• Proceedings of the KSRS Conference
• /
• 2002.10a
• /
• pp.75-80
• /
• 2002

The mainly used technique to rectify satellite images with distortion is to develop a mathematical relationship between the pixel coordinates on the image and the corresponding points on the ground. By defining the relationship between two coordinate systems, a polynomial model is designed and various linear transformations are used. These GCP based geometric correction has performed overall plane to plane mapping. In the overall plane mapping, overall structure of a scene is considered, but local variation is discarded. The highly variant height of region is resampled with distortion in the rectified image. To solve this problem this paper proposed the TIN-based rectification on a satellite image. The TIN based rectification is good to correct local distortion, but insufficient to reflect overall structure of one scene. So, this paper shows the experimental result and the analysis of each rectification model. It also describes the relationship GCP distribution and rectification model. We can choose a geometric correction model as the structural characteristic of a satellite image and the acquired GCP distribution.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.7 no.1
• /
• pp.37-48
• /
• 1989

Electronic Distance Meter(EDM) is widely used for the traverse surveying and trilateration net recently, therefore, the study on reliability of EDM is very important. In this study, the reliability of EDM is examined by calculating the distortion of traverse surveying net, statistically analyzing the results of side length between triangulation and trilateration. As the result of this study, correction equation of EDM and steel-tape is obtained. And also, linear regression equations with correlation coefficient (0.89-0.98) show resulting from the error analysis of each side length. In addition to checking the distortion of traverse surveying net, distortion calculated with correction EDM appears to be the smallest value.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.25 no.2
• /
• pp.281-286
• /
• 1995

Tooth length determination is a crucial step in endodontic treatment. Traditionally, radiographs are used to confirm working length of the root length. This study was performed to evaluate the radiographic distortion(magnification) and calculate correction coefficients for the object-film distance. Ninty-six radiographs were made of eight extracted teeth(two upper first premolars, two lower first premolars, two upper first molars, and two lower first molars) by using the 16 inch long cone paralelling techniques with 1mm interval from 5 to 16mm tooth-film distance. The results were as follows. 1. The least mean radiographic distortion from 5 to 16mm tooth-film distance was 2.42±0.68％(the length of mesiobuccal cusp-mesial root of lower first molars), the greatest distortion was 4.74±1.36％(the length of mesiobuccal cusp-mesiobuccal root of upper first molars). 2. The greatest correction coefficient was 0.986(the mesiobuccal cusp-mesial root of lower first molars, the lowest one was 0.937(the mesiobuccal cusp-mesiobuccal root of upper first molars).

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.11
• /
• pp.1645-1650
• /
• 2015

This paper presents the 3-dimensional electromagnetic field analysis method and correction of sensor distortion that is used by a motor speed sensor. The magnetic sensors are being expanded due to lower price than the other speed sensors such as resolver and encoder. Magnetic sensor generates sine and cosine waves when the motor rotates. However, the sine and cosine signals are distorted due to magnetic noise, which makes the angle error of the sensor, generated near by the Hall element. This paper defines an optimal design variables by using the Taguchi method to minimize output distortion of the magnetic sensor and permanent magnet. To enhance reliability of the magnetic position sensor from sensitivity error, assembly amplitude mismatch and the electrical angle, 3-Dimensional electromagnetic finite element method and correction algorithm errors were performed in due of the magnetic sensor in order to improve the quality of the initial production model.

• Journal of Korean Association for Spatial Structures
• /
• v.2 no.1 s.3
• /
• pp.67-73
• /
• 2002

Measurement of fluctuating pressure by tube system is carefully designed due to the organ-pipe resonance. It is necessary to correct the pressure before analysis. The three method for correction the distortion fluctuation pressure short tube length and the frequency response functions and insert a restrictor in the tube to increase the damping. The first method is useful when the tube length is short. In second method, the distorted signal through the tubing transformed into the frequency domain, dividing by transfer function and inverse fourier transforming back into the time domain gives the required pressure signal. In this paper three types of tubing which have different length of 100cm, 150cm, 200cm were experimented the distorted signal and correct the distortion signal

• Journal of Power Electronics
• /
• v.18 no.2
• /
• pp.323-331
• /
• 2018

Buck power factor correction (PFC) converters, compared with conventional boost PFC converters, exhibit high efficiency performance in the entire range of universal line voltage. This feature has gotten more attention for eliminating the zero crossing dead angle of buck PFC rectifiers. Furthermore, bridgeless structures for the reduction of conduction losses have been proposed. The aim of this paper is to introduce a single-phase buck rectifier that simultaneously has unity power factor (PF) and bridgeless structure while operating in the continuous conduction mode (CCM). For this purpose, two auxiliary flyback converters without any active switches are applied to a bridgeless buck rectifier to eliminate the zero crossing dead angle and achieve unity power factor, low total harmonic distortion (THD) and high efficiency. The operation and design considerations of the proposed rectifier are verified on a 150W, 48V prototype using a conventional peak-current-mode control. The measurement results show that the proposed rectifier has nearly unity power factor, THD less than 7% and high efficiency.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.299-301
• /
• 1996

Since a standard lens has small sight angle, a fish-eye lens can be used in order to obtain wide sight angle for the robot vision system. In spite of the advantage, the image through the lens has variable resolution; the central information of the lens is of high resolution, but the peripheral information is of low resolution. Owing to this difference of resolution, the variable resolution image should be transformed to a uniform resolution image in order to determine the positions of the objects in the image. In this work, the correction method for the distorted image is presented and the performance is analyzed. Furthermore, the camera with a fish eye lens can be used to determine the real world coordinates. The performance is shown through experiments.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2015.10a
• /
• pp.1406-1407
• /
• 2015

본 논문에서는 도로 위 숫자 및 기호인식에 적합한 Calibration Model에 대하여 연구하였다. 기존에 제시된 Geometric Transform, Fisheye Projection, Caltech Toolbox 기반 방법으로 얻은 Calibration Model의 성능을 비교하였다. Geometric Transform은 Fisheye Distortion Correction에 부적합한 결과를 얻었고, Fisheye Projection은 성능은 좋으나 시스템에 사용할 Camera Lens의 Specification을 모르기 때문에 이를 예측해야 하는 단점이 있다. 마지막으로 Caltech Tool box 기반 방법은 Calibration을 위한 Keypoint를 수동으로 지정하다 보니까 이로 인한 오차가 존재하게 된다. Calibration을 시도 할 때마다 결과에 차이가 있었으며, Calibration 결과의 측면에서 Fisheye Projection이 가시적으로 가장 좋은 결과를 나타냈다.

• ETRI Journal
• /
• v.35 no.6
• /
• pp.1115-1125
• /
• 2013

This paper presents a scheme for geometric correction of projected content for planar and quadratic projection surfaces. The scheme does not require the projection surface to be perfectly quadratic or planar and is therefore suitable for uneven low-cost commercial and home projection surfaces. An approach based on the recursive subdivision of second-order B$\acute{e}$zier patches is proposed for the estimation of projection distortion owing to surface imperfections. Unlike existing schemes, the proposed scheme is completely automatic, requires no prior knowledge of the projection surface, and uses a single uncalibrated camera without requiring any physical markers on the projection surface. Furthermore, the scheme is scalable for geometric calibration of multi-projector setups. The efficacy of the proposed scheme is demonstrated using simulations and via practical experiments on various surfaces. A relative distortion error metric is also introduced that provides a quantitative measure of the suppression of geometric distortions, which occurs as the result of an imperfect projection surface.

• Spatial Information Research
• /
• v.11 no.4
• /
• pp.421-437
• /
• 2003

In order to calculate the position of parcel boundary points, the area of the Parcel, and the length of the parcel boundary lines using a digitalized cadastral map or maps, the distortion of the map has to be corrected. The correction methods, such as the method of 2D affine transformation using 4 comer points of the edge lines, the method of tessellation into 9 subregions, the method of using the original surveying sheets, and the method of straightening the 4 edge lines, have been developed. In this Paper, the four methods were programed and applied to some sample cadastral maps and the correction accuracies were obtained and analysed. No method could prefectly correct the distortions because the distortions were irregular throughout the maps. However, it is found that tile method of straightening the 4 edge lines is the one which can minimize the distortions when the method is applied after applying the 2D projective transformation on the maps using the 4 comer points of the edges.