RU2769637C1 - Method for determining proper coordinates from three surveying targets and videogrammetric system for implementation thereof - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment and can be used in coordinate measuring apparatuses and vision systems for determining the proper coordinates and for spatial orientation relative to three surveying targets flashing at predetermined frequencies, located in a horizontal plane at the same distance from each other. The method for determining the proper coordinates using a videogrammetric system consisting of a videogrammetric apparatus and three surveying targets is characterised by the fact that the surveying targets are positioned in a horizontal plane at the same distance from each other and form a spherical coordinate system with the origin of coordinates in the geometric centre thereof, wherein the surveying targets flash at different frequencies, allowing the videogrammetric apparatus to detect and distinguish the targets, measure the angular coordinates and calculate the distance to the geometric centre formed by said surveying targets, resulting in determining the proper coordinates of the videogrammetric apparatus. The videogrammetric system for determining the proper coordinates consists of a videogrammetric apparatus and three surveying targets and is characterised by the fact that the surveying targets have different enumerations, wherein the videogrammetric apparatus identifies the surveying targets by the flashing frequency, determines the combination of enumerations of the surveying targets in the ordered sequence formed by the targets on the video image, and calculates the proper azimuth angle in the spherical coordinate system formed by the surveying targets.

EFFECT: automation of the process of determining the proper coordinates and design of the system ensuring higher speed and safety of work.

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Description

The invention relates to measuring technology and can be used in coordinate measuring devices and vision systems to determine their own coordinates and orientation in space relative to three sighting targets flashing at specified frequencies, which are located in a horizontal plane at the same distance from each other.

Known system [1], designed to passively determine the coordinates of the radiation source (horizontal angle, elevation angle and distance) by means of two identical infrared devices of a passive type for panoramic surveillance (cameras). Video cameras in this system are located on one common vertical axis, around which they can rotate synchronously, and at a distance known from each other in such a way that their optical axes are always in the same vertical plane. In this case, the distance is determined by the method of triangulation according to the angles of the visible displacement of the radiation source received from each of the cameras. The disadvantages of this technical solution is the impossibility of determining the system's own coordinates from one light source and the need to use two video cameras, which increases the size of the system and reduces its reliability.

Closest to the claimed method is adopted as a prototype method of reverse angular resection [2], which can be implemented using a theodolite or tacheometer to determine its own coordinates for three sighting targets with known coordinates. According to this method, the directional angles of the original direction of the tacheometer to sighting targets are measured, and the coordinates of the tacheometer are determined using trigonometry formulas. The disadvantages of this technical solution are the need for a preliminary determination of the coordinates of each sighting target and the total station's inability to distinguish these sighting targets from each other. In addition, to detect sighting targets in the total station, a source of laser radiation is used, which is not safe for the human eye.

The objective of the invention is to determine its own position in the coordinate system formed by three sighting targets, without initial data on their coordinates. In this case, the coordinates must be determined from any point in space, within the line of sight of sighting targets. The technical result of the invention is the automation of the process of determining one's own coordinates, as well as the design of the system, which provides a higher speed and safety of work.

The problem is solved due to the fact that in the method of determining one's own coordinates by three target targets, a videogrammetric system is used, consisting of a videogrammetric device and three target targets located in a horizontal plane at an equal distance from each other, which flash at specified frequencies, which allows the videogrammetric device detect and distinguish them, calculate the azimuthal angles of these sighting targets, and determine their own coordinates using trigonometry formulas.

The claimed technical result is also achieved by the fact that the characterizing elements of the system for determining one's own coordinates, according to the invention, are three sighting targets that flash at different frequencies, as well as a videogrammetric device consisting of a two-axis platform, a digital video camera, a controller and an embedded computer.

The essence of the method and the system that implements it are illustrated by drawings. Figure 1 shows a spherical coordinate system formed by three sighting targets, figure 2 - general view of the videogrammetric device, figure 3 - functional diagram of the videogrammetric system, figure 4 - schematic diagram of determining the own coordinates of the videogrammetric device: a) top view; b) view from the left.

Spherical coordinate system (r, θ, ϕ) with the origin at the geometric center formed by three sighting targets, which are located in the horizontal plane at the same distance b from each other (figure 1). The main elements of the system are the videogrammetric device 1 and sighting targets 2. The videogrammetric device (figure 2) includes: a tripod 3, a tribrach 4, a two-axis platform 5, a controller 6, an embedded computer 7, a digital video camera 8, encoders 9, a lens 10.

The operation of the videogrammetric device (figure 3) is provided by an embedded computer 7, which serves to process the video image and control the device. With its help, the frequency of change in the brightness of objects in the video image is determined and sighting targets 2 are detected. By means of the controller 6, control signals are generated for the two-axis platform 5 and the video camera 8 is aimed at the sighting target 2. The main optical axis of the video camera 12 is directed to the center of the sighting target 2. As a result In this case, sighting target 2 is projected onto the image plane of video camera 11 with the help of lens 10. In this case, the projection center of sighting target 2 coincides with the origin D of the image plane of video camera 11. Using encoders 9, the direction (ω, λ) of the main optical axis of video camera 12 is determined. Results calculations of the device's own coordinates are displayed on the embedded computer 7.

The search for sighting targets is carried out by changing the viewing direction of the video camera (ω, λ) with an angular step not exceeding its viewing angles. Each sighting target V _i has its own flashing frequency ν _i , emitting visible light in a given range of electromagnetic wavelengths. When a sighting target enters the field of view of the video camera, the color of the visible light emitted by it and the blinking frequency are determined.

To detect sighting targets, the vector function of the difference over two consecutive video frames is used:

, (1)

, (one)

where k is the threshold coefficient for changing the brightness of the sighting target in the image;

s ₁ , s ₂ - target color on two successive video frames.

In this case, the values of the vector function are reset to zero every second Δс _i =0. Within a second, the function Δс _i accumulates the ongoing changes in the video image. Before resetting the function, only those pixel coordinates in the image are fixed at which the accumulated function values coincided with frequencies from a given set of frequencies (ν ₁ , ν ₂ , ν ₃ ). After the sighting target is detected, the video camera is aimed at the sighting target and its angular position is determined, given by the zenith (and azimuth (angles.

в порядке их обнаружения. Вычисляются разности между азимутальными углами каждой пары визирных целей в этой последовательности:Having found all three sighting targets, a cyclic sequence is obtained

in the order they were found. The differences between the azimuth angles of each pair of sighting targets are calculated in this sequence:

(2)

(2)

This sequence is then ordered by finding the index of the first element that has the largest difference in azimuth angles:

(3)

(3)

, состоящую из крайней левой, центральной и крайней правой визирных целей, соответственно. Каждая из трех визирных целей имеет свое цифровое обозначение: 1, 2, 3. Они размещаются в горизонтальной плоскости по часовой стрелке в порядке возрастания цифрового обозначения. При этом каждая визирная цель имеет свою частоту мигания, по которой ее идентифицируют. Положение видеограмметрического устройства ϕ₀ относительно визирных целей определяется образованной комбинацией цифровых обозначений визирных целей в их упорядоченной последовательности (табл.1).The result is an ordered sequence

, consisting of the leftmost, central and rightmost sighting targets, respectively. Each of the three sighting targets has its own digital designation: 1, 2, 3. They are placed in the horizontal plane clockwise in ascending order of the digital designation. In addition, each sighting target has its own flashing frequency, by which it is identified. The position of the videogrammetric device ϕ ₀ relative to sighting targets is determined by the formed combination of digital designations of sighting targets in their ordered sequence (Table 1).

Table 1. Correspondence of the position of the videogrammetric device with a combination of digital designations of target targets

Combination 213 123 132 312 321 231 ϕ ₀ 0° 60° 120° 180° 240° 300°

These combinations are conditionally divided into two groups. Group G1 contains combinations of numerical designations of target targets: 123, 312, 231. Group G2 contains combinations: 213, 132, 321.

The angles are calculated (figure 4, a) formed by the projecting beam coming from the central sighting target and the projecting beams coming from the two extreme sighting targets from the expressions:

; (4)

; (4)

, (5)

, (5)

where λ ₁ , λ ₂ , λ ₃ - azimuth angles of the extreme left, central and extreme right sighting targets, respectively.

According to the theorems of trigonometry, the angle formed by the straight line connecting the leftmost target with the central sighting target and the projecting beam coming from the central sighting target is calculated. For group G1 of combinations of numerical designations of target targets, the expression is applied:

(6)

(6)

For group G2 combinations, the expression is applied:

(7)

(7)

Then the angle between the straight line connecting the leftmost target with the geometric center formed by the three targets and the projecting beam from the leftmost target is calculated. For group G1 combinations, the expression is applied:

(8)

(eight)

For group G2 combinations, the expression is applied:

(9)

(nine)

The azimuth angle of the geometric center formed by three sighting targets for the group of combinations G1 is determined from the expression:

(10)

(ten)

The azimuth angle of the geometric center formed by three sighting targets for the group of combinations G2 is determined from the expression:

(11)

(eleven)

To determine the azimuth angle of the videogrammetric device in the coordinate system of sighting targets, the following expression is used:

(12)

(12)

Then, the lengths of projections onto the horizontal plane of the segments connecting the center of the video camera image plane with the leftmost and central sighting targets are found from the expressions:

; (13)

; (thirteen)

(14)

(fourteen)

The length of the projection on the horizontal plane of the segment connecting the center of the image plane of the video camera with the rightmost sighting target for the group of combinations G1 is determined from the expression:

(15)

(fifteen)

The length of the projection onto the horizontal plane of this segment for the group of combinations G2 is determined from the expression:

(16)

(sixteen)

The length of the projection on the horizontal plane of the segment connecting the center of the image plane of the video camera with the geometric center of the three sighting targets is determined from the expression:

(17)

(17)

To determine the zenith angle of the videogrammetric device in the coordinate system of sighting targets, the following expression is used:

, (18)

, (eighteen)

where ω ₁ , ω ₂ , ω ₃ - zenith angles of the extreme left, central and extreme right sighting targets, respectively.

The range to the geometric center of three sighting targets is determined from the expression:

(19)

(nineteen)

As an example, consider the quadrilateral ABCD (Fig.4, a), formed by three sighting targets A, B, C and a videogrammetric device at point D. Applying the sine theorem for triangles ABD and BCD, the following system of equations is obtained:

(20)

(20)

Solving the system of equations, we get the expression:

(21)

(21)

From expression (21) find a formula for calculating the angle γ ₃ :

(22)

(22)

Then the angle γ4 is calculated:

(23)

(23)

The length of segment AD is calculated from the expression:

(24)

(24)

The length of the segment BD is calculated from the expression:

(25)

(25)

The length of the segment CD is calculated from the expression:

(26)

(26)

The geometric center of points A, B, C is located at point O. The length of the segment OD is calculated from the expression:

(27)

(27)

The length of the segment AO is calculated from the expression:

(28)

(28)

Expression (27) after substitution of expressions (24, 28) takes the following form:

(29)

(29)

Angle ω ₀ (figure 4, b), formed by a straight line OD with a vertical, is determined from the expression:

(30)

(thirty)

The range to the geometric center of three sighting targets located in a horizontal plane and equidistant from each other is determined from the expression:

(31)

(31)

In this way, the own coordinates of the videogrammetric device are determined by three sighting targets located in a horizontal plane and equidistant from each other, blinking at specified frequencies.

Information sources

1. European patent EP No. 0379425 A1, IPC G01S 5/16, for the invention "System for determining the position of at least one target by means of triangulation".

2. Reference book of the surveyor. Book 2 / ed. V.D. Bolshakov and G.P. Levchuk. - 3rd ed., revised. and add. - M.: Nedra, 1985. - 440 p.

Claims (2)

1. A method for determining own coordinates using a videogrammetric system consisting of a videogrammetric device and three sighting targets, characterized in that the sighting targets are located in the horizontal plane at the same distance from each other and form a spherical coordinate system with the origin in their geometric center, with In this case, the sighting targets flash at different frequencies, allowing the videogrammetry device to detect and distinguish them, measure the angular coordinates and calculate the range to the geometric center formed by these sighting targets, as a result of which the videogrammetry device's own coordinates are determined. 2. A videogrammetric system for determining one's own coordinates, consisting of a videogrammetric device and three sighting targets, characterized in that the sighting targets have different digital designations, while the videogrammetric device identifies sighting targets by blinking frequency, determines a combination of digital designations of sighting targets in their formed ordered order. sequence on the video image and from this combination calculates its own azimuth angle in the spherical coordinate system formed by sighting targets.

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