• 한국측량학회:학술대회논문집
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• 한국측량학회 2007년도 춘계학술발표회 논문집
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• pp.153-156
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• 2007

There have been many studies on extracting building boundaries from LiDAR(Light Detection And Ranging) data. In such studies, points are first segmented, then are further processed to get straight boundary lines that better approximate the real boundaries. In most research in this area, processes like generalization or regularization assume that buildings have only right angles, i.e. all the line segments of the building boundaries are either parallel or perpendicular. However, this assumption is not valid for many buildings. We present a new approach consisting of three steps that is applicable to more complex building boundaries. The three steps consist of boundary tracing, generalization, and regularization. Each step contains algorithms that range from slight modifications of conventional algorithms to entirely new concepts. Four typical building shapes were selected to test the performance of out new approach and the results were compared with digital maps. The results show that the proposed approach has good potential for extracting building boundaries of various shapes.

• 대한원격탐사학회지
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• 제23권3호
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• pp.199-209
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• 2007

Traditionally, aerial images have been used as main sources for compiling topographic maps. In recent years, lidar data has been exploited as another type of mapping data. Regarding their performances, aerial imagery has the ability to delineate object boundaries but omits much of these boundaries during feature extraction. Lidar provides direct information about heights of object surfaces but have limitations with respect to boundary localization. Considering the characteristics of the sensors, this paper proposes an approach to extracting buildings from lidar and aerial imagery, which is based on the complementary characteristics of optical and range sensors. For detecting building regions, relationships among elevation contours are represented into directional graphs and searched for the contours corresponding to external boundaries of buildings. For generating building models, a wing model is proposed to assemble roof surface patches into a complete building model. Then, building models are projected and checked with features in aerial images. Experimental results show that the proposed approach provides an efficient and accurate way to extract building models.

• 대한공간정보학회지
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• 제20권4호
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• pp.117-125
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• 2012

항공라이다 데이터를 이용한 건물 추출 연구가 많이 진행되어 오고 있으나 대부분의 연구는 건물경계를 직선으로 가정하기 때문에 곡선경계가 포함된 건물의 경계를 올바르게 모델링하지 못하는 한계가 있다. 본 논문은 곡선경계를 포함하는 건물을 항공라이다 데이터로부터 직선과 곡선이 혼합된 경계로 모델링하는 것을 목적으로 한다. 건물점들에 대하여 적응적 컨벡스헐 알고리즘과 큰 반경의 국지적 컨벡스헐 알고리즘을 적용하여 두 세트의 경계점을 추출한다. 경계점들의 평균 점 간격 및 수직이등분선의 교차 비율에 의하여 곡선 세그먼트를 판별한 후, 직선과 곡선 세그먼트에 대하여 각각 다른 정규화 방법을 적용하여 건물경계를 모델링한다. 실험결과, 곡선 세그먼트의 추출 완전성과 정확성이 각각 69%, 100%로서 본 연구의 방법을 통해 대부분의 곡선경계를 올바르게 추출 및 모델링 할 수 있었다. 본 연구의 결과는 수치지도 제작기준을 만족하는 건물경계를 자동으로 생성하는데 효과적으로 활용될 수 있을 것이다.

• Earthquakes and Structures
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• 제8권1호
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• pp.275-304
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• 2015

The objective of this paper is to investigate the validity of transmitting boundaries in dynamic analysis of soil-structure interaction problems. As a case study, the proposed Baghdad metro line is considered. The information about the dimensions and the material properties of the concrete tunnel and surrounding soil were obtained from a previous study. A parametric study is carried out to investigate the effect of several parameters including the peak value of the horizontal component of earthquake displacement records and the frequency of the dynamic load. The computer program (Mod-MIXDYN) is used for the analysis. The numerical results are analyzed for three conditions; finite boundaries (traditional boundaries), infinite boundaries modelled by infinite elements (5-node mapped infinite element) presented by Selvadurai and Karpurapu, 1988), and infinite boundaries modelled by dashpot elements (viscous boundaries). It was found that the transmitting boundary absorbs most of the incident energy. The distinct reflections observed for the "fixed boundaries" disappear by using "transmitted boundaries". This is true for both cases of using viscous boundaries or mapped infinite elements. The type and location of the dynamic load represent two controlling factors in deciding the importance of using infinite boundaries. It was found that the results present significant differences when earthquake is applied as a base motion or a pressure load is applied at the surface ground. The peak value of the vertical displacement at nodes A, B, E and F (located at the tunnel's crown and side walls, and at the surface above the tunnel and at the surface 6.5 m away from tunnel's centre respectively) increases with the frequency of the surface pressure load for both cases 1 and 2 (traditional boundaries and mapped infinite elements respectively) while it decreases for case 3 (viscous boundaries). The modular ratio Ec/Es (modulus of elasticity of the concrete lining to that of the surrounding soil) has a considerable effect on the peak value of the horizontal displacement at node B (on the side wall of the tunnel lining) increase about (17.5) times, for the three cases (1, 2, and 3).

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.141-144
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• 2008

Many studies have been conducted on extracting buildings from ALS(Airborne Laser Scanning) data. After segmentation or classification of building points, additional steps such as generalization is required to get straight boundary lines that better approximate the real ones. In much research, orthogonal constraints are used to improve accuracies and qualities. All the lines of the building boundaries are assumed to be either parallel or perpendicular mutually. However, this assumption is not valid in many cases and more complex shapes of buildings have been increased. A new algorithm is presented that is applicable to various complex buildings. It consists of three steps of boundary tracing, grouping, and regularization. The performance of our approach was evaluated by applying the algorithm to some buildings and the results showed that our proposed method has good potential for extracting building boundaries of various shapes.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.246-251
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• 1998

This paper proposes a new building segmentation method from 1m resolution imagery using an Active Contour Model, known as "Balloons". The original balloons, which was designed by Cohen(Cohen, 1991) to extract features from medical images, are modified for building segmentation. The proposed method consists of two phases. Firstly, building boundaries are extracted by balloons with a given position on buildings from an operator. Since balloons actively adjust their shapes according to the boundaries, there is no more shape limitations on detecting buildings. Secondly, buildings are segmented by connecting the corners detected from the building boundaries, because most buildings, which are man-made objects, are effectively described by polygons. The test results show that most buildings are segmented efficiently and easily. The proposed method is new and timely as 1m resolution spaceborne imagery will be available in the very near future. The proposed method can be used fur operational building segmentation from such imagery.

• 방송공학회논문지
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• 제13권2호
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• pp.236-244
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• 2008

본 논문에서는 칼라 세그멘테이션, 에지 정합, 지각적 그룹핑 등을 사용하여 Lidar 데이터와 광학 영상의 정보 융합에 의한 새로운 구조물 검출 및 복원 알고리듬을 제안한다. 제안하는 알고리듬은 두 가지 단계로 구성된다. 첫 번째로, 항공 Lidar 데이터로부터 초기 구조물 추출 결과와 영상의 칼라 세그멘테이션 결과를 사용하여 coarse building boundary를 추출한다. 두 번째로, coarse building boundary와 에지 정합 및 지각적 그룹핑에 의해 보다 정밀한 구조물 추출 결과인 precise building boundary를 추출한다. 본 논문에서 제안하는 알고리듬은 보다 신뢰성 있는 구조물 검출을 위해, 광학 영상으로부터 칼라 정보를 사용한다. 이를 통해, Lidar에 의해 획득된 붕괴된 형태의 구조물 외곽선을 보완한다. 또한, 인공지물의 특징으로서, 에지의 직선성 및 다면체 형태의 지붕모양을 반영함으로써 신뢰성 있는 구조물을 검출한다. 다중 센서 데이터에 대한 실험은 제안하는 알고리듬이 Lidar 단일 센서 결과에 비해 정밀하고 신뢰성 있는 결과를 보여준다.

• ETRI Journal
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• 제33권4호
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• pp.547-557
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• 2011

This study presents an approach for extracting boundaries of various buildings, which have concave boundaries, inner yards, non-right-angled corners, and nonlinear edges. The approach comprises four steps: building point segmentation, boundary tracing, boundary grouping, and regularization. In the second and third steps, conventional algorithms are improved for more accurate boundary extraction, and in the final step, a new algorithm is presented to extract nonlinear edges. The unique characteristics of airborne light detection and ranging (LIDAR) data are considered in some steps. The performance and practicality of the presented algorithm were evaluated for buildings of various shapes, and the average omission and commission error of building polygon areas were 0.038 and 0.033, respectively.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.241-244
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• 2005

Many building detection methods mainly rely on line segments extracted from aerial or satellite imagery. Building detection methods based on line segments, however, are difficult to succeed in high resolution satellite imagery such as IKONOS imagery, for most buildings in IKONOS imagery have small size of roofs with low contrast between roof and background. In this paper, we propose an efficient method to extract line segments and group them at the same time. First, edge preserving filtering is applied to the imagery to remove the noise. Second, we segment the imagery by watershed method, which collects the pixels with similar intensities to obtain homogeneous region. The boundaries of homogeneous region are not completely coincident with roof boundaries due to low contrast in the vicinity of the roof boundaries. Finally, to resolve this problem, we set up snake model with segmented region boundaries as initial snake's positions. We used a greedy algorithm to fit a snake to roof boundary. Experimental results show our method can obtain more .correct roof boundary with small size and low contrast from IKONOS imagery. Snake algorithm, building roof detection, watershed segmentation, edge-preserving filtering

• 한국측량학회지
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• 제34권5호
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• pp.503-514
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• 2016

객체 외곽선의 정확한 묘사는 수치지형도, 건물모델, 공간정보 데이터베이스와 같은 공간정보 성과물을 신뢰성 있게 제공하기 위해 중요하다. 라이다 데이터에서 건물의 실제 경계는 지붕에 있는 최외곽점들과 건물 주변의 지표면 상에 있는 점 사이에 존재한다. 그러므로 건물 지붕에 있는 점들 만으로 결정된 외곽선은 건물의 실제 경계와 일치하지 않는다. 본 논문은 라이다 데이터를 이용하여 건물의 실제 외곽선에 근접한 외곽선을 추정하는 것이 목적이며, 격자화 되지 않은 원래 데이터에서의 건물과 지표면 데이터로부터 최종 외곽선을 결정하였다. 최종 외곽선 결정방법은 두 영역 간의 해상 경계선 결정에 적용하는 방법과 유사하다. 제안한 방법은 분할된 데이터로부터 초기 외곽선을 결정하고, 지붕의 점들과 지표면 상의 점들을 이용한 외곽선을 추정하였다. 또한 점밀도가 극히 낮은 데이터에도 적용하여 제안한 방법의 신뢰성을 검증하였다. 시뮬레이션 및 실제 라이다 데이터를 이용하여 실험을 수행하여 타당성과 효용성을 검증하였지만, 향후 개선되고 향상될 부분이 있다고 사료된다.