Method for aiming a surveying instrument at a point of interest

Abstract

A computer-implemented method for aiming a surveying instrument at a point of interest in a work site in which the surveying instrument is deployed, the method comprising the steps of: instructing the aiming camera to capture a first image of the work site; instructing the display unit to display the first image; waiting for the point of interest to be selected in the first image; upon selection of the point of interest, instructing the aiming camera to execute an autofocus algorithm, preferably for a region of interest comprising the point of interest; determining a distance value from the autofocus algorithm; calculating first angle data in the first plane and / or second angle data in the second plane based on the determined distance value and the location of the point of interest on the image sensor of the aiming camera; and instructing the drive system to rotate the support around the first angle data and / or to rotate the measuring head around the second angle data.

Description

Technical Field

[0001] The present invention relates to a computer-implemented method for aiming a surveying instrument at a point of interest in the workplace as defined in claim 1, a computer program as defined in claim 8, and an apparatus as defined in claim 9. Background Technology

[0002] In surveying instruments, the use of cameras can enable improved user convenience and new functionalities. In particular, views provided by the camera and displayed on the surveying instrument's monitor (such as image or video feeds) can be used to assist in target selection, target tracking, and to provide the operator with an overview of potential points of interest.

[0003] For surveying instruments where the camera center and instrument center are eccentric, the center of the image captured by the camera does not coincide with the point measured by the distance measurement capability of the surveying instrument. To correctly draw a virtual indicator (such as a crosshair) at the correct measurement location in the displayed camera image, the target distance must be taken into account. For an assumed target distance equal to infinity, the camera eccentricity can be ignored, and the virtual crosshair can be drawn at the camera's principal point (typically at the center of the camera image). However, as the target distance decreases, the correct position of the virtual crosshair moves further and further away from the principal point due to the camera eccentricity.

[0004] A method for aiming a mapping instrument at a point of interest in a workplace where a mapping instrument is deployed is known from US 7,930,835 B2; a computer program for performing the method for aiming the mapping instrument is also known, as well as an apparatus including means for performing the method for aiming the mapping instrument. The mapping instrument includes: a base; a support member rotatable relative to the base about a first axis of rotation; a measuring head rotatable relative to the support member about a second axis of rotation; a drive system configured to rotate the support member about the first axis of rotation and / or rotate the measuring head about the second axis of rotation; a first angle encoder configured to determine a first angle in a first plane relative to the rotation of the support member about the first axis of rotation; a second angle encoder configured to determine a second angle in a second plane relative to the rotation of the measuring head about the second axis of rotation; a computer device or system having evaluation, data processing, and / or control functions; and a display unit configured to display an image captured by a camera. The measuring head includes: a distance measuring device configured to emit a distance measuring beam defining an aiming axis; and a camera having a field of view, a camera axis arranged offset relative to the aiming axis, and a camera center.

[0005] The method for aiming a surveying instrument at a point of interest includes the following steps:

[0006] ■ Indicates that the camera captured an image of the workplace.

[0007] ■ Instructs the display unit to display the image.

[0008] ■Wait for the point of interest to be selected in the displayed image.

[0009] ■ When selecting the point of interest, first angle data in the first plane and / or second angle data in the second plane are calculated based on the distance value and the position of the point of interest on the image sensor of the camera.

[0010] ■ Instructs the drive system to rotate the support member around the first angle data and / or to rotate the measuring head around the second angle data.

[0011] ■ Indicates the corrected distance value measured by the distance measuring device to the point of interest.

[0012] ■Based on the corrected distance value and the position of the point of interest on the camera's image sensor, calculate the corrected first angle data in the first plane and / or the corrected second angle data in the second plane, and

[0013] ■ Instructs the drive system to rotate the support around the calibrated first angle data and / or to rotate the measuring head around the calibrated second angle data.

[0014] To compensate for the offset between the aiming axis and the camera axis caused by the camera's eccentricity, first angle data in the first plane and / or second angle data in the second plane are calculated at least twice. Accurate distance data can only be measured via a distance measuring device when the offset between the aiming axis and the camera axis is fully compensated. Summary of the Invention

[0015] Therefore, a method is needed for aiming a mapping instrument at a point of interest, which allows for compensation of the offset between the aiming axis and the camera axis in a single step.

[0016] These objectives are achieved by implementing the features of the independent claims. The dependent claims describe features that further develop the invention in an advantageous manner.

[0017] According to one aspect of the invention, a computer-implemented method is provided for aiming a surveying instrument at a point of interest in a workplace where such an instrument is deployed, the surveying instrument comprising: a base; a support member rotatable relative to the base about a first rotation axis; a measuring head rotatable relative to the support member about a second rotation axis; a drive system configured to rotate the support member about the first rotation axis and / or rotate the measuring head about the second rotation axis; and a first angle encoder configured to rotate relative to the rotation of the support member about the first rotation axis in a first plane. The method comprises: a first angle; a second angle encoder configured to determine a second angle in a second plane relative to rotation of the measuring head about a second axis of rotation; a computer system having evaluation, data processing, and / or control functions; and a display unit configured to display an image captured by a camera. The measuring head includes: a distance measuring device configured to emit a distance measuring beam defining an aiming axis; and an aiming camera having a first field of view, a first camera axis arranged with a first offset relative to the aiming axis, and a first camera center. The method is performed by the computer system and includes the following steps:

[0018] ■ Indicates that the targeting camera captured the first image of the workplace.

[0019] ■ Instructs the display unit to display the first image.

[0020] ■Wait for the point of interest to be selected in the first image.

[0021] ■ When selecting the point of interest, instruct the aiming camera to preferably perform an autofocus algorithm on the region of interest including the point of interest.

[0022] ■ The distance value is determined from this autofocus algorithm.

[0023] ■Based on the determined distance value and the position of the point of interest on the image sensor of the aiming camera, calculate the first angle data in the first plane and / or the second angle data in the second plane, and

[0024] ■ Instructs the drive system to rotate the support around the first angle data and / or to rotate the measuring head around the second angle data.

[0025] The method is characterized in that the aiming camera is instructed by the computer system to perform an autofocus algorithm preferably targeting a region of interest including the point of interest, and the distance value from the mapping instrument to the point of interest is determined from the autofocus algorithm. The aiming camera will change the focal position of the image and analyze a predefined region of the image, such as the central region. The contrast of the image can be calculated, and the distance is determined using the position with the highest contrast. The distance to the point of interest is determined by the distance value determined from the autofocus algorithm, rather than the distance to a point offset from the selected point of interest. This correction is calculated by the computer system via triangulation based on the distance value and the position of the point of interest on the pixelated image sensor of the aiming camera. If the first offset has a component in a first plane and / or a second plane, first angle data and / or second angle data are calculated. To compensate for the effect of eccentricity, the drive system is instructed to rotate the support around the first angle data and / or rotate the measuring head around the second angle data.

[0026] Preferably, the method further includes: while rotating the support member around the first angle data and / or rotating the measuring head around the second angle data, the distance measuring device is instructed by the computer system to measure an updated distance value. The calculation of this correction can be repeated by the computer system.

[0027] In a first preferred embodiment, the first camera axis is arranged parallel to the aiming axis. By using the optical system of a mapping instrument with parallel aiming and camera axes, the optical paths of the distance measuring device and the aiming camera are separated and can be individually adapted to the specific requirements of the distance measuring device and the aiming camera.

[0028] In a second preferred embodiment, the first camera axis is tilted relative to the aiming axis at a first tilt angle other than 0°, and the first offset is defined as the normal distance of the aiming axis extending through the center of the first camera. By using a tilted first camera axis, the workload of compensating for the first offset can be reduced. The first tilt angle is different from 0° and is typically in the range of less than 1°. The first tilt angle is selected such that for a target distance equal to infinity, the offset distance is zero and decreases as the distance between the mapping instrument and the target plane increases.

[0029] Preferably, the measuring head further includes an aiming light source configured to emit aiming light. This aiming light source can support the identification of points of interest under all ambient lighting conditions, even in darkness. Preferably, the aiming light source is adapted to the aiming camera, such as a white light source for an aiming camera operating in the visible spectrum. Light sources emitting wavelengths of approximately 380 nm to 750 nm are considered to operate in the visible spectrum, and light sources emitting wavelengths of approximately 780 nm to 1 mm are considered to operate in the infrared spectrum.

[0030] Preferably, the measuring head further includes a second camera having a second field of view, a second camera axis arranged with a second offset relative to the aiming axis, and a second camera center. The second camera may be a tracking camera operating in the infrared spectrum, or it may be an overview camera operating in the visible spectrum. Wavelengths from approximately 380 nm to 750 nm are considered to operate in the visible spectrum, and wavelengths from approximately 780 nm to 1 mm are considered to operate in the infrared spectrum.

[0031] Preferably, the measuring head further includes a second light source configured to emit a second light. This second light source is adapted to the second camera, such as an infrared light source for a tracking camera or a white light source for a survey camera.

[0032] According to another aspect of the invention, a computer program is provided, comprising instructions that, when executed by a computer device or system, cause the computer device or system to perform the method according to the invention.

[0033] The computer program may be stored on the computer system or on a computer-readable medium communicatively connected to the computer system. The term "computer-readable medium" includes, but is not limited to, portable or non-portable storage devices, optical storage devices, and various other media capable of storing, containing, or carrying instructions and / or data.

[0034] According to another aspect of the invention, an apparatus is provided that includes means for performing the method according to the invention. Attached Figure Description

[0035] The following description or explanation of various aspects of the invention is by way of example only, with reference to the schematic examples shown in the accompanying drawings. Identical elements are labeled with the same reference numerals in the drawings. The described embodiments are generally not shown to scale and should not be construed as limiting the invention. Specifically:

[0036] Figure 1 The image shows an operator using a surveying instrument deployed in the workplace. The instrument includes a measuring unit mounted on a tripod and a remote control connected to the measuring unit via a communication link.

[0037] Figure 2A , Figure 2B It shows in Figure 1 An exemplary version of the measuring unit used in the surveying instrument ( Figure 2A ) and block diagram of the main components of the surveying instrument ( Figure 2B ),

[0038] Figure 3An exemplary version is shown Figure 1 The optical components of the measuring unit used in surveying instruments.

[0039] Figure 4 An exemplary version of the method for aiming a surveying instrument according to the present invention is illustrated in a flowchart.

[0040] Figure 5 An image captured by a targeting camera is shown schematically. Detailed Implementation

[0041] Reference will now be made in detail to this preferred embodiment, examples of which are illustrated in the accompanying drawings. It should be understood that the technology disclosed herein is not intended to limit its application to the construction details and component arrangements set forth in the following description or shown in the drawings. The technology disclosed herein can have other embodiments and can be practiced or implemented in various ways.

[0042] Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered restrictive. All definitions defined and used herein should be understood to supersede dictionary definitions, definitions in referenced documents, and / or general meanings of the terms defined.

[0043] The use of “comprising,” “including,” or “having,” and variations thereof in this document is intended to cover the items listed thereafter and their equivalents, as well as additional items. Unless otherwise limited, the terms “connection,” “link,” and “installation,” and variations thereof, are used extensively herein and cover direct and indirect connections, links, and installations. Furthermore, the terms “connection” and “link,” and variations thereof, are not limited to physical or mechanical connections or links.

[0044] Figure 1 The diagram illustrates an operator using a surveying instrument 10 deployed at a workplace 11. Workplace 11 can be a construction site (indoor or outdoor) or a surveying site, etc. In addition to the surveying instrument 10, a target 12, located away from the surveying instrument 10, can be deployed at workplace 11. Target 12 may include a reflector 13, such as a prism and / or a peephole, mounted on top of a pole 14.

[0045] The surveying instrument 10 is configured as a total station and includes a measuring unit 15 mounted on a support structure in the form of a tripod 16. The surveying instrument 10 also includes a removable control panel in the form of a remote controller 17, which can be used to remotely control the measuring unit 15 via a wireless connection 18.

[0046] Figure 2A , Figure 2B Shown in 3D Figure 1An exemplary version of the measuring unit 15 used in the surveying instrument 10 ( Figure 2A ) and block diagram of the main components of the surveying instrument 10 ( Figure 2B ).

[0047] The surveying instrument 10 is designed as a robotic total station, and the measuring unit 15 includes a base 21, a support 22, and a measuring head 23. The measuring head 23 is enclosed by a housing 24, which includes an exit window 25. Within the housing 24, a distance measuring device capable of emitting a distance measuring beam and a tracking device capable of emitting a tracking beam are arranged. The distance measuring beam and the tracking beam are emitted out of the housing 24 through the exit window 25.

[0048] In Figure 2A In an exemplary version, the support 22 is U-shaped and includes a bottom portion 27, a first side portion 28, and a second side portion 29. The support 22 can rotate completely around its circumference about a first axis of rotation 31 at a full 360° angle relative to the base 21. The measuring head 23 is pivotally mounted to the support 22 about a second axis of rotation 32 and is arranged between the first side portion 28 and the second side portion 29 of the support. Typically, the first axis of rotation 31 is aligned parallel to the local gravity direction 33, and the second axis of rotation 32 is aligned perpendicular to the local gravity direction 33.

[0049] An azimuth motor and a first angle encoder may be located in the bottom portion 27 of the support 22, allowing the measuring unit 15 to rotate about a first rotation axis 31 and determine the direction of the distance measuring beam in a first plane 34 perpendicular to the first rotation axis 31. An elevation motor and a second angle encoder may be located in the first side portion 28 of the support 22, allowing the measuring head 23 to pivot about a second rotation axis 32 and determine the direction of the distance measuring beam in a second plane 35 perpendicular to the second rotation axis 32. To make the instrument 12 fully automatic, a self-leveling device may be included, which may be arranged in the bottom portion 27 of the support 22.

[0050] Figure 2B A block diagram of the main components of the total station 10 is shown. The total station 10 includes a control unit 41, a distance measuring device 42, a first angle encoder 43, an azimuth motor unit 44, a second angle encoder 45, and an elevation motor unit 46. The main components 41, 42, 43, 44, 45, and 46 are mandatory for robotic total stations, while the azimuth motor unit 44 and the elevation motor unit 46 are not included in manual total stations. The azimuth motor unit 44 and the elevation motor unit 46 are summarized as the drive system of the measuring unit 15.

[0051] The distance measuring device 42 may include a laser transmitter, a laser driver circuit, a photoelectric sensor, and a laser receiver interface circuit. The laser driver circuit provides current to the laser transmitter that emits the distance measuring beam 47. The photoelectric sensor receives at least a portion of the distance measuring beam 47 reflected at a target or surface in the workplace, and the current signal output by the photoelectric sensor is directed to the laser receiver interface circuit. After appropriate amplification and demodulation, the signal is sent to the control device 41.

[0052] The first angle encoder 43 provides a signal to the control device 41 so that it knows exactly what first angle the distance measuring beam 47 is arranged in the first plane 34, and the second angle encoder 45 provides a signal to the control device 41 so that it knows exactly what second angle the distance measuring beam 47 is arranged in the second plane 35.

[0053] The angle encoder that can be set to the required accuracy for the total station 10 is either a magnetic encoder or an optical encoder. Optical encoders use a transmission scale made of glass or plastic, with LED illumination on one side of the scale and an image or line sensor on the other side; the scale has codes to provide absolute readings at any angle. US 7,589,313 B2 describes possible encoder technologies that can be used for both first and second angle encoders.

[0054] The azimuth motor device 44 may include an azimuth motor and an azimuth motor driver circuit. The azimuth motor is the driving force for rotating the main housing 22 of the measuring unit 15 about a first rotation axis 31. The azimuth motor driver circuit provides appropriate current and voltage to drive the azimuth motor. The elevation motor device 46 may include an elevation motor and an elevation motor driver circuit. The elevation motor is the driving force for pivoting the measuring head 23 about a second rotation axis 32. The elevation motor driver circuit provides appropriate current and voltage to drive the elevation motor.

[0055] To enable the total station 10 to aim at a point of interest (POI), the total station 10 includes an aiming camera 48 and an aiming light source 49 that optionally emits an aiming light 50. The aiming camera 48 may be a visual camera that allows the user to aim at the POI. The camera needs high resolution to see the details of the target, the full RGB color space, and a suitable field of view that allows the user to see the entire target at both the shortest and longest aiming distances. If the field of view of the aiming camera 48 is insufficient to see the entire target at the shortest aiming distance, a second camera may be used. To enable the total station 10 to aim at the POI under all ambient lighting conditions, even in darkness, the aiming light source 49 is used to generate the necessary illumination for the aiming camera 48.

[0056] The control device 41 mainly includes a processing unit 51, a storage unit 52, an image processing unit 53, an image acquisition control unit 54, an image storage unit 55, a display unit 56, and an input unit 57. The processing unit 51, the image processing unit 53, and the image acquisition control unit 54 define a computer system having evaluation, data processing, and / or control functions for the surveying instrument 10.

[0057] Within storage unit 52, there may be a program storage area for different types of computer programs and a data storage area for storing data (such as the results of distance and angle measurements). The program storage area can store various types of computer programs. These computer programs may include calculation programs for calculating coordinates from distance and angle measurements, image processing programs for performing image processing, sequence programs for selecting points of interest in an image, distance measurements performed at the selected points of interest, tracking programs for tracking reflector targets, search programs for searching for reflector targets when they are not visible, and other programs.

[0058] Image storage unit 55 may include a first image storage unit 55A, a second image storage unit 55B, and a third image storage unit 55C. Images when the aiming light source 49 is on and images when the aiming light source 49 is off can be acquired by the aiming camera 48 through the opening and closing operations of an electronic shutter synchronized with the flashing of the aiming light source 49. Image data when the aiming light 50 is on can be stored in the first image storage unit 55A, and image data when the aiming light 50 is off can be stored in the second image storage unit 55B. Image processing unit 53 subtracts image data when the aiming light 50 is off, such as that stored in the second image storage unit 55B, from the image data when the aiming light 50 is on, such as that stored in the first image storage unit 55A, and acquires only the target image. The image data of the acquired target image is stored in the third image storage unit 55C.

[0059] The control unit 41 includes a display unit 56 for displaying images captured by the camera. The display unit 56 may be an integral part of the measurement unit 15, but more preferably, it is included in a remote controller 17 that can be used for remote control of the total station 10. It is even conceivable that the total station 10 is fully remotely controlled, wherein the display unit 56 may be in the form of a remotely accessible computer screen, and wherein information to and from the total station 10 is transmitted via a wireless network. The display unit 56 may include a screen, a touchscreen, etc.

[0060] The control device 41 includes an input unit 57, which may be an integral part of the measurement unit 15, but more preferably, the input unit 57 is included in a remote controller 17 that can be used for remote control of the total station 10. The input unit 57 may include various input elements, such as a mouse, keyboard, touch screen, etc.

[0061] Figure 3 The optical components of the measuring head 23 are shown in an exemplary version. The measuring head 23 includes a distance measuring device 42, a targeting camera 48, and a targeting light source 49. The targeting light source 49 is an optional component for generating the necessary illumination for the targeting camera 48 under all ambient lighting conditions, even in darkness.

[0062] The measuring head 23 may further include a second camera 61 and a second light source 62. The second camera 61 may be a tracking camera operating in the infrared spectrum, or it may be a survey camera operating in the visible spectrum. The wavelength of the second light source 62 should be suitable for the second camera 61.

[0063] The distance measuring device 42 emits a distance measuring beam 47 that defines the aiming axis 63. The aiming camera 48 includes a first image sensor 64 and a first optical lens 65. The aiming camera 48 has a first field of view (FoV-1), a first camera axis (CA-1), and a first camera center (CC-1). The first camera axis (CA-1) is arranged with a first offset (OFF-1) relative to the aiming axis 63. In an exemplary version, the focal length of the aiming camera 48 is adaptable within a range between a minimum and maximum focal length via a motor unit 66. A typical image sensor for the aiming camera is a monochrome or RGB Bayer filter CMOS sensor with small pixels and a global shutter. The focus of the second camera 61 can be changed by using a controllable liquid optical lens, by moving a lens block, and / or by moving the image sensor.

[0064] Optionally, the second camera 61 may include a second image sensor 68 and a second optical lens 69. In an exemplary version, the focal length of the second camera 61 is fixed. The second camera 61 may have a second field of view FoV-2, a second camera axis CA-2, and a second camera center CC-2. The second camera axis CA-2 is arranged to have a second offset OFF-2 relative to the aiming axis 63.

[0065] Figure 4 A flowchart illustrates a method according to the present invention for aiming a surveying instrument at a point of interest, and Figure 5 An image captured by aiming camera 48 and used in the method according to the invention is illustrated schematically. The method is executed by computer systems 51, 53, and 54 and includes the following steps:

[0066] ■ Instructs the aiming camera 48 to capture the first image 71 of the workplace 11 (step S10).

[0067] ■ The indicator display unit 56 displays the first image 71 (step S20).

[0068] ■ Waiting to select the point of interest (POI) in the first image 71 (step S30).

[0069] ■ When selecting a point of interest (POI), the aiming camera 48 is instructed to preferably perform an autofocus algorithm on the region of interest (AOI) that includes the POI (step S40).

[0070] ■ Determine the distance value from the autofocus algorithm (step S50).

[0071] ■Based on the determined distance value and the position of the point of interest (POI) on the image sensor 64 of the aiming camera 48, calculate the first angle data α1 in the first plane 34 and / or the second angle data α2 in the second plane 35 (step S60), and

[0072] ■ The drive systems 44 and 46 indicate that the support 22 rotates around the first angle data α1 and / or the measuring head 23 rotates around the second angle data α2 (step S70).

[0073] Figure 5 A first image 71, captured by the aiming camera 48 and displayed on the display unit 56, is shown (step S20). Due to the eccentricity of the aiming camera 48 relative to the distance measuring device 42, the crosshair 72 of the aiming camera 48, representing the first camera axis CA-1, does not coincide with the laser spot 73 generated by the distance measuring beam 47. Operator interaction is required to continue the method. When selecting a point of interest (POI), the aiming camera 48 is instructed to preferably perform an autofocus algorithm for the region of interest (AOI) including the POI (step S40), and a distance value is determined from the autofocus algorithm (step S50).

[0074] To account for eccentricity, the computer system calculates first angle data α1 in the first plane 34 and / or second angle data α2 in the second plane 35 based on the determined distance value and the position of the point of interest (POI) on the image sensor 64 of the aiming camera 48 (step S60). To compensate for the first angle data and / or the second angle data, the azimuth motor device 44 is instructed to rotate the support member 22 around the first angle data α1 and / or the elevation motor device 46 is instructed to rotate the measuring head 23 around the second angle data α2 (step S70).

Claims

1. A computer-implemented method for aiming a mapping instrument (10) at a point of interest (POI) in a workplace (11) where a mapping instrument (10) is deployed, the mapping instrument (10) comprising: Base (21); support (22) which is rotatable relative to the base (21) about a first axis of rotation (31); The measuring head (23) is rotatable relative to the support (22) about a second rotation axis (32); A drive system (44, 46) configured to rotate the support (22) about the first rotation axis (31) and / or rotate the measuring head (23) about the second rotation axis (32); A first angle encoder (42) is configured to determine a first angle in a first plane (34) relative to the rotation of the support (22) about the first axis of rotation (31); A second angle encoder (45) configured to determine a second angle in a second plane (35) relative to the rotation of the measuring head (23) about the second axis of rotation (32); and a computer system (51, 53, 54) having evaluation, data processing and / or control functions. and a display unit (56) configured to display an image captured by a camera, wherein the measuring head (23) includes: a distance measuring device (42) configured to emit a distance measuring beam (47) defining an aiming axis (63); and an aiming camera (48) having a first field of view (FoV-1), a first camera axis (CA-1) arranged with a first offset (OFF-1) relative to the aiming axis (63), and a first camera center (CC-1), wherein the aiming method is performed by the computer system (51, 53, 54) and includes: ■ Instructs the aiming camera (48) to capture the first image (71) of the workplace (11). ■ Instructs the display unit (56) to display the first image (71). ■ Waiting for the point of interest (POI) to be selected in the first image. ■ When selecting the point of interest (POI), the aiming camera (48) is instructed to preferably perform an autofocus algorithm on the region of interest (AOI) including the POI. ■ The distance value is determined from this autofocus algorithm. ■Based on the determined distance value and the position of the point of interest (POI) on the image sensor (64) of the aiming camera (48), calculate the first angle data (α1) in the first plane (34) and / or the second angle data (α2) in the second plane (35), and ■ Instruct the drive system (44, 46) to rotate the support (22) around the first angle data (α1) and / or to rotate the measuring head (23) around the second angle data (α2).

2. The method as described in claim 1, wherein, When the support (22) is rotated about the first angle data (α1) and / or the measuring head (23) is rotated about the second angle data (α2), the distance measuring device (42) is instructed by the computer system to measure the updated distance value.

3. The method according to any one of claims 1 to 2, wherein, The first camera axis (CA-1) is arranged parallel to the aiming axis (63).

4. The method according to any one of claims 1 to 2, wherein, The first camera axis (CA-1) is tilted relative to the aiming axis (63) at a first tilt angle (φ1) different from 0°, and the first offset (OFF-1) is defined as the normal distance of the aiming axis (63) extending through the center of the first camera (CC-1).

5. The method according to any one of claims 1 to 4, wherein, The measuring head (23) further includes a targeting light source (49) configured to emit a targeting light (50).

6. The method according to any one of claims 1 to 5, wherein, The measuring head (23) further includes a second camera (61) having a second field of view (FoV-2), a second camera axis (CA-2) arranged with a second offset (OFF-2) relative to the aiming axis (63), and a second camera center (CC-2).

7. The method of claim 6, wherein, The measuring head (23) further includes a second light source (62) configured to emit a second light.

8. A computer program comprising instructions that, when executed by a computer device (51, 53, 54), cause the computer system (51, 53, 54) to perform the method according to any one of claims 1 to 7.

9. An apparatus comprising means for performing the method according to any one of claims 1 to 7.

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