• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.3
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• pp.67-73
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• 2005

An accuracy of theodolite system may be affected by a measurement environment and a measurement distance change from theodolite to scale bar and/or targets. This study was performed for measuring an accuracy when the distance from thodolite system to scale bar was changed $2\~6m$ on the distance 4m between two theodolites. The results showed that an accuracy was ${\pm}0.025mm$ or better when the distance from theodolite system to targets was 3, 4 and 5m. According to the results, it was found that the best distance from theodolite system to scale bar was $3\~4m$ when the collimation distance was $3\~4m$.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.48-54
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• 2005

The theodolite system consists of two theodolites, a scale bar and a target bu. A measurement accuracy of theodolite system is affected by a measurement distance of each equipment. This study was performed fir measuring an accuracy when the distance from theodolite to scale bar was changed 2~ 6 m on two theodolites distance 3 a The results showed thai the measurement accuracy could be $\pm$0.021 mm when the distance from theodolite to target was 2,3 and 6 n Specially, it was found that the maximum measurement accuracy was 10.017mm on theodolite collimation distance 3m and the distance 4 m of the theodolite and scale bar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.106-109
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• 2004

In this project, we have developed the eye-safe LRF system of 1.54 ${\mu}{\textrm}{m}$ wavelength using OPO. The maximum measured distance was 3.7km in outdoor experiment. We used Nd：YAG (1064nm) as a laser medium. It was applied BBO to construct the system. We also developed a time-counter for the range finder using a method of TOF (time of flight). The counter-clock used at the time counter was 320MHz making resolution within $\pm$1m. Start and stop signals were detected by two channel systems using PIN and APD. The LRF's repetition rate was 4 times per minute. The energy was measured to be over 9mJ. And, pulse-duration was 23ns. Resolution was $\pm$2m at the distance measurement using a target.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.74-80
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• 2005

A new dimension measuring method for the measurement of diameter of an object has been developed using laser triangulation. The 3D data of an object was calculated from the 2 dimensional image information obtained by the laser stripe using the laser triangulation. The system that use existing theory can measure the diameter of hole not only in a normal plane but also ill an incline plane. However, in the existing theory, since the lens with fixed feral length was used, the area of measurement was fixed. The simplest way to solve this problem is to change distance between a CCD camera and object. Other way is to use a zoom lens having variable focal length. In this paper, the zoom lens with variable focal length was used. Therefore, we ran experiment with magnification that is optimized according to size of object using zoom lens with variable focal length.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.914-919
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• 2010

It is confirmed that as the distance measurements accuracy of the SDS-TWR(Symmetric Double-Sided Two-Way Ranging) based on CSS(Chirp Spread Spectrum) is considerably degraded due to frequency interference and it causes to severe errors in the localization applications. In this paper, the compensation algorithm based on error rate offset of distance measurement ($CA_d$) is proposed for the purpose to reduce the ranging errors due to by the SDS-TWR ranging problems. The $CA_d$ measures the distance values between two nodes by means of 1m interval about 1~25m distances in the SDS-TWR, and compensates the distance values using the parameters related to the distance compensation. From the experiments, it is analyzed that the $CA_d$. have reduced the distance error to average 95cm and maximum 526cm, and the distance error by the $CA_d$ was below about 60cm in the 25m distances. In particular, the performance of the distance measurements accuracy by the $CA_d$ is very high in LOS(Line Of Sight) environments.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.13-21
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• 2005

The affected factors for an accuracy of theodolite system are not only the measurement environment of temperature, illumination, etc. but also the measurement processes of the distance between two theodolites, the distance from theodolite system to scale bar and the distance from theodolite system to targets. We have known that the best collimation distance between two theodolites and the best distance from theodolite system to scale bar is $3{\sim}4m$. This study was performed for searching the best distance from theodolite system to targets on above measurement configuration. And, we could know that the best distance from theodolite system to targets is $2{\sim}6m$ and the system accuracy could be within ${\pm}0.025mm$.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.689-694
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• 2008

댐 유입량은 댐 운영의 필수 인자이기 때문에 매우 중요하고, 하천유량에 비해 신뢰도가 높은 것으로 평가되고 있기 때문에 수자원의 운영 뿐 아니라 계획에도 활용되고 있다. 그러나 계산된 유입량은 평갈수기에 진폭이 너무 크게 나타나고 심지어 음 유입량이 발생하는 등 개선이 요구돼 왔다. 본 연구에서는 시간간격을 10분, 30분, 1시간 등으로 하고, 수위와 방류량이 유입량에 직접 영향을 끼치고, 관측수위의 단위가 크고, 그 진폭이 자연현상과 거리가 있어, 수위 이동평균, 수위 보간, 방류량 이동평균 등의 조합에 따라 댐 유입량의 계산을 개선할 수 있는 방법을 제안하였고, 이를 쉽게 분석, 평가할 수 있도록 시스템으로 개발하였으며, 유역면적 $4,134km^2$인 대청댐과 유역면적 $108,335mi^2$인 미국의 Lake Powell의 사례에서 크게 개선된 결과를 보여주었다. 그러나 정확하게 측정된 댐 유입량 자료가 없기 때문에 개선된 계산 유입량이 참 값이다 주장할 수 없는 것이 본 연구의 한계이며, 연구결과의 신뢰를 높이기 위해 현재 정밀하게 측정된 댐 유입량 사례를 조사 중에 있다. 그림 1은 Lake Powell의 처리전의 댐 유입량 계산 예이고 그림 2는 처리후의 개선된 유입량이다. 그림에서 유입량이 크게 개선돼 계산된 것으로 나타나고 있으나 결과가 참값인지 아직 판단할 수 없다. 대청댐의 경우도 이와 비슷한 결과를 보여주었다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.164.2-164.2
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• 2012

인공위성레이저추적(SLR, Satellite Laser Ranging) 시스템은 인공위성까지 레이저를 발사하여 되돌아오는 시간간격을 측정함으로서 위성까지의 거리를 측정하는 시스템으로 현존하는 인공위성 궤도결정 시스템으로는 가장 정밀하다. 한국천문연구원은 우주추적 및 감시의 필요성이 증가함에 따라 2008년부터 40cm급 이동형 인공위성레이저추적 시스템을 개발을 시작하였고, 현재 개발을 완료하여 시험운영 중에 있다. 시스템 개발 과정 중에 발생할 수 있는 문제점들을 최소화하기 위해, 설계 단계에서 부품을 포함한 광기계 구조물에 대한 구조해석과, 실험실 프로토타입 구성 등을 실시하였다. 제작된 각 서브시스템별 조립 및 평가는 한국천문연구원이 보유한 광학계 조립 및 평가 시설을 이용하였다. 개발된 이동형 레이저 추적 시스템의 광학부는 추적마운트에 장착되었고, 현장 시험관측을 통해 수신광학계 및 광신호유도계의 정렬 및 제어항목 교정 등을 실시하였으며, 성공적으로 시험 영상 관측을 완료하였다. 이 발표에서는 이동형 레이저 추적 시스템 광학계의 개발 과정과 그 결과에 대해 보고한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.12
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• pp.1135-1142
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• 2007

STSAT-2 has an on-board satellite retroreflector array for precise orbit determination. Satellite retroreflector array reflects photon emitted from laser and uses to determine precisely the distance from ground station to satellite by the round-trip travel time of photon. The retroreflector array of protoflight model has been developed and verified through environmental tests. This paper describes the protoflight model of retroreflector array and reports environmental test results. The environmental tests of protoflight model retroreflector array were performed successfully without damage of corner cube prism occurred in engineering model development.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.279-282
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• 2017

Kinect depth sensor, a depth camera developed by Microsoft as a natural user interface for game appeared as a very useful tool in computer vision field. In this paper, due to kinect's depth sensor and its high frame rate, we developed a distance measurement system using Kinect camera to test it for unmanned vehicles which need vision systems to perceive the surrounding environment like human do in order to detect objects in their path. Therefore, kinect depth sensor is used to detect objects in its field of view and enhance the distance measurement system from objects to the vision sensor. Detected object is identified in accuracy way to determine if it is a real object or a pixel nose to reduce the processing time by ignoring pixels which are not a part of a real object. Using depth segmentation techniques along with Open CV library for image processing, we can identify present objects within Kinect camera's field of view and measure the distance from them to the sensor. Tests show promising results that this system can be used as well for autonomous vehicles equipped with low-cost range sensor, Kinect camera, for further processing depending on the application type when they reach a certain distance far from detected objects.