Academic literature on the topic 'Passive triangulation'

Vision measurement for non-cooperative targets in space is an essential technique in space counterwork, fragment disposal, satellite on-orbit service, spacecraft rendezvous, because the position and attitude of the target aircraft or the object should be detected first of all in the process. The 2D passive camera loses the depth information and can not measure the position and attitude of non-cooperative target. Several kinds of range imaging methods are alternatives. The traditional triangulation method can provide very high precision range measurement at close range but the nature of the triangulation geometry means that the uncertainty grows when the range increases. Laser radar (LIDAR) based on TOF (time of flight) or phase difference principle is suitable for middle and long range, but it can not fit for short range. A novel structure system is put forward, in which a so-called synchronous scanning triangulation method is adopted combining a LIDAR system. The synchronous scanning triangulation system plays a role at the range from 0.5m to 10m for object’s attitude, and the LIDAR system plays a role at the range from 10m to 200m for object’s position (direction and range).They are merged into one path, and do not influence each other because of using two different wavelengths respectively. This mechanism makes the system more compact and less weight. The system performances, such as the measurement range and precision, are analyzed according to the system parameters. The principle prototype is designed and established, and the experimental results confirm that its performance is promising and can satisfy the requirement for space application.

In target tracking using the passive infrared sensors, the principle of triangulation distance measurement is normally used as the basic method. However, when the target directions are nearly collinear relative to the baseline, this method merely based on EKF and angle measurements produces poor results. To solve this problem, we propose a target tracking solution based on dual infrared sensors in the cluttered environment. This method is a joint estimation algorithm of target motion state and atmospheric parameter such as the extinction coefficient. The method combines the probability data association algorithm with the augmented extended Kalman filter algorithm, into which we introduce the rate of infrared energy absorbed by the sensors at the ends of the baseline as additional measurement vector. Simulation results show that the proposed method performs better than the standard extended Kalman filter method, even in the case that the targets position is near the baseline in the cluttered environment.

Abstract The measurement of the particle size distribution plays an important role in mineral processing. Due to the high costs and time-consumption of the screening process, modern machine vision methods based on the acquisition and analysis of recorded photographic images. But the image analysis methods used so far, do not provide information on the three-dimensional shape of the grain. In the coal industry, the application scope of these methods is substantially limited by the low reflectivity of the black coal particle surface. These circumstances hinder proper segmentation of coal stream surface image. The limited information contained in two-dimensional image of the raw mineral stream surface, makes it difficult to identify proper size of grains partially overlapped by other particles and skewed particles. Particle height estimation based on the shadow length measurement becomes very difficult in industrial environment because of the fast movement of the conveyor belt and because of spatial arrangement of these particles, usually touching and overlapping. Method of laser triangulation connected with the movement of the conveyor belt makes it possible to create three-dimensional depth maps. Application of passive triangulation methods (e.g. stereovision) can be impeded because of the low contrast of the black coal on the black conveyor belt. This forces the use of active triangulation methods, directly identifying position of the analyzed image pixel. High contrast of the image can be obtained by a direct pointwise laser lighting. For the simultaneous identification of the entire section of the raw material stream it is useful to apply a linear laser (a planar sheet of the laser light). There have been presented basic formulas for conversion of pixel position on the camera CCD matrix to the real-word coordinates. A laboratory stand has been described. This stand includes a linear laser, two high-definition (2Mpix) cameras and stepper motor driver. The triangulation head moves on the rails along the belt conveyor section. There have been compared acquired depth maps and photographic images. Depth maps much better describe spatial arrangement of coal particles, and have a much lower noise level resulting from the specular light reflections from the shiny fragments of the particle surface. This makes possible an identification of the coal particles partially overlapped by other particles and obliquely arranged particles. It enables a partial elimination or compensation of image disturbances affecting the final result of the estimated particle size distribution. Because of the possibility of the reflected laser beam overriding by other particles it is advantageous to use a system of two cameras. Results of the experimental research confirmed the usefulness of the described method in spite of low reflectance factor of coal surface. The fast detection of changes in particle size distribution makes possible an on-line optimization of complex technological systems - especially those involving coal cleaning in jigs - thus leading to better stabilization of quality parameters of the enrichment output products. An additional application of the described method can be achieved by measuring the total volume of the stream of the transported materials. Together with the measurement signal from the belt conveyor weight it makes possible to estimate the bulk density of the raw mineral stream. The low complexity of the signal processing in the laser triangulation method is associated with the acquisition of high contrast images and analysis based on simple trigonometric dependencies.

<p class="Abstract">This study described the kinds of a question asked by novice teacher on mathematics learning process of senior high school. The data were collected by passive participation observation and a semi-structured interview. The validity of data was obtained through the triangulation of method, triangulation of time and member check. The data analysis technique used in this study is descriptive analysis. The result of this study showed that at the preliminary activity, the question asked by the novice teacher based on objective only compliance question. At the main activity, the novice teacher asked compliance question, prompting question, probing question and sometimes rhetorical question. The kind of questions based on the cognitive dimension of Revised Bloom’s Taxonomy that was asked by novice teacher only remembering question. At the main activity, the novice teacher asked the question of remember, understand, apply, analyse and evaluate. At the closing activity, the teacher does not ask the question based on objective and Revised Bloom’s Taxonomy. </p>