A structure displacement measurement system and a measurement method thereof

Abstract

The present application relates to a kind of structural displacement measurement systems, including intelligent camera, feature target being arranged on the structure to be measured and smart device, the intelligent camera has embedded pixel proportion algorithm and automatic identification program;The feature target is a standard circle, which is uniformly distributed with several feature codes, each of the feature codes enters the serial number, size and its serial number information in the feature target;Intelligent camera is arranged opposite by lens and the measured plane of the structure to be measured, and its lens can simultaneously observe multiple feature targets in multiple measured planes in the field of view range, and can automatically identify all feature targets, and obtain the serial number and size information of feature target according to the feature code on known feature target, the present application saves instrument cost, greatly improves monitoring precision, and is convenient, efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of displacement measurement, in particular to a structure displacement measurement system using feature targets and a measurement method thereof. BACKGROUND

[0002] The civil engineering infrastructure is characterized by large quantity, large volume, long service period, and once the structure is damaged, it will cause serious engineering accidents, resulting in national property loss, personnel casualties, and adverse social impact. Therefore, safety monitoring of infrastructure structures is particularly important. Different structures have different structural characteristics, and the physical quantities affecting their safety factors are also different. Based on the most important and common monitoring physical quantity of most structures, displacement, including horizontal displacement and vertical displacement, the current structure adopts displacement measurement as the main choice.

[0003] There are many kinds of displacement monitoring methods for structures, such as total station measurement, displacement sensor measurement (static leveling system measures vertical displacement, laser sensor measures horizontal displacement), or GNSS displacement measurement system, etc. Among them, the total station belongs to a precision electronic instrument, which is not only expensive, but also requires a suitable and large space for measurement, and manual monitoring is required. The displacement sensor installation requires water pipes and cables, which is time-consuming and laborious, and the instrument needs to be protected for a long time. The measurement accuracy is greatly affected by external environmental interference, and the measurement error is difficult to solve. The GNSS displacement measurement system is easily affected by regional electronic interference and the strength change of satellite geometry in displacement measurement, thereby reducing the measurement efficiency, and the cost of the system is relatively high.

[0004] In recent years, some displacement measurement methods based on image recognition have appeared. In the Chinese patent with application number 201811048952.5, CCD camera is used to measure displacement. However, the method based on image recognition measurement technology in this patent needs a scale as a reference, which is greatly affected by external environmental changes and needs to be protected. Manual observation and maintenance are required on site.

[0005] Currently, remote measurement technology based on image recognition of cameras and targets has appeared in the market. When a camera monitors multiple targets at the same time, the optical parameters of each target need to be measured, including the focal length of the camera, the object distance, etc. Meanwhile, an inclinometer needs to be installed to measure the angle between the optical axis of the camera and each target, and the actual displacement of the structure is calculated by the object distance and the angle. The focal length of the camera will be affected by environmental temperature and humidity and long-term stress changes of materials, resulting in measurement errors. In order to eliminate material errors, the camera needs to be calibrated regularly, which is very inconvenient in long-term outdoor measurement. This technology not only has low efficiency for multiple target measurement, but also brings additional errors in structure displacement measurement due to measurement errors of optical parameters and angles.

[0006] Therefore, it is necessary to provide a new structure displacement measurement system and a measurement method thereof to solve the above problems. SUMMARY

[0007] In order to improve the prior art, the present application proposes a camera vision displacement measurement system using a standard circular feature target, which can non-contactly measure the planar bidirectional displacement and the rotation angle in the plane of multiple targets on multiple measurement planes of a structure.

[0008] The present application will achieve technical improvement through the following technical solutions: a structure displacement measurement system, comprising an intelligent camera, a feature target arranged on a measured structure, and a smart device, the intelligent camera having an embedded pixel ratio algorithm and an automatic recognition program; the feature target is a standard circle, which uniformly distributes a plurality of feature codes, each of which records the number, size and serial number information of the feature target in the feature target; the intelligent camera is arranged opposite to the measurement plane of the measured structure through a lens, and can simultaneously observe multiple feature targets in multiple measurement planes within the field of view, and can automatically recognize all feature targets and obtain the number and size information of the feature targets according to the feature codes on each feature target.

[0009] Further, the pixel ratio algorithm in the intelligent camera establishes a unique proportional relationship according to the diameter of the known feature target and the pixels occupied by the image, and can correct the imaging measurement when the feature target and the optical axis of the intelligent camera are orthogonal or there is an angle, perform on-site calculation and analysis, and convert the displacement of the feature target in the object plane according to the actual size information of the feature target, so as to calculate the actual displacement data of the structure.

[0010] Further, the pixel ratio algorithm of the intelligent camera can calculate the rotation angle of the measured feature target in the installation plane according to the rotation of the line connecting the center of a feature code in the feature target and the center of the feature target.

[0011] Further, the feature code is a special encoding pattern such as a two-dimensional code or a bar code.

[0012] Further, the feature target is arranged on the structure by installation, attachment or spray printing.

[0013] Further, the actual displacement data of the structure calculated by the intelligent camera is transmitted to the cloud platform through wireless network, and then the user can read the information through the smart device.

[0014] Further, the smart device is a device that can perform human-computer interaction reading, such as a computer, a tablet computer or a smart phone.

[0015] Further, the wireless network transmission is by 3G, 4G, 5G or WIFI.

[0016] The application also provides a measurement method of a structure displacement measurement system, wherein the measurement system is the structure of the displacement measurement system, and when the optical axis of the lens of the intelligent camera is orthogonal to the plane where the feature target and the measured structure are located, the displacement measurement method is implemented in the following steps:

[0017] 1) All feature targets are arranged at corresponding positions on the surface of the measured structure;

[0018] 2) The intelligent camera is installed at a relatively stable position of the structure to be measured, and the lens thereof can observe all the feature targets;

[0019] 3) The intelligent camera searches for all the feature targets in the field of view in advance and identifies them through an automatic identification program, and according to the feature codes on the feature targets, automatically acquires the size and number information of the feature targets, the feature target is a standard circle, the center of which is the polar coordinate origin (x0, y0), a plurality of feature codes are uniformly distributed according to the angle, the feature code contains the number, size and sequence number information of the feature code in the feature target, so that the automatic identification program in the intelligent camera can identify the information of all the feature targets and feature codes, and start measurement;

[0020] 4) The user confirms through the intelligent device interface, the whole system is initialized, the initial information of all the identified feature targets is recorded, and the initial center coordinate information (x0, y0) of each feature target 2 and the rotation angle coordinate Φ0 of the feature code on the feature target are stored;

[0021] 5) When the feature target moves in the plane, the system automatically identifies the new coordinate positions (x1, y1) of the center of each feature target and the rotation angle Φ1, and calculates the change according to the initialized coordinate information, so as to measure the vertical displacement Δy, the horizontal displacement Δx and the plane rotation angle ΔΦ of the structure:

[0022] Δy = y1 - y0 Δx = x1 - x0 ΔΦ = Φ1 - Φ0

[0023] Further, when the optical axis of the lens of the intelligent camera is not orthogonal to the plane where the feature target and the measured structure are located, the displacement measurement method adds the following steps,

[0024] 6) Error processing of non-orthogonal plane measurement:

[0025] The angle between the optical axis of the lens of the intelligent camera and the center of the measured characteristic target is alpha, and the characteristic target should be moved vertically from the solid line position to the dashed line position relative to the case that the optical axis is orthogonal to the measured characteristic target, the actual moving distance is vertical displacement Delta y, and then on the object plane, the characteristic target moves Delta y α The relationship is:

[0026] Delta y α = Delta y * cos alpha d α = d * cos alpha

[0027] Wherein: Delta y α : the vertical displacement of the projection of the characteristic target on the normal plane;

[0028] Delta y: the actual vertical displacement of the characteristic target;

[0029] d α : the vertical diameter of the projection of the characteristic target on the normal plane;

[0030] d: the actual diameter of the characteristic target;

[0031] The ratio of the imaging vertical displacement of the characteristic target in the intelligent camera to the imaging vertical diameter is equal to the ratio of the vertical displacement of the projection of the characteristic target on the normal plane to the diameter, and there is:

[0032] Delta y p / d p = Delta y α / d α = (Delta y * cos alpha) / (d * cos alpha) = Delta y / d

[0033] Therefore, it is concluded that Delta y = Delta y p * d / d p

[0034] Wherein: Delta y p : the vertical displacement of the imaging of the characteristic target in the intelligent camera;

[0035] d p : the vertical diameter of the imaging of the characteristic target in the intelligent camera.

[0036] The present application adopts special target design combined with pixel ratio algorithm of the intelligent camera, which avoids the problems in the prior art. Some existing measurement technologies use square or rectangular targets, or even targets with different shapes. When the camera is obliquely photographed, if the target has different degrees of corner turning in the plane, the size of the target in the vertical direction cannot be determined, that is, the actual size of the size d cannot be determined after the corner turning, so the vertical displacement of the target cannot be calculated by known parameters. The present application adopts a circular characteristic target, and the actual size of the target in the vertical direction is a constant value (diameter d) regardless of any corner turning.

[0037] The traditional technology measures displacement by proportion conversion of optical parameters measured by a camera, and when the focal length of the camera is known, the object distance in the normal plane must be measured before each sampling, and since the object distance of the structure monitoring is generally large, large measurement error is caused. The application adopts a circular characteristic target, and no matter how the object distance changes, the proportion conversion can be carried out through the size of the target itself. Meanwhile, in order to eliminate the measurement error caused by the change of environmental temperature and humidity and material stress, the focal length of the camera also needs to be calibrated regularly. However, the pixel proportion algorithm in the application can obtain the displacement pixel and the diameter pixel of the characteristic target at the same time through the intelligent camera measurement, and the measurement error caused by the change of the focal length can be eliminated through the ratio of the two.

[0038] The application has the following beneficial effects:

[0039] The bidirectional displacement of the structure in the plane can be established into a unique proportion relationship through the known size of the characteristic target and the image pixel observed by the intelligent camera, that is, the application discloses 1) when the optical axis of the intelligent camera is orthogonal to the plane where the characteristic target and the measured structure are located, the bidirectional displacement is Δy=y1-y0 and Δx=x1-x0; 2) when the optical axis of the intelligent camera is not orthogonal to the plane where the characteristic target and the measured structure are located, the vertical displacement Δy=Δy p ×d / d p It can be known that the proportion formula conversion shown in the application can offset the measurement error caused by the included angle between the optical axis and the characteristic target, the system does not need to measure the included angle alpha, and only needs to calculate the actual displacement of the characteristic target on the measured plane according to the diameter of the characteristic target and the pixel size of the image, so that the standard circular special target of the application does not need to be installed through the inclinometer, does not need to measure the object distance of all the measured objects, and does not need to obtain the optical parameters, and only needs to calculate the actual displacement of the characteristic target on the measured plane according to the diameter of the characteristic target and the pixel size of the image, so that the cost of the instrument is saved, the measurement error of the object distance is avoided, and the monitoring precision is greatly improved. When the large structure is measured, the intelligent camera can automatically load the identity information and geometric size information of the characteristic target through the characteristic code of the characteristic target, automatically search and identify all the characteristic targets, does not need to interact with the artificial, can automatically extract the monitoring information and calculate, and the system is convenient and efficient. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a structural schematic diagram of the orthogonal photography measurement of the intelligent camera of the application;

[0041] Figure 2a is a schematic diagram of the initial position of the characteristic target in the object plane when the camera optical axis of the intelligent camera is orthogonal to the horizontal plane;

[0042] Figure 2is a schematic diagram of the displacement of the characteristic target in the object plane when the camera optical axis of the intelligent camera of the present application is orthogonal to the horizontal plane;

[0043] Figure 3 is a structural schematic diagram when the camera optical axis of the intelligent camera of the present application has an included angle with the horizontal plane;

[0044] Figure 4a is a schematic diagram of the initial position of the characteristic target in the object plane when the camera optical axis of the intelligent camera of the present application has an included angle with the horizontal plane;

[0045] Figure 4b is a schematic diagram of the displacement of the characteristic target in the object plane when the camera optical axis of the intelligent camera of the present application has an included angle with the horizontal plane.

[0046] In the figure: 1, intelligent camera; 2, characteristic target; 21, characteristic code; 3, structure; 5, intelligent device. DETAILED DESCRIPTION

[0047] The present application is further illustrated by specific examples in conjunction with the accompanying drawings.

[0048] Please refer to Figure 1 As shown in FIG. 4, the structure displacement measurement system in the present application includes an intelligent camera 1, a characteristic target 2, and a remote intelligent device 5. The characteristic target 2 is a standard circle, on which a plurality of (4 in the example shown in the figure) circular characteristic information codes 21 (characteristic codes) are uniformly distributed. Each of the characteristic codes 21 records the number, size, and serial number information of the characteristic target 2 in the characteristic target 2.

[0049] The characteristic target 2 is generally arranged on a structure 3, and can be arranged by mounting, attaching, or printing, etc.

[0050] The intelligent camera 1 is arranged opposite to the measured plane of the measured structure through a lens, and can simultaneously observe a plurality of characteristic targets 2 in a plurality of measured planes within the field of view, and can automatically identify all the characteristic targets 2, and obtain the number and size information of the characteristic targets 2 according to the characteristic codes 21 on each of the characteristic targets 2.

[0051] The intelligent camera 1 has an embedded pixel proportion algorithm and an automatic identification program. The pixel proportion of the intelligent camera 1 establishes a unique proportional relationship according to the diameter of the known characteristic target 2 and the pixels occupied by the image, and can correct the imaging measurement when the optical axis of the characteristic target 2 is orthogonal to the optical axis of the intelligent camera 1 or when the optical axis has an included angle, perform on-site calculation and analysis, and convert the displacement of the characteristic target 2 in the object plane according to the actual size information of the characteristic target 2, so as to calculate the actual displacement data of the structure.

[0052] The pixel proportion algorithm of the intelligent camera 1 can calculate the rotation angle of the measured feature target 2 in the installation plane according to the rotation of the line connecting the center of a feature code 21 of the feature target 2 and the center of the feature target 2.

[0053] The actual displacement data of the structure calculated by the intelligent camera 1 is transmitted to the cloud platform through a wireless network, and then the user can read the information through the intelligent device 5. The wireless network transmission is transmitted by 3G, 4G, 5G or WIFI.

[0054] In use, the embodiment is implemented in the following steps:

[0055] When the optical axis of the lens of the intelligent camera 1 is orthogonal to the planes where the feature target 2 and the measured structure 3 are located, the displacement measurement method is implemented in the following steps:

[0056] 1) Set all the feature targets 2 at corresponding positions on the surface of the measured structure 3.

[0057] 2) Install the intelligent camera 1 at a relatively stable position of the structure to be measured 3, and the lens thereof can observe all the feature targets 2.

[0058] 3) The intelligent camera 1 searches for and identifies all the feature targets 2 in the field of view through the lens by an automatic identification program, and automatically obtains the size and number information of the feature targets 2 according to the feature codes 21 on the feature targets 2 (any one of the feature codes 21 on the target is identified).

[0059] As shown in Figure 2 and Figure 2a , the feature target 2 is a standard circle, the center of which is the polar coordinate origin (x0, y0), and several feature codes 21 (the feature codes 21 are two-dimensional codes or bar codes, but are not limited thereto) are uniformly distributed according to the angle. The feature codes 21 contain the number, size (diameter d) of the feature target 2 and the serial number information of the feature codes 21 in the feature target 2 (in the example, the serial numbers of the four feature codes are A, B, C and D), so that the automatic identification program in the intelligent camera 1 can identify the information of all the feature targets 2 and the feature codes 21, and start the measurement.

[0060] 4) The user confirms through the interface of the remote intelligent device 5, the whole system is initialized, the initial information of all the feature targets 2 identified is recorded, and the initial center coordinate information (x0, y0) of each feature target 2 and the rotation angle coordinate Φ0 of the feature code 21 on the feature target 2 are stored.

[0061] 5) When the feature target 2 moves in the plane, the system automatically identifies the new coordinate position (x1, y1) of each feature target 2 center and the rotation angle Φ1, and calculates the change amount according to the initialized coordinate information, so as to measure the plane vertical displacement Δy, horizontal displacement Δx and plane rotation angle ΔΦ of the structure 3:

[0062] Δy = y1 - y0 Δx = x1 - x0 ΔΦ = Φ1 - Φ0

[0063] As shown in Figure 3 , Figure 4a and Figure 4b , the optical axis of the lens of the intelligent camera 1 is not necessarily completely orthogonal to the plane where the feature target 2 and the measured structure 3 are located, so the displacement measurement method adds the following steps:

[0064] 6) Error processing of non-orthogonal plane measurement:

[0065] The angle between the optical axis of the lens of the intelligent camera 1 and the center of the measured feature target 2 is α, and compared with the case where the optical axis is orthogonal to the measured feature target 2, the feature target 2 should be vertically moved from the solid line position to the dashed line position, and the actual moving distance is the vertical displacement Δy, then on the object plane, the feature target 2 moves Δy α , and the relationship is:

[0066] Δy α = Δy × cosα d α = d × cosα

[0067] Where: Δy α : the vertical displacement of the feature target projected on the normal plane;

[0068] Δy: the actual vertical displacement of the feature target;

[0069] d α : the vertical diameter of the feature target projected on the normal plane;

[0070] d: the actual diameter of the feature target;

[0071] The ratio of the imaging vertical displacement of the feature target 2 in the intelligent camera 1 to the imaging vertical diameter is equal to the ratio of the vertical displacement of the feature target projected on the normal plane to the diameter, that is:

[0072] Δy p / d p = Δy α / d α = (Δy × cosα) / (d × cosα) = Δy / d

[0073] Therefore: Δy = Δy p × d / d p

[0074] wherein: Ay p : vertical displacement of the feature target imaged in the smart camera 1;

[0075] d p : vertical diameter of the feature target imaged in the smart camera 1.

[0076] That is, by the above-mentioned proportional conversion, the measurement error caused by the included angle between the optical axis and the feature target 2 can be offset, and the system does not need to measure the included angle a, but only needs to calculate the actual displacement of the feature target 2 on the plane of the measured structure 3 according to the diameter of the feature target 2 and the pixel size of the image.

[0077] The horizontal displacement measurement method of the structure 3 is the same as the above-mentioned vertical displacement measurement.

[0078] The structural features of the embodiment are as follows:

[0079] Without the need to install an inclinometer, without the need to measure the object distance of all measured objects, without the need to obtain optical parameters, only by establishing a unique proportional relationship between the size of the known feature target 2 and the image pixels observed by the smart camera 1, the bidirectional displacement of the structure 3 in the plane can be calculated.

[0080] By using the pixel proportional algorithm described in the embodiment combined with the standard circular feature target 2 to calculate the actual displacement of the structure, not only the system cost is saved, but also the monitoring accuracy is improved.

[0081] When measuring large structures, the smart camera 1 can automatically load identity information and geometric size information through the feature code 21 of the feature target 2, automatically search and identify all feature targets 2, without the need for human interaction, so as to automatically extract monitoring information and perform calculation, and the system is convenient and efficient.

[0082] The smart device 5 in the application is a computer, a tablet computer, or a smart phone, etc. which can be read by human-computer interaction.

[0083] The structure displacement measurement system and the measurement method thereof in the application are suitable for civil engineering monitoring, such as displacement monitoring of slopes, tunnels, bridges, and tail reservoirs, but are not limited thereto.

[0084] Although the content of the application has been described in detail through the above-mentioned preferred embodiments, it should be recognized that the above-mentioned description should not be considered as a limitation of the application. After reading the above-mentioned content by those skilled in the art, various modifications and alternatives of the application will be obvious. Therefore, the protection scope of the application should be defined by the appended claims.

Claims

1. A structure displacement measurement system, comprising a smart camera (1), a feature target (2) arranged on a structure (3) to be measured, and a smart device (5), characterized in that: the smart camera (1) has a pixel ratio algorithm and an automatic recognition program; the feature target (2) is a standard circle with a plurality of feature codes (21) uniformly distributed thereon, each of the feature codes (21) recording the number, size and sequence number information of the feature target (2) in the feature target (2); the smart camera (1) is arranged opposite to the measured plane of the structure (3) to be measured through a lens, and can simultaneously observe a plurality of feature targets (2) in a plurality of measured planes within the field of view range of the lens, and can automatically recognize all the feature targets (2) and obtain the number and size information of the feature targets (2) according to the feature codes (21) on each feature target (2); the pixel ratio algorithm of the smart camera (1) establishes a unique proportional relationship according to the diameter of the known feature target (2) and the pixels occupied by the image, and can correct the imaging measurement when the feature target (2) and the optical axis of the smart camera (1) are orthogonal or there is an angle, perform on-site calculation and analysis, and convert the displacement of the feature target (2) in the object plane according to the actual size information of the feature target (2) to calculate the actual displacement data of the structure.

2. The structural displacement measurement system of claim 1, wherein: The pixel ratio algorithm of the smart camera (1) can calculate the rotation angle of the measured feature target (2) in the installation plane according to the rotation of the line connecting the center of a feature code (21) in the feature target (2) and the center of the feature target (2).

3. The structural displacement measurement system of claim 1, wherein: The feature code (21) is a two-dimensional code or a bar code.

4. The structural displacement measurement system of claim 1, wherein: The feature target (2) is arranged on the structure (3) by installation.

5. The structural displacement measurement system of claim 2, wherein: The actual displacement data of the structure calculated by the smart camera (1) is transmitted to the cloud platform through the wireless network, and then the user can read the information through the smart device (5).

6. The structural displacement measurement system of claim 5, wherein: The smart device (5) is a computer, a tablet computer or a smart phone.

7. The structural displacement measurement system of claim 5, wherein: The wireless network transmission is transmitted by 3G, 4G, 5G or WIFI.

8. A method of measurement of a structural displacement measurement system, wherein, The displacement measurement system is the structure displacement measurement system of any one of claims 1-7, characterized in that when the optical axis of the lens of the smart camera (1) is orthogonal to the plane where the feature target (2) and the structure (3) to be measured are located, the measurement method is implemented in the following steps: 1) all feature targets (2) are arranged at corresponding positions on the surface of the structure (3) to be measured; 2) the smart camera (1) is installed at a relatively stable position of a structure (3) to be measured, and the lens thereof can observe all the feature targets (2). 3) Intelligent camera (1) through the lens will be pre-searched in the field of view and all the features of the target (2) by automatic identification program to identify the characteristics of the target (2) on the code (21), automatic acquisition of the size and number of information of the feature target (2), the feature target (2) is a standard circle, the center of which is the polar coordinate origin (x0, y0), a plurality of characteristic codes (21) are uniformly distributed according to the angle, the characteristic code (21) contains the number, size and serial number of the characteristic code (21) in the characteristic target (2), so that the automatic identification program in the intelligent camera (1) can identify the information of all the characteristic targets (2) and the characteristic code (21), and start measuring; 4) The user confirms through the interface of the intelligent device (5), the whole system is initialized, the initial information of all the identified characteristic targets (2) is recorded, and the polar coordinate origin (x0, y0) of each characteristic target (2) and the corner coordinate Φ0 of the characteristic code (21) on the characteristic target (2) are stored; 5) When the characteristic target (2) moves in the plane, the system automatically identifies the new coordinate position (x1, y1) of the center of each characteristic target (2) and the corner Φ1, calculates the change according to the initialized coordinate information, and measures the plane vertical displacement Δy, horizontal displacement Δx and plane corner ΔΦ of the structure (3): Δy = y1 - y0; Δx = x1 - x0; ΔΦ = Φ1 - Φ0.

9. The method of measuring of claim 8, wherein: When the optical axis of the lens of the intelligent camera (1) is not orthogonal to the characteristic target (2) and the plane where the measured structure (3) is located, the measurement method adds the following steps, 6) Error processing of non-orthogonal plane measurement: The angle between the optical axis of the lens of the intelligent camera (1) and the center of the measured feature target (2) is α. Relative to the case where the optical axis is orthogonal to the measured feature target (2), the feature target (2) should be vertically moved from the solid line position to the dashed line position, and the actual moving distance is the vertical displacement Δy. Then on the object plane, the feature target (2) moves Δy α The relationship is: Δy α = Δy x cos α; d α = d x cos α where: Ay α : vertical displacement of the feature target projected on the horizontal plane; Δy: the actual plane vertical displacement of the characteristic target; d α : vertical diameter of the projection of the feature target on the plane of the flat; d: the actual diameter of the characteristic target; The ratio of the imaging vertical displacement of the characteristic target (2) in the intelligent camera (1) to the imaging vertical diameter is equal to the ratio of the vertical displacement to the diameter of the characteristic target projected on the normal plane, which has: Δy p / d p = Δy α / d α = (Δy x cos α) / (d x cos α) = Δy / d Thus, Δy = Δy p x d / d p where: Ay p : vertical displacement of the feature target imaged in the smart camera (1); d p : Vertical direction diameter of the feature target in the smart camera (1).

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