Surveying instrument and method for calibrating the same, and computer readable medium

Abstract

Surveying instrument and method for calibrating the same, and computer readable medium. The invention relates to a surveying instrument comprising a single point measurement unit, a point cloud measurement module, and a computing unit. The single point measurement unit is configured to generate first measurement data comprising coordinates of one point. The point cloud measurement module has a fixed pose opposite to the single point measurement unit and is configured to generate second measurement data comprising coordinates of a plurality of points. The computing unit stores calibration parameters and is configured to generate a point cloud based on the second measurement data, to merge the point cloud with the first measurement data, and to detect surface and object edges in the point cloud. The surveying instrument is configured to perform calibration using object edges in the environment. The single point measurement unit acquires a set of single measurement points comprising at least two points on respective flat surfaces of the object edges. The computing unit derives a vertex formed by the distribution of the measurement points. The computing unit updates the calibration parameters based on an alignment of the object edges with the derived vertex.

Description

Technical Field

[0001] This invention relates to a geodetic survey instrument comprising a single point measuring unit and a point cloud measuring module, a method for referenceless field calibration of the geodetic survey instrument, and a computer program product based on the method. Background Technology

[0002] To capture topographic information about the surface of an object, particularly a building or construction site, a scanning method is typically used. This environment's topography is usually represented by a continuous point cloud (specifically, a point cloud with a resolution of at least 1000 points per square meter at a distance of 5 meters from the point cloud measurement module, or in other words, at least 2.5 points per mSr). A common method for scanning surfaces is to utilize a scanning module, particularly a laser scanning module, which uses a scanning beam, particularly a laser beam, to scan the surface of the object and generates the environment's topography by combining the measured distance information with the beam's emission angle. By way of example, the laser scanner is presented here as a representative of a general point cloud measurement module or instrument. Specific features of other types of point cloud measurement modules or instruments (especially time-of-flight cameras) can be applied accordingly.

[0003] Laser scanning modules and methods of utilizing them are known in the prior art and are disclosed, for example, in WO 97 / 40342. Scanning is typically performed by deflecting the beam using appropriate optical elements (e.g., rapidly rotating mirrors). A typical use of scanning modules is to mount them on a fixed base including at least one other motorized axis to change, measure, and record the emission angle in two degrees of freedom.

[0004] Another possibility is a mobile scanning system, in which the scanning module is mounted on a mobile platform, particularly one that allows movement on a linear track, and the scanning of the environment occurs during the movement of the scanning platform. Such a system is particularly useful for scanning linearly navigable environments (e.g., tunnels, airport runways, or sections of road or railway tracks).

[0005] This setup, which depends on the required point-to-point resolution, allows for continuous and time-efficient scanning of the environment; however, the accuracy of the point coordinates is insufficient to meet high geodetic accuracy standards.

[0006] For dynamic environments, especially construction sites, the task is not only to capture topographic information but also to combine that information with the relative or absolute locations of key features. Location information must also meet geodetic accuracy standards, specifically requiring locations to be known with centimeter-level accuracy or better. The task may also involve tracking moving objects and providing at least their relative positions to key features of the environment.

[0007] To obtain information with the required accuracy from stationary or moving objects, geodetic surveying instruments are typically used, particularly total stations, stadia systems, and motorized theodolites. Geodetic surveying instruments include point measurement units configured to provide polar coordinates and / or derived Cartesian coordinates for one or more points, according to geodetic accuracy standards.

[0008] Total stations are a common type of geodetic surveying instrument. Through illustrative examples, the total station is presented here as a representative of general-purpose geodetic surveying instruments. Specific features of other types of geodetic surveying instruments can be applied accordingly. A total station basically consists of an aiming unit, a single-point distance measuring element (especially a laser rangefinder), and an angle sensor (with an accuracy in the arcsecond range).

[0009] Modern total stations are typically characterized by their compact design, often comprising a coaxial single-point ranging element (especially a laser rangefinder) within a single portable unit, along with aiming, computing, control, and data storage units. Total stations are often used in conjunction with retroreflective targets, particularly circular prisms, and for this application, they typically include automatic target search and tracking capabilities. Objects equipped with retroreflective targets are generally referred to as cooperative targets, while other targets, especially diffuse targets, are typically referred to as non-cooperative targets.

[0010] To sight and target a designated target point, a general-purpose total station is equipped with a telescope sight, such as an optical telescope. The telescope sight can be aligned with the target point by pivoting and tilting the total station system. For example, the aiming device of such a geodetic apparatus is described in EP 2219011. The polar coordinates of the target point are then determined. The distance to the target is determined by a ranging method (particularly using a laser rangefinder), while the elevation and azimuth angles are derived from angle readings provided by angle sensors included in the survey instrument, particularly from angle readings provided by angle sensors included in the single-point measuring unit. As an example, the coaxial aiming unit and the single-point measuring element are referred to hereafter as the aiming / rangefinder unit. As an example, unless otherwise specified, the distance to / from the survey instrument will refer to the distance to the single-point measuring unit (particularly to the aiming / rangefinder unit). As an example, unless otherwise specified, the azimuth angle is the angle relative to a reference direction, particularly to true north, while the elevation angle is the angle relative to the horizon, particularly to a calibrated horizon.

[0011] Despite having an optical magnification of 30x, targets are often difficult to aim at with sufficient accuracy for geodesy. Therefore, modern total stations can be equipped with Automatic Target Recognition (ATR) for cooperative targets. EP2141450 discloses a surveying device with ATR functionality.

[0012] In the prior art, for example, US 6,411,371 B1 also discloses an apparatus and measurement protocol for marking and measuring the location of non-cooperative targets.

[0013] Modern total stations can also reference an external coordinate system by accurately recording reference markers in the environment. When such an external coordinate system is determined, all coordinated operations can be referenced to that external or global coordinate system.

[0014] Modern total stations can also be equipped with a set of wireless modules that enable the total station to communicate with different types of external units. The non-exclusive list of external units includes another survey instrument, a handheld data acquisition device, a field computer, or cloud services.

[0015] Single-point measurement units are configured to determine the location of a finite number of points and to track moving objects with the accuracy required for geodetic surveying. However, due to the cumbersome nature of the measurements, they are not ideal for generating environmental scans with the desired point-to-point resolution.

[0016] The benefits of combining a single-point measurement unit that can provide high single-point accuracy with a dedicated point cloud measurement module (especially a laser scanner) capable of providing a point cloud representation of the environment with high point-to-point resolution have been recognized and are known in the prior art. For example, WO2013 / 113759A1 or EP 3495769 B1 discloses a surveying instrument that includes a single-point measurement unit and a dedicated point cloud measurement module.

[0017] Positioning two optical systems along a common optical axis is known in the art. For example, US 2014 / 0226145 A1 discloses such a device. This choice provides a common gimbal location for both systems; however, the design is constrained by the need for common optical elements, forcing designers to make suboptimal choices regarding the point cloud measurement module and the single-point measurement unit, particularly in the selection of the beam deflection mechanism, or aperture, or laser wavelength.

[0018] Providing two dedicated optical paths for the point cloud measurement module and the single-point measurement unit can maximize the benefits of combining the two instruments. However, in this setup, at least the relative orientation of the point cloud measurement module with respect to the single-point measurement unit must be determined. The relative orientation includes the distance between the two instruments and the orientation difference of their optical axes. Some solutions to this problem are known from the prior art. EP 3483554 B1 discloses an exemplary calibration routine based on a method in which an operator aims at at least three points for every three surfaces. These calibration methods are either based on measurements of a reference object (i.e., a dedicated cooperative target, particularly a previously positioned retroreflector) or guide the operator's actions by specifying multiple points to be aimed at by the single-point measurement unit. Summary of the Invention

[0019] The purpose of this invention

[0020] In view of the above, the purpose of this invention is to provide an automated, reference-free field calibration method for a geodetic surveying instrument, which includes a single-point measurement unit, a point cloud measurement module, and a computing unit.

[0021] Invention Summary

[0022] This invention relates to a surveying instrument (particularly a total station, stadia, theodolite, laser tracker, or indoor positioning system), which includes: a single-point measurement unit, a point cloud measurement module (particularly a laser scanner), and a computing unit.

[0023] The single-point measurement unit is configured to generate first measurement data, which includes the distance, elevation angle, and azimuth angle of the single point from the surveying instrument. The first measurement data may include the distance, elevation angle, and azimuth angle of multiple single points from the surveying instrument. The first measurement data may also include other data derived from other segments of the first measurement data, particularly Cartesian coordinates, or mathematical objects fitted to the coordinates of multiple single points, or even more particularly lines and planes.

[0024] The first measurement data may also include the absolute position of a single-point measuring unit in a local or global reference frame. The absolute position of the single-point measuring unit can be obtained by measuring the distance, elevation angle, and azimuth angle of a pre-known reference point from the surveying instrument. Needless to say, the absolute position of the single-point measuring unit can also be provided by other means. The surveying instrument according to the invention is configured to provide first measurement data that meets geodetic accuracy standards, particularly providing absolute or relative coordinates with at least centimeter accuracy.

[0025] As an example, a single-point measurement unit may include one or more angle sensors, or may retrieve data from other angle sensors included in the surveying instrument. The single-point measurement unit is configured to emit a measurement beam (particularly a laser beam) to determine the distance to the surveying instrument.

[0026] The point cloud measurement module is configured to generate second measurement data by scanning the environment. This second measurement data includes the coordinates of multiple scan points. The point density of the scan points meets the requirements of a continuous point cloud; specifically, the point density is at least 1,000 points per square meter at a distance of 5 meters from the point cloud measurement module, or alternatively, 2.5 points per mSr.

[0027] A point cloud measurement module can be set to, or can be set to, a single-point measurement unit. At least during calibration and subsequent post-calibration measurement operations, the point cloud measurement module maintains a fixed attitude relative to the single-point measurement unit. The fixed attitude according to the invention can be a permanent attitude, wherein the point cloud measurement module is inseparable. The fixed attitude can also be a temporary attitude, wherein the point cloud measurement module can be detachable and reattached to a substantially identical attitude. For some embodiments of the surveying instrument according to the invention, it is also possible to reattach the point cloud measurement module so that its new fixed attitude relative to the single-point measurement module is substantially different from its previous fixed attitude. It is self-evident to those skilled in the art that disassembling and reattaching the point cloud measurement module may result in the need for further calibration.

[0028] In some specific implementations, the point cloud measurement module is a laser scanner. In some more specific implementations, the laser scanner includes a motorized rotatable beam deflector.

[0029] Needless to say, other implementations of the point cloud measurement module are also possible. The point cloud measurement module may be based on or may include one or more cameras, particularly one or more time-of-flight cameras.

[0030] In some embodiments, the point cloud measurement module is arranged laterally on the surveying instrument. Other arrangements (specifically, more than one point cloud measurement module) are possible for some embodiments of the surveying instrument according to the invention. As an example, unless otherwise specified, the surveying system comprises a single point cloud measurement module. Specific features of surveying systems comprising multiple point cloud measurement modules or instruments can be applied accordingly.

[0031] The computing unit stores calibration parameters, which include a fixed attitude between the single-point measurement unit and the point cloud measurement module. The calibration parameters may also include intrinsic calibration parameters of the point cloud measurement module. The computing unit is configured to generate a calibration point cloud based on second measurement data, wherein the calibration point cloud represents the environment; and to merge the calibration point cloud with first measurement data based on the calibration parameters. The computing unit is also configured to detect flat surfaces and object edges in the environment by analyzing the calibration point cloud. Needless to say, the computing unit is configured to perform general mathematical operations, specifically determining distances and angles in the merged data.

[0032] It is equally self-evident that during the merging of the first and second measurement data, the source of the data can be preserved, i.e., whether a particular data segment originated from the first measurement data or from the second measurement data. The resulting data segment can also be characterized accordingly, whether it originates solely from a data segment with the first measurement data source, solely from a data segment with the second measurement data source, or from a data segment with both first and second measurement data sources. During data processing, the computing unit can consider the source of the data segment; that is, if a particular data segment originates from the first measurement data, the computing unit can perform only some mathematical operations, and vice versa.

[0033] Survey instruments can be configured to perform ATR (Automatic Tracing) functionality. This means the instrument can identify targets, particularly retroreflected targets, and determine their absolute or relative positions without operator intervention. If the target point has moved, the instrument can also update initial measurement data, including distance, elevation, and azimuth. The instrument can then locate target points with known absolute positions to determine its own absolute position.

[0034] The surveying instrument according to the invention is configured to perform a calibration function. The calibration function includes automatically performing the following steps: A point cloud measurement module acquires second measurement data as a calibration point cloud. A calculation unit identifies at least two non-parallel object edges in the calibration point cloud. The object edges are defined by corresponding first and second flat surfaces. For each of the at least two object edges, a single-point measurement unit scans across the object edge using a measurement beam and acquires a set of single measuring points including at least two points on each flat surface of the object edge. The measuring points are located on a straight-line scan path, meaning that the azimuth angle and elevation angle of the measuring points exhibit a linear relationship. Alternatively, the single-point measurement unit and the set of measuring points are located in a common plane. Or, from the point of view of the surveying instrument, the measuring points are aligned with a line. The calculation unit derives a vertex formed by the distribution of the measuring points, where the vertex corresponds to the object edge. Calibration parameters are updated based on the alignment of the object edge with the derived vertex.

[0035] In some specific implementations, environmental scanning, calibration point cloud generation, object edge detection, object edge selection, and other calibration steps are performed within a single, uninterrupted calibration process. However, the calibration process may include one or more pauses. As an example, the calibration process may be paused after acquiring second measurement data, where the computing unit stores the second measurement data and the calibration phase. Upon request to continue the calibration process, further calibration steps are performed based on the stored calibration parameters. Some other non-exclusive lists of possible calibration process pauses include: after generating the calibration point cloud, after detecting suitable object edges, and after selecting a first and a second object edge. The computing unit stores the state of the calibration process, the generated data, and further resumes the calibration upon request to continue. Needless to say, the operator or the computing unit itself may also abort the calibration process, especially upon detecting an error.

[0036] In some embodiments, the computing unit is permanently mounted on the point measurement unit. In other embodiments, the computing unit is temporarily mounted or can be mounted on the point measurement unit. The computing unit can also be a separate entity, particularly a field computer or handheld device. In embodiments where the computing unit is not mounted on the point measurement unit, the surveying instrument may include a corresponding wired or wireless interface configured for data exchange between the computing unit and other components of the surveying instrument.

[0037] In some specific embodiments, the single-point measurement unit includes: an aiming / rangefinder unit configured to tilt about a tilting axis, and a first angle sensor configured to measure a first angle as the tilt angle of the aiming / rangefinder unit. A calculation unit is configured to retrieve the first angle.

[0038] In some embodiments, the single-point measuring unit is mounted on a base and configured to rotate relative to the base about a rotation axis, particularly about a vertical axis. The surveying instrument also includes a second angle sensor configured to measure a second angle of the single-point measuring unit relative to the base. A calculation unit is configured to retrieve this second angle.

[0039] The present invention also relates to a calibration method for surveying instruments (particularly total stations, stadia instruments, theodolites, laser trackers, or indoor positioning systems). The surveying instrument includes: a single-point measurement unit, a point cloud measurement module (particularly a laser scanner), and a computing unit.

[0040] The calibration method includes the following steps: 1.) Acquire second measurement data as a calibration point cloud using a point cloud measurement module; 2.) Identify at least two non-parallel object edges in the calibration point cloud, wherein each of these object edges is defined as the intersection of a first flat surface and a second flat surface of the corresponding object edge; 3.) For each of the at least two object edges, scan across the object edge using a single-point measurement unit, wherein a set of single measurement points including at least two points on each flat surface of the object edge is acquired, the single measurement points being located on a straight scanning path; 4.) Derive vertices formed by the distribution of measurement points, the vertices corresponding to the object edges, and optionally repeat steps 3 to 4 if adding other optional edges is considered beneficial; 5.) Update calibration parameters based on the alignment of the object edges with the derived vertices.

[0041] In some specific embodiments of the method, the determination of vertices includes: 1.) dividing a set of single measurement points into a first set of points located on a first flat surface and a second set of points located on a second flat surface; 2.) using a computing unit to fit the first set of points and the second set of points using a weighted fitting method (in particular, weighted least squares fitting) to determine the corresponding first line and corresponding second line of each object edge in the object edge; 3.) using a computing unit to determine vertices for each object edge in the object edge, wherein the vertex is the intersection of the first line and the second line.

[0042] While it is not mandatory to determine another set of measurement points for the corresponding object edge, in particular the first set of points, another second set of points, another first line, another second line, and another vertex (in particular another intersection), the calibration method is not limited to generating a single vertex for each object edge.

[0043] According to the present invention, the calibration step is performed in the form of an automatic calibration routine, wherein no further steps from the operator are required.

[0044] The computing unit can store the absolute or relative position of the detected object edge. The absolute position of the surveying instrument, or the relative position of the surveying instrument with respect to the stored absolute or relative position of the object edge, can be determined at any stage.

[0045] In some specific implementations, for at least one of the object edges, the set of single measurement points is located in a plane perpendicular to the object edge.

[0046] In some specific embodiments, for at least one of the object edges, the set of single measurement points is acquired by continuous scanning, i.e., the rates of change of the first angle and the second angle are constant during the acquisition process. An alternative embodiment of the surveying instrument / calibration method according to the invention, in which the movement of the surveying instrument's axis is paused during acquisition or alternative approach path selection, is also possible, wherein the surveying instrument does not follow a straight scanning path between single measurement points.

[0047] In some specific implementations, for at least one of the object edges, the set of single measurement points is acquired so that the first angle or the second angle remains fixed during acquisition.

[0048] In some specific embodiments, at least one point measured on a flat surface of at least one of the object edges is a reference marker. In some more specific embodiments, the calibration parameters include the absolute position of the reference marker.

[0049] In some specific embodiments, other object edges are selected. In some more specific embodiments, the selected object edges are characterized by at least one, preferably all, of the following: 1.) For at least two object edges, the distances from the point cloud measurement module differ substantially, for example, by more than a factor of 2; 2.) The azimuth angles of at least two object edges are substantially different, for example, by at least 90°, preferably by about 180°; 3.) For two object edges, the elevation angles are substantially different, for example, by at least 20°.

[0050] In some embodiments, the first object edge and the second object edge are perpendicular to each other. In some more specific embodiments, a third object edge is also selected, wherein the third object edge is perpendicular to both the first object edge and the second object edge.

[0051] In some implementations, the selection of object edges is based on a merit function, which includes parameters based on at least one of the following: 1.) the radius of curvature of the object edge, 2.) the length of the object edge, 3.) the corner angle, 4.) the incident angle of the first and second flat surfaces, 5.) the flatness of the first and second flat surfaces, or 6.) the average intensity of the first and second flat surfaces. Needless to say, the selection based on the merit function can also be combined with other selection methods, particularly those disclosed above.

[0052] The present invention also relates to a computer-readable medium for a surveying instrument, and the computer-readable medium includes executable instructions that, when executed by a computing unit, cause the steps of a selected embodiment of a calibration method to be performed automatically.

[0053] The executable instructions may also include different options for selecting a merit function, wherein the merit function includes parameters based on at least one of the following: 1.) the radius of curvature of the object edge, 2.) the length of the object edge, 3.) the corner angle, 4.) the incident angle of the first flat surface and the second flat surface, 5.) the flatness of the first flat surface and the second flat surface, or 6.) the average intensity of the first flat surface and the second flat surface.

[0054] The executable instructions may also include a data sharing function, which allows data exchange between other survey instruments, other computing units, or servers (especially servers providing cloud services). The shared data may include: calibration point clouds, absolute positions of single-point measurement unit instruments, and absolute and / or relative positions of object edges and / or reference markers. Attached Figure Description

[0055] Specific embodiments of the invention will be described more fully below with reference to the accompanying drawings, by way of example only, wherein:

[0056] Figure 1a The survey instrument shown includes a single-point measurement unit, a point cloud measurement module, and a computing unit integrated into a single portable instrument.

[0057] Figure 1bThe relevant angles and distances used to generate the first measurement data are shown.

[0058] Figure 2 An environment containing flat surfaces and object edges is shown. The point cloud measurement module scans the environment, while the computing unit generates a calibration point cloud representing the environment.

[0059] Figure 3 The diagram shows a calibration point cloud representing the environment including the edge of an object that is defined as the intersection of two flat surfaces.

[0060] Figure 4a The diagram shows a set of single measurement points divided into a first group of points and a second group of points, a first line and a second line, and the generation of vertices as intersection points.

[0061] Figure 4b The positions of the first set of points and the second set of points, the first line and the second line, and the vertices of the intersection points as viewed along the edge of the object are shown. Detailed Implementation

[0062] Figure 1a A schematic depiction of a first embodiment of a surveying instrument according to the present invention, comprising a single-point measurement unit, a point cloud measurement module 20, and a computing unit 30, is shown. The single-point measurement unit includes an aiming / rangefinder unit 10. As an example, the single-point measurement unit, the point cloud measurement module 20, and the computing unit 30 are integrated into a portable surveying instrument 40. An alternative embodiment is also possible in which only the single-point measurement unit and the point cloud measurement module 20 are disposed in a single device, and the computing unit 30 is a separate entity. In the embodiment where the computing unit 30 is a separate entity, the computing unit 30 may be temporarily disposed on or disposed on the single-point measurement unit.

[0063] The main frame of the portable surveying instrument 40 includes a first post 41 and a second post 42, wherein the aiming / rangefinder unit 10 is attached to the two posts 41, 42 to allow the aiming / rangefinder unit to tilt about a tilt axis 61. The tilting of the aiming / rangefinder unit 10 is preferably achieved by a motorized shaft 62. In some cases, manual tilting about the tilt axis 61 is also possible. The surveying instrument includes a first angle sensor 63 configured to measure a first angle 64 of the tilt axis 61. The point cloud measurement module 20 in the depicted embodiment is disposed on the side of the first post 41 of the main frame of the instrument 40. The fixed attitude of the point cloud measurement module 20 relative to the single-point measurement unit includes: the distance to the aiming / rangefinder unit 10 in vector form, and the orientation difference between the transmission axes of the point cloud measurement module 20 and the aiming / rangefinder unit 10.

[0064] Will Figure 1aThe portable integrated surveying instrument 40 depicted is configured to be mounted on a base 50 and rotatable about a rotation axis 51. During calibration and measurement operations, the rotation axis 51 can be a vertical axis. The surveying instrument 40 can be rotated manually in some cases, or preferably via a motorized axis 52. The surveying instrument includes a second angle sensor 53 configured to measure a second angle 54 of a single-point measurement unit relative to the base 50. The first (tilt) angle 64 and the second (rotation) angle 54 retrieved by the first angle sensor 63 and the second angle sensor 53 are transmitted to the computing unit 30.

[0065] Figure 1b A single-point measurement unit is shown that generates first measurement data, including the distance 101, elevation angle 102, and azimuth angle 103 of one or more points from the surveying instrument. The single-point measurement unit is configured to generate a measurement beam 11, particularly a laser beam. In the depicted embodiment, the single-point measurement unit generates the distance 101 from the surveying instrument via laser ranging principles (particularly time-of-flight measurement of laser pulses or laser interferometry). The elevation angle 102 and azimuth angle 103 of the measured single point can be derived from the first angle 64 and the second angle 54 measured by the first angle sensor 63 and the second angle sensor 53. The first measurement data may also include the absolute position of the single-point measurement unit. The target object 1 may be a reference mark having a known absolute position. The first measurement data may include the known absolute position of the target object 1; alternatively, the absolute positions of multiple reference marks may be used to determine the absolute position of the single-point measurement unit.

[0066] The relative and absolute positions of the measured single point or multiple measured single points, derived from the first measurement data, meet the geodetic accuracy standards, particularly the centimeter accuracy of the relative or absolute positions.

[0067] The surveying instrument 40 can be configured to perform ATR (Automatic Transmission) functions. This means that the surveying instrument 40 can automatically generate and update first measurement data, which includes the distance 101 of the target point 1 from the surveying instrument, the elevation angle 102, and the azimuth angle 103.

[0068] Figure 2An environment 2 comprising multiple objects is shown. As an example, a surveying instrument 40 including a single-point measurement unit includes an aiming / rangefinder unit 10, and a point cloud measurement module 20 is rotatably mounted on a base 50. As an example, the point cloud measurement module 20 is arranged laterally on the surveying instrument 40. Other arrangements of the point cloud measurement module in the surveying instrument 40 according to the invention are also possible. It is also possible to provide multiple point cloud measurement modules 20 according to the invention. The point cloud measurement module 20 can also be detachable and reattachable.

[0069] In the depicted embodiment, the point cloud measurement module 20 emits a scanning beam 21 (particularly a laser beam), which is deflected by a beam deflection element (particularly a motorized, rapidly rotating mirror). The second measurement data generated by the point cloud measurement module 20 includes: the emission angle 112 of the scanning beam 21, the azimuth angle 113 of the point cloud measurement module 20 (which can be derived from the second angle 54 measured by the second angle sensor 53), and the distance 111 from the measurement point to the point cloud measurement module for multiple measurement points.

[0070] In the depicted embodiment, the computing unit 30 is implemented as a separate unit. In the depicted embodiment, the surveying instrument 40 includes a wireless interface 71. The computing unit 30 includes another wireless interface 72. The wireless interfaces 71 and 72 are configured to allow data exchange between the computing unit 30 and other components of the surveying instrument 40. Data exchange using a wired interface is also possible. The wireless interfaces 71 and 72, or wired interfaces with equivalent functionality, can also be configured to exchange data with other surveying instruments, other computing units, or with a server (particularly a server providing cloud services).

[0071] The computing unit 30 is configured to generate a calibration point cloud 130 based on the second measurement data. The computing unit 30 is also configured to perform mathematical operations within the calibration point cloud 130, particularly the detection of flat surfaces and object edges.

[0072] The computing unit 30 is also configured to store calibration parameters including the fixed attitude of the point cloud measurement module 20 relative to the single-point measurement unit. The calibration parameters may include other parameters, particularly the inherent calibration parameters of the point cloud measurement module 20. The computing unit 30 is also configured to merge the calibrated point cloud 130 with the first measurement data based on the calibration parameters. The computing unit 30 is configured to perform general mathematical operations, particularly determining distances and angles in the merged data. During the merging of the first and second measurement data, the source of the data can be preserved, i.e., whether a particular piece of data was generated from the first measurement data or from the second measurement data. The resulting data pieces can also be characterized accordingly: derived only from data pieces with the first measurement data source, derived only from data pieces with the second measurement data source, or derived from data pieces with both the first and second measurement data sources. During data processing, the computing unit 30 can consider the source of the data pieces; that is, if a particular data piece was generated from the first measurement data, the computing unit 30 can perform only some mathematical operations, and vice versa.

[0073] Figure 3 A calibration point cloud 130 is depicted. A first object edge 140 is defined as the intersection of flat surfaces 141 and 142, and a second object edge 150 is defined as the intersection of flat surfaces 151 and 152. While not mandatory for performing the calibration process, a third object edge 160 can also be defined as the intersection of flat surfaces 161 and 162. Any other object edge can be defined according to the depicted schematic. The second object edge 150 is selected so that it is not parallel to the first object edge 140.

[0074] The calibration method does not include limitations on the angles between the first flat surfaces 141, 151, 161 and the second flat surfaces 142, 152, 162, but only includes the presence of clearly identifiable object edges 140, 150, 160. It is preferable that the angles between the first flat surfaces 141, 151, 161 and the second flat surfaces 142, 152, 162 are greater than 40° but less than 140° for the object edges 140, 150, 160. It is even more preferable that the first flat surfaces 141, 151, 161 are perpendicular to the second flat surfaces 142, 152, 162 for the object edges 140, 150, 160.

[0075] In another embodiment, the first object edge 140 and the second object edge 150 are perpendicular to each other. If defined, the third object edge 160 may also be perpendicular to the first object edge 140 and the second object edge 150.

[0076] In another specific embodiment, the computing unit 30 may define a plurality of object edges 140, 150, 160. The computing unit may preferably select object edges 140, 150, 160, wherein the selected object edges 140, 150, 160 are characterized by at least one, preferably all, of the following: 1.) the distances 111 from at least two object edges 140, 150, 160 to the point cloud measurement module 20 are substantially different, for example, by more than a factor of 2; 2.) the azimuth angles 113 of the at least two object edges 140, 150, 160 are substantially different, for example, by at least 90°, preferably by about 180°; 3.) the emission angles 112 of the at least two object edges 140, 150, 160 are substantially different, for example, by at least 20°.

[0077] Figure 4a A schematic diagram illustrating a specific implementation of deriving the corresponding alignment deviation 149 from a set of deviations is shown. A first object edge 140, defined as the intersection of a first flat surface 141 and a second flat surface 142, is depicted. The derivation of the alignment deviations for the second object edge 150, and, if applicable, the third object edge 160 and any other object edge, is similar.

[0078] The single-point measurement unit measures first measurement data from a set of single measurement points 147, including at least two points on the first flat surface 141 and at least two points on the second flat surface 142. The points comprised of this set of single measurement points 147 and the single-point measurement unit are located in a common plane.

[0079] The set of single measurement points 147 is divided into a first set of points 143 located on a first flat surface 141 and a second set of points 144 located on a second flat surface 142. Then, a weighted fitting method is used to define a first line 145 and a second line 146 of the corresponding flat surfaces using the coordinates of a set of points on the same flat surface. The vertex of the object edge 140 is determined as the intersection point 148 of the first line 145 and the second line 146. The corresponding alignment deviation 149 of the object edge 140 is calculated based on the distance between the object edge 140 and the intersection point 148. The deviation 149 can be equal to the distance from the intersection point 148 to the object edge 140, in scalar or vector form.

[0080] To better understand the method used to arrive at deviation 149 Figure 4b The diagram shows the positions of a first set of points 143, a first line 145, a second set of points 144, a second line 146, and the vertex at the intersection point 148, as viewed along the edge 140 of the first object. The distribution of the points is not drawn to scale.

[0081] Alternatively, a common plane defined by the set of single measurement points 147 can be first derived. This common plane can be constrained to include the single-point measurement unit as its origin. In this embodiment, the first line 145 and the second line 146 can be projected onto the common plane. The vertex in this embodiment can be defined as the intersection of the projections of the first line and the second line.

[0082] In some specific embodiments, for at least one of the object edges 140, 150, 160, the set of single measurement points 147 is acquired by continuous scanning, that is, the rate of change of the first angle 64 and the second angle 54 are constant during the acquisition process.

[0083] In some implementations, a single tilt or rotation of the single-point measurement unit generates a given set of measurement points. This means that either the first angle 64 or the second angle 54 remains fixed during the generation of all points in that set of single measurement points 147.

[0084] In some specific embodiments, the set of measurement points 147 are located in a plane perpendicular to the edge of the corresponding object.

[0085] In some specific implementations, one of the selected object edges 140, 150, 160 is vertical.

[0086] Needless to say, features of a particular embodiment can be combined with each other if the geometry of environment 2 allows, for example, a combination of vertical first surfaces 141, 151, 161 and second surfaces 142, 152, 162 with vertical object edges 140, 150, 160, and the points in the set of measurement points 147 are located in a plane perpendicular to the vertical object edges 140, 150, 160 and are acquired such that the first angle 64 remains fixed during acquisition.

[0087] Although the field calibration method according to the invention is configured to be performed using only non-cooperative diffuse scattering targets, in some embodiments of the method, one or more of a set or more groups of single measurement points 147 generated on flat surfaces 141, 142, 151, 152, 161, 162 may be reference markers, particularly retroreflectors. This is particularly advantageous if the absolute position of the reference markers is combined with the calibration point cloud. The calibration parameters according to this embodiment of the invention may also include the absolute position of the reference markers.

[0088] The computing unit 30, including wireless interface 72 or a wired interface with equivalent functionality, can transmit the point cloud of the representation environment 2 and / or calibration point cloud 130, which is merged with the absolute coordinates of the reference marker, to other surveying instruments, other computing units, or to a server. Furthermore, the computing unit 30 can also receive the point cloud of the representation environment 2, merged with the absolute coordinates of the reference marker, via the same interface 72. Needless to say, the surveying instrument 40, including wireless interface 71 or a wired interface with equivalent functionality, can also perform the same operation.

[0089] In one embodiment of the method, the calculation unit 30 classifies the detected object edges according to a merit function. The merit function may include information about at least one of the following: 1.) the curvature radius of object edges 140, 150, and 160; 2.) the length of object edges 140, 150, and 160; 3.) the corner angle; 4.) the incidence angle of the first flat surfaces 141, 151, and 161 and the second flat surfaces 142, 152, and 162; 5.) the flatness of the first flat surfaces 141, 151, and 161 and the second flat surfaces 142, 152, and 162; or 6.) the average intensity of the first flat surfaces 141, 151, and 161 and the second flat surfaces 142, 152, and 162. The calculation unit 30 may assign lower weights to object edges with low value during the optimization of calibration parameters, or discard them entirely from further steps of the calibration method.

[0090] Although the invention has been illustrated above, reference has been made in part to certain specific embodiments. It must be understood that many modifications and combinations of different features can be made to these embodiments. All such modifications fall within the scope of the appended claims.

Claims

1. A surveying instrument, the surveying instrument comprising a single-point measurement unit, a point cloud measurement module, and a computing unit, wherein, The single-point measurement unit is configured to generate first measurement data, which includes the distance, elevation angle, and azimuth angle of the single point. The point cloud measurement module: It has a fixed posture relative to the single-point measurement unit, and It is configured to generate second measurement data by scanning the environment, the second measurement data including the coordinates of multiple scan points. The computing unit stores calibration parameters, including the fixed attitude between the single-point measurement unit and the point cloud measurement module. Its features are, The surveying instrument is configured to automatically perform calibration functions so that: - The point cloud measurement module acquires the second measurement data as a calibration point cloud. - The computing unit identifies at least two non-parallel object edges in the calibration point cloud. - For each of the at least two object edges: ○ The single-point measurement unit scans across the object edge, wherein it acquires a set of single measurement points, including at least two points on each flat surface of the object edge, wherein the single measurement points are located on a straight scanning path. The calculation unit derives vertices formed by the distribution of the single measurement points, the vertices corresponding to the edges of the object. The computing unit updates the calibration parameters based on the alignment of the object edges with the resulting vertices.

2. The surveying instrument according to claim 1, wherein, The computing unit, the point cloud measurement module, and the single-point measurement unit are integrated into a single portable surveying instrument.

3. The surveying instrument according to claim 1, wherein, The point cloud measurement module is a laser scanning module.

4. The surveying instrument according to claim 1, wherein, The point cloud measurement module is horizontally mounted on the surveying instrument.

5. The surveying instrument according to claim 1, wherein, The single-point measurement unit includes: - A targeting / rangefinder unit, the targeting / rangefinder unit being configured to tilt about a tilt axis, and - At least a first angle sensor, wherein the first angle sensor is configured to measure a first angle as the tilt angle of the aiming / rangefinder unit, and wherein the calculation unit is configured to retrieve the first angle.

6. The surveying instrument according to claim 5, wherein, The single-point measurement unit is mounted on a base and configured to rotate about a rotation axis, and wherein the surveying instrument includes a second angle sensor configured to measure a second angle of the single-point measurement unit relative to the base, and wherein the calculation unit is configured to retrieve the second angle.

7. A method for calibrating a surveying instrument according to any one of claims 1 to 6, the method comprising the following steps: - The second measurement data is obtained using the point cloud measurement module and used as the calibration point cloud; - Identify at least two non-parallel object edges in the calibration point cloud; - For each of the at least two object edges: ○ The single-point measurement unit is used to scan across the edge of the object, wherein the set of single measurement points, including at least two points on each flat surface of the object edge, are acquired, and the single measurement points are located on a straight scanning path; ○ The vertices formed by the distribution of the single measurement points are derived, and the vertices correspond to the edges of the object. - Update the calibration parameters based on the alignment of the object edges with the resulting vertices.

8. The method according to claim 7, wherein, The vertex is obtained according to the following steps: - Divide the set of single measurement points into a first set of points located on a first flat surface and a second set of points located on a second flat surface. - Using the aforementioned computing unit, a weighted fitting method is used to fit the first set of points and the second set of points to determine the corresponding first line and corresponding second line of each object edge in the object edge. Using the computing unit, for each object edge in the object edge, the vertex is determined as the corresponding intersection point of the first line and the second line.

9. The method according to claim 7, wherein, For at least one of the object edges, the set of single measurement points lies in a plane perpendicular to the corresponding object edge.

10. The method according to claim 7, wherein, For at least one of the object edges, the set of single measurement points is acquired by continuous scanning, i.e., the rates of change of the first angle and the second angle are constant during the acquisition process.

11. The method according to claim 7, wherein, At least one point measured on the flat surface of at least one of the object edges is a reference marker.

12. The method according to claim 11, wherein, The calibration parameters also include the absolute position of the reference marker.

13. The method according to claim 7, wherein, The edges of the first object and the second object are perpendicular to each other.

14. The method according to claim 8, wherein, The selection of object edges is based on a value function, which includes parameters based on at least one of the following: - The radius of curvature of the edge of the object, - The length of the object's edge, - Corner angle, - The incident angles of the first flat surface and the second flat surface. - The flatness of the first flat surface and the second flat surface, or - The average strength of the first flat surface and the second flat surface.

15. A computer-readable medium for a surveying instrument, the computer-readable medium comprising executable instructions that, when executed by a computing unit, cause the steps of the method according to any one of claims 7 to 14 to be performed automatically.

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