1,721,624 research outputs found
Topological Relationships and Their Use
No full textTopological relations between spatial objects have been widely recognized, implemented, and used in GIS. They provide a notion of the general structure and the interactions of spatial objects. Topology avoids dealing with geometry by introducing topological primitives, namely, boundary, interior, and exterior.Accepted Author ManuscriptUrban Data Scienc
Access to Destinations: Travel Time Estimation on Arterials
No full textThe primary objective of this project was to identify and evaluate parametric models for making default estimates of travel times on arterial links. A review of the literature revealed several candidate models, including the Bureau of Public Roads (BPR) function, Spiess's conical volume delay function, the Singapore model, the Skabardonis-Dowling model, and the Highway Capacity Manual's model. A license plate method was applied to a sample of 50 arterial links located in the Twin Cities seven county metropolitan area, to obtain measurements of average travel time. Also obtained were the lengths of each link, measurements of traffic volume, and signal timing information. Default values for model parameters were obtained from the Twin Cities planning model's database. Using network default parameters, we found that the BPR and conical volume-delay models produced mean average percent errors (MAPE) of about 25%, while the Singapore and Skabardonis-Dowling models, using maximal site-specific information, produced MAPE values of around 6.5%. As site-specific information was replaced by default information the performance of the latter two models deteriorated, but even under conditions of minimal information the models produced MAPE values of around 20%. A cross-validation study of the Skabardonis-Dowling model showed essentially similar performance when predicting travel times on links not used to estimate default parameter values.Minnesota Department of TransportationDavis, Gary A.; Xiong, Hui. (2007). Access to Destinations: Travel Time Estimation on Arterials. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/5589
3D Indoor Models and Their Applications
No full textIndoor environments are often referred as to enclosed spaces. However, the general definition of space can already indicate that a space can be bounded. Wordnet (http://wordnet.priceton.edu) defines space as “an empty areas usually bounded in some way between things.”3D Geo-Informatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Estimating the Crash Reduction and Vehicle Dynamics Effects of Flashing LED Stop Signs
Full text linkA flashing LED stop sign is essentially a normal octagonal stop sign with light emitted diodes (LED) on the stop sign’s corners. A hierarchical Bayes observational before/after study found an estimated reduction of about 41.5% in right-angle crashes, but with 95% confidence this reduction could be anywhere between 0% and 70.8%. In a field study, portable video equipment was used to record vehicle approaches at an intersection before and after installation of flashing LED stop signs. After installing the flashing stop signs, there was no change in the relative proportion of clear stops to clear non-stops when minor approach drivers did not face opposing traffic, but the relative proportion of clear stops increased for drivers who did encounter opposing traffic. Random samples of 60 minor approach vehicles were selected before and after installation of flashing LED stop signs and speeds for these vehicles when about 500 feet from the intersection, and average deceleration rates over the final 500 feet, were estimated using trajectory-based
methods. Average approach speeds tended to be highest in June, somewhat lower in July, and lower yet in September and November, with September and November having roughly equal average speeds. The average deceleration rates showed a similar pattern.Department of Civil Engineering, University of MinnesotaDavis, Gary A.; Hourdos, John; Xiong, Hui. (2014). Estimating the Crash Reduction and Vehicle Dynamics Effects of Flashing LED Stop Signs. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/162793
Discovering Co-location Patterns from Spatial Datasets: A General Approach
No full textGiven a collection of boolean spatial features, the co-location pattern discovery process finds the subsets of features frequently located together. For example, the analysis of an ecology dataset may reveal the frequent co-location of a fire ignition source feature with a needle vegetation type feature and a drought feature. The spatial co-location rule problem is different from the association rule problem. Even though boolean spatial feature types (also called spatial events) may correspond to items in association rules over market-basket datasets, there is no natural notion of transactions. This creates difficulty in using traditional measures (e.g. support, confidence) and applying association rule mining algorithms which use support-based pruning. We propose a notion of user-specifiedneighborhoods in place of transactions to specify groups of items. New interest measures for spatial co-location patterns are proposed which are robust in the face of potentially infinite overlapping neighborhoods. We also propose a family of algorithms to mine frequent spatial co-location patterns. Experimental results are provided to show the strength of each algorithm and design decisions related to performance tuning.Huang, Yan; Shekhar, Shashi; Xiong, Hui. (2002). Discovering Co-location Patterns from Spatial Datasets: A General Approach. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/215536
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