Dmitriy A. Gura¹, Grittel G. Shevchenko², Nelli A. Dyakova³

1−3  Kuban State Technological University (Krasnodar, Russia) 1 2 3

 gda-kuban@mail.ru,  grettel@yandex.ru,  nellidya@mail.ru

Laser scanners are increasingly used in various fields of human activity, including laser scanning data can be used to create geographic information systems and monitoring. Laser scanners can directly measure the 3D coordinates of a huge number of points in a short period.

To determine the spatial position and coverage of the area of interest on one scan, special marks are placed around the scanner. These marks are points of the workspace, and for the accuracy of the subsequent comparison of the point clouds, multiple measurements of the centers of special marks are performed. However, the process of recognizing the data center of marks during field survey, as an individual task, separate from the scanning process itself, is poorly understood.

To study the process of recognizing the center of marks during field work, you must: check the dependence of the correctness of recognition of the center of the mark on its size; to determine the dependence of the correctness of recognition of the center of the mark on its geometry; establish the dependence of the correctness of the mark center recognition on the color of the mark sectors. To achieve the set tasks, the process of recognizing the center of the mark was investigated using three-dimensional laser scanning technologies using a ground-based laser scanner Leica ScanStation C10. The experiment was based on a classic black and white stamp used in production. This is a standard 74.1 mm black and white stamp, two opposite sectors of which are black and the other two are white.

Before performing the experiment, the scanner was installed at a distance of 5 meters from the wall, the marks were glued to the wall so that the sighting beam was perpendicular to the plane of the mark. The experiment was carried out under the same conditions, without changing the position of the scanner and the same instrument settings. Thus, the influence of the distance from the device to the mark, a change in the angle between the laser beam and the plane of the mark could not affect the correct recognition of the center of the mark.

During the experiment with grade 1, no effect on the size of this grade was found. The influence of mark geometry on the recognition of its center was tested on mark 2, mark 3 and mark 4. Scanning these marks showed that center recognition is not based on orientation to the center of the circle (mark 2). Changing the geometry of the opposite sectors also does not affect the recognition of the center (mark 3). When initially aiming at areas distant from the center, recognition passes without errors (mark 4).

Since white surfaces are non-selectively reflective and black surfaces are non-selectively absorbent, it was assumed that the contrast between white and black is necessary for the program to recognize the center of the mark. In this regard, a study of mark 5 was carried out, the center of which was absent, but the device determined its center.

To check the next dependence, the color of the standard grade was changed to blue and yellow (grade 6), but the scanner recognized the center of this grade. Making an assumption about the possibility of the influence of opposite sectors of the white color, an experiment was carried out with grade 7. In the experiment with grade 7, all sectors were replaced with primary colors with an optical spectrum: red 625…780 nm, yellow 565…590 nm, green 500…565 nm, blue 440…485 nm, the scanner was unable to identify the center of mark 7.

Replacing the sectors of the standard brand with yellow, blue and two opposite ones with red, it was concluded that 2 identical opposite sectors are of great importance. This dependence was noticed earlier on stamps 1−6, where it was necessary to find dependence on the size, geometry and color of the sectors.

This experiment showed that in the process of recognizing the center of a brand, not individual characteristics of a brand are taken into account, but their totality.

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