• Title/Summary/Keyword: Calibration Map

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Application of the New Calibration Algorithm of a Straight-Type Five-Hole Pressure Probe (직선형 5공 압력프로브의 새로운 교정 알고리듬 적용)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.11
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    • pp.863-869
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    • 2008
  • This paper investigated the new calibration algorithm of a straight-type five-hole pressure probe for measuring three-dimensional flow velocity components. This new calibration algorithm was used for velocity data reduction from the calibration map and based on the combination of a look-up, a binary search algorithm and a geometry transformation including the translation and reflection of nodes in a calibration map. The calibration map was expanded up to the application angle, ${\pm}55^{\circ}$ of a probe. This velocity data reduction method showed a perfect performance without any kind of interpolating errors in calculating yaw and pitch angles from the calibration map. Moreover, when it was applied to an actual flow field including a swirling flow, a good result came out on the whole.

Development of a Camera Self-calibration Method for 10-parameter Mapping Function

  • Park, Sung-Min;Lee, Chang-je;Kong, Dae-Kyeong;Hwang, Kwang-il;Doh, Deog-Hee;Cho, Gyeong-Rae
    • Journal of Ocean Engineering and Technology
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    • v.35 no.3
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    • pp.183-190
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    • 2021
  • Tomographic particle image velocimetry (PIV) is a widely used method that measures a three-dimensional (3D) flow field by reconstructing camera images into voxel images. In 3D measurements, the setting and calibration of the camera's mapping function significantly impact the obtained results. In this study, a camera self-calibration technique is applied to tomographic PIV to reduce the occurrence of errors arising from such functions. The measured 3D particles are superimposed on the image to create a disparity map. Camera self-calibration is performed by reflecting the error of the disparity map to the center value of the particles. Vortex ring synthetic images are generated and the developed algorithm is applied. The optimal result is obtained by applying self-calibration once when the center error is less than 1 pixel and by applying self-calibration 2-3 times when it was more than 1 pixel; the maximum recovery ratio is 96%. Further self-correlation did not improve the results. The algorithm is evaluated by performing an actual rotational flow experiment, and the optimal result was obtained when self-calibration was applied once, as shown in the virtual image result. Therefore, the developed algorithm is expected to be utilized for the performance improvement of 3D flow measurements.

Wifi Fingerprint Calibration Using Semi-Supervised Self Organizing Map (반지도식 자기조직화지도를 이용한 wifi fingerprint 보정 방법)

  • Thai, Quang Tung;Chung, Ki-Sook;Keum, Changsup
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.42 no.2
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    • pp.536-544
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    • 2017
  • Wireless RSSI (Received Signal Strength Indication) fingerprinting is one of the most popular methods for indoor positioning as it provides reasonable accuracy while being able to exploit existing wireless infrastructure. However, the process of radio map construction (aka fingerprint calibration) is laborious and time consuming as precise physical coordinates and wireless signals have to be measured at multiple locations of target environment. This paper proposes a method to build the map from a combination of RSSIs without location information collected in a crowdsourcing fashion, and a handful of labeled RSSIs using a semi-supervised self organizing map learning algorithm. Experiment on simulated data shows promising results as the method is able to recover the full map effectively with only 1% RSSI samples from the fingerprint database.

A New Calibration Algorithm of a Five-Hole Pressure Probe for Flow Velocity Measurement (유동속도계측을 위한 5공압력프로브의 새로운 교정 알고리듬)

  • Kim, J.K.;Oh, S.H.
    • Journal of Power System Engineering
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    • v.12 no.4
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    • pp.18-25
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    • 2008
  • This paper investigated the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new data reduction method Includes a look-up, a geometry transformation such as the translation and reflection of nodes, and a binary search algorithm. This new calibration map was applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, this data reduction method showed a perfect performance without any kind of interpolation errors In calculating yaw and pitch angle from the calibration map.

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The Performance Assessment of a Straight-Type Five-Hole Pressure Probe Using a Zone Partition and Two-Dimensional Curve-Fitting Functions (영역분할과 2차원 커브피팅 함수들을 이용하는 직선형 5공 압력프로브의 성능 평가)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of Power System Engineering
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    • v.18 no.1
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    • pp.22-31
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    • 2014
  • This paper introduced the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new velocity data reduction method using both a commercial two-dimensional curve-fitting program and the zone partition method of a calibration map was firstly introduced in this study. This new calibration method can be applied up to the wide flow angle of ${\pm}80^{\circ}$ despite of using a five-hole pressure probe because this data reduction method showed a comparatively good performance in calculating yaw and pitch angles from the calibration map.

Calibration of HSPF Hydrology Parameters Using HSPEXP Model Performance Criteria (HSPEXP 모형평가지표 이용한 HSPF 모형의 수문매개변수 보정)

  • Kim, Sang-Min;Seong, Choung-Hyun;Park, Seung-Woo
    • Journal of The Korean Society of Agricultural Engineers
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    • v.51 no.4
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    • pp.15-20
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    • 2009
  • The purpose of this study was to test the applicability of the HSPEXP model performance criteria for calibrating hydrologic parameters of HSPF. Baran watershed, located at Whasung city, was selected as a study watershed in this study. Input data for the HSPF model were obtained from the digital elevation map, landuse map, soil map and others. Water flow data from 1996 to 2000 was used for calibration and from 2002 to 2007 was for validation. Using the HSPEXP decision-support software, hydrology parameters were adjusted based on total volume, then low flows, storm flows, and finally seasonal flows. Suggested criteria for each model performance variables were referenced from the previous research. For the calibration period, all the HSPEXP model performance criteria were satisfied while two criteria were slightly violated for the validation period.

Evaluation of Applicability and Hydrologic Parameter Calibration for HSPF Model using Expert System for HSPF (매개변수 보정 전문가시스템을 이용한 HSPF 모형의 수문 매개변수 보정 및 적용성 평가)

  • Kim, Sung Min;Kim, Sang Min
    • Journal of The Korean Society of Agricultural Engineers
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    • v.55 no.4
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    • pp.13-20
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    • 2013
  • The purpose of this study was to evaluate the applicability of the HSPEXP expert system for the calibration of the Hydrological Simulation Program - Fortran (HSPF) for the study watershed. HSPEXP offers advice to the modeler, suggesting parameter changes that might result in better representation of a river basin and provides explanations supporting the recommended parameter changes. The study watershed, Sancheong, is located within the Nakdong River Basin and having the size of $1,072.4km^2$. Input data for the HSPF model were obtained from the landuse map, digital elevation map, meteorological data and others. Water flow data from 2006 to 2008 were used for calibration and from 2009 to 2010 were for validation. Using the HSPEXP expert system, hydrological parameters were adjusted based on total volume, then low flows, storm flows, and finally seasonal flows. For the calibration and validation period, all the HSPEXP model performance criteria were satisfied.

Refinements of Multi-sensor based 3D Reconstruction using a Multi-sensor Fusion Disparity Map (다중센서 융합 상이 지도를 통한 다중센서 기반 3차원 복원 결과 개선)

  • Kim, Si-Jong;An, Kwang-Ho;Sung, Chang-Hun;Chung, Myung-Jin
    • The Journal of Korea Robotics Society
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    • v.4 no.4
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    • pp.298-304
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    • 2009
  • This paper describes an algorithm that improves 3D reconstruction result using a multi-sensor fusion disparity map. We can project LRF (Laser Range Finder) 3D points onto image pixel coordinatesusing extrinsic calibration matrixes of a camera-LRF (${\Phi}$, ${\Delta}$) and a camera calibration matrix (K). The LRF disparity map can be generated by interpolating projected LRF points. In the stereo reconstruction, we can compensate invalid points caused by repeated pattern and textureless region using the LRF disparity map. The result disparity map of compensation process is the multi-sensor fusion disparity map. We can refine the multi-sensor 3D reconstruction based on stereo vision and LRF using the multi-sensor fusion disparity map. The refinement algorithm of multi-sensor based 3D reconstruction is specified in four subsections dealing with virtual LRF stereo image generation, LRF disparity map generation, multi-sensor fusion disparity map generation, and 3D reconstruction process. It has been tested by synchronized stereo image pair and LRF 3D scan data.

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Position Estimation Using Magnetic Field Map (자기장 지도를 이용한 위치 추정)

  • Kim, Han-Sol;Moon, Woo-Sung;Seo, Woo-Jin;Baek, Kwang-Ryul
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.4
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    • pp.290-298
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    • 2013
  • Geomagnetic is refracted by building's wall and pillar. Therefore refracted geomagnetic is able to be used as feature point. In a specific space, a mobile device that is equipped with magnetic sensor array measures 3-axis magnetic field for each point. Magnetic field map is acquired by collecting the every sample point in the magnetic field. The measured magnetic field must be calibrated, because each magnetic sensor has a distortion. For this reason, sensor distortion model and sensor calibration method are proposed in this paper. Magnetic field that is measured by mobile device matches magnetic field map. Result of the matching is used for position estimation. This paper implements hardware system for position estimation method using magnetic field map.

Hybrid Sensor Calibration Scheme for Mobile Crowdsensing-Based City-Scale Environmental Measurements

  • Son, Seung-Chul;Lee, Byung-Tak;Ko, Seok Kap;Kang, Kyungran
    • ETRI Journal
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    • v.38 no.3
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    • pp.551-559
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    • 2016
  • In this paper, we propose a hybrid sensor calibration scheme for mobile crowdsensing applications. As the number of newly produced mobile devices containing embedded sensors continues to rise, the potential to use mobile devices as a sensor data source increases. However, because mobile device sensors are generally of a lower performance and cost than dedicated sensors, sensor calibration is crucial. To enable more accurate measurements of natural phenomena through the use of mobile device sensors, we propose a hybrid sensor calibration scheme for such sensors; the scheme makes use of mobile device sensors and existing sensing infrastructure, such as weather stations, to obtain dense data. Simulation results show that the proposed scheme supports low mean square errors. As a practical application of our proposed scheme, we built a temperature map of a city using six mobile phone sensors and six reference sensors. Thanks to the mobility of the sensors and the proposed scheme, our map presents more detailed information than infrastructure-based measurements.