Position measurement device, position measurement system, positioning measurement method and computer program product

Abstract

The invention relates to a position measuring device (10) for measuring a position (P) of an object (12) on a construction site (14), for example an above-ground or an underground construction site, comprising at least one camera (16, 18, 20, 22, 24, 26). The position measuring device (10) has at least six cameras (16, 18, 20, 22, 24, 26) which are spaced apart from one another, wherein the cameras (16, 18, 20, 22, 24, 26) together have at least 18 MP, wherein the position measuring device (10) is configured to determine the position (P) of the object (12) by evaluating images from the at least six cameras (16, 18, 20, 22, 24, 26). The invention further relates to a position measuring system (100), a method (1000) and a computer program product (36). It allows a cost-effective precise measurement of positions (P) on a construction site (14).

Description

[0001] This invention is based on a position measuring device for measuring the position of objects on a construction site. The position measuring device has at least one camera. Such a position measuring device (e.g., in the form of a total station) is used on the construction site to stake out positions recorded in the construction plan onto the construction site, so as to record the positions on the construction site at the corresponding positions in the construction plan, or to compare the positions on the construction site with the corresponding positions in the construction plan.

[0002] Total stations typically incorporate a laser-based rangefinder. This rangefinder is coupled to a high-resolution angle sensor. The beam direction of the rangefinder is adjustable. Therefore, the rangefinder can be used to locate a target position on a construction site and measure the distance to that target. Simultaneously, the beam direction of the rangefinder's laser can be determined using the angle sensor. Thus, the target position relative to the total station's inherent coordinate system can be measured.

[0003] Total stations typically also include a camera. For example, the camera may include a telephoto lens. Then, for instance, the camera can be used to view the target location in a magnified display. It can be checked whether the rangefinder actually hit the target location with a laser beam.

[0004] In order to determine the coordinates of the target location in a coordinate system independent of the total station (such as the coordinate system used in construction planning), the total station itself must first be calibrated separately based on calibration markers measured at the construction site. In particular, the mapping from the total station's inherent coordinate system to the independent coordinate system must be determined.

[0005] When measuring locations on a construction site, a measurement error of up to 5 mm is typically acceptable. To ensure that the total station meets this measurement error tolerance, extremely high accuracy requirements must be placed on the angle sensor and the mechanical stability of the entire total station.

[0006] Due to the high accuracy requirements, total stations are very expensive and complex to manufacture.

[0007] Therefore, the object of the present invention is to provide an apparatus and method that enables cost-effective and accurate measurement of locations on a construction site.

[0008] This objective is achieved firstly by a location measuring device for measuring the position of objects on a construction site (e.g., an above-ground or underground construction site), the location measuring device comprising cameras, wherein the location measuring device has at least six cameras spaced apart from each other, wherein these cameras have a total of at least 18 MP.

[0009] The position measuring device is configured to determine the position of an object by evaluating images from at least six cameras. Therefore, the cameras can not only be used to present a magnified representation of the target area to the user of the position measuring device, but also provide data for position measurement themselves.

[0010] Each of the six cameras can have at least 3 MP. Here, a 1 MP camera can be understood to mean a camera that includes an image sensor with at least 1 million pixels (that is, image elements). Therefore, a 3 MP camera has at least 3 million pixels. Thus, the total number of these at least six cameras is at least 18 million pixels.

[0011] In the case of a color imaging camera, a pixel can correspond to a tripartite point, meaning that a set of three sensor units on the image sensor are used to capture three color components, such as red, green, and blue. In the case of a monochrome camera, a pixel can correspond to a single sensor unit.

[0012] The camera's field of view can horizontally cover at least 135°, particularly at least 180°, and especially preferably at least 270°. The field of view can vertically cover at least 90°, particularly at least 135°, and especially preferably at least 170°. The camera's field of view can overlap at least in pairs, particularly horizontally and vertically.

[0013] At least one of these cameras, preferably all of them, can have an image format corresponding to 3:2, 4:3, 5:4, 16:9, or 16:10. The image format can correspond to the so-called 4K standard or higher, particularly at least 8K, such as 16K. Higher standards are associated with a greater number of sensor units. A greater number of sensor units, in turn, generally enables higher angular resolution.

[0014] It is particularly conceivable that the camera is at least a monochrome camera. Monochrome cameras can provide high pixel resolution at a low cost.

[0015] It is also conceivable that at least one camera has significantly more pixels in one direction than in the other. For example, the horizontal pixels of the camera could be at least four times the vertical pixels. Thus, the camera could be a line scan camera; however, line scan cameras offer limited resolution in their second dimension. Therefore, such a camera can provide exceptionally high angular resolution in at least one of the two dimensions of its image sensor. Such a camera can also provide a very wide field of view in at least one of the two dimensions, and sufficient angular resolution in that dimension.

[0016] Here, the invention is based in particular on the surprising discovery that the accuracy of positioning, which can be determined by multiple cameras, depends on the number of cameras in a highly nonlinear manner. In particular, there is a range of camera numbers that allows for an optimal balance between achievable accuracy and production costs, component costs, and calibration costs.

[0017] This discovery, along with other improvements and exemplary embodiments, will be explained in more detail based on the following description of the accompanying drawings.

[0018] Exemplary embodiments of the invention are shown in the schematic diagrams and will be explained in more detail in the following description.

[0019] In the attached diagram:

[0020] Figure 1 A schematic three-dimensional illustration of the position measuring device is shown.

[0021] Figures 2 to 4 and Figure 6 It showed the results of a series of tests.

[0022] Figure 5 This shows important sources of measurement error.

[0023] Figure 7 The image shows a location measurement system and its user, as well as...

[0024] Figure 8 A method for measuring locations on a construction site is shown.

[0025] In the following description of the accompanying drawings, the use of the same reference numerals for the same or functionally corresponding elements in each case will help in understanding the invention.

[0026] Figure 1 A schematic perspective view of a position measuring device 10 for measuring the position P of an object 12 on a construction site 14 above ground is shown. For example, object 12 is a wall of a building. A hole is drilled at position P of object 12 (i.e., the wall). Position P is measured relative to coordinate system K. If position P in coordinate system K is known, this position can be compared with planning data, for example, from a BIM (Building Information Modeling) model or a CAD model. Other applications where position P in coordinate system K should be known are also conceivable. To establish a reference to coordinate system K, multiple position markers 102 are measured and arranged as calibration points for coordinate system K on the construction site 14 above ground.

[0027] The position measuring device 10 has six cameras 16, 18, 20, 22, 24, and 26. Cameras 16, 18, 20, 22, 24, and 26 are arranged in pairs on a support 28. The camera pair of cameras 16 and 18 is oriented to the left. The camera pair of cameras 20 and 22 is oriented forward. The camera pair of cameras 24 and 26 is oriented to the right.

[0028] Cameras 16, 18, 20, 22, 24, and 26 are grayscale cameras. It is conceivable that cameras 16, 18, 20, 22, 24, and 26 are color cameras, such as RGB cameras. In another exemplary embodiment, at least one of cameras 16, 20, 22, 24, and 26 may be designed to record depth information. For example, this at least one camera may be a color and depth information camera, such as an RGBD camera, resulting in particularly accurate image evaluation, especially by photogrammetric methods and / or by SLAM algorithms. It is also conceivable that the at least one camera is a more cost-effective grayscale and depth information camera.

[0029] Therefore, each camera pair is arranged in such a way that it is rotated 90 degrees relative to at least one other camera pair in its respective configuration. Thus, in each configuration, at least one of cameras 16, 18, 20, 22, 24, 26 is arranged on the support 28 in such a way that it is rotated 90 degrees relative to at least one other camera among cameras 16, 18, 20, 22, 24, 26. Furthermore, all cameras 16, 18, 20, 22, 24, 26 are spaced apart from each other.

[0030] Each of cameras 16, 18, 20, 22, 24, and 26 has an autofocus lens. Cameras 16, 18, 20, 22, 24, and 26 are therefore capable of autofocus. Each of these cameras may include a telephoto lens, particularly a motor-adjustable telephoto lens. Each of these cameras may have at least 3 MP. For this purpose, these cameras may have a resolution of, for example, at least 2048 × 1536 pixels, and particularly an aspect ratio of 4:3.

[0031] The support 28 is mounted on the tripod 30. The tripod 30 may be height-adjustable. The tripod 30 may have vibration damping.

[0032] The position measuring device 10 also includes a controller 32. The controller 32 includes a computer, such as a tablet PC or smartphone. Specifically, the controller 32 has a memory 34 in which a computer program product 36 is stored so that it can be retrieved and executed on the controller 32. The computer program product 36 is configured to be used by means of the rest of the position measuring device 10, particularly according to the method described in more detail below, especially with reference to... Figure 8 To measure position P.

[0033] The controller 32 also includes, in particular, a gravity direction sensor 38 and an acceleration sensor 40 for detecting vibrations.

[0034] Extensive individual tests were conducted using variants of the position measuring device 10, in which different features have been systematically altered.

[0035] Specifically, this position measuring device 10 has been used to cover a circular path with a length of approximately 80 meters.

[0036] For these tests, the computer program product 36 includes SLAM algorithms, such as ORB-SLAM2 from Raul Mur-Artal et al. or SVO2.0 from Davide Scaramuzza et al., to track the distance covered by the corresponding position measurement device 10 relative to the starting point.

[0037] For each test run, the mean square measurement error is determined, which is the corresponding mean square cumulative drift over the entire distance covered. To determine the measurement error, comparative measurements are performed using a total station.

[0038] The first test series examined the extent to which the number of pixels in the camera's image sensor affected the measurement error. For this purpose, only two cameras were used instead of six.

[0039] Figure 2 The graphs showing the mean square measurement error, measured in mm, for each of the two cameras used (e.g., cameras 20 and 22) with different pixel counts (specified in MP) are illustrated. It can be seen that in this dual-camera solution, if cameras with at least 12 MP each are used, the overall measurement error can be kept within the range of up to 5 mm.

[0040] Each camera pair has 3 MP, resulting in a mean square measurement error of approximately 1 cm. Therefore, it can be concluded that when the distance is reduced to, for example, 40 meters or less, the measurement error can be expected to be within the expected range of at most 5 mm.

[0041] Another test series examined the impact of the number of cameras used on measurement error. To this end, Figure 3 A graph showing the mean square measurement error, measured in mm, based on the number of cameras used. Each of the cameras used has a 3 MP image sensor.

[0042] As in Figure 2 Subsequently, as expected, a mean square measurement error of approximately 1 cm was obtained again in the case of two cameras.

[0043] Surprisingly, it was found that increasing the number of cameras used significantly reduced the mean square measurement error, up to a maximum of six cameras.

[0044] However, if the number of cameras is increased to more than six, surprisingly there is almost no further significant improvement. In particular, using six cameras keeps the mean square measurement error significantly below the required 5 mm limit.

[0045] Since the production cost of the position measuring device 10 increases approximately linearly with the number of cameras used, an optimal value is obtained in the range of approximately six cameras.

[0046] Another series of tests examined the impact of the image quality of the recorded images on the measurement error. In particular, the impact on exposure duration was examined as a measure of any motion blur, as well as a measure of overall brightness, and therefore as a measure of image noise.

[0047] As from Figure 4 As can be seen from the figure, the extended exposure time TS during the movement of the position measuring device 10 along the circular path leads to an increase in the degree of motion blur, and thus a significant increase in the measurement error measured in mm. Even low motion blur can increase the measurement error by two, three, or even more times.

[0048] In contrast, image noise SNR (measured as signal-to-noise ratio, for example in dB) only affects the measurement error to a very small extent, and can be ignored as long as it is below a certain threshold.

[0049] Therefore, it is obvious that blurriness in the images recorded by cameras 16, 18, 20, 22, 24, and 26 should be minimized or even avoided as much as possible.

[0050] Even after individual focusing by the lenses of cameras 16, 18, 20, 22, 24, and 26, blurriness may still arise from the movement of the position measuring device 10 and / or from the movement of the object 12 to be analyzed.

[0051] For example, an accelerometer 40 can be used to detect individual movements of the position measuring device 10. For instance, it is conceivable that the recorded images are evaluated only if no vibration or other movement of the cameras 16, 18, 20, 22, 24, 26 is detected, or only if the camera vibration and / or other movement is below a defined movement threshold.

[0052] If the accelerometer 40 provides motion-related data, such as direction of movement and / or speed of movement, it is also conceivable that at least one image, in particular all of the recorded images, can be calculated for the motion and thus made clear.

[0053] It is also conceivable to determine the image sharpness value directly from the recorded image. This is particularly conceivable for image recording of known objects (e.g., position marker 102 used as a calibration marker).

[0054] Images that do not meet the desired image sharpness value may be rejected and / or re-recorded. Further analysis may be limited to those images with a defined minimum image sharpness.

[0055] Exposure time can also be limited to avoid motion blur. The exposure time used to record the image can be set to, for example, less than 1 / 500 s, and especially less than one millisecond. According to... Figure 4 The result is that, if appropriate, a (slight) increase in image noise is acceptable.

[0056] Further examination compared the impact of positioning errors of cameras 16, 18, 20, 22, 24, and 26 relative to each other's different types of positioning errors.

[0057] To this end, image recordings from cameras 16, 18, 20, 22, 24, and 26 were simulated. Specifically, the following were examined: Figure 5 The diagram illustrates the error types: distance error AF, oblique angle error SF, and tilt error NF. Distance error AF corresponds to the unintentional approach or distance between one of cameras 16, 18, 20, 22, 24, and 26 and at least one of the other cameras 16, 18, 20, 22, 24, and 26; that is, unintentional translation. Oblique angle error SF corresponds to an unintentional rotation about axis y, causing the two cameras in a camera pair to be oriented in mutually non-parallel directions within a plane spanned by their viewing directions and their connecting lines. Tilt error NF corresponds to an unintentional rotation about axis x, causing the two cameras in a camera pair to span planes with different orientations through their viewing directions and their connecting lines.

[0058] Figure 6 The simulation results are shown as a graph of the measurement error, based on the degree of the corresponding error measured in pixels, particularly pixel fractions.

[0059] The distance error AF affects the mean square measurement error to a very small extent.

[0060] Therefore, the measurement error is mainly affected by the rotation error.

[0061] The oblique angle error SF has an approximately linear effect.

[0062] Surprisingly, it has been shown that the tilt error NF only slightly affects the measurement error to a certain extent. However, if the tilt error NF exceeds a threshold, the measurement error increases disproportionately.

[0063] In the simulation, the obtained tilt error threshold was approximately 0.3 pixels, thus the tilt error NF had a considerable impact. For example, increasing the tilt error NF from 0.3 pixels to 0.5 pixels resulted in a six-fold increase in error (i.e., cumulative drift).

[0064] For example, for a camera with a 90° field of view imaging onto 1536 pixels in the vertical direction, an error of 0.3 pixels corresponds to the following angular error:

[0065] 0.3 pixels × 90° / 1536 pixels = approximately 0.018°.

[0066] One reason for this situation may be the fact that the SLAM method used is able to successfully assign at least some of the elements contained in the images from the various cameras 16, 18, 20, 22, 24, 26 to each other until the tilt error threshold is reached.

[0067] Therefore, the particularly advantageous position measuring device 10 stands out from the fact that the tilt error NF between cameras 16, 18, 20, 22, 24, 26 in at least one camera pair of the camera pair is at most 0.3 pixels.

[0068] The position measuring device 10 can be configured to automatically measure, correct, and / or calculate the tilt error NF between at least one camera pair in the camera pair. In particular, the tilt error NF can be, or can be limited to, at most 0.3 pixels. This can be performed, for example, by configuring the position measuring device 10 (in particular the controller 32) to calibrate the relevant camera pairs, particularly all camera pairs.

[0069] Calibration can be performed by recording images of known content using related cameras 16, 18, 20, 22, 24, and 26 in a related camera pair. The image recordings should have identical elements in dimensions in which the two cameras in the camera pair should not be offset or rotated relative to each other. For example, if an image of a point is recorded, and if the two cameras are offset horizontally but not vertically relative to each other, and if the cameras are oriented identically in the vertical direction, then the correspondingly recorded image will be imaged at the same vertical position within the correspondingly recorded image. The corresponding vertical offset can then be calculated from the subsequently recorded image. Alternatively or additionally, the camera can be adjustablely mounted on bracket 28. The camera can be arranged on bracket 28 so that it can be adjusted, for example, by a motor. Mechanical correction can then be performed so that, in subsequent calibrations, only a small offset can be established, or ideally, no offset can be established. Needless to say, this correction method can also be applied to dimensions other than the vertical dimension mentioned herein, particularly to the horizontal dimension perpendicular to the vertical dimension.

[0070] It is also conceivable to perform this calibration repeatedly, in particular to calculate compensation and / or (where the required mechanical components are available) mechanical correction.

[0071] For example, if the position of a location marker has been measured, and the appearance of the location marker, particularly its dimensions, is fully known, calibration can be performed using an image recording of the location marker in a manner similar to the procedure described in the preceding examples. For instance, location marker 102, provided as a calibration marker, can be used for this purpose. If the appearance of the corresponding location marker is known, other location markers, either in place of location marker 102 or in addition to it, can also be used for this purpose.

[0072] Therefore, it is conceivable that the position measuring device 10 is configured to correct and / or calculate the distance error AF, the oblique angle error SF, and / or the tilt angle error NF of at least two objects by means of image recordings from at least two of the cameras in particular the camera pair 16, 18, 20, 22, 24, 26, the positions of the at least two objects and preferably their appearances are known, for example, by at least two of the position markers 102 used as calibration markers.

[0073] For this purpose, the position measuring device 10 can be configured to identify the position marker 102 in at least one image record from one of the cameras 16, 18, 20, 22, 24, 26, and particularly in multiple image records from different cameras 16, 18, 20, 22, 24, 26.

[0074] Figure 7A position measurement system 100 is shown on a ground construction site 14 having a base 104 and walls 106. The position measurement system 100 has a position measuring device 10 and a measuring rod 108, which is specifically guided by or can be guided by a user 106. Unless otherwise described below, the position measuring device 10 may correspond to one of the position measuring devices described above.

[0075] The orientation and position of the measuring rod 108, particularly the orientation and position of its end 109, and thus the position P that the measuring end 109 contacts, can be measured by the position measuring system 100.

[0076] For this purpose, the measuring rod 108 has three position markers 110, 112, and 114. Position markers 110, 112, and 114 each protrude from the central rod 116 of the measuring rod 108. The rod 116 and the position markers 110, 112, and 114 can be formed of a material with low thermal expansion, such as so-called "INVAR" steel.

[0077] The relative positions of position markers 110, 112, and 114 with respect to each other and with respect to rod 116 and end 109 are known. Position markers 110, 112, and 114 collectively expand a certain volume and thus collectively form a three-dimensional position marker 115. Therefore, even if the measuring rod 108 is not precisely vertically oriented, the position of end 109 and thus the position P can be clearly inferred from the positions of position markers 110, 112, and 114.

[0078] The position measuring device 10 is configured to record position markers 102 and 110, 112 and 114 by means of its six cameras 16, 18, 20, 22, 24 and 26, particularly those cameras 16, 18, 20, 22, 24 and 26 whose fields of view capture the corresponding position markers 110, 112 and 114, and to evaluate the corresponding images in order to determine the position P from them, for example, by photogrammetry.

[0079] Specifically, cameras 16, 18, 20, 22, 24, and 26 of the position measuring device 10 can record images of position markers 110, 112, and 114. Based on stereoscopic or multi-stereoscopic images, the position measuring device 10, particularly its controller 32, can identify the position markers 110, 112, and 114 in the recorded images and position them at their corresponding image locations. The positions of the position markers 110, 112, and 114 can be determined based on the identified image locations. Based on these locations and considering the geometry of the rod 116, particularly the relative position of the end 109, the position measuring device 10 can then calculate the position of the end 109, and thus the position P.

[0080] To improve accuracy, the position measuring device 10 may include a rangefinder 118. The rangefinder 118 may include a laser. Specifically, the rangefinder may be arranged on the position measuring device 10 such that it can be preferably adjusted by a motor, enabling it to position, for example, a target 120 (e.g., a prism) on a rod 116 and to track that target. When determining the position of point P, the distance dx between the rangefinder 118 and the target 120, measured by the rangefinder 118, can be used additionally. In particular, position determination can be performed relative to the inherent coordinate system of the position measuring device 10.

[0081] In order to reference the position P in the independent coordinate system K and thus be able to compare it, for example, with a BIM model, multiple position markers 102 are arranged on the bottom 104 and the walls 106 of the construction site 14. These position markers are all located within the field of view of the camera of the position measuring device 10. These position markers are pre-measured and their coordinates relative to coordinate system K are known. Therefore, the position markers 102 can further be used as calibration markers.

[0082] In order to represent the fuselage's inherent coordinate system in coordinate system K, as described above, an image of the position marker 102 can be recorded and the required transformation data can be determined photogrammetrically from it, so that the position P can be determined in the coordinates of coordinate system K. For this purpose, accuracy can also be improved by measuring the corresponding distances between the rangefinder 118 and the position marker 102 with the aid of the rangefinder 118 and taking them into account when calculating the transformation data.

[0083] In another exemplary embodiment, one or more of the position markers 110, 112, 114 and / or 102 may also be designed as active position markers. Specifically, these active position markers can automatically emit optical signals. The optical signals can be encoded. For example, the optical signals can pulse at one or more specific frequencies.

[0084] The cameras 16, 18, 20, 22, 24, and 26 of the position measuring device 10 can record a series of images.

[0085] The light spots generated by the active position marker can be filtered out from the image series based on their encoding, specifically to improve the signal-to-noise ratio and reduce image noise. The filtered image can then be used for position determination of location P.

[0086] In another exemplary embodiment, it may be provided that calibration is performed by means of one or more of the position markers 102, 110, 112, 114, and preferably also by means of the corresponding distance from the respective position marker, in particular measuring, correcting and / or calculating at least one tilt error of at least one camera pair.

[0087] For example, in the case of the active position marker 102, knowing the actual relative position and orientation of the position marker 102, calibration can be performed by comparing these actual relative positions and orientations with those measured using the recorded images and additionally by comparing them with the distance directly measured by the rangefinder 118. If the cameras in the camera pair to be calibrated are motor-adjustable, then calibration can be performed around its axis y (see [reference]) as long as the deviations of the relative positions and orientations relative to each other and the deviations from the directly measured distances are minimized. Figure 5 Adjustments can be made based on the known geometry of the three-dimensional position marker 115 and its relative position and orientation and distance dx relative to the target 120.

[0088] In addition to or in addition to mechanical adjustments of the camera, images recorded by the camera can also be computationally offset and / or distorted according to a correction representation until a computational correction representation has been determined in which the deviation is also reduced to a minimum.

[0089] This calibration can be performed repeatedly. For example, the calibration can be performed continuously, such as each time position P is determined, that is, each time the positions of position markers 110, 112, and 114 are determined.

[0090] In particular, at least one image error can be measured and / or calculated. Particularly preferred is the determination, correction, and / or calculation of the tilt error between cameras in at least one camera pair.

[0091] Figure 8 A flowchart of method 1000 is shown.

[0092] For ease of understanding, the reference numerals in the accompanying drawings described above will be used to explain method 1000 below. (Using...) Figure 1 The case of executing method 1000 is taken as an example.

[0093] Specifically, method 1000 is a method for measuring the position P of an object 12 on a construction site 14, such as an above-ground construction site or an underground construction site, using a position measurement system 100 of the type described above.

[0094] In phase 1010, the position measuring device 10 uses its six cameras 16, 18, 20, 22, 24, and 26 to record images, which together have a total of 18 MP. At least two of the recorded images contain the position P to be determined, and at least two other images, or identical images, contain at least one of the position markers 102 used as calibration markers, specifically all of the position markers 102. If appropriate, for this purpose, the position measuring device 10 is suitably positioned on the construction site 14.

[0095] In stage 1020, that is, before the actual measurement of position (P), at least one tilt error NF is initially measured based on images from cameras in the camera pair, such as capturing, for example, the clearly identifiable image position of one of the position markers 102 designed as calibration markers and / or another within the field of view of the camera pair. In subsequent image processing steps, the tilt error, determined in pixels or pixel fractions, is then corrected and / or calculated. In particular, the tilt error NF can then be calculated based on the degree of tilt error NF, by means of a calculated offset of the images relative to each other.

[0096] In stage 1030, sharpness is determined for each image in the image to be evaluated. If the sharpness is below a certain sharpness threshold, the corresponding image is recorded again. After a certain number of failed attempts, that is, if the sharpness threshold is not reached despite repetition, method 1000 is terminated with an error message. Instead of determining sharpness, or in addition to determining sharpness, vibrations of the position measuring device 10 can be captured and compared with a vibration threshold in a similar manner, and image recording can be repeated if appropriate, or method 1000 can be terminated with an error message after multiple unsuccessful repetitions.

[0097] In stage 1040, using currently available images, such as photogrammetry and / or using SLAM algorithms, while taking into account the geometry of the position measuring device 10, particularly the relative positions and orientations of cameras 16, 18, 20, 22, 24, 26, the position of at least one of the position markers (102) defined as calibration markers relative to the coordinate system (K) is determined.

[0098] Subsequently, location P was determined based on the available images in a similar manner.

[0099] Based on the position of the position marker 102 in coordinate system K and its position in the image, the position P is converted into coordinates in coordinate system K.

[0100] Another variation of method 1000 is achieved by considering the combination of the foregoing. Figures 1 to 7It appears as one or more of the configuration options described.

[0101] Further features and advantages of the invention will become apparent from the foregoing detailed description of exemplary embodiments of the invention with reference to the accompanying drawings, which illustrate essential details of the invention. Features shown in the drawings are not necessarily considered to be true to scale, but are presented in a manner that clearly visualizes particular features. In variations of the invention, various features may be implemented individually or collectively in any combination.

[0102] List of reference numerals

[0103] 10 Position measuring device

[0104] 12 objects

[0105] 14 Construction site

[0106] 16 cameras

[0107] 18 cameras

[0108] 20 cameras

[0109] 22 cameras

[0110] 24 cameras

[0111] 26 cameras

[0112] 28 brackets

[0113] 30 Tripod

[0114] 32 controllers

[0115] 34 Memory

[0116] 36 Computer program products

[0117] 38 Gravity Orientation Sensor

[0118] 40 Accelerometer

[0119] 100 Position Measurement System

[0120] 102 Location Markers

[0121] 104 Bottom

[0122] 106 Walls

[0123] 106 users

[0124] 108 Measuring Rod

[0125] 109 end

[0126] 110 Location Marker

[0127] 112 Location Marker

[0128] 114 Location Marker

[0129] 115 Three-dimensional position marker

[0130] 116 strokes

[0131] 118 rangefinder

[0132] 120 target

[0133] 1000 methods

[0134] 1010 stage

[0135] 1020 stage

[0136] 1030 stage

[0137] 1040 stage

[0138] AF distance error

[0139] dx distance

[0140] K coordinate system

[0141] NF tilt angle error

[0142] P position

[0143] SF Oblique Viewpoint Error

[0144] SNR Image Noise

[0145] TS Exposure Time

[0146] xx axis

[0147] yy axis.

Claims

1. A position measuring device (10) for measuring the position (P) of an object (12) at a construction site (14), such as an above-ground construction site or an underground construction site, the position measuring device comprising at least one camera (16, 18, 20, 22, 24, 26). Its features are, The position measuring device (10) includes at least six cameras (16, 18, 20, 22, 24, 26) spaced apart from each other, wherein the cameras (16, 18, 20, 22, 24, 26) have a total of at least 18 MP, wherein the position measuring device (10) is configured to determine the position (P) of the object (12) by evaluating images from the at least six cameras (16, 18, 20, 22, 24, 26).

2. The position measuring device (10) as described in the preceding claim, characterized in that, At least one of these cameras (16, 18, 20, 22, 24, 26) is arranged in such a way that it is rotated 90° relative to at least one of the other cameras (16, 18, 20, 22, 24, 26).

3. The position measuring device (10) as described in any one of the preceding claims, characterized in that, At least two cameras in the camera pair (16, 18, 20, 22, 24, 26) are oriented forward, two cameras in the camera pair (16, 18, 20, 22, 24, 26) are oriented to the right, and two cameras in the camera pair (16, 18, 20, 22, 24, 26) are oriented to the left.

4. The position measuring device (10) as described in any one of the preceding claims, characterized in that, The tilt error (NF) between cameras (16, 18, 20, 22, 24, 26) in at least one of these camera pairs is at most 0.3 pixels.

5. The position measuring device (10) as described in any one of the preceding claims, characterized in that, The position measuring device (10) is configured to automatically correct and / or calculate the tilt error (NF) between cameras (16, 18, 20, 22, 24, 26) in at least one of these camera pairs, and in particular, limit it to at most 0.3 pixels.

6. The position measuring device (10) as described in any one of the preceding claims, characterized in that, The position measuring device (10) has a tilt sensor, such as a level and / or a gravity orientation sensor (38).

7. The position measuring device (10) as described in any one of the preceding claims, characterized in that, The position measuring device (10) has a motion sensor and / or a vibration sensor.

8. A position measurement system (100) comprising a measuring rod (108) and a position measuring device (10) as described in any one of the preceding claims, wherein a position marker (102) is arranged and / or formed on the measuring rod.

9. A method (1000) for measuring the position (P) of an object (12) at a construction site (14), such as an above-ground construction site or an underground construction site, using a position measurement system (100) as described in any one of the preceding claims, wherein, Evaluate images from a total of at least six cameras (16, 18, 20, 22, 24, 26), where these cameras (16, 18, 20, 22, 24, 26) have a total of at least 18 MP.

10. The method as described in the preceding claim, characterized in that, Before and / or during the measurement of the location (P), at least one image error is measured, corrected, and / or calculated.

11. The method as described in the preceding claim, characterized in that, Determine, correct, and / or calculate the tilt error (NF) between cameras in at least one of these camera pairs.

12. The method as described in any one of the preceding two patent claims, characterized in that, Determine sharpness or blur in at least one image from these cameras (16, 18, 20, 22, 24, 26), particularly blur caused by motion, and determine the sharpness or blur depending on the specific image. - Use this image when measuring the position (P) of the object (12). - When measuring the position (P) of the object (12), especially when the sharpness reaches or falls below a threshold or the blur reaches or exceeds a threshold, the image is not used, and / or - Correct the image's sharpness for further use.

13. The method according to any one of claims 9 to 12, characterized in that, Detect whether the position measuring device (10) and / or the position marker (102) vibrate and / or move, especially whether the vibration threshold is exceeded.

14. The method according to any one of claims 9 to 13, characterized in that, In addition to determining the position (P), at least one position (P) of the position marker (102) defined as the calibration marker is determined relative to the coordinate system (K).

15. A computer program product (36) stored on a storage medium and configured to perform the method (1000) as described in any one of claims 9 to 14 when executed on a controller (32) of a position measuring device (10) as described in any one of claims 1 to 8.

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