Portland, OR, United States
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Deng H.,Beijing Normal University | Zhang L.,Beijing Normal University | Ma J.,PTV America Inc. | Kang Z.,University of Science and Technology of China
Computers and Geosciences | Year: 2011

In 3D terrain navigation applications, the views based on general perspective projection often find features of interest (FOIs) being occluded. As an alternative, panorama-like views preserve the similarity between 3D scenes before and after the deformations while ensuring the visibility of interested features. In this paper, an automatic method for generating panoramic map-like views is proposed in mountainous areas. The created panorama-like views by moving up the view position as well as the terrain deformation can successfully avoid occlusions of the FOIs. The final views also ensure the resemblance in appearance for the FOIs and landscapes, and thus satisfy the demand for interactive occlusion-free navigation in 3D complex terrain environments. © 2011 Elsevier Ltd.


Deng H.,Beijing Normal University | Zhang L.,Beijing Normal University | Ma J.,PTV America Inc. | Chen D.,Beijing Normal University
Photogrammetric Engineering and Remote Sensing | Year: 2012

When a car drives in mountainous regions, the views based on conventional perspective projection often suffer from features of interest being occluded. We propose a method for generating disocclusion views in mountainous regions. The terrain is segmented to build a potential set of occluders; and then an optimized viewpoint is determined, and elevations are rearranged. To obtain a smooth deformed terrain, a smooth displacement function is introduced to deform the level-of-detail terrain models. Compared with previous methods, the merit of this study lies in automatically generating disocclusion views with temporal coherence, while keeping the details of the deformed terrain the same as the original terrain. Experiments performed on the 4098 pixel × 4098 pixel mountainous terrain landscape prove that the disocclusion views can achieve 42 to 58 frames/second. Moreover, the shapes of the features of interest on the driving route without occlusion and the spatial configuration of geographical landmarks in its neighborhood can be easily recognized. © 2012 American Society for Photogrammetry and Remote Sensing.


Liu L.,Beijing Normal University | Zhang L.Q.,Beijing Normal University | Ma J.T.,PTV America Inc. | Zhang L.,Beijing University of Civil Engineering and Architecture | And 3 more authors.
Science China Information Sciences | Year: 2010

This paper presents an efficient method for implementing visibility analysis on complex landscapes based on an improved LOS (line of sight) algorithm. The method determines the viewshed by analyzing the geometric relationship between the target points and viewpoint. It differentiates the visibility of the target points by the elevation information. Eventually the visual results related to the given viewpoint are rendered on three-dimensional landscapes. The visibility of some target points is computed by comparing their elevations with the viewpoint's height, thus is able to enhance the efficiency of the visibility analysis. This method can not only be applied in the visibility analysis of forest scenes, but also used in the analysis of the urban environment. Experiments show that the proposed method results in high efficiency and precision. © Science China Press and Springer-Verlag Berlin Heidelberg 2010.


Chen C.,Beijing Normal University | Zhang L.,Beijing Normal University | Ma J.,PTV America Inc. | Kang Z.,University of Science and Technology of China | And 2 more authors.
International Journal of Geographical Information Science | Year: 2010

Labeling plays an important role in map production, attaching specific texts to related geographic elements to provide clear environmental references. In three-dimensional geographical information systems (3DGISs), however, cluttering happens fairly commonly because of the unexpected overlapping and occlusion among labels and related objects, and results in an ambiguous and obscure environment. It generally also takes large computing power and memory to visualize spatial entities. Aimed at both unambiguous and efficient 3D map display, this article proposes an adaptive multi-resolution labeling method to deal with point, polyline, and polygon features labeling in a 3D landscape. It implements adaptive placement and view-driven label filtering without obscuring other visual features. The experiments indicated that the display of overlapping labels and label popping are reduced significantly with less computation burden while retaining the rendering quality. © 2010 Taylor & Francis.


Yang L.,Beijing Normal University | Zhang L.,Beijing Normal University | Ma J.,PTV America Inc. | Xie J.,Beijing Normal University | Liu L.,Beijing Normal University
International Journal of Geographical Information Science | Year: 2011

Multi-resolution visualization of massive urban buildings is one of the most important components for a cyber city. Urban is a highly humanized system, and thus visualizing urban buildings needs to abide by people's habits of cognizing spatial relations between objects for their accurate and quick understanding of urban spatial information. This article proposes an approach to generalize and render urban building models in the context of Gestalt psychology and urban legibility. We introduce a new distance measurement method as the distance metric for the single-link clustering algorithm, which is used to group building footprints into clusters. Each cluster is merged based on the Delaunay triangulation and the polyline generalization algorithm. We then construct a hierarchical tree to store multi-resolution building models and implement interactive three-dimensional visualization of large-scale and high-density urban buildings. Experimental results indicate that the proposed methodology not only reduces the geometric complexity of urban models but also preserves urban legibility successfully and follow Gestalt principles. © 2011 Taylor & Francis.


Kima J.,800 Airport Center Dr Ste 102 | Park B.,University of Virginia | Leeb J.,University of Virginia | Won J.,PTV America Inc.
Engineering Applications of Artificial Intelligence | Year: 2011

Travel time is the most intuitive measure of effectiveness for road users and transportation agency operators. However, travel times derived from speed data measured at fixed point sensors often varies from actualtravel time. This is,inpart, due to the intentional positioning of sensorsto avoid lane changing and/orto inadequate numbersof sensors capturing the dynamiccharacteristics inherent infreeway traffic flow. This paper presents an approach that optimizes the location of sensors in a freeway to support more accurate estimations of travel times than those obtained from conventionally deployed fixed point sensors. Evaluation results, under varying traffic conditions, including incidents, showed that the proposed approach produced average travel time estimation errors within 10% and performed much better than the conventional approach. Thus, the proposed approach provides a promising tool tosupport re-positioning of the existing non-intrusive point sensors (e.g., video sensors) or deployment of new sets of point sensors for improving travel time estimation. © 2010 Elsevier Ltd. All rights reserved.


Yuan F.,PTV America Inc. | Han L.D.,University of Tennessee at Knoxville
Procedia Engineering | Year: 2010

Evacuation time is often the choice of measure of effectiveness (MOE) and the objective function to minimize for evacuation planning, as time is sometime considered a surrogate for risk. However, the actual risk of evacuation operations also depends significantly on other factors, such as the space and time-space based factors related to hazard type and meteorological and geographical conditions. By analyzing different risk factors at evacuations, this paper presents a multi-objective optimization approach for evacuation planning. Through two case studies, it shows by combing the space-based risk and the travel time in route searching and traffic assignment, efficiency and safety of evacuation operations may be balanced and improved.


Wang Y.,State Key Laboratory of Remote Sensing Science | Zhang L.,State Key Laboratory of Remote Sensing Science | Ma J.,PTV America Inc. | Liu L.,State Key Laboratory of Remote Sensing Science | You D.,State Key Laboratory of Remote Sensing Science
IEEE Computer Graphics and Applications | Year: 2011

Extended hierarchical node-relation model (EHI-NRM) approach has been used to represent a building's internal structure. The approach employs the improved cellular-automata model (ICA) to consider route-choice behavior. The EHI-NRM adds the minimum bounding box (MBB) of the discrete 3D objects and information relevant to rescue and evacuation to the geometric model. According to the principles for computing a hierarchical path, a building story is abstracted to boundary nodes representing its stairways and exits. For large complex buildings, each subgraph's internal evacuation paths are relatively independent. In preprocessing, any hallways were simplified, transforming those with twists and turns into several straight-line segments. After importing the building model, the EHI-NRM is automatically generated. This approach supports emergency managers in planning and training for responding to emergencies in the preemergency phase, and in coordinating and implementing evacuation or rescue operations during the emergency response.


Won J.,PTV America Inc. | Perone S.,PTV America Inc. | Bauer T.,PTV America Inc. | Dale J.,PTV America Inc.
17th ITS World Congress | Year: 2010

With the increasing application of macroscopic travel demand models and microscopic simulation models within the same project, the need for integrating models in different levels to facilitate transferring data is becoming essential. This paper describes an example project where an integrated macroscopic-microscopic model was applied to perform analyses at different levels of detail. The example project was a freeway corridor application in Portland, Oregon using the integrated PTV Vision Suite software. The level of integrated enabled network consistency to be maintained across models used for different projects, facilitated the development of 15-minute O-D matrices and paths and expedited the coding of geometry data and signal timing plans for local intersections and ramp meters. Ultimately, the integrated workflow saved a considerable amount of time and allowed the 3-month project to be delivered on schedule. Also, integrated network now can be used for any additional project with minimal effort.


Hallmark S.L.,Iowa State University | Fitzsimmons E.J.,Iowa State University | Isebrands H.N.,Iowa State University | Giese K.L.,PTV America Inc.
Transportation Research Record | Year: 2010

Typically, roundabouts in the United States are installed at isolated intersections to address location-specific safety or operational needs. The use of roundabouts in signalized corridors, however, has not been well evaluated. It is commonly believed that roundabouts can improve traffic flow and travel speeds along an urban corridor by reducing delay caused by idling at intersections. Concern exists, however, that a roundabout in a coordinated signalized corridor will disrupt continuous traffic flow: downstream signals can more efficiently process vehicles in a platoon, and roundabouts disperse rather than form platoons. Roundabouts also can discharge vehicles more efficiently when traffic arrives randomly. Thus unnecessary queuing may result when roundabouts are downstream of signalized intersections. Since little research was available to compare the traffic flow impacts of roundabouts within a signalized corridor, two case studies were evaluated with the microscopic traffic simulation package, VISSIM. A roundabout and two signalized alternatives, as well as a roundabout and a four-way, stop-controlled alternative, were compared at intersections along signalized corridors in Ames, Iowa, and Woodbury, Minnesota, respectively. The traffic data and corridor geometry were coded into VISSIM, and traditional intersection traffic control within the corridors was compared with a scenario that had a two-lane roundabout. With the microsimulation software, average travel time, stopped delay, and average delay for the entire corridor were compared.

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