Point-like coded mark and identification method and identification system thereof
By introducing central positioning points and check points into dot-like encoding marks, combined with affine transformation matrix, the problems of low stability and decoding errors in the prior art are solved, and the dot-like with high accuracy and high encoding capacity are achieved Encoding flag recognition.
Patent Information
- Application Number
- CN202411532735.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-30
- Publication Date
- 2024-12-17
AI Technical Summary
The existing dot-shaped coded flags have problems with low stability and decoding errors in the recognition process, especially in the absence of a central positioning point, it is difficult to accurately obtain two-dimensional or three-dimensional spatial locations, resulting in inaccurate decoding of the coded flags.
Design a dot-like coding mark, which includes a central positioning point, a collinear positioning point, a symmetrical positioning point, a code point and a check point. Through the coordination of affine transformation matrix and a check point, a stable and fast decoding process is achieved. And improve coding capacity and identification accuracy.
Through the design of the central positioning point and verification point, the stable decoding of the point-shaped coded flag is ensured, decoding errors are reduced, and the recognition accuracy and encoding capacity are improved. It is suitable for pointing operations of total stations and RTK equipment.
Smart Images
Figure CN119150905A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of photogrammetry and image processing, and in particular to a point-shaped coding mark and a recognition method and a recognition system thereof. Background Art
[0002] In close-range photogrammetry, most of the measured objects do not have obvious feature points. In order to accurately locate the target point when shooting the measured object in different directions, it is necessary to design artificial marks to assist in measurement. In order to distinguish multiple targets at the same time, it is necessary to design coding marks. The coding marks conform to the same coding principle, but each coding mark is different and has a unique coding value.
[0003] Coding marks can be roughly divided into circular coding marks and dot coding marks. Figure 1 and Figure 2 As shown in the figure, the coding information of the circular coding mark is on its coding ring. The coding ring is divided into several segments, each segment of the coding ring represents binary 0 and 1. The coding ring is decoded to obtain a string of binary codes, and then the coding value is obtained. The dot coding mark is composed of a series of circles according to certain rules. Some circles are used for positioning, and the remaining circles are used for coding. Different positions of the circles represent different coding values.
[0004] The principle of circular coding mark is simple and easy to identify, but the coding capacity is small. The recognition process of dot coding mark is more complicated, the recognition stability is high, and the coding capacity is larger than that of circular coding.
[0005] Some existing dot-coded signs, such as Figures 3 to 6 As shown, Figure 3 It is a dot-coded mark. Figure 4 for Figure 3 Schematic diagram of dot-coded marking; Figure 5 It is another dot-coded mark. Figure 6 for Figure 5 The schematic diagram. Its coding points are O, A, B, D, E, and the coding points are located on the edge of the mark, while there is no positioning point designed in the center of the mark. Such point-coded marks can be decoded during measurement to obtain the same-name points on the image. However, sometimes a point is needed to represent the three-dimensional spatial position of the mark point for use in total station or RTK equipment marking. Sometimes it is necessary to obtain the two-dimensional image coordinates of the mark point. At this time, it is inconvenient if there is no positioning point in the center of the mark.
[0006] In the prior art, there is a solution using positioning points, but it cannot guarantee that the encoding points are correctly identified, and mapping errors will occur during the decoding process, ultimately leading to the problem of encoding mark decoding errors.
[0007] Therefore, there is an urgent need to develop a dot-coded mark and its recognition method and recognition system, with a positioning point at the center, a large coding capacity, and check points for verification, so as to achieve verification accuracy while ensuring a stable and fast decoding process.
[0008] The above information disclosed in the Background section is only for enhancement of understanding of the background of the present application and therefore it may contain information that does not constitute the prior art that is already known to a person of ordinary skill in the art. Summary of the invention
[0009] The main purpose of the present invention is to overcome the problem of slow and inaccurate recognition of dot-coded marks, and to provide a dot-coded mark and its recognition method and recognition system. The center point of the dot-coded mark has a positioning point, a large coding capacity, and a check point for verification, thereby ensuring a stable and fast decoding process while achieving verification accuracy.
[0010] To achieve the above-mentioned purpose, the first aspect of the present invention provides a dot-shaped coding mark, comprising: a mark bottom surface, 5 positioning points, a plurality of coding points and 2 check points;
[0011] The bottom surface of the sign is a rectangle, with 5 positioning points, multiple encoding points and 2 check points distributed on the bottom surface of the sign;
[0012] The positions of the five positioning points on the bottom surface of the sign are fixed, and the five positioning points include a central positioning point, a first collinear positioning point, a second collinear positioning point, a first symmetrical positioning point, and a second symmetrical positioning point; the central positioning point is located at the center of the bottom surface of the sign, the first collinear positioning point, the central positioning point, and the second collinear positioning point are on the same straight line, which is the axis of symmetry of the first symmetrical positioning point and the second symmetrical positioning point, and the intersection of the line connecting the first symmetrical positioning point and the second symmetrical positioning point and the straight line where the first collinear positioning point, the central positioning point, and the second collinear positioning point are located is located between the first collinear positioning point and the second collinear positioning point and is not the central positioning point;
[0013] Multiple code points are distributed at other positions of the positioning point and do not intersect with the positioning point;
[0014] The two check points and the second collinear positioning point are on the same straight line, and the straight line is perpendicular to the straight line where the first collinear positioning point and the second collinear positioning point are located; the distances from the two check points to the second collinear positioning point are equal, and the distance is equal to the distance from the first symmetrical positioning point to the straight line where the first collinear positioning point and the second collinear positioning point are located.
[0015] According to an exemplary embodiment of the present invention, the straight line where the first collinear positioning point, the central positioning point and the second collinear positioning point are located is vertically arranged; the distance from the first collinear positioning point to the central positioning point is equal to the distance from the second collinear positioning point to the central positioning point.
[0016] According to an exemplary embodiment of the present invention, a plurality of encoding points are set at preset positions, which are symmetrically arranged on both sides of the straight line where the first collinear positioning point and the second collinear positioning point are located. The preset points are arranged in an array and are encoded in sequence on each side according to the bow structure.
[0017] According to an exemplary embodiment of the present invention, one coding point corresponds to one preset point position; each dot-shaped coding mark displays at least three coding points.
[0018] According to an exemplary embodiment of the present invention, the two check points include an X check point and a Y check point. If the sum of the displayed code points is an even number, the X check point is displayed, otherwise the Y check point is displayed.
[0019] As a second aspect of the present invention, the present invention provides a method for identifying a dot-coded mark, comprising the following steps:
[0020] S1: Obtain a photo of the dot-shaped coding mark;
[0021] S2: Identify the dots in the dot-shaped coding mark and obtain the center point of each dot;
[0022] S3: Find and obtain the code of the code point;
[0023] S4: Check whether the code point complies with the rules, and perform error correction if it does not.
[0024] S5: Obtain the code number of the point coding mark according to the index table and the coding of the coding point.
[0025] According to an exemplary embodiment of the present invention, in step S2, identifying dots in the dot-shaped coding mark includes:
[0026] Perform ellipse detection on the dot-coded marks and cluster the ellipses to obtain more than 8 ellipses.
[0027] According to an exemplary embodiment of the present invention, in step S3, the method of finding and obtaining the code of the code point includes:
[0028] S31: Find three collinear points to obtain a central positioning point, a first collinear positioning point, and a second collinear positioning point;
[0029] S32: Find two points on the same line whose connecting line is perpendicular to the three points, and obtain a first symmetrical positioning point and a second symmetrical positioning point;
[0030] S33: obtaining an affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark;
[0031] S34: Obtaining fixed coordinates of the coding point on the dot coding mark according to the affine transformation matrix and the actual coordinates of the coding point;
[0032] S35: Obtain the code of the code point according to the fixed coordinates of the code point at the dot-shaped code mark.
[0033] According to an exemplary embodiment of the present invention, in step S31, finding two points on a line perpendicular to three points comprises:
[0034] Find the points on both sides of the common line of three points;
[0035] Get the intersection of the collinear lines of two points and three points;
[0036] If the intersection ratio calculated from the three circular points and the intersection point, a total of four points, is equal to the predetermined intersection ratio, it is considered that the first symmetric positioning point and the second symmetric positioning point are found.
[0037] According to an exemplary embodiment of the present invention, in step S32, obtaining an affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark includes:
[0038] Establish an affine transformation equation; bring the actual coordinates and fixed coordinates of the positioning point into the affine transformation equation, and use the least squares method to solve the affine transformation matrix.
[0039] According to an exemplary embodiment of the present invention, the affine transformation matrix adopts the following formula:
[0040]
[0041] Among them, H Affine represents the affine transformation matrix, a 1,1 、a 1,2 ,t x ,t y 、a 2,1 、a 2,2 All are natural numbers.
[0042] According to an exemplary embodiment of the present invention, in step S4, the method of checking whether the code point complies with the rule includes:
[0043] S41: Check the check point. If the position coordinate relationship between the check point and the positioning point is incorrect, the recognition of the dot-shaped coding mark is terminated.
[0044] S42: Determine whether the sum of the code points is an even number. If it is an even number and the check point is an X check point, or it is not an even number and the check point is a Y check point, it is considered to comply with the rules. Otherwise, it is considered not to comply with the rules.
[0045] According to an exemplary embodiment of the present invention, in step S4, the method for performing error correction includes:
[0046] Calculate the distance from the mapping point of the center point of the code point to the nearest code point, select the mapping point with the largest distance as the error point, find the code point closest to the error point, and select the code point closest to the mapping point as the new code point among the code points adjacent to the nearest code point.
[0047] As a third aspect of the present invention, there is provided a system for identifying dot-shaped coded marks, comprising: a dot-shaped coded mark acquisition module, a dot recognition module, a coded point code acquisition module, a code check and error correction module, an index table and a code number acquisition module;
[0048] The dot-coded mark acquisition module is used to acquire a photo of the dot-coded mark;
[0049] The dot recognition module is used to recognize the dots in the dot-shaped coding mark and obtain the center point of each dot;
[0050] The code point code acquisition module is used to find and obtain the code of the code point;
[0051] The coding verification and error correction module is used to verify whether the coding point complies with the rules, and to correct the error if it does not;
[0052] The index table includes the code of the code point and the code number of the corresponding point code mark;
[0053] The code number acquisition module is used to obtain the code of the code point according to the fixed coordinates of the code point, and obtain the code number of the point code mark according to the index table and the code of the code point.
[0054] According to an exemplary embodiment of the present invention, the coding point code acquisition module includes a collinear three-point recognition module, a symmetrical two-point recognition module, an affine transformation matrix generation module, a coding point fixed coordinate solution module and a coding module;
[0055] The collinear three-point recognition module is used to find three collinear points and obtain the central positioning point, the first collinear positioning point and the second collinear positioning point;
[0056] The symmetrical two-point recognition module is used to find two points on the same line whose connecting line is perpendicular to the three circular points, and obtain a first symmetrical positioning point and a second symmetrical positioning point;
[0057] The affine transformation matrix generation module is used to obtain the affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark;
[0058] The coding point fixed coordinate solution module is used to obtain the fixed coordinates of the coding point in the dot coding mark according to the affine transformation matrix and the actual coordinates of the coding point;
[0059] The encoding module is used to obtain the encoding of the encoding point according to the fixed coordinates of the encoding point at the dot encoding mark.
[0060] This solution designs a dot-shaped coded mark with a center positioning point, and realizes the decoding of the coded mark. The center positioning point of the coded mark can represent the position of the entire mark, which is very convenient for the total station and RTK equipment to mark points. The mark decoding method in the present invention has a large number of verifications, a stable algorithm, and is not prone to errors in decoding, and can cope with the situation where there are multiple coded marks in one image.
[0061] Traditional dot-coded marks only have positioning points and coding points. The positioning points are used to determine the coordinate system, and the coding points are mapped to the coordinate system. The coding value of the mark is determined based on the position of the coding points. However, if there is a small error in the positioning point, the position of the coding point will be mapped incorrectly, which will eventually lead to decoding errors of the coded mark. This solution adds a check point. By comparing the coding point with the check point, the offset problem of the coding point can be found, and then the corresponding correct coding point can be given to improve the accuracy of recognition. BRIEF DESCRIPTION OF THE DRAWINGS
[0062] The above and other objects, features and advantages of the present application will become more apparent by describing in detail the exemplary embodiments thereof with reference to the accompanying drawings. The accompanying drawings described below are only some embodiments of the present application, and it is clear to a person skilled in the art that other accompanying drawings can be obtained from these accompanying drawings without creative effort.
[0063] Figure 1 A schematic diagram of an existing annular coding mark is schematically shown.
[0064] Figure 2 Schematically shows Figure 1 Schematic diagram.
[0065] Figure 3 A schematic diagram of an existing dot-shaped coding mark is schematically shown.
[0066] Figure 4 Schematically shows Figure 3 Schematic diagram.
[0067] Figure 5 A schematic diagram of another existing dot-shaped coding mark is schematically shown.
[0068] Figure 6 Schematically shows Figure 5 Schematic diagram.
[0069] Figure 7 The principle diagram of the dot-shaped coding mark is shown schematically.
[0070] Figure 8 An example diagram of a dot-shaped coding mark is schematically shown.
[0071] Fig. 9 The following is a schematic diagram showing the steps of a method for identifying a dot-shaped coded mark.
[0072] Fig.10 The diagram schematically shows the positional relationship between mapping points and encoding points.
[0073] Among them, A is the first collinear positioning point, B is the second collinear positioning point, C is the center positioning point, D is the first symmetrical positioning point, E is the second symmetrical positioning point, X is the X check point, Y is the Y check point, and 1 to 20 are preset points. DETAILED DESCRIPTION
[0074] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.
[0075] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.
[0076] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.
[0077] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.
[0078] It should be understood that although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present application. As used herein, the term "and / or" includes any one of the associated listed items and all combinations of one or more.
[0079] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the scope of protection of the present application.
[0080] According to a first specific embodiment of the present invention, the present invention provides a dot-coded mark, such as Figure 7 As shown, it includes: the bottom surface of the logo, 5 positioning points, multiple encoding points and 2 check points.
[0081] The bottom surface of the sign is a rectangle, and 5 positioning points, multiple encoding points and 2 check points are distributed on the bottom surface of the sign. As a preferred embodiment, the bottom surface of the sign is a square. Figure 7 The bottom of the center mark is painted black, and the positioning points, coding points and check points are painted white.
[0082] The positions of the five positioning points on the bottom surface of the sign are fixed, and the five positioning points include the center positioning point C, the first collinear positioning point A, the second collinear positioning point B, the first symmetrical positioning point D and the second symmetrical positioning point E; the center positioning point C is located at the center of the bottom surface of the sign, the first collinear positioning point A, the center positioning point C and the second collinear positioning point B are on the same straight line, and the straight line is the symmetry axis of the first symmetrical positioning point D and the second symmetrical positioning point E, and the intersection of the line connecting the first symmetrical positioning point D and the second symmetrical positioning point E and the straight line where the first collinear positioning point A, the center positioning point C and the second collinear positioning point B are located is located between the first collinear positioning point A and the second collinear positioning point B and is not the center positioning point C. The straight line where the first collinear positioning point A, the center positioning point C and the second collinear positioning point B are located is vertically arranged; the distance from the first collinear positioning point A to the center positioning point C is equal to the distance from the second collinear positioning point B to the center positioning point C. As a preferred embodiment, Figure 7 As shown, the intersection of the line connecting the first symmetrical positioning point D and the second symmetrical positioning point E and the straight line where the first collinear positioning point A, the central positioning point C and the second collinear positioning point B are located is located between the central positioning point C and the second collinear positioning point B.
[0083] Multiple code points are distributed at other locations of the anchor point and do not intersect with the anchor point. Figure 8 As shown in , there are at least 3 code points. Figure 7As shown, multiple coding points are set at preset points, which are symmetrically arranged on both sides of the straight line (where the first collinear positioning point A, the central position point C, and the second collinear positioning point B are located), and the preset points are arranged in an array, and are encoded in sequence on each side according to the arch structure. As a preferred embodiment, Figure 7 There are 20 preset points, the left preset points are 5 rows and 2 columns, the right preset points are 5 rows and 2 columns, and the codes of the preset points are 1 to 20. One code point corresponds to one preset point, and each dot-shaped code mark displays at least 3 code points, and the codes of the displayed code points are not adjacent. The serial number encoding method of the code point is characterized in that the codes above, below, left and right of the odd code point are all even code points, and the codes above, below, left and right of the even code point are all odd code points. Its advantage is that it will be more accurate when performing odd-even check on the code point, and it can find the situation where the code point is wrongly judged as the code point around it.
[0084] The two check points and the second collinear positioning point B are on the same straight line, and the straight line is perpendicular to the straight line where the first collinear positioning point A and the second collinear positioning point B are located. The distances from the two check points to the second collinear positioning point B are equal, and the distance is equal to the distance from the first symmetrical positioning point D to the straight line where the first collinear positioning point A and the second collinear positioning point B are located.
[0085] The two checkpoints include X checkpoint X and Y checkpoint Y. If the sum of the displayed code points is an even number, X checkpoint X is displayed, otherwise Y checkpoint Y is displayed. Figure 8 is an example of a dot-coded mark.
[0086] like Figure 7 As shown, a coordinate system is established, including ordinates and abscissas. The ordinates of the X check point X and the Y check point Y are equal to the second collinear positioning point B, the abscissas of the X check point X and the first symmetrical positioning point D are equal, and the abscissas of the Y check point Y and the second symmetrical positioning point E are equal. Through the positional relationship between the check points and the positioning points, it can be determined whether the basis of the coding recognition is correct.
[0087] According to a second specific embodiment of the present invention, the present invention provides a system for identifying dot-coded marks, including: a dot-coded mark acquisition module, a dot recognition module, a coded point code acquisition module, a code verification and error correction module, an index table and a code number acquisition module.
[0088] The dot-coded mark acquisition module is used to acquire a photo of the dot-coded mark of the first specific implementation manner.
[0089] The dot recognition module is used to recognize the dots in the dot-shaped coding mark and obtain the center point of each dot.
[0090] The code point code acquisition module is used to find and obtain the code of the code point.
[0091] The coding verification and error correction module is used to verify whether the coding point complies with the rules, and to perform error correction if it does not.
[0092] The index table includes the code of the code point and the code number of the corresponding point code mark.
[0093] The code number acquisition module is used to obtain the code of the code point according to the fixed coordinates of the code point, and obtain the code number of the point code mark according to the index table and the code of the code point.
[0094] The coding point code acquisition module includes a collinear three-point recognition module, a symmetrical two-point recognition module, an affine transformation matrix generation module, a coding point fixed coordinate solution module and a coding module.
[0095] The collinear three-point recognition module is used to find three collinear points to obtain a central positioning point, a first collinear positioning point and a second collinear positioning point.
[0096] The symmetrical two-point recognition module is used to find two points on the same line whose connecting line is perpendicular to the three circular points, and obtain a first symmetrical positioning point and a second symmetrical positioning point.
[0097] The affine transformation matrix generation module is used to obtain the affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark.
[0098] The coding point fixed coordinate solution module is used to obtain the fixed coordinates of the coding point in the dot coding mark according to the affine transformation matrix and the actual coordinates of the coding point.
[0099] The encoding module is used to obtain the encoding of the encoding point according to the fixed coordinates of the encoding point at the dot encoding mark.
[0100] According to a third specific embodiment of the present invention, the present invention provides a method for identifying a dot-shaped coded mark, using the dot-shaped coded mark identification system of the second specific embodiment, such as Fig. 9 As shown, the following steps are included:
[0101] S1: Obtain a photo of the dot-shaped coding mark.
[0102] The dot-shaped coding mark is the dot-shaped coding mark of the first specific implementation manner.
[0103] The photograph of the dot-coded mark is taken perpendicular to the dot-coded mark.
[0104] S2: Identify the dots in the dot-shaped coding mark and obtain the center point of each dot.
[0105] Identify the dots in the dot-coded mark including:
[0106] Perform ellipse detection on the dot-coded marks and cluster the ellipses to obtain more than 8 ellipses.
[0107] Specifically, ellipse detection is performed in the image: the ellipse detection algorithm in the ED algorithm or the ellipse detection algorithm based on the Hough transform is used to perform ellipse detection in the captured image. Two thresholds are set to screen all ellipses. If the major semi-axis of the ellipse is between the two thresholds, it is retained; if not, it is discarded.
[0108] Clustering ellipses: In an image, there may be multiple dot-coded marks. It is necessary to cluster multiple ellipses in a dot-coded mark into one category. Set the distance coefficient k, traverse all ellipses, calculate the semi-major axis of the current ellipse as a, search for other ellipses within the range of k×a of the current ellipse, and classify the searched ellipses and the current ellipse into one category. If the number of ellipses in the current category is equal to or greater than the sum of the number of positioning points and coding points in a dot-coded mark, then keep it. If the number of surrounding ellipses is less than the sum of the number, then give up. Repeat the search until all ellipses are traversed.
[0109] S3: Find and obtain the code of the code point.
[0110] The encoding of finding and obtaining the encoding point includes:
[0111] S31: Find three collinear points to obtain a central positioning point C, a first collinear positioning point A, and a second collinear positioning point B.
[0112] For each ellipse, calculate the center of the ellipse. Assuming there are N ellipses in the set, get N center points.
[0113] Select three points in the set. If the three points are collinear, the end point is recorded as the center positioning point C, and the points at both ends are recorded as the first collinear positioning point A and the second collinear positioning point B. If the three points are not collinear, reselect the points.
[0114] S32: Find two points on the same line whose connecting line is perpendicular to the three dots, and obtain a first symmetrical positioning point and a second symmetrical positioning point.
[0115] The method of finding two points on the same line whose connecting line is perpendicular to the three points includes:
[0116] Find the points on both sides of the common line of three points;
[0117] Get the intersection of the collinear lines of two points and three points;
[0118] If the intersection ratio calculated from the three circular points and the intersection point, a total of four points, is equal to the predetermined intersection ratio, it is considered that the first symmetric positioning point and the second symmetric positioning point are found.
[0119] The predetermined cross-ratio is the cross-ratio designed in the schematic diagram.
[0120] Specifically, select any two points from the remaining N-3 points in the set and record them as the first symmetric positioning point D and the second symmetric positioning point E. If the two points are on both sides of the straight line where the first collinear positioning point A and the second collinear positioning point B are located, then calculate the intersection of the straight line where the first symmetric positioning point D and the second symmetric positioning point E are located and the straight line where the first collinear positioning point A and the second collinear positioning point B are located, and record them as P.
[0121] Calculate the intersection ratio R(A, C, P, B) composed of the four points A, C, P, and B.
[0122]
[0123] If the cross ratio in the image is equal to the cross ratio designed in the schematic diagram of the dot-shaped coding mark, it is considered that five positioning points have been found, otherwise the first symmetrical positioning point D and the second symmetrical positioning point E are reselected.
[0124] This solution determines the positional relationship by calculating the intersection ratio. The intersection ratio calculated for different intersection points is different. If the calculated intersection ratio is the same as the design, D and E are considered to have been found. The formula is as follows:
[0125] The reason why the cross ratio can be used is that the proportional relationship (cross ratio) of points on a line remains unchanged before and after the projection / affine transformation.
[0126] If the first symmetrical positioning point D and the second symmetrical positioning point E cannot be found after traversing N-3 points, return to step S31 to reselect the central positioning point C, the first collinear positioning point A and the second collinear positioning point B.
[0127] S33: Obtain an affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark.
[0128] The method of obtaining an affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark includes:
[0129] Establish an affine transformation equation; bring the actual coordinates and fixed coordinates of the positioning point into the affine transformation equation, and use the least squares method to solve the affine transformation matrix.
[0130] Specifically, since the points in the dot-shaped coding mark and the actual imaging points satisfy the affine transformation, the formula is as follows:
[0131]
[0132] Among them, (x, y) is the fixed coordinate of the positioning point on the dot-shaped coding mark, (x', y') is the actual coordinate of the positioning point, and a 1,1、a 1,2 ,t x ,t y 、a 2,1 、a 2,2 All are natural numbers.
[0133] The affine transformation matrix uses the following formula:
[0134]
[0135] Among them, H Affine represents the affine transformation matrix, a 1,1 、a 1,2 ,t x ,t y 、a 2,1 、a 2,2 All are natural numbers.
[0136] a 1,1 、a 1,2、 a 2,1、 a 2,2 is any natural number that can control the rotation, scaling, and shearing transformation of the image. x， t y is any natural number, controlling the translation, where t x Controls the horizontal translation, t y Controls the vertical translation. The horizontal direction is the horizontal direction of the image, and the vertical direction is the vertical direction of the image.
[0137] The coordinates of the five positioning points in the real image have been obtained through the above steps, and the fixed coordinates of these five points in the coding mark have been determined during the design. The coordinates of these five points are substituted into the affine transformation equation, and the least squares method is used to solve the affine transformation matrix.
[0138] S34: Obtain the fixed coordinates of the coding point in the dot coding mark according to the affine transformation matrix and the actual coordinates of the coding point.
[0139] S35: Obtain the code of the code point according to the fixed coordinates of the code point at the dot-shaped code mark.
[0140] S4: Check whether the code point complies with the rules, and perform error correction if it does not.
[0141] Methods for checking whether the code point complies with the rules include:
[0142] S41: Verify the check point. If the position coordinate relationship between the check point and the positioning point is incorrect, the recognition of the dot-shaped coding mark is terminated.
[0143] Based on the coordinates of the checkpoint, determine whether the checkpoint is X checkpoint X or Y checkpoint Y. Determine whether the ordinate of the checkpoint is consistent with the ordinate of the second collinear positioning point B, and determine whether the abscissa of the checkpoint is consistent with the first symmetrical positioning point D or the second symmetrical positioning point E. If they are inconsistent, it is considered that the decoding has failed and the recognition coding is terminated.
[0144] S42: Determine whether the sum of the code points is an even number. If it is an even number and the check point is an X check point, or it is not an even number and the check point is a Y check point, it is considered to comply with the rules. Otherwise, it is considered not to comply with the rules.
[0145] like Figure 8 As shown, Figure 8 The three code points are 1, 6, and 14. Since 1+6+14=21, the sum is not an even number, so the Y check point Y will appear on the sign, and the check complies with the rules.
[0146] Methods for error correction include:
[0147] Calculate the distance from the mapping point of the center point of the code point to the nearest code point, select the mapping point with the largest distance as the error point, find the code point closest to the error point, and select the code point closest to the mapping point as the new code point among the code points adjacent to the nearest code point.
[0148] like Fig.10 As shown in the figure, the asterisk is the mapping point of the center point of the code point, and 1-6 are preset points. In the normal decoding process, because the mapping point is closest to 3, it will be considered that the mapping point is code point 3. However, if it is confirmed after verification that code point 3 is recognized incorrectly, then reselect from 2, 4, and 6 around code point 3. Fig.10 Because it is closest to code point 4, code point 4 is used as the new code point.
[0149] The above method is used to increase the error correction capability of the code point. When a problem occurs in the position recognition of a certain code point and the code point verification fails, error correction can be performed.
[0150] If the decoding process does not go through the error correction part, the confidence level is considered to be 1. If the decoding process goes through the error correction part, the confidence level is 0.6, but the decoding result is still provided.
[0151] S5: Obtain the code number of the point coding mark according to the index table and the coding of the coding point.
[0152] Determine the code value corresponding to the current set. Use affine transformation to transform the remaining points in the set back into the dot-coded mark image, compare with the coordinates of each code point, and obtain the codes of the three code points, so as to determine the code value of the dot-coded mark, and obtain the code number corresponding to the dot-coded mark according to the index table and the code value.
[0153] Figure 8 The codes of the three selected code points are 1, 6, and 14, and the corresponding code value is 2 1 +2 6 +2 14 = 16450. From the coding principle, it can be seen that the code value generated by this coding method is discontinuous and the code value is relatively large. Therefore, an index table needs to be made to correspond the code value and the code number one by one.
[0154] This solution designs a dot-coded mark with a center positioning point, and realizes the decoding of the dot-coded mark. The center positioning point of the dot-coded mark can represent the position of the entire mark, which is very convenient for the total station and RTK equipment to mark points. The decoding method in this solution has been verified many times, the algorithm is stable, the decoding is not prone to errors, and it can handle the situation where there are multiple dot-coded marks in an image.
[0155] Traditional dot-coded marks only have positioning points and coding points. The positioning points are used to determine the coordinate system, and the coding points are mapped to the coordinate system. The coding value of the mark is determined based on the position of the coding points. However, if there is a small error in the positioning point, the position of the coding point will be mapped incorrectly, which will eventually lead to decoding errors of the coded mark. This solution adds a check point. By comparing the coding point with the check point, the offset problem of the coding point can be found, and then the corresponding correct coding point can be given to improve the accuracy of recognition.
[0156] The exemplary embodiments of the present invention are specifically shown and described above. It should be understood that the present invention is not limited to the detailed structure, configuration or implementation method described herein; on the contrary, the present invention is intended to cover various modifications and equivalent configurations included in the spirit and scope of the appended claims.
Claims
1. A dot-coded mark, characterized in that: include: The bottom of the logo has 5 positioning points, multiple coding points and 2 check points; The bottom surface of the sign is a rectangle, with 5 positioning points, multiple encoding points and 2 check points distributed on the bottom surface of the sign; The positions of the five positioning points on the bottom surface of the sign are fixed, and the five positioning points include a central positioning point, a first collinear positioning point, a second collinear positioning point, a first symmetrical positioning point, and a second symmetrical positioning point; the central positioning point is located at the center of the bottom surface of the sign, the first collinear positioning point, the central positioning point, and the second collinear positioning point are on the same straight line, which is the axis of symmetry of the first symmetrical positioning point and the second symmetrical positioning point, and the intersection of the line connecting the first symmetrical positioning point and the second symmetrical positioning point and the straight line where the first collinear positioning point, the central positioning point, and the second collinear positioning point are located is located between the first collinear positioning point and the second collinear positioning point and is not the central positioning point; Multiple code points are distributed at other positions of the positioning point and do not intersect with the positioning point; The two check points and the second collinear positioning point are on the same straight line, and the straight line is perpendicular to the straight line where the first collinear positioning point and the second collinear positioning point are located; the distances from the two check points to the second collinear positioning point are equal, and the distance is equal to the distance from the first symmetrical positioning point to the straight line where the first collinear positioning point and the second collinear positioning point are located.
2. The dot-coded mark according to claim 1, characterized in that: The straight line where the first collinear positioning point, the central positioning point and the second collinear positioning point are located is arranged vertically; the distance from the first collinear positioning point to the central positioning point is equal to the distance from the second collinear positioning point to the central positioning point.
3. The dot-coded mark according to claim 2, characterized in that: Multiple encoding points are set at preset points, which are symmetrically arranged on both sides of the straight line where the first colinear positioning point and the second colinear positioning point are located. The preset points are arranged in an array and are encoded in sequence on each side according to the arch structure.
4. The dot-coded mark according to claim 3, characterized in that: One coding point corresponds to one preset point; each dot coding mark displays at least 3 coding points.
5. The dot-coded mark according to claim 4, characterized in that: The two checkpoints include an X checkpoint and a Y checkpoint. If the sum of the displayed code points is an even number, the X checkpoint is displayed, otherwise the Y checkpoint is displayed.
6. A method for identifying a dot-coded mark, characterized in that: The following steps are involved: S1: Obtain a photograph of the dot-coded mark according to any one of claims 1 to 5; S2: Identify the dots in the dot-shaped coding mark and obtain the center point of each dot; S3: Find and obtain the code of the code point; S4: Check whether the code point complies with the rules, and perform error correction if it does not. S5: Obtain the code number of the point coding mark according to the index table and the coding of the coding point.
7. The method for identifying a dot-coded mark according to claim 6, characterized in that: In step S3, the method of finding and obtaining the code of the code point includes: S31: Find three collinear points to obtain a central positioning point, a first collinear positioning point, and a second collinear positioning point; S32: Find two points on the same line whose connecting line is perpendicular to the three points, and obtain a first symmetrical positioning point and a second symmetrical positioning point; S33: obtaining an affine transformation matrix according to the actual coordinates of the positioning point and the fixed coordinates of the positioning point on the dot-shaped coding mark; S34: Obtaining fixed coordinates of the coding point on the dot coding mark according to the affine transformation matrix and the actual coordinates of the coding point; S35: Obtain the code of the code point according to the fixed coordinates of the code point at the dot-shaped code mark.
8. The method for identifying a dot-coded mark according to claim 5, characterized in that: In step S4, the method of checking whether the code point complies with the rules includes: S41: Check the check point. If the position coordinate relationship between the check point and the positioning point is incorrect, the recognition of the dot-shaped coding mark is terminated. S42: Determine whether the sum of the code points is an even number. If it is an even number and the check point is an X check point, or it is not an even number and the check point is a Y check point, it is considered to comply with the rules. Otherwise, it is considered not to comply with the rules.
9. The method for identifying a dot-coded mark according to claim 5, characterized in that: In step S4, the error correction method includes: Calculate the distance from the mapping point of the center point of the code point to the nearest code point, select the mapping point with the largest distance as the error point, find the code point closest to the error point, and select the code point closest to the mapping point as the new code point among the code points adjacent to the nearest code point.
10. A system for identifying dot-coded marks, characterized in that: include: Dot code mark acquisition module, dot recognition module, code point code acquisition module, code verification and error correction module, index table and code number acquisition module; The dot-coded mark acquisition module is used to acquire a photo of the dot-coded mark described in any one of claims 1 to 5; The dot recognition module is used to recognize the dots in the dot-shaped coding mark and obtain the center point of each dot; The code point code acquisition module is used to find and obtain the code of the code point; The coding verification and error correction module is used to verify whether the coding point complies with the rules, and to correct the error if it does not; The index table includes the code of the code point and the code number of the corresponding point code mark; The code number acquisition module is used to obtain the code of the code point according to the fixed coordinates of the code point, and obtain the code number of the point code mark according to the index table and the code of the code point.