• 도시과학
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• 제7권2호
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• pp.53-60
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• 2018

Digital Twin is a technology that creates a photocopy of real-world objects on a computer and analyzes the past and present operational status by fusing the structure, context, and operation of various physical systems with property information, and predicts the future society's countermeasures. In particular, 3D rendering technology (UAS, LiDAR, GNSS, etc.) is a core technology in digital twin. so, the research and application are actively performed in the industry in recent years. However, UAS (Unmanned Aerial System) and LiDAR (Light Detection And Ranging) have to be solved by compensating blind spot which is not reconstructed according to the object shape. In addition, the terrestrial LiDAR can acquire the point cloud of the object more precisely and quickly at a short distance, but a blind spot is generated at the upper part of the object, thereby imposing restrictions on the forward digital twin modeling. The UAS is capable of modeling a specific range of objects with high accuracy by using high resolution images at low altitudes, and has the advantage of generating a high density point group based on SfM (Structure-from-Motion) image analysis technology. However, It is relatively far from the target LiDAR than the terrestrial LiDAR, and it takes time to analyze the image. In particular, it is necessary to reduce the accuracy of the side part and compensate the blind spot. By re-optimizing it after fusion with UAS and Terrestrial LiDAR, the residual error of each modeling method was compensated and the mutual correction result was obtained. The accuracy of fusion-based 3D model is less than 1cm and it is expected to be useful for digital twin construction.

• 한국환경과학회지
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• 제31권6호
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• pp.479-490
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• 2022

This study was to evaluate the utilization of terrestrial light detection and ranging for forest inventory in coniferous forests. Heights and diameter of the stand trees were measured manually using the traditional measurement method and the method using terrestrial LiDAR. The results of two methods were compared and analyzed to evaluate accuracy and feasibility. The terrestrial LiDAR used fixed and handy types to compare the accuracy between different operational methods. Comparative analyses used a paired t-test and Bland-Altman plot analysis. In the case of tree heights, the average of difference between the traditional method and terrestrial LiDAR for each plot was 0.81 m, -0.07 m, and 0.13 m for fixed type; 2.88 m, 1.19 m, and 0.93 m for the handy type. In the case of tree diameter at breast height, the average value of the difference between traditional methods and terrestrial LiDAR for each plot was 0.13 cm, -0.66 cm, and -0.03 cm for fixed type; 2.36 cm, 2.13 cm, and 1.92 cm for the handy type. The values from the method using the fixed type was highly consistent with that using the traditional measurement methods; the average difference was closer to zero. The crown density influences the precision of the height measurement using terrestrial LiDAR in coniferous forests. Therefore, future studies should focus on verifying the accuracy of terrestrial LiDAR in forests and on expanding the utilization of terrestrial LiDARs according to their operational methods.

• Spatial Information Research
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• 제20권1호
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• pp.27-38
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• 2012

최근 CFD 기술 발전과 보편화를 통해 소규모 지역에서의 수치기상모의 영향평가와 설계반영 기법이 단지계획과 엔지니어링 설계에 반영되는 추세이지만 수치지도에서의 건물이나 지물 높이정보 부재와 그에 따른 입력방법의 부정확성 등으로 인해 수치기상모의 결과의 신뢰성이 저하되어, 산업 현장에서 실험적 연구로만 진행될 뿐 일반 업무로는 확대되고 있지 않는 실정이다. 따라서 본 연구는 현재 대도시를 중심으로 구축되고 있는 항공 LiDAR 기술을 통해 수집된 데이터들로부터 수치기상모의에 필요한 기본 입력 자료를 자동 추출 및 구축하여 수치기상모의에 활용하고자 기존의 수치지도 및 현장조사 자료를 기반으로 하는 수치모의와 비교한 결과, 모의 범위 및 해상도가 증가할수록 초기입력자료(.in)의 생상효율성이 증가하였으며, 자료의 품질 및 해상도 또한 향상된 결과를 얻을 수 있었다. 이를 통해 향후, 도시 재개발로 인해 발생하는 입체적인 도시의 물리적 구조 변화를 항공 LiDAR 데이터를 이용함으로써 환경변화예측을 위한 수치모의에 빠르게 이용할 수 있을 것이다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.106-109
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• 2006

Over the years, many researches have been performed to create 3D digital maps. Nevertheless, it is still time-consuming and involves a high cost because a large part of 3D digital mapping is conducted manually. To compensate this limitation, we propose methodologies to represent 3D objects as 3D symbols and locate these symbols into a base map automatically. First of all, we constructed the 3D symbol library to represent 3D objects as 3D symbols. In the 3D symbol library, the attribute and geometry information are stored, which defines factors related to the types of symbols and related to the shapes respectively. These factors were used to match 3D objects and 3D symbols. For automatic mapping of 3D symbols into a base map, we used predefined parameters such as the size, the height, the rotation angle and the center of gravity of 3D objects which are extracted from Light Detection and Ranging (LIDAR) data and 2D digital maps. Finally, the 3D map in urban area was constructed and the mapping results were tested using aerial photos as reference data. Through this research, we can identify that the developed the algorithms can be used as effective techniques for 3D digital cartographic techniques

• 한국건축시공학회지
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• 제23권3호
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• pp.273-284
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• 2023

건설프로젝트 진행 시 골조공사 후 시공상태를 점검하는 업무가 필수적이며, 이에 골조의 수직 및 수평 정확도를 점검하고 결함에 대한 보수작업을 수행한다. 하지만 기존의 업무방식은 점검자의 주관적 판단 및 인적오류의 발생 가능성으로 인한 신뢰성 문제, 수작업으로 인한 인력 및 시간 소모적 문제 등이 존재한다. 이에 본 연구는 상기 문제점을 해결하고, 골조공사 시공상태 점검 및 결과공유 과정의 효율을 높이고자 LiDAR 및 AR 기술의 활용방안을 제안하였다. 본 연구에서는 LiDAR를 통해 골조의 3D Point Cloud 데이터를 취득하여 시공상태 점검에 적용하는 방안과, 점검결과 데이터를 BIM 모델에 입력 후, AR을 통해 시각화하는 방안을 제안하였다. 이는 기존 방식 대비 점검과정의 객관성, 결과공유의 신속성 및 정확도 측면에서 효율적인 방식임을 확인하였으며, 더불어 건설프로젝트 전체의 품질 및 생산성 향상에 기여할수 있을 것으로 기대된다.

• 한국지리정보학회지
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• 제13권2호
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• pp.54-63
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• 2010

2009년 7월 9일부터 14일까지 누적강우 455mm의 집중호우에 의해 제천시 일대에 다수의 토석류 사태가 발생하였다. 토석류 발생에 따른 지형변화를 분석하기 위하여 수치지도와 라이다(LiDAR) 자료를 이용하여 고해상도의 수치고도모델(DEM)을 생성하였다. 라이다측량을 위해서 고해상도의 디지털 카메라와 GPS가 탑재된 3차원 스캐너 시스템 (RIEGLE LMS-Z390i)을 이용하였다. 라이다 스캐닝에 의해 생성된 포인트 자료는 클리핑과 필터링 작업을 거친 후 수치지도에 중첩시켜 토석류 발생 후의 지형의 DEM을 생성한다. 이렇게 토석류 발생 전후의 DEM 비교결과, 토석류 발생에 의한 침식과 퇴적량은 각각 $17,586m^3$, $7,520m^3$으로 평가되었다. 이러한 고해상도 지상라이다시스템을 이용하여 지형변화 관측을 통해 장래 토석류 모델 연구에 기여할 수 있을 것으로 판단되었다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.500-503
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• 2006

To adjust the discrepancy between Light Detection and Ranging (LIDAR) strips, previous researches generally have been conducted using conjugate features, which are called feature-based approaches. However, irrespective of the type of features used, the adjustment process relies upon the existence of suitable conjugate features within the overlapping area and the ability of employed methods to detect and extract the features. These limitations make the process complex and sometimes limit the applicability of developed methodologies because of a lack of suitable features in overlapping areas. To address these drawbacks, this paper presents a methodology using area-based algorithms. This approach is based on the scheme that discrepancies make complex the local height variations of LIDAR data whithin overlapping area. This scheme can be helpful to determine an appropriate transformation for adjustment in the way that minimizes the geographical complexity. During the process, the contour tree (CT) was used to represent the geological characteristics of LIDAR points in overlapping area and the Iterative Closest Points (ICP) algorithm was applied to automatically determine parameters of transformation. After transformation, discrepancies were measured again and the results were evaluated statistically. This research provides a robust methodology without restrictions involved in methods that employ conjugate features. Our method also makes the overall adjustment process generally applicable and automated.

• 한국측량학회지
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• 제25권6_1호
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• pp.507-516
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• 2007

Segmentation and organization of the LiDAR (Light Detection and Ranging) data of the Earth's surface are difficult tasks because the captured LiDAR data are composed of irregularly distributed point clouds with lack of semantic information. The reason for this difficulty in processing LiDAR data is that the data provide huge amount of the spatial coordinates without topological and/or relational information among the points. This study introduces LiDAR data segmentation technique by utilizing histograms of the LiDAR height image data and analyzing roof shape for 3D reconstruction and visualization of the buildings. One of the advantages in utilizing LiDAR height image data is no registration required because the LiDAR data are geo-referenced and ortho-projected data. In consequence, measurements on the image provide absolute reference coordinates. The LiDAR image allows measurement of the initial building boundaries to estimate locations of the side walls and to form the planar surfaces which represent approximate building footprints. LiDAR points close to each side wall were grouped together then the least-square planar surface fitting with the segmented point clouds was performed to determine precise location of each wall of an building. Finally, roof shape analysis was performed by accumulated slopes along the profiles of the roof top. However, simulated LiDAR data were used for analyzing roof shape because buildings with various shapes of the roof do not exist in the test area. The proposed approach has been tested on the heavily built-up urban residential area. 3D digital vector map produced by digitizing complied aerial photographs was used to evaluate accuracy of the results. Experimental results show efficiency of the proposed methodology for 3D building reconstruction and large scale digital mapping especially for the urban area.

• 한국농공학회논문집
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• 제66권3호
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• pp.1-14
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• 2024

Gaining an accurate 3D stream geometry has become feasible with Unmanned Aerial Vehicle (UAV), which is crucial for better understanding stream hydrodynamic processes. The objective of this study was to investigate series of filters to remove stream vegetation and propose the best method for generating Digital Terrain Models (DTMs) using UAV-based point clouds. A stream reach approximately 500 m of the Bokha stream in Icheon city was selected as the study area. Point clouds were obtained in August 1st, 2023, using Phantom 4 multispectral and Zenmuse L1 for Structure from Motion (SfM) and Light Detection And Ranging (LiDAR) respectively. Three vegetation filters, two morphological filters, and six composite filters which combined vegetation and morphological filters were applied in this study. The Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were used to assess each filters comparing with the two cross-sections measured by leveling survey. The vegetation filters performed better in SfM, especially for short vegetation areas, while the morphological filters demonstrated superior performance on LiDAR, particularly for taller vegetation areas. Overall, the composite filters combining advantages of two types of filters performed better than single filter application. The best method was the combination of Progressive TIN (PTIN) and Color Indicies of Vegetation Extraction (CIVE) for SfM, showing the smallest MAE of 0.169 m. The proposed method in this study can be utilized for constructing DTMs of stream and thus contribute to improving the accuracy of stream hydrodynamic simulations.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2005년도 추계학술대회
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• pp.81-104
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• 2005

가상공간 시현이나 GIS 및 이동통신과 같은 다양한 응용분야에 정확한 3차원 도시모델은 기본적인 자료가 되고 있다. LiDAR 시스템은 대상물의 3차원 정보를 직접적으로 획득할 수 있는 새로운 시스템이다. LiDAR 자료로부터 수동적으로 3차원 정보를 구축하는 것은 많은 시간과 비용을 필요로 한다. 이와 같은 이유로 많은 연구가 자동화에 그 초점을 맞추고 있다. 본 연구에서는 필터링기법을 이용해서 LiDAR 자료로부터 지면과 비지면을 분류하고, 지면점을 이용하여 DTM을 생성하고, 비지면점을 이용해서 건물을 구축하였다. 정확도의 평가결과 DTM은 고층아파트지역에서 약 0.16m, 저층주거지역에서 0.59m의 오류가 나타났으며, 건물의 경우 1/5,000 수치지형도의 정밀도와 부합하는 결과를 나타냈다.