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  • 2015-2019  (5)
  • 1
    Online Resource
    Online Resource
    Wiley ; 2015
    In:  Journal of Sensors Vol. 2015 ( 2015), p. 1-5
    In: Journal of Sensors, Wiley, Vol. 2015 ( 2015), p. 1-5
    Abstract: Document management is a usual way to organize spatial data in mobile terminals. And the compressed CGML spatial data has been widely used in location based services. Referring to the thoughts of map set in cartography, nine closely connected and equal sized rectangles are used as the scope for requesting mobile map data, and these nine closely connected rectangles are built to be nine tiles model. Therefore, in view of the method of block requesting and storing on mobile spatial data following nine tiles model, as well as the large quantity of mobile spatial data and its complex geometry relation, this paper puts forward the construction mechanism of nine tiles model and cache organization of CGML spatial data in mobile terminals that abide by nine tiles model. This way of organization and management of mobile spatial data is good to increase the efficiency of heavy spatial data accessing in the low band and reliability of wireless network environment.
    Type of Medium: Online Resource
    ISSN: 1687-725X , 1687-7268
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2397931-8
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  • 2
    Online Resource
    Online Resource
    MDPI AG ; 2019
    In:  ISPRS International Journal of Geo-Information Vol. 8, No. 11 ( 2019-10-24), p. 477-
    In: ISPRS International Journal of Geo-Information, MDPI AG, Vol. 8, No. 11 ( 2019-10-24), p. 477-
    Abstract: Data about the movements of diverse objects, including human beings, animals, and commodities, are collected in growing amounts as location-aware technologies become pervasive. Clustering has become an increasingly important analytical tool for revealing travel patterns from large-scale movement datasets. Most existing methods for origin-destination (OD) flow clustering focus on the geographic properties of an OD flow but ignore the temporal information preserved in the OD flow, which reflects the dynamic changes in the travel patterns over time. In addition, most methods require some predetermined parameters as inputs and are difficult to adjust considering the changes in the users’ demands. To overcome such limitations, we present a novel OD flow clustering method, namely, TOCOFC (Tree-based and Optimum Cut-based Origin-Destination Flow Clustering). A similarity measurement method is proposed to quantify the spatial similarity relationship between OD flows, and it can be extended to measure the spatiotemporal similarity between OD flows. By constructing a maximum spanning tree and splitting it into several unrelated parts, we effectively remove the noise in the flow data. Furthermore, a recursive two-way optimum cut-based method is utilized to partition the graph composed of OD flows into OD flow clusters. Moreover, a criterion called CSSC (Child tree/Child graph Self-Similarity Criterion) is formulated to determine if the clusters meet the output requirements. By modifying the parameters, TOCOFC can obtain clustering results for different time scales and spatial scales, which makes it possible to study movement patterns from a multiscale perspective. However, TOCOFC has the disadvantages of low efficiency and large memory consumption, and it is not conducive to quickly handling large-scale data. Compared with previous works, TOCOFC has a better clustering performance, which is reflected in the fact that TOCOFC can guarantee a balance between clusters and help to fully understand the corresponding patterns. Being able to perform the spatiotemporal clustering of OD flows is also a highlight of TOCOFC, which will help to capture the differences in the patterns at different times for a deeper analysis. Extensive experiments on both artificial spatial datasets and real-world spatiotemporal datasets have demonstrated the effectiveness and flexibility of TOCOFC.
    Type of Medium: Online Resource
    ISSN: 2220-9964
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2655790-3
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  • 3
    Online Resource
    Online Resource
    SAGE Publications ; 2015
    In:  International Journal of Distributed Sensor Networks Vol. 11, No. 11 ( 2015-11-01), p. 463749-
    In: International Journal of Distributed Sensor Networks, SAGE Publications, Vol. 11, No. 11 ( 2015-11-01), p. 463749-
    Abstract: To solve the problems from the existing moving objects data models, such as modeling spatiotemporal object continuous action, multidimensional representation, and querying sophisticated spatiotemporal position, we firstly established an object-oriented all-time-domain data model for moving objects. The model added dynamic attributes into object-oriented model, which supported all-time-domain data storage and query. Secondly, we proposed a new dynamic threshold location updating strategy. The location updating threshold was given dynamically in accordance with the velocity, accuracy, and azimuth positioning information from the GPS. Thirdly, we presented several different position estimation methods to estimate the historical location and future location. The cubic Hermite interpolation function is used to estimate the historical location. Linear extended positioning method, velocity mean value positioning method, and cubic exponential smoothing positioning method were designed to estimate the future location. We further implemented the model by abstracting the data types of moving object, which was established by PL∖SQL and extended Oracle Spatial. Furthermore, the model was tested through the different moving objects. The experimental results illustrate that the location updating frequency can be effectively reduced, and thus the position information transmission flow and the data storage were reduced without affecting the moving objects trajectory precision.
    Type of Medium: Online Resource
    ISSN: 1550-1477 , 1550-1477
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2015
    detail.hit.zdb_id: 2192922-1
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  • 4
    Online Resource
    Online Resource
    SAGE Publications ; 2015
    In:  International Journal of Distributed Sensor Networks Vol. 11, No. 11 ( 2015-11-01), p. 528747-
    In: International Journal of Distributed Sensor Networks, SAGE Publications, Vol. 11, No. 11 ( 2015-11-01), p. 528747-
    Abstract: RSSI wireless signal is a reference information that is widely used in indoor positioning. However, due to the wireless multipath influence, the value of the received RSSI will have large fluctuations and cause large distance error when RSSI is fitted to distance. But experimental data showed that, being affected by the combined factors of the environment, the received RSSI feature vector which is formed by lots of RSSI values from different APs is a certain stability. Therefore, the paper proposed RSSI-based fingerprint feature vector algorithm which divides location area into grids, and mobile devices are localized through the similarity matching between the real-time RSSI feature vector and RSSI fingerprint database feature vectors. Test shows that the algorithm can achieve positioning accuracy up to 2–4 meters in a typical indoor environment.
    Type of Medium: Online Resource
    ISSN: 1550-1477 , 1550-1477
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2015
    detail.hit.zdb_id: 2192922-1
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  • 5
    Online Resource
    Online Resource
    Elsevier BV ; 2018
    In:  China Economic Review Vol. 50 ( 2018-08), p. 206-217
    In: China Economic Review, Elsevier BV, Vol. 50 ( 2018-08), p. 206-217
    Type of Medium: Online Resource
    ISSN: 1043-951X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 2019641-6
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