CN111578862A - Point cloud precision calibration device and method for ground three-dimensional laser scanner - Google Patents

Abstract

The invention discloses a point cloud accuracy checking device and method for a terrestrial three-dimensional laser scanner, comprising: a moving carrier, wherein a rotating part is arranged on the moving carrier, and the rotating parts are respectively connected to lifts for carrying the laser scanner part and a scanner telescopic part for carrying the target; the scanning angle of the laser scanner can be adjusted to check the influence of the scanning horizontal inclination on the accuracy of the point cloud; the difference between the direction of the target and the incident direction of the laser scanner The angle between them can be adjusted to check the influence of the scanning vertical inclination on the accuracy of the point cloud. The invention has the beneficial effects that the practical accuracy check of the ground three-dimensional laser scanner in engineering practice is realized, and the accuracy and reliability of the accuracy check are improved.

Description

A point cloud accuracy calibration device and method for a terrestrial three-dimensional laser scanner

technical field

The invention relates to the technical field of point cloud accuracy detection of laser scanners, in particular to a point cloud accuracy calibration device and method of a terrestrial three-dimensional laser scanner.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

3D laser scanning technology is known as "another technological revolution in the field of surveying and mapping since GPS technology". 3D laser scanning technology breaks through the traditional single-point measurement method, can quickly extract massive 3D coordinate data and texture data on the surface of objects, and is widely used in engineering practice due to its advantages of non-contact, rapidity and initiative . However, the scanner will inevitably produce errors when acquiring data. With the rapid development of terrestrial 3D laser scanners, the problem of point cloud accuracy has received more and more attention.

The inventor found in the research that: in engineering practice, the ground 3D laser scanner may be used for a long time, wear, vibrate or other reasons, which may lead to a decrease in measurement accuracy or even measurement errors, and may cause engineering accidents in serious cases. The evaluation and verification of the measurement accuracy of the laser scanning system is very important for the control of the quality of point cloud data and the quality of engineering results; in different engineering fields or in the face of different surveying and mapping projects and surveying and mapping objects, 3D laser scanners may also Differences in the environment or detection targets cause different degrees of detection errors. Therefore, different projects have very different requirements for the accuracy of the point cloud obtained and the allowable error threshold. It is necessary to formulate specific detection schemes for different projects.

SUMMARY OF THE INVENTION

In view of this, the present invention proposes a point cloud accuracy calibration device and method for a terrestrial three-dimensional laser scanner, which can test and analyze the influencing factors of point cloud accuracy for different types of three-dimensional laser scanners, and perform the matching accuracy inside and outside the instrument. Accurate calculation to achieve more standardized and practical accuracy calibration of ground 3D laser scanners in engineering practice.

The first aspect of the embodiments of the present invention discloses a point cloud accuracy calibration device for a terrestrial three-dimensional laser scanner, comprising: a mobile carrier, the mobile carrier is provided with a rotating part, and the rotating parts are respectively connected for The lifting part for carrying the laser scanner and the telescopic part of the scanner for carrying the target;

The adjustment of the scanning angle of the laser scanner is adjustable to check the influence of the scanning horizontal inclination on the accuracy of the point cloud; the angle between the target object direction and the incident direction of the laser scanner is adjustable to check the vertical scanning inclination Impact on point cloud accuracy.

In a second aspect of the embodiments of the present invention, a method for calibrating point cloud accuracy of a terrestrial three-dimensional laser scanner is disclosed, including:

Determine the target orientation of the target, so that the center of the laser scanner is aligned with the target;

When exploring the influence of the scanning horizontal inclination on the accuracy of the point cloud, the direction of the target remains unchanged, and the horizontal incident angle of the laser scanner is adjusted; the point cloud information under different horizontal incident angles is collected respectively;

When exploring the influence of the scanning vertical inclination on the point cloud accuracy, the horizontal incident angle of the laser scanner remains unchanged, and the angle between the direction of the target and the incident direction of the laser scanner is changed to obtain the point cloud information at different angles. ;

When exploring the influence of scanning distance on point cloud accuracy, the horizontal and vertical incident angles of the laser scanner remain unchanged, and the measurement distance between the target and the scanner is changed to obtain point cloud information at different distances respectively;

When exploring the effect of color on the accuracy of point cloud, the colors of the objects installed on the fixed plate of different objects are different, and the point cloud information of objects of different colors are collected respectively;

When exploring the influence of the environment on the accuracy of the point cloud, the mobile carrier is controlled to collect the point cloud information of the target in different environments.

Further, it also includes:

Extract the number of point clouds per unit area, as well as the characteristic length and width information of the target, calculate the internal and external coincidence accuracy of the scanner through formulas, and explore the influence of various factors on the point cloud accuracy.

Compared with the prior art, the beneficial effects of the present invention are:

The lifting device of the present invention can be installed with various types of scanners, which facilitates the comparison of instrument accuracy and selects a three-dimensional laser scanner suitable for actual engineering projects.

The rotatable disc device of the present invention can be installed with multiple telescopic arm devices, and multiple control groups can be set up, and the telescopic arm device can be rotated in the horizontal plane, which ensures the "three-dimensional scanner and the target object" in each group of tests in the horizontal incident angle test. distance" is the same variable.

The telescopic arm of the invention can be retracted and rotated, and the target object fixing device can fix the target object and can rotate the angle, which is convenient for the adjustment of the incident horizontal inclination angle, the vertical inclination angle and the distance. The variable "distance between the 3D scanner and the target" in each group of tests is the same, which avoids the comparison work of using the total station in the traditional accuracy calibration test, improves the accuracy of the internal and external compliance accuracy calibration of the scanner, and The target can be replaced at any time without resorting to walls, etc.

Other features and advantages of additional aspects of the invention will be set forth in part from the description that follows, and in part will become apparent from the description below, or will be learned by practice of the present aspects.

Description of drawings

1 shows a schematic structural diagram of a point cloud accuracy calibration device for a terrestrial three-dimensional laser scanner provided by an embodiment of the present invention;

FIG. 2 shows a schematic structural diagram of a mobile carrier and a lifting portion provided by an embodiment of the present invention;

FIG. 3 shows a schematic structural diagram of a rotating part provided by an embodiment of the present invention;

FIG. 4 shows a schematic structural diagram of a telescopic part of a scanner provided by an embodiment of the present invention;

FIG. 5 shows a schematic structural diagram of a target fixing device provided by an embodiment of the present invention;

FIG. 6 shows a schematic working diagram of a point cloud accuracy calibration device for a terrestrial three-dimensional laser scanner provided by an embodiment of the present invention;

7 shows a schematic top view of a horizontal inclination angle calibration provided by an embodiment of the present invention;

FIG. 8 shows a schematic left view of a vertical inclination angle calibration provided by an embodiment of the present invention;

Among them, 1 engineering vehicle, 2 scanner lifting part, 3 rotating part, 4 telescopic part, 5 target fixing device, 6 infrared emitting device;

1-1 main body of engineering vehicle, 1-2 wheels;

2-1 Lifting body, 2-2 Lifting rod, 2-3 Scanner mounting base;

3-1 disc body, 3-2 first rotating hinge support, 3-3 connecting bearing;

4-1 The first telescopic arm, 4-2 The second telescopic arm, 4-3 spherical hinge;

5-1 Target fixing plate, 5-2 First connecting bolt, 5-3 Second rotating hinge support, 5-4 Lifting and rotating base, 5-5 Second connecting bolt, 5-6 Bolt hole.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

Embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Example 1

According to the patented embodiment of the present invention, an embodiment of a point cloud accuracy calibration device of a terrestrial 3D laser scanner is provided. FIG. 1 is a point cloud accuracy calibration device of a terrestrial 3D laser scanner according to an embodiment of the present invention. Schematic diagram of the structure.

Referring to FIG. 1 , the point cloud accuracy calibration device of the terrestrial three-dimensional laser scanner includes: a mobile carrier, and a rotating part 3 is arranged on the mobile carrier. The rotating part 3 is respectively connected to the scanner lifting part 2 for carrying the laser scanner and the The telescopic part 4 carrying the target; the scanner lifting part 2 is also provided with an infrared emitting device 6 for determining the orientation of the target and ensuring the accuracy of the distance in the distance calibration test.

Among them, the mobile carrier adopts an engineering vehicle 1. Referring to FIG. 2, the structure of the engineering vehicle 1 includes: an engineering vehicle main body 1-1, which is used to fix and carry the entire device; The movement of the vehicle 1; the rotating part 3 and the scanner lifting part 2 are all arranged on the main body 1-1 of the construction vehicle.

The construction vehicle 1 is movable, and can perform the accuracy check of the scanner in various detection environments. According to the detection results, a detection scheme that is more beneficial to the project can be designed in the actual engineering.

The lifting part 2 of the scanner includes: a lifting body 2-1, a lifting rod 2-2 connected with the lifting body 2-1, and a mounting seat connected with the lifting rod 2-2. Referring to Fig. 2, the lift body 2-1 is used to carry the lift rod 2-2, the scanner mounting base 2-3 and the three-dimensional laser scanner for testing and other devices.

The rotating part 3 includes: a disc main body 3-1 that can rotate in a horizontal direction, and at least one first rotating hinge support 3- 2; the disc main body 3-1 is connected with the moving carrier and the scanner lifting part 2 through the connecting bearing 3-3 respectively.

Specifically, referring to FIG. 3 , the rotating part 3 is embedded in the main body 1-1 of the construction vehicle, and six first rotating hinge supports 3-2 are installed on the circumference of the main body 3-1 of the disc.

In a specific embodiment, the construction vehicle 1 can be moved by means of the wheels 1-2, the lifting rod 2-2 on the lifting body 2-1 can be lifted and lowered, and the disc body 3-1 can be rotated in the horizontal direction.

The telescopic part 4 includes: at least two telescopic arms connected by hinges; one telescopic arm is hinged with the rotating part 3 , and the other telescopic arm is connected to the target fixing device 5 .

Specifically, referring to FIG. 4 , the telescopic part 4 includes a first telescopic arm 4-1, a second telescopic arm 4-2 and a spherical hinge 4-3. Both telescopic arms can be telescopic through the spherical hinge 4-3. The connection ensures the freedom of the second telescopic arm 4-2 in space. The first telescopic arm 4-1 is connected to the disc main body 3-1 through the first rotating hinge support 3-2.

The target fixing device 5 includes: a connecting piece connected with the second telescopic arm 4-2, a lifting and rotating base 5-4 connected with the connecting piece, and a second rotating hinge support 5-4 is installed on the lifting and rotating base 5-4. 3. The target fixing plate 5-1 is connected to the second rotating hinge support 5-3.

Specifically, referring to FIG. 5 , the target fixing device 5 is connected with the second telescopic arm 4-2 through the second connecting bolt 5-5, and a second rotating hinge support 5-3 is installed on the lifting and rotating base 5-4, The second rotating hinge support 5-3 is connected to the target fixing plate 5-1 through the first connecting bolt 5-2, and the target fixing plate 5-1 has reserved bolt holes 5-6 for installing the prism. The function of the prism is to install the prism to determine the angle or distance before each measurement of the target A4 paper in the process of angle measurement and distance measurement.

The second rotating hinge support 5-3 can be rotated in the horizontal plane under the rotation of the lifting rotating base 5-4; the rotating hinge support 5-3 is fixed on the lifting shaft of the lifting rotating support 5-4, which can be extended up and down. The lifting shaft can realize the lifting of 5-3 height, and the base of rotating 5-4 can drive the rotation of 5-3.

At the same time, the second rotating hinge support 5-3 can rotate in the vertical direction to drive the position of the target fixing plate 5-1 to move in space. The target fixing plate is connected with the rotating shaft of the rotating hinge support 5-3 through bolts 5-2, and the shaft can be rotated, which drives the rotation of the target fixing plate 5-1 in the vertical plane.

In a specific embodiment, when the height and angle of the target need to be adjusted, the telescopic arm and the target fixing device 5 need to be coordinated at the same time. The first rotating hinge support 3-2 ensures that the telescopic arm rotates and lifts in the vertical plane, the spherical hinge 4-3 ensures that the second telescopic arm 4-2 can rotate in space, and the lifting and rotating base 5-4 can ensure For the lifting and lowering of the target in the vertical direction and the rotation in the horizontal plane, the second rotating hinge support 5-3 can ensure the rotation of the target in the vertical plane.

Embodiment 2

According to the patented embodiment of the present invention, an embodiment of a point cloud accuracy calibration method of a terrestrial three-dimensional laser scanner is provided, which specifically includes the following processes:

(1) Before starting the inspection, the mobile engineering vehicle 1 arrives at the designated inspection location, fixes its position, installs the three-dimensional laser scanner on the scanner lifting part 2, adjusts the height of the lifting body 2-1, and makes the three-dimensional laser scanner The instrument is 1.5 meters high, and the instrument is leveled.

(2) Connect the telescopic part 4 to the rotatable disc through the first rotating hinge support 3-2, at this time the overall view of the device is shown in Figure 6, and then connect the prism to the rotatable disk through the reserved bolt holes 5-6 on the target fixing plate 5-1.

(3) When exploring the influence of the scanning horizontal inclination angle on the point cloud accuracy, adjust the inclination angle of the second telescopic arm 4-2 to make it parallel to the ground, and then adjust the inclination angle of the first telescopic arm 4-1, using The infrared emitting device 6 emits infrared rays to determine the position of the target object on the target object fixing plate 5-1, so that the center position of the three-dimensional laser scanner is flush with the center position of the target object. At this time, the telescopic length of the second telescopic arm 4-2 is adjusted, Make the distance between the 3D laser scanner and the target 2 meters (the distance can be set by yourself).

The position at this time is the initial position of the target in the test, the horizontal incident angle of scanning is 90°, and the prism is scanned. At this time, the 3D laser scanner will automatically record this point (the 3D scanners on the market scan to The position of the prism point will be recorded after the prism), and the position of the scan point will be set as the initial position and initial angle in the control panel of the scanner. Then remove the prism, stick a piece of black A4 paper (this is the target of this test) on the target fixing plate 5-1, scan the target for the first time and save the data. Next, by controlling the rotation of the rotating part 3, the system composed of the telescopic arm and the target fixing device 5 is rotated by 15° relative to the first scan, and the prism is installed on the 5-1 again and scanned, and then controlled by the scanner. Check whether the direction information of the point in the panel has moved 15° relative to the initial position. If the angle is deviated, fine-tune the rotating part 3. Next, paste the black A4 paper of the target on 5-1 to scan and save the data. Then rotate the rotating part 3 by 30°, 45°, 60° and 75° in turn, and realize the rotation in the horizontal plane by adjusting the lifting and rotating base 5-4 in the target fixing device 5, so that the target fixing plate 5-1 Always parallel to the first scan, as shown in Figure 7.

At this time, the horizontal incidence angles of the scanner are 75°, 60°, 45°, 30° and 15°, respectively. Every time the angle is adjusted, install the prism to record and adjust the point position, then remove the prism to fix and scan the target, and save the scanned point cloud data each time.

(4) When exploring the influence of the scanning vertical inclination on the accuracy of the point cloud, fix and adjust the target to the initial position. At this time, the vertical incident angle of the scanning is 90°, install the prism and scan and record the point position, and then fix it. The target is scanned and the data is saved. Next, the rotation in the vertical plane is realized by adjusting the second rotating hinge support 5-3 of the target fixing device 5, so that the vertical incident angles of the scanning are 75°, 60°, 45°, 30° and 75°, respectively. 15°, as shown in Figure 8.

Each time the angle is adjusted, install a prism to scan and fine-tune the angle, then fix the target for scanning and record and save the scanned point cloud data.

(5) When exploring the influence of the scanning distance on the accuracy of the point cloud, move the engineering vehicle 1 to a wider flat ground, determine a positive direction of the 3D scanner, and emit infrared rays to determine a straight line, on which the distance to the scanner 5 Place a tripod and install a prism at the meter, adjust the tripod so that the prism is flush with the center of the 3D laser scanner, scan the prism to record the point position, install the target fixing device 5 on the tripod and place A4 paper for scanning.

Experiments were carried out along a straight line at intervals of 10 meters, 20 meters, 30 meters, 40 meters, 50 meters, and 100 meters, respectively, and the scanned point cloud data were saved.

In this embodiment, each time the prism is scanned before the target object is scanned, and the scanned prism position information will be recorded by the scanner, which can ensure that the horizontal incident angle, vertical incident angle and scanning distance are scanned after adjusting the position of the target object each time. accuracy.

(6) When exploring the influence of the color of the target on the accuracy of the point cloud, replace the A4 paper of different colors on the target fixing plate 5-1 at the initial position, and scan and record and save the data respectively. It is also possible to install a plurality of telescopic arms and target fixing devices 5 on the rotating part 3 through the first rotating hinge support 3-2, and install targets of different colors on each device and adjust them to the initial positions, scan and save them respectively. Scan point cloud data.

(7) When exploring the influence of the environment on the accuracy of the point cloud, remote control the engineering vehicle 1 to the designated location, install the telescopic arm and the target fixing device 5, adjust the target to the initial position, and fix the scanning distance, angle, color and other variables , collect the point cloud information of the target in different environments, such as different times of the day, or at the same time on sunny, cloudy, and foggy days, and save the scanned point cloud data.

In this embodiment, a plurality of telescopic arms can be installed on the disc main body 3-1 of the rotating part 3. Therefore, a control group can be set up to explore the influence of each factor in the test, and the above steps can be repeated to obtain point cloud data to improve the data. The accuracy of the analysis results.

The evaluation of the accuracy of the point cloud data obtained in this embodiment under the conditions of different detection factors will be carried out from the following three aspects:

1) The number of point clouds per unit area. The number of point clouds can directly reflect the interval between adjacent points obtained by scanning, and indirectly reflect the scanning accuracy;

2) The characteristic length and width of the target. Through statistics and analysis of these two aspects in each experimental data, the influence of each factor on the accuracy of the scanned point cloud can be judged;

3) The internal and external compliance accuracy of the instrument can be expressed by the following formula

In the formula, m represents the middle error; n represents the number of observations; v represents the correction number.

The length characteristics of the target object (the standard length of a piece of A4 paper is 297mm) are selected as an example to illustrate the influence of different horizontal inclination angles on the accuracy of the instrument's internal and external compliance:

Table 1 Observation data at different horizontal incident angles

The internal coincidence accuracy of the scanner refers to the multiple observations of the same target at the same position and the same parameter settings, and the dispersion between the observed values is compared. This index can reflect the internal stability of the instrument under different observation conditions. .

When the horizontal incident inclination angle is 15°, the in-instrument coincidence accuracy can be expressed as

The median error under different horizontal incident inclination angles is calculated respectively, and the influence of the horizontal incident inclination angle on the accuracy of the instrument is analyzed. The smaller the |m ₁ | value is, the better the internal stability of the instrument is.

The external coincidence accuracy of the scanner refers to multiple observations of the same target at the same position and the same parameter settings, and the deviation of each observation value from the target standard true value is compared. This index can reflect the measurement accuracy.

When the horizontal incident inclination is 15°, the out-of-instrument coincidence accuracy can be expressed as

The median error under different horizontal incident inclination angles was calculated respectively, and the influence of the horizontal incident inclination angle on the accuracy of out-of-instrument coincidence was analyzed. The smaller the |m ₂ | value, the higher the accuracy.

In this embodiment, when exploring the influence of the horizontal inclination angle, vertical inclination angle, scanning distance, target color and environmental factors on the accuracy of the point cloud, the angle, distance, target color, and Variables such as environment are designed or changed by themselves to meet the needs of different users and different projects.

The embodiment of the present invention realizes a more practical accuracy check of the terrestrial three-dimensional laser scanner in engineering practice, and improves the accuracy and reliability of the accuracy check.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or deformations that can be made are still within the protection scope of the present invention.

Claims (10)

1. The utility model provides a device is examined and proofreaded to ground three-dimensional laser scanner's point cloud precision which characterized in that includes: the laser scanning device comprises a movable carrier, wherein the movable carrier is provided with a rotating part, and the rotating part is respectively connected with a lifting part for carrying a laser scanner and a scanner telescopic part for carrying a target object;

the scanning angle of the adjusting laser scanner is adjustable so as to check the influence of the scanning horizontal inclination angle on the point cloud precision; the angle between the direction of the target object and the incident direction of the laser scanner is adjustable so as to check the influence of the scanning vertical inclination angle on the point cloud precision.

2. The apparatus for calibrating point cloud accuracy of a three-dimensional laser scanner for ground as claimed in claim 1, wherein the rotating part comprises: the scanner comprises a disc main body capable of rotating in the horizontal direction, and at least one mounting support arranged in the circumferential direction of the disc main body and used for connecting a telescopic part of a scanner; the disc main body is connected with the movable carrier and the lifting part through connecting bearings respectively.

3. The apparatus for calibrating point cloud accuracy of a three-dimensional laser scanner for ground as claimed in claim 1, wherein said elevating section comprises: the lifting body, with the lifter of this body coupling that goes up and down, and with the mount pad that the lifter is connected.

4. The apparatus for calibrating point cloud accuracy of a three-dimensional laser scanner for ground as claimed in claim 1, wherein said scanner expansion part comprises: at least two sections of telescopic arms connected through hinges; one section of telescopic arm is hinged with the rotating part, and the other section of telescopic arm is connected with the target object fixing device.

5. The apparatus for calibrating point cloud accuracy of a three-dimensional laser scanner for ground as claimed in claim 4, wherein the target fixing means comprises: the device comprises a connecting piece connected with a telescopic arm and a lifting rotary base connected with the connecting piece, wherein a rotary hinged support is installed on the lifting rotary base, and a target fixing plate is connected with the rotary hinged support.

6. The device for calibrating the point cloud precision of the ground three-dimensional laser scanner as claimed in claim 5, wherein the rotating hinge support can rotate in a horizontal plane under the rotation of the lifting rotating base; meanwhile, the rotary hinged support can rotate in the vertical direction to drive the position of the target object fixing plate to move in the space.

7. The device for calibrating point cloud accuracy of three-dimensional laser scanner on the ground as claimed in claim 5, wherein the target fixing plate is provided with bolt holes for installing prisms.

8. The device for calibrating point cloud accuracy of a three-dimensional laser scanner for ground as claimed in claim 1, wherein said elevating portion is further provided with an infrared emitting device.

9. A point cloud precision calibration method of a ground three-dimensional laser scanner is characterized by comprising the following steps:

determining a target position of a target object, so that the center of the laser scanner is aligned with the target object;

when the influence of a scanning horizontal inclination angle on the point cloud precision is researched, the direction of a target object is unchanged, and the horizontal incidence angle of the laser scanner is adjusted; respectively collecting point cloud information under different horizontal incident angles;

when the influence of scanning vertical inclination angles on point cloud precision is researched, the horizontal incidence angle of the laser scanner is unchanged, the included angle between the direction of a target object and the incidence direction of the laser scanner is changed, and point cloud information under different included angles is respectively obtained;

when the influence of the scanning distance on the point cloud precision is researched, the horizontal and vertical incidence angles of the laser scanner are kept unchanged, the measuring distance between a target object and the scanner is changed, and point cloud information under different distances is respectively obtained;

when the influence of colors on the point cloud precision is researched, the colors of the target objects arranged on different target object fixing plates are different, and point cloud information of the target objects with different colors is respectively collected;

when the influence of the environment on the point cloud precision is researched, the mobile carrier is controlled to collect the point cloud information of the target object under different environments.

10. The method for calibrating point cloud accuracy of the three-dimensional laser scanner on the ground as claimed in claim 9, further comprising: the number of point clouds in a unit area and the characteristic length and width information of a target are extracted, the internal and external coincidence precision of the scanner is calculated through a formula, and the influence of each factor on the point cloud precision is researched.

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