• Korean Journal of Remote Sensing
• /
• v.38 no.6_1
• /
• pp.1257-1271
• /
• 2022

Recently, many Earth observation optical satellites have been developed, as their demands were increasing. Therefore, a rapid preprocessing of satellites became one of the most important problem for an active utilization of satellite images. Satellite image matching is a technique in which two images are transformed and represented in one specific coordinate system. This technique is used for aligning different bands or correcting of relative positions error between two satellite images. In this paper, we propose an automatic image matching method among satellite images with different ground sampling distances (GSDs). Our method is based on improved feature matching and robust estimation of transformation between satellite images. The proposed method consists of five processes: calculation of overlapping area, improved feature detection, feature matching, robust estimation of transformation, and image resampling. For feature detection, we extract overlapping areas and resample them to equalize their GSDs. For feature matching, we used Oriented FAST and rotated BRIEF (ORB) to improve matching performance. We performed image registration experiments with images KOMPSAT-3A and RapidEye. The performance verification of the proposed method was checked in qualitative and quantitative methods. The reprojection errors of image matching were in the range of 1.277 to 1.608 pixels accuracy with respect to the GSD of RapidEye images. Finally, we confirmed the possibility of satellite image matching with heterogeneous GSDs through the proposed method.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.27 no.3
• /
• pp.144-157
• /
• 2022

Noble gases, which are chemically inert and behave conservatively in marine environments, have been used as tracers of physical processes such as air-sea gas exchange, mixing of water masses, and distribution of glacial meltwater in the ocean. For precise measurements of Ne, Ar, and Kr, we developed a mass spectrometric system consisting of a quadrupole mass spectrometer (QMS), a high vacuum preparation line, an activated charcoal cryogenic trap (ACC), and a set of isotope standard gases. The high vacuum line consists of three sections: (1) a sample extraction section that extracts the dissolved gases in the sample and mixes them with the standard gases, (2) a gas preparation section that removes reactive gases using getters and separates the noble gases according to their evaporation points with the ACC, and (3) a gas analysis section that measures concentrations of each noble gas. The ACC attached to the gas preparation section markedly lowered the partial pressures of Ar and CO₂ in the QMS, which resulted in a reduced uncertainty of Ne isotope analysis. The isotope standard gases were prepared by mixing ²²Ne, ³⁶Ar, and ⁸⁶Kr. The amounts of each element in the mixed standard gases were determined by the reverse isotope dilution method with repeated measurements of the atmosphere. The analytical system achieved precisions for Ne, Ar, and Kr concentrations of 0.7%, 0.7%, and 0.4%, respectively. The accuracies confirmed by the analyses of air-equilibrated water were 0.5%, 1.0%, and 1.7% for Ne, Ar, and Kr, respectively.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.1
• /
• pp.13-18
• /
• 2009

Accurate solar radiation data are critical to evaluate major physiological responses of plants. For most upland crops and orchard plants growing in complex terrain, however, it is not easy for farmers or agronomists to access solar irradiance data. Here we suggest a simple method using a sun-slope geometry based topographical coefficient to estimate daily solar irradiance on any sloping surfaces from global solar radiation measured at a nearby weather station. An hourly solar irradiance ratio ($W_i$) between sloping and horizontal surface is defined as multiplication of the relative solar intensity($k_i$) and the slope irradiance ratio($r_i$) at an hourly interval. The $k_i$ is the ratio of hourly solar radiation to the 24 hour cumulative radiation on a horizontal surface under clear sky conditions. The $r_i$ is the ratio of clear sky radiation on a given slope to that on a horizontal reference. Daily coefficient for slope correction is simply the sum of $W_i$ on each date. We calculated daily solar irradiance at 8 side slope locations circumventing a cone-shaped parasitic volcano(c.a., 570m diameter for the bottom circle and 90m bottom-to-top height) by multiplying these coefficients to the global solar radiation measured horizontally. Comparison with the measured slope irradiance from April 2007 to March 2008 resulted in the root mean square error(RMSE) of $1.61MJ\;m^{-2}$ for the whole period but the RMSE for April to October(i.e., major cropping season in Korea) was much lower and satisfied the 5% error tolerance for radiation measurement. The RMSE was smallest in October regardless of slope aspect, and the aspect dependent variation of RMSE was greatest in November. Annual variation in RMSE was greatest on north and south facing slopes, followed by southwest, southeast, and northwest slopes in decreasing order. Once the coefficients are prepared, global solar radiation data from nearby stations can be easily converted to the solar irradiance map at landscape scales with the operational reliability in cropping season.

• The Journal of Korean Society for Radiation Therapy
• /
• v.18 no.1
• /
• pp.1-5
• /
• 2006

Purpose: IMRT quality assurance(Q.A) is consist of the absolute dosimetry using ionization chamber and relative dosimetry using the film. We have in general used 0.015 cc ionization chamber, because small size and measure the point dose. But this ionization chamber is too small to give an accurate measurement value. In this study, we have examined the degree of calculated to measured dose difference in intensity modulated radiotherapy(IMRT) based on the observed/expected ratio using various kinds of ion chambers, which were used for absolute dosimetry. Materials and Methods: we peformed the 6 cases of IMRT sliding-window method for head and neck cases. Radiation was delivered by using a Clinac 21EX unit(Varian, USA) generating a 6 MV x-ray beam, which is equipped with an integrated multileaf collimator. The dose rate for IMRT treatment is set to 300 MU/min. The ion chamber was located 5cm below the surface of phantom giving 100cm as a source-axis distance(SAD). The various types of ion chambers were used including 0.015cc(pin point type 31014, PTW. Germany), 0.125 cc(micro type 31002, PTW, Germany) and 0.6 cc(famer type 30002, PTW, Germany). The measurement point was carefully chosen to be located at low-gradient area. Results: The experimental results show that the average differences between plan value and measured value are ${\pm}0.91%$ for 0.015 cc pin point chamber, ${\pm}0.52%$ for 0.125 cc micro type chamber and ${\pm}0.76%$ for farmer type 0.6cc chamber. The 0.125 cc micro type chamber is appropriate size for dose measure in IMRT. Conclusion: IMRT Q.A is the important procedure. Based on the various types of ion chamber measurements, we have demonstrated that the dose discrepancy between calculated dose distribution and measured dose distribution for IMRT plans is dependent on the size of ion chambers. The reason is small size ionization chamber have the high signal-to-noise ratio and big size ionization chamber is not located accurate measurement point. Therefore our results suggest the 0.125 cc farmer type chamber is appropriate size for dose measure in IMRT.

• The Journal of the Acoustical Society of Korea
• /
• v.16 no.4
• /
• pp.49-56
• /
• 1997

In mobile communications, it is very important that we predict the propagation environments of radiation pattern, in order to decide the service area, select the best location of the best station, design the cell etc. Therefore, by analyzing the propagation prediction model that is varied according to the kind of antenna, the beam angle, the terrain and obstacles, we expect that the economic operating of communication networks, the calling quality and the service of subscriber will be enhanced. In this paper, we select the around of Seji base station in Naju-city Chonnam for modern suburban area and measure the field strength to propose the optimal propagation prediction model for suburban areas. We propose the propagation prediction model that, it is not found in the other models until now, consists of the correction coefficient with the relative differences of antenna effective height of the base station and mobile station for minimizing errors. Finally, comparing the results of the field test with the computer simulation(PPGIS : Propagation Prediction Geographic Information System) results for the Hata model, the Egri model, the Carey model and the propose model, we confirm the property of the proposed model.

• 한국HCI학회:학술대회논문집
• /
• 2006.02a
• /
• pp.362-367
• /
• 2006

지능형 주거공간에서 손 지시 명령을 통하여 가전기기를 선택하거나 로봇에게 이동하여야 하는 장소를 알려 주기 위해, 기존의 시스템은 선택되는 대상 기기의 3 차원 절대 위치를 미리 알고 있어야 한다. 또한 카메라 위치가 변동되었을 경우, 카메라의 위치를 절대좌표계 기준으로 새롭게 측정해야 하는 불편함이 있다. 이를 해결하기 위해 본 논문에서는 팬/틸트 모듈을 가진 두 대의 USB 카메라를 임의의 위치에 배치하더라도, 두 번의 손 지시만으로 선택 대상이 되는 기기의 3 차원 위치를 파악하고 이를 동작시키는 방법을 다룬다. 제안하는 방법에서는 두 대의 카메라 간의 상대 좌표계를 형성하기 위해 각 카메라에 표식을 부착한다. 각 카메라에서 다른 카메라의 표식을 관찰하면 카메라 간의 거리 및 각도를 구할 수 있기 때문에, 하나의 카메라를 기준으로 3 차원 절대 좌표계를 자동으로 설정할 수 있다. 또한, 두 대의 카메라로 사용자의 얼굴과 손을 검출하면 얻어진 기준 좌표계에 대해 얼굴과 손의 3 차원 위치를 계산하고, 두 지점을 연결하는 방향 벡터를 구함으로써 사용자가 손으로 지시하는 방향을 찾는다. 따라서, 카메라를 임의의 위치에 두더라도 사용자의 손 지시 동작만으로 대상체의 차원 위치를 파악할 수 있게 된다. 개발된 시스템의 유용성을 검증하기 위해 각 가전기기의 위치를 제안한 방법으로 구하고 실제 위치와의 오차를 분석하였다. 제안한 방법은 두 대의 USB 카메라와 일반 PC 또는 마이크로 프로세서만으로 구현할 수 있기 때문에 비용이 적게 들고 실시간 처리가 가능하며 사용자의 환경에서 편리성을 높이는 등 많은 장점을 가진다.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.39 no.3
• /
• pp.49-57
• /
• 2002

In this paper, we deal with a real time implementation of the integrated image-based navigation parameter extraction system using the TMS320C80 MVP(multimedia video processor). Our system consists of relative position estimation and absolute position compensation, which is further divided into high-resolution aerial image matching, DEM(Digital elevation model) matching, and IRS (Indian remote sensing) satellite image matching. Those algorithms are implemented in real time using the MVP. To achieve a real-time operation, an attempt is made to partition the aerial image and process the partitioned images in parallel using the four parallel processors in the MVP. We also examine the performance of the implemented integrated system in terms of the estimation accuracy, confirming a proper operation of the our system.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.9
• /
• pp.347-352
• /
• 2012

In this paper, an 2D spatial-map construction for workers identification and avoidance of AGV using the detection scheme of the spatial coordinates based on stereo camera is proposed. In the proposed system, face area of a moving person is detected from a left image among the stereo image pairs by using the YCbCr color model and its center coordinates are computed by using the centroid method and then using these data, the stereo camera embedded on the mobile robot can be controlled for tracking the moving target in real-time. Moreover, using the disparity map obtained from the left and right images captured by the tracking-controlled stereo camera system and the perspective transformation between a 3-D scene and an image plane, depth map can be detected. From some experiments on AGV driving with 240 frames of the stereo images, it is analyzed that error ratio between the calculated and measured values of the worker's width is found to be very low value of 2.19% and 1.52% on average.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.6
• /
• pp.419-424
• /
• 2017

TDoA (Time Difference-of Arrival) or DoA (Direction-of-Arrival) can be used for source localization. However, the localizing performance is dependent on relative position between source and receivers, receivers' geometric structure, sound speed, and so on. In this paper we propose a source localization method with enhanced performance that combines multiple information. The proposed method uses the time TDoA, DoA and sound speed as variables. LM (Levenberg-Marquardt) method which is one of nonlinear optimizations is applied. The performances of the proposed method was evaluated by simulation. As result of simulation, the proposed method has the lower average localizing error performance than the previous method.

• Korean Journal of Optics and Photonics
• /
• v.8 no.4
• /
• pp.333-339
• /
• 1997

We fabricated a sensor head which consists of spliced different-diameter fiber gratings for discrimination between strain and temperature. Because the fibers were drawn from the same preform, their temperature characteristics were the same but not for strain sensitivities which are inversely proportional to fibers cross-sectional areas. In measurement range of 0-1500$\mu$strain and 20-10$0^{\circ}C$, we could obtain, by using the matrix calculation, the unknown physical quantities within 10% of calculation error compared with the micrometer and thermocouple values. To improve the strain measurement accuracy, we suggest a new, novel method which deploys an unbalanced fiber Mach-Zehnder interferometer. This new signal processing technique converts the strain information to interference signal amplitude variation, temperature-independently. we obtained measurement accuracy nearly 80 times better than that obtainable with the conventional optical spectrum analyzer usage.