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In this paper, we present a means of solving the problem of camera calibration by using the sphere and the line passing through two projections of the spherical center. By analyzing the relationships among the eigenvalue, eigenvector, and projection of the right circular cone formed by the camera optical center and sphere, the line passing through two projections of the spherical center can be determined. Three lines passing through two projections of the spherical center are employed to obtain the projections of the spherical center. The image of the circular points can thereby be determined. The camera intrinsic parameters can be obtained by the constraint conditions of the image of the absolute conic and the image of the circular points. Results of simulation experiments using real data and a three-dimensional reconstruction showed the effectiveness and feasibility of the proposed method.

This paper utilizes the CFD simulation analysis method, calculates and analyzes the distribution characteristics of streaming around the typical steel tubular transmission tower body and the pressure field, researches the change law of wind load force (torque) coefficient along with each main shaft direction o tower body, and then compares it with corresponding wind tunnel test result, and verifies the adaptability of this CFD simulation result. The result shows that the pole member in the upwind direction on the steel tubular tower has obvious disturbance and shielding effect to wind speed distribution around the pole member of downwind direction. The wind direction has obvious influence on the aerodynamic (torque) parameters of tower body, especially the steel tubular - angle steel combined tower body. The above research result provides a certain theoretical support and value taking basis for the wind-resistant design of steel tubular transmission tower body.

A novel method for camera calibration is proposed based on an analysis of lens distortion in camera imaging. In the method, a line through the centre of concentric circles is used as a template in which orthogonal directions can be determined from an angle of circumference that corresponds to a diameter. By using three lines through the centre of concentric circles, based on the invariance of the cross-ratio, an image at the centre of the concentric circles can be used to obtain the vanishing point. The intrinsic parameters of the camera can be computed based on the constraints of the orthogonal vanishing points and the imaged absolute conic. The lens distortion causes points in the template to have a position offset. In the proposed method, we optimize the positions of the distortion points such that they gradually approach those of the ideal points. The simulated and real-world experiments demonstrate that the proposed method is efficient and feasible.

Three-dimensional stratified reconstruction from images requires acquisition of circular points. This study proposes a new algorithm for calibrating camera intrinsic parameters using the properties of the polar of circular points (PCPs). Because the PCPs are asymptotic, which are self-conjugate diameters of the circle, the obtained PCPs can determine the image of the circular points and a group of orthogonal vanishing points in the image plane. On this basis, the camera parameters can be calibrated. The results of the simulation experiment and the data of the real experiment prove that the proposed method is effective and feasible.

Ice shedding from conductors may easily induce electrical and mechanical accidents, which cause serious threat to the safe operation of transmission lines. In this paper, a three dimensional finite element model of tower-conductor-ground wire-insulator system for a 500kV transmission line was established in ANSYS, and the dynamic responses of ice shedding under different load cases were analyzed for the transmission tower-line system. Newmark method is applied for the solution of the nonlinear transient dynamic analysis. Three variables were considered in the ice-shedding simulating analysis, which includes tower-line coupled effect, phase combination of the ice-shedding conductors as well as thickness of the accreted ice. Influences of all the variables on the dynamic responses of jumping heights, loads at the end of insulators and the forces of transmission tower were mainly studied.