• Journal of Korea Spatial Information System Society
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• v.10 no.3
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• pp.67-78
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• 2008

With the rapid development of wireless communication and mobile equipment, many applications for location-based services have been emerging. Moving objects such as vehicles and ships change their positions over time. Moving objects have their moving path, called the trajectory, because they move continuously. To monitor the trajectory of moving objects in a large scale database system, an efficient Indexing scheme to processed queries related to trajectories is required. In this paper, we focus on the issues of minimizing the dead space of index structures. The Minimum Bounding Boxes (MBBs) of non-leaf nodes in trajectory-preserving indexing schemes have large amounts of dead space since trajectory preservation is achieved at the sacrifice of the spatial locality of trajectories. In this thesis, we propose entry relocating techniques to reduce dead space and overlaps in non-leaf nodes. we present performance studies that compare the proposed index schemes with the TB-tree and the R*-tree under a varying set of spatio-temporal queries.

• Journal of KIISE
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• v.43 no.1
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• pp.40-46
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• 2016

Digital road map generation is primarily based on artificial satellite photographing or in-site manual survey work. Therefore, these map generation procedures require a lot of time and a large budget to create and update road maps. Consequently, people have tried to develop automated map generation systems using GPS trajectory data sets obtained by public vehicles. A fundamental problem in this road generation procedure involves the extraction of representative trajectory such as main roads. Extracting a representative trajectory requires the base data set of piecewise line segments(GPS-trajectories), which have close starting and ending points. So, geometrically similar trajectories are selected for clustering before extracting one representative trajectory from among them. This paper proposes a new divide- and-conquer approach by partitioning the whole map region into regular grid sub-spaces. We then try to find similar trajectories by sweeping. Also, we applied the $Fr{\acute{e}}chet$ distance measure to compute the similarity between a pair of trajectories. We conducted experiments using a set of real GPS data with more than 500 vehicle trajectories obtained from Gangnam-gu, Seoul. The experiment shows that our grid partitioning approach is fast and stable and can be used in real applications for vehicle trajectory clustering.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.548-552
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• 2017

본 논문에서는 얀센 메커니즘을 활용한 보행 로봇의 궤적을 최적화 하기 위한 알고리즘을 연구하였다. 궤적의 최적화 목표는 지면에 닿는 시간이 길고 지면에 평행하며 빠른 이동을 위해 넓은 보폭을 생성 하는 것으로 두었다. 초기 값은 Edison design의 m.sketch를 사용하여 결정하였고 최적화 과정에서는 MATLAB을 사용하였으며 가능한 빠른 계산이 가능한 것에 초점을 두고 알고리즘을 작성하였다. 최적화된 결과 값에서는 지면에 닿는 궤적의 범위와 보폭의 크기, 궤적의 높이가 가장 큰 값을 결정하였다.

• KIISE Transactions on Computing Practices
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• v.22 no.4
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• pp.189-194
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• 2016

A trajectory is the motion path of a moving object. The advances in IT have made it possible to collect an immeasurable amount of various type of trajectory data from a moving object using location detection devices like GPS. The trajectories of moving objects are widely used in many different fields of research, including the geographic information system (GIS) field. In the GIS field, several attempts have been made to automatically generate digital maps of roads by using the vehicle trajectory data. To achieve this goal, the method to cluster the trajectories on the same road is needed. Usually, the $Fr{\acute{e}}chet$ distance measure is used to calculate the distance between a pair of trajectories. However, the $Fr{\acute{e}}chet$ distance measure requires prolonged calculation time for a large amount of trajectories. In this paper, we presented a fast heuristic algorithm to distinguish whether the trajectories are in close distance or not using the discrete $Fr{\acute{e}}chet$ distance measure. This algorithm trades the accuracy of the resulting distance with decreased calculation time. By experiments, we showed that the algorithm could distinguish between the trajectory within 10 meters and the distant trajectory with 95% accuracy and, at worst, 65% of calculation reduction, as compared with the discrete $Fr{\acute{e}}chet$ distance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2057-2064
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• 2010

With the development of wireless network technology, the location information of a spatiotemporal object which changes their location is used in various application. Each spatiotemporal object has many location information, hence it is inefficient to search all trajectory information of spatiotemporal objects for a range query. In this paper, we propose an efficient method which divides a trajectory and stores its division data on restricted storage space. Using suboptimal split algorithm, an extended split algorithm that minimizes the volume of EMBRs(Extended Minimum Bounding Box) is designed and simulated. Our experimental evaluation confirms the effectiveness and efficiency of our proposed splitting policy

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.356-359
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• 2015

본 연구는 웹사이트의 효율적이고 경험 디자인(User Experience Design : UX 디자인)적 설계가 가능하도록 사용자의 시각궤적을 통해 주시빈도를 확인한다. 사용자 경험치에 따라 웹 포털 사이트를 세 가지로 분류하고 와이어프레임을 제시하여 각 사이트의 화면분할과 정보영역을 분석한다. 시선추적 장치를 통해 세 가지 와이어프레임의 시각궤적 및 주시빈도를 확인하여 시선이 머무는 히트맵을 제시한다. 이를 통해 웹사이트의 디자인 설계시 페이지나 화면에 보이는 요소들의 효율적 배치를 위한 주시영역을 살펴본다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.382-385
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• 2016

본 연구는 포털사이트의 효율적이고 경험 디자인(User Experience Design : UX 디자인)적 설계가 가능하도록 제작하기 위하여 와이어 프레임에 대한 사용자의 시각궤적과 주시빈도를 확인한다. 국내 주요 포털 사이트를 점유비율에 따라 세 가지를 제시하고 로고의 유무에 따른 와이어 프레임을 제작하여 각 사이트의 화면분할과 정보영역을 분석한다. 시선추적 장치를 통해 총 6가지 와이어 프레임의 시각궤적 및 주시빈도를 확인하여 시선이 머무는 히트맵을 제시한다. 이를 통해 웹사이트의 디자인 설계시 페이지나 화면에 보이는 요소들의 효율적 배치를 위한 주시영역을 살펴본다.

• Journal of Korea Spatial Information System Society
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• v.9 no.1
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• pp.1-13
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• 2007

The necessity of future index is increasing to predict the future location of moving objects promptly for various location-based services. A representative research topic related to future index is the probability trajectory prediction technique that improves reliability using the past trajectory information of moving objects in the road network environment. However, the prediction performance of this technique is lowered by the heavy load of extensive future trajectory search in long-range future queries, and its index maintenance cost is high due to the frequent update of future trajectory. Thus, this paper proposes the Probability Cell Trajectory-Tree (PCT-Tree), a cell-based future indexing technique for efficient long-range future location prediction. The PCT-Tree reduces the size of index by rebuilding the probability of extensive past trajectories in the unit of cell, and improves the prediction performance of long-range future queries. In addition, it predicts reliable future trajectories using information on past trajectories and, by doing so, minimizes the cost of communication resulting from errors in future trajectory prediction and the cost of index rebuilding for updating future trajectories. Through experiment, we proved the superiority of the PCT-Tree over existing indexing techniques in the performance of long-range future queries.

• Journal of Korea Multimedia Society
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• v.13 no.8
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• pp.1128-1141
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• 2010

This paper proposes a method of moving object detection in crowded scene using clustered trajectory. Unlike previous appearance based approaches, the proposed method employes motion information only to isolate moving objects. In the proposed method, feature points are extracted from input frames first and then feature tracking is followed to create feature trajectories. Based on an assumption that feature points originated from the same objects shows similar motion as the object moves, the proposed method detects moving objects by clustering trajectories of similar motions. For this purpose an energy function based on spatial proximity, motion coherence, and temporal continuity is defined to measure the similarity between two trajectories and the clustering is achieved by minimizing the energy function in CRFs (conditional random fields). Compared to previous methods, which are unable to separate falsely merged trajectories during the clustering process, the proposed method is able to rearrange the falsely merged trajectories during iteration because the clustering is solved my energy minimization in CRFs. Experiment results with three different crowded scenes show about 94% detection rate with 7% false alarm rate.

• Journal of KIISE:Databases
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• v.30 no.1
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• pp.14-26
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• 2003

Moving objects' trajectories play an important role in indexing video data on their content and semantics for content-based video retrieval. In this paper, we propose new similar sub-trajectory retrieval schemes based on k-warping algorithm for efficient retrieval on moving objects' trajectories in video data. The proposed schemes are fixed-replication similar sub-trajectory retrieval(FRSR) and variable-replication similar sub-trajectory retrieval(VRSR). The former can replicate motions with a fixed number for all motions being composed of the trajectory. The latter can replicate motions with a variable number. Our schemes support multiple properties including direction, distance, and time interval as well as a single property of direction, which is mainly used for modeling moving objects' trajectories. Finally, we show from our experiment that our schemes outperform Li's scheme(no-warping) and Shan's scheme(infinite-warping) in terns of precision and recall measures.