometry, but provides insights that can lead to moving objects data analytics with practical applications (e.g., animal movement, vehicle energy consumption and emissions, bicycles and other forms of active transportation)
Kuijpers, B., Miller, H.J. and Othman, W., (2017) “Kinetic prisms: incorporating acceleration limits into space-time prisms,” International Journal of Geographic Information Science, 31, 2164-2194.
Abstract: Presently, data concerning moving objects abound. These data mainly consist of time-stamped geographical locations, which are collected by location aware devices, such as Global Positioning System receivers. Space–time prisms are used to model the spatio-temporal space of potential movement in between measured locations (called anchors). They rely on the knowledge of the maximal speed of travel of an object and they capture all space–time paths that respect this speed limit. However, the classic space–time path and prism model is not physically realistic, in the sense that it contains spatio-temporal paths of moving objects can alter their direction and speed instantaneously. Since this is physically impossible, the classical model is not acceptable in applications where mechanics and kinetics are vital. We propose a more realistic version of space–time prisms, in which not only speed but also acceleration is bounded. This additional bound results in a physically realistic model, which we refer to as kinetic prisms. Furthermore, we study how imposing constraints on the speed and heading at anchor points affects the geometry of kinetic prisms. In this paper, we give analytical descriptions of kinetic prisms and algorithms for their construction for movement in one- and two-dimensional space.
Keywords: Spatio-temporal data models, moving-object data, space–time prisms
New publication: Proffitt, D., Bartholomew, K., Ewing, R. and Miller, H.J. (2017) “Accessibility planning in American metropolitan areas: Are we there yet?” Urban Studies. Article first published online: June 13, 2017. DOI: https://doi.org/10.1177/0042098017710122
Transportation-planning researchers have long argued that the end goal of a transportation system is increasing accessibility, or opportunities for individuals to meet their daily needs, but that US practice tends to focus on increasing mobility, or opportunities to travel farther and faster. This study finds evidence that the gap between theory and practice may be closing when it comes to accessibility, but that significant barriers still exist to the wider adoption of the accessibility paradigm among metropolitan planning organisations, the main entities responsible for regional transportation planning in the USA. We measure this gap by creating an accessibility index based on content analysis of a nationally representative sample of 42 US regional transportation plans (RTPs). We then use regression-tree analysis to determine the characteristics of metropolitan areas that are most likely to employ accessibility concepts. Finally, we identify barriers to a wider adoption of the accessibility paradigm. Most RTPs include accessibility-related goals, but few define the term or use accessibility-oriented performance measures. The lack of clarity on accessibility leaves vehicle speed as the fundamental criterion for success in most plans. Our analysis finds that MPOs serving large regions with high per capita income are the most likely to produce plans that focus on accessibility. We argue that such places produce more accessibility-oriented RTPs because they have greater planning capacity and recommend changes to federal planning guidelines that could speed the adoption of the accessibility paradigm in RTPs.
Keywords accessibility, metropolitan planning organisations, mobility, regional planning, transportation planning
The second of three GIS status update reports commissioned by PiHG:
Miller, H. J. (2017) “Geographic information science II: Mesogeography: Social physics, GIScience and the quest for geographic knowledge” Progress in Human Geography. Online publication date: June 9, 2017. DOI: https://doi.org/10.1177/0309132517712154
Abstract: The 20th century witnessed the rise of social physics: the application of models and techniques developed for physical processes to social phenomena. Social physics left an enduring legacy in human geography via its stepchildren, spatial analysis and GIS, shifting geography from microgeography (description-seeking) and towards macrogeography (law-seeking). Social physics is back in the 21st century, and its renaissance with a concurrent rise in computational and data-driven approaches to science and policy raises a wide range of concerns, including the claim that this is just macrogeography writ large: a single-minded pursuit of social laws at the cost of treating people as particles and spatial context as abstract and sterile. I argue that this time is different: a more sophisticated social physics, spatial analysis and GIScience are emerging that emphasize heterogeneity and spatial context as key drivers of interesting behavior. I also argue that new social physics suggests another path to geographic knowledge somewhere in the middle: mesogeography – a focus on how processes evolve in spatial context. I discuss GIScience techniques and approaches that can facilitate the quest for mesogeographic knowledge.
Keywords: GIScience, social physics, spatial analysis, spatial context, spatial heterogeneity