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Study of the method for focal length determination in digital cameras

Hlotov Volodymyr, Hunina Alla

Geomatics, Landmanagement and Landscape

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2019

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no. 4

145--154

EN

The authors analysed the methods for determining the focal length in digital cameras (DC) and proposed a method, the implementation of which is to survey the correct triangular metal prism from the left and right points of the basis. Next, on the stereo pair of digital images obtained from the surveying, the corresponding coordinates of the points on the near and far edges of the prism are measured, and the focal length of the non-metric DC is determined. To test the method, the focal length of the Sony ILCE-7R and Canon EOS 450D cameras was determined. In order to establish the precision parameters of the method, the following parameters were taken into account: determining the accuracy of measurment on the basis of surveying, the accuracy of measuring the heights, the accuracy of calculation of the longitudinal parallax, the accuracy of calculating the difference between the parallaxes.

2

Statistical properties of complex network for seismicity using depth-incorporated influence radius

He Xuan, Wang Luyang, Zhu Hongbo, Liu Zheng

Acta Geophysica

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2019

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Vol. 67, no. 6

1515--1523

EN

In recent years, seismic time series has been used to construct complex network models in order to describe the seismic complexity. The effect of the factor focal depth has been elided in some of these models. In this paper, we aim to construct a new complex network model for seismicity by considering depth factor from the earthquake catalog and investigate the statistical properties of the network. Since the networks have been proved to be scale-free and small-world properties, the new network models should be studied whether the properties have changed. The results show that the new network model by considering depth factor is still scale-free and small-world. However, it is found that its average degree is smaller than the original network. The clustering coefficient increases at the year including mainshocks. The assortativity coefficient, which demonstrates preferential attachment of nodes, is positive and shows consistent pattern when main shocks occur.

3

Method for determining the focal length in a digital non-metric camera

Hlotov V., Hunina A., Yurkiv M.

Geomatics, Landmanagement and Landscape

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2017

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no. 3

71--81

EN

The authors analysed the methods for determining the focal length in digital cameras (DC) and proposed a method, according to which the control-measuring grid (CMG) is located vertically at a distance from the DC and a photograph of the CMG is made, then the latter (the CMG) is moved along the optical axis of the digital camera to the distance, which is fixed with a micrometre screw and, repeatedly, a series of photographs of the CMG is taken. After that, on the received digital images, the coordinates are measured on the corresponding intersections of the CMG, and subsequently, the focal length for the DC is determined. The a priori estimation of accuracy of determining the focal length for the DC by the proposed method is calculated. For approbation of the method, the focal length in the following cameras was determined: Canon EOS 350D, Canon EOS 450D, Canon EOS 5D.