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《International Journal of Digital Earth》2013,6(10):771-788
Virtual globes (VGs) allow Internet users to view geographic data of heterogeneous quality created by other users. This article presents a new approach for collecting and visualizing information about the perceived quality of 3D data in VGs. It aims at improving users' awareness of the quality of 3D objects. Instead of relying on the existing metadata or on formal accuracy assessments that are often impossible in practice, we propose a crowd-sourced quality recommender system based on the five-star visualization method successful in other types of Web applications. Four alternative five-star visualizations were implemented in a Google Earth-based prototype and tested through a formal user evaluation. These tests helped identifying the most effective method for a 3D environment. Results indicate that while most websites use a visualization approach that shows a ‘number of stars’, this method was the least preferred by participants. Instead, participants ranked the ‘number within a star’ method highest as it allowed reducing the visual clutter in urban settings, suggesting that 3D environments such as VGs require different design approaches than 2D or non-geographic applications. Results also confirmed that expert and non-expert users in geographic data share similar preferences for the most and least preferred visualization methods. 相似文献
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E.G. Paredes M. Bóo M. Amor J.D. Bruguera J. Döllner 《International journal of geographical information science》2013,27(5):771-793
Hybrid terrains are a convenient approach for the representation of digital terrain models, integrating heterogeneous data from different sources. In this article, we present a general, efficient scheme for achieving interactive level-of-detail rendering of hybrid terrain models, without the need for a costly preprocessing or resampling of the original data. The presented method works with hybrid digital terrains combining regular grid data and local high-resolution triangulated irregular networks. Since grid and triangulated irregular network data may belong to different datasets, a straightforward combination of both geometries would lead to meshes with holes and overlapping triangles. Our method generates a single multiresolution model integrating the different parts in a coherent way, by performing an adaptive tessellation of the region between their boundaries. Hence, our solution is one of the few existing approaches for integrating different multiresolution algorithms within the same terrain model, achieving a simple interactive rendering of complex hybrid terrains. 相似文献
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E. Safra Y. Kanza Y. Sagiv Y. Doytsher 《International journal of geographical information science》2013,27(1):114-153
In integration of road maps modeled as road vector data, the main task is matching pairs of objects that represent, in different maps, the same segment of a real-world road. In an ad hoc integration, the matching is done for a specific need and, thus, is performed in real time, where only a limited preprocessing is possible. Usually, ad hoc integration is performed as part of some interaction with a user and, hence, the matching algorithm is required to complete its task in time that is short enough for human users to provide feedback to the application, that is, in no more than a few seconds. Such interaction is typical of services on the World Wide Web and to applications in car-navigation systems or in handheld devices. Several algorithms were proposed in the past for matching road vector data; however, these algorithms are not efficient enough for ad hoc integration. This article presents algorithms for ad hoc integration of maps in which roads are represented as polylines. The main novelty of these algorithms is in using only the locations of the endpoints of the polylines rather than trying to match whole lines. The efficiency of the algorithms is shown both analytically and experimentally. In particular, these algorithms do not require the existence of a spatial index, and they are more efficient than an alternative approach based on using a grid index. Extensive experiments using various maps of three different cities show that our approach to matching road networks is efficient and accurate (i.e., it provides high recall and precision). General Terms:Algorithms, Experimentation 相似文献
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Shi-ju Kang Bang-rong HuangTing Kang Ji-hua LiangYong-gang Zheng 《Chinese Astronomy and Astrophysics》2012
Based on the log-parabolic spectral energy distribution of electrons, and the homogeneous one-zone synchrotron self-Compton (SSC) model, the multiband spectral energy distribution of the BL Lac object S5 0716+714 is calculated. Compared with Paggi's result which is obtained by means of δ-function approximation, it is found that a certain difference exists between our result and Paggi's. The main reason leading to this difference may be that the δ-function approximation on the synchrotron radiation of a single electron loses a part of electron energy, and therefore affects the result of inverse Compton scattering. Applying this model to the results of the multi-band observations made at three different states of Mark 421: high, medium, and low, the results of theoretical calculations are coincident very well with the observational results under the three different states of the object. An analysis indicates that the observed different states of Mark 421 are probably caused by the variation of the electron distribution in the jet. 相似文献
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针对动态目标检测中的图像背景实时提取问题,采用红绿蓝三分量综合考虑的方法,进行了比较深入的算法研究。研究表明,如果图像序列时间段过短,背景中就会有目标空洞,如果图像序列时间段过长,则不能反映实时背景,在后续目标检测中就会引起较大误差。考虑合理的视频场景区域的动态目标密集程度因素,就可以较好地兼顾提取背景的实时性和背景中目标空洞的消除。 相似文献