7. TOPOGRAPHIC SURVEY DURING ENGINEERING AND GEODETIC SURVEYS OF RAILWAYS USING A QUADROCOPTER

Abstract

Abstract: The article considers the justification of the possibility of using aerial photography by geodetic quadcopter in order to obtain a topographic basis for the design of highways. The topographic basis is obtained in the form of an orthophotoplan of the terrain with accuracy corresponding to regulatory requirements.

Keywords: railway design, digital terrain model, quadcopter, unmannedaerial vehicle (UAV), point cloud, identification mark, orthophotoplane.

ТОПОГРАФИЧЕСКАЯ СЪЕМКА ПРИ ИНЖЕНЕРНО-ГЕОДЕЗИЧЕСКИХ ИЗЫСКАНИЯХ ЖЕЛЕЗНЫХ ДОРОГ С ИСПОЛЬЗОВАНИЕМ КВАДРОКОПТЕРА

Мирханова Мавжуда Михайиловна

Ташкентский государственный университет транспорта, старший преподаватель.

Умаралиев Шохжахон Мухаммадрузи угли

Ташкентский государственный университет транспорта, ассистент.

Ембергенов Авезмурат Бекмуратович

Ташкентский государственный университет транспорта, ассистент.

Абдуалиев Элёрбек Бегалиевич

Ташкентский государственный университет транспорта, доктарант.

Аннотация: В статье рассматривается обоснование возможности использования аэрофотосъемки геодезическим квадрокоптером с целью получения топографической основы для проектирования автомобильных дорог. Топографическая основа получена в виде ортофотоплана местности с точностью, соответствующей нормативным требованиям.

Ключевые слова: проектирование железных дорог, цифровая модель местности, квадрокоптер, беспилотный летательный аппарат (БПЛА), облако точек, опознавательный знак, ортофотоплан.

Introduction. Drones are used to build images, create maps and spatial analysis in areas such as topographic aerial photography of the area. Today, it is no exaggeration to say that quadrocopters are the fastest and most effective method of aerial photography. In addition, unlike shooting from manned aircraft, the use of drones is much cheaper, and also makes it possible to get better results. The main advantages quadrocopters for geodesy: reduction of time costs, simplification of work, the ability to shoot in hard-to-reach places.The survey of the terrain by a quadcopter for the purpose of further designing a highway can be attributed to such a type of survey as topographic and geodetic surveys (TGI). According to the results of the TGI, topographic and geodetic data and materials should be obtained to compare options for highway routes and prepare documentation for territory planning under the placement of the selected railway option. The design documentation should substantiate the design needs for the chosen route direction, provide materials for choosing the location of sections of crossings over natural and artificial obstacles, comparison and evaluation of route options, recommendations for choosing the optimal railway route option for subsequent stages of design and survey work (PIR) [1,2,3,4].

Aerial photography is one from methods of drawing up topographic maps and plans large scale. The results of the work are orthophotoplans, topographic maps and plans, digital models of terrain and relief (CMR and CMR), which can be used to solve the problems of design, construction and reconstruction of railways. The use of aerial photography from UAVs is due to economic feasibility or lack of other technical and practical possibilities for obtaining reliable topographic materials, however, the use of UAVs in construction is currently not legally fixed, there are no methods and recommendations for the use of geodetic quadrocopters in obtaining a topographic basis for design. The kit for aerial photography should include a UAV with an on-board and / or ground-based GNSS receiver of geodetic accuracy, an on-board complex control, avionics, payload and ground control station. According to I. 5.1.1.16 SP 47.13330.2012, the average errors in determining the planned position of objects and terrain contours with clear, easily recognizable outlines (boundaries) relative to the nearest points (points) of the geodetic basis should not exceed 0.5 mm for open areas and 0.7 mm for mountainous and forested areas on the scale of the plan in undeveloped territories. Following these requirements, the error in determining the planned coordinates is presented in Table 1 [5,6,7,8,9,10].

Table 1. Errors in determining the contours of objects

The scale of the plan

Errors, m

open country

mountainous and forested areas

1:500

0,25

0,35

1:1000

0,5

0,7

1:2000

1,0

1,4

1:5000

2,5

3,5

When aerial photography with UAVs, it is necessary to take into account factors that hinder the work (the presence of vegetation, terrain fractures, the inability to decipher individual elements of the survey, seasonality, the presence of shadows, clouds, industrial smoke and atmospheric haze, complicating or excluding the process of decoding, the presence of objects with high reflectivity, the presence and height of buildings). The technical equipment of the UAV should ensure the safe performance of flights, taking into account the geographical features of the territory of the Republic of Uzbekistan. The purpose of this work is to substantiate the possibility of conducting topographic surveys using a quadrocopter during engineering and geodetic surveys of railways. The assessment was carried out on the basis of aerial photography data from a quadrocopter DJI Mavic 2 Pro and their subsequent processing.

Source data: aerial photography results (527 photos from the camera of the DJI Mavic 2 quadcopter Pro), the first part of the images has a nadir view, the other part is perspective; the coordinates of the terrain, 5 pieces. The data was loaded into photogrammetric processing software, in our case — AgisoZ Metashape. After uploading the images, the program aligns the photos and builds a sparse point cloud. The entire assessment of the accuracy of the reconstructed scene and the output results is evaluated on it. After its construction, the coordinates of the ground identification signs are loaded to control the accuracy on them[11,12].

If necessary, they can be used to fit the model as a support. The tasks that we will solve with the helpof the Metashape program are carried out in four stages:

1. Determination of the parameters of the external and internal orientation of the cameras. At the first stage, Metashape finds common points of photos and uses them to determine all camera parameters: position, orientation, internal geometry (focal length, distortion parameters, etc.). The results are a sparse cloud of common points in the 3D model space and data on the position and orientation of cameras. The data on the position and orientation of the cameras is used in further processing stages.
2. Building a dense point cloud. Before proceeding to the next stage of creating a 3D model or beforeby exporting the model, a dense point cloud can be edited and classified.
3. Construction of a three-dimensional surface: a polygonal model and/or CMM. A three-dimensional polygonal model describes the shape of an object based on a dense point cloud.

Fig. 1. Digital terrain model (the size of the CMM is 10590x10140, at 6.73 cm / pixels)

1. Building a texture for a polygonal model (if it was built), as well as building an orthophotoplane. The finished orthophotoplane is shown in Figure 2.

Fig. 2. Orthophotoplane.

The orthophotoplane we have obtained has the size 36006x34329 pixels, at 1.76 cm/ pixels. The standard error does not exceed 3.7 cm, which, according to Table 1, may correspond to a 1:500 scale plan. According to the results of the work, it becomes obvious that the use of quadrocopters in conducting engineering and geodetic surveys is no longer the technology of the future, but the technology of the present. Accordingly, the problem of the lack of regulatory documentation on this topic was a significant gap in the organization of work.

Conclusion. In addition to everything, it is worth adding that, using quadrocopter, it is not necessary to dwell only on engineering and geodetic surveys, since the darkening of the quadrocopter opens up wide opportunities in such areas as:

— monitoring of the condition of the roadway;

— control over construction and repair works;

— obtaining information about the condition of the roadway (detection of defects of the roadway and their parameters);

— determination of transport flow parameters.

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