SCAN SETUP AND PROCEDURE FOR SCANNING AN OBJECT

Description

[0001] The invention relates to a scanning arrangement according to the preamble of claim 1 and a method for scanning an object.

[0002] The 3D measurement of objects using laser scanners is becoming increasingly important in practice. For complex or difficult-to-access objects, multiple laser scans are always taken sequentially from different viewpoints and saved in a common project folder. These scans then need to be transformed into a common, higher-level coordinate system. This process is called "registration." To calculate the transformations of the individual viewpoints into the higher-level coordinate system, it is necessary to locate specific points in the respective scans that are known within the higher-level system and calculate a transformation based on their position. This transformation is then applied to the entire point cloud.

[0003] From DE 20 2010 013 825 U1, a scanning arrangement for the 3D measurement of objects is known, in which a laser beam is directed at an object by means of a beam deflection system and the measurement beams reflected by the object are evaluated by a processing unit. The known scanning arrangement further includes a navigation unit that enables a rough determination of the location.

[0004] With current technology, the scanning system can be operated using a mobile device, such as a smartphone. The actual evaluation of the scans is performed by the internal computer, so the mobile device merely acts as a remote control.

[0005] Furthermore, the position of the points to be located in the scan must be known very precisely, otherwise the transformation cannot be calculated correctly and the position of the various laser scans, both relative to each other and to the higher-level coordinate system, will only be given with low accuracy. For this reason, as described in the applicant's DE 10 2008 034 198 B4, a large number of targets are currently placed in the area to be surveyed. These targets often have a marking, such as a serial number, printed on them for identification purposes, which is recorded manually during evaluation. For quality assurance, all targets should be measured (enclosed) and recorded using a so-called "total station" / "tachymeter"—this process involves additional measurement effort and requires additional metrological expertise. The positioning must be such that at least three targets are visible in each scan.

[0006] To reduce this effort, targetless registration of the three-dimensional point clouds can also be performed. In this case, registration is largely automated based on the information from the object measurement points. However, this requires that the object has certain characteristics that allow for the unambiguous automatic assignment of the individual scans and that the scans have some overlapping areas. Real-world environments, however, often exhibit ambiguities (e.g., columns at regular intervals in a production hall or identical doors in office corridors) that can lead to incorrect assignments. Furthermore, with often several hundred laser scans being acquired, the associated exponential increase in computation time makes it impossible to compare each scan with every other for the purpose of automatic registration. Registering solely based on the previous scan is not always practical, for example, if it is located behind a shadow.For these reasons, a certain degree of pre-orientation (position and alignment) of the scans to be registered is usually essential. This has typically been achieved by roughly manually "moving" or "aligning" the scanner position / orientation (location) in the "field book" (a representation of the laser scanner position and the scan just taken on an electronic map in top view). However, this method offers insufficient control in the field (on-site) to ensure that scans taken and roughly positioned using this method can actually be registered later (on the computer in the office). Currently, it is not possible for the user to immediately check the registration of the scan data on-site or even to process the data further – they are left only with the option of performing the scans from the predetermined locations and then hoping that the scan positions can be registered during the subsequent evaluation in the "office."

[0007] The usual workflow is as follows: For evaluation, the scan data is typically downloaded from the laser scanner to a PC. Each individual scan is then opened using registration and evaluation software (e.g., Lasercontrol®) and the individual targets within the scan are identified.

[0008] US patent 2003 / 0137449 A1 describes a scanning setup in which a scanner is connected to a satellite computer. The satellite computer is specifically designed to program the scanner.

[0009] US patent 2006 / 0188143 A1 discloses a scanning system for three-dimensional objects, whereby point clouds are captured from multiple scans. The scans can be evaluated on a satellite computer, with the evaluation of the scan data taking place after the scanning process.

[0010] From DE 10 2013 102 554 A1, a device for optically scanning and measuring an environment, designed as a laser scanner, is known. Furthermore, a control and evaluation device is known that determines at least the distance to an object to be measured for a multitude of measuring points. The laser scanner is also wirelessly connected to a network.

[0011] If the images were created without targets, neighboring scans are manually linked for targetless registration, using natural objects or structures.

[0012] As explained above, the starting value for targetless registration requires knowledge of the scanner position and scanner orientation, which is why the rough values ​​from the field book must be manually adjusted to precisely match neighboring scans.

[0013] If, during this evaluation, it turns out that the scans cannot be registered due to a lack of overlap areas or other reasons, there is no immediate possibility of rectification, since, as mentioned, this evaluation does not take place in the field.

[0014] Simple measurements of the object are usually only possible on a PC after the scan has been registered. However, this is disadvantageous in some applications, for example, if the data sets generated during the measurement are confidential and must not leave the system. This means that all decisions, evaluations, and data collection must be carried out on-site, so that subsequent measurements of the object during the post-processing described above are not permitted.

[0015] In contrast, the invention is based on the objective of creating a scanning arrangement and a method for scanning an object, which enables simplified data evaluation.

[0016] This problem is solved by a scanning arrangement having the features of claim 1 or by a method for scanning an object having the features of dependent claim 8.

[0017] Advantageous further developments of the invention are the subject of the dependent claims.

[0018] The scanning arrangement according to the invention comprises at least one laser scanner for 2D or 3D measurement of objects and a memory for storing project-related data (project file, for example, the scan data, scanner position, and scanner orientation). The scanning arrangement further comprises a navigation unit for capturing this scanner position and scanner orientation, or a scanner relative position with respect to a starting position, and a handheld device or tablet located in the field (on-site). A data connection to the handheld device or tablet, implemented as a wireless connection, is also provided. The scanning arrangement is equipped with a suitable device for transferring the acquired scans to the handheld device or tablet, which is designed to register the respective scan in a higher-level (project-specific) coordinate system, depending on the respective scanner position / orientation.The handheld device or tablet is designed to allow scan registration both with and without targets, and also to control the laser scanner. This means that the handheld device or tablet can be used in the field to evaluate scans for fully or semi-automatic registration and, if necessary, to control the laser scanner for retaking, re-capturing of a specific area, or performing a scan from a different position.

[0019] According to the invention, the data stored on the laser scanner are updated by transferring (uploading) the results calculated on the tablet, thus ensuring data consistency between the laser scanner and the tablet.

[0020] This scan arrangement enables very convenient scan data processing and registration in the field, whereby faulty or insufficient measurements are automatically detected in the field, and user oversights are revealed on site, which could otherwise lead to problems later.

[0021] A further advantage of the arrangement according to the invention is that the relatively time-consuming registration can be carried out in parallel with a subsequent scanning process using the laser scanner by outsourcing it to the handheld device or tablet. This allows the waiting time during the measurement process at a location to be used for evaluating the measurement at the previously measured location. Scanning and evaluating the scan is therefore significantly faster than with conventional solutions.

[0022] According to a preferred embodiment, the handheld device or tablet may further include a device for generating an error message if the registration of a scan has failed.

[0023] Setting up the scan arrangement is particularly easy when data transmission is via Bluetooth connection, mobile network or WiFi standard, but it can also be wired.

[0024] The time required to capture an object can be further minimized if multiple laser scanners are assigned to a common handheld device or tablet, so that the evaluation of the different scans takes place centrally on site.

[0025] The coordination of the individual laser scanners can be done either directly via the handheld or tablet, or via a shared server or project management computer that is in data connection with the handheld(s) or tablets and through which a joint evaluation and coordination of the scanning processes takes place.

[0026] In a particularly convenient solution, the scanning setup can be equipped with an interface for controlling an automatic positioning system to move the laser scanner to a suitable scanning location. This could, for example, be a robot that moves the laser scanner to the optimal position specified by the software.

[0027] To capture color information, the scanning setup can be additionally equipped with a color camera or other sensors, for example for recording thermographic data. These can also be integrated into the scanner.

[0028] According to the inventive method for scanning an object, preferably with a scan arrangement of the type described above, the following steps are involved: A scan is acquired using at least one laser scanner, and the location and orientation of the laser scanner are determined. The resulting 3D point cloud of the scan and the scanner's navigation data are then transmitted to the local handheld device or tablet. This transmission preferably occurs wirelessly, for example via Bluetooth, Wi-Fi, or cellular network. Alternatively, wired communication can also be used. Using the software available on the device (e.g., Lasercontrol "Scout®<"), the scan is automatically registered with or without a target, depending on the scanner's location and orientation, either in a higher-level coordinate system or relative to a previous scan.

[0029] According to the invention, the data stored on the laser scanner are updated by transferring (uploading) the results calculated on the tablet, thus ensuring data consistency between the laser scanner and the tablet.

[0030] Automatic registration is typically divided into two steps: 1) Pre-registration, which automatically calculates the rough position and orientation of the captured scan. Alternatively, this can also be performed by the user by manually "moving / rotating" the laser scan in the electronic field book. 2) Fine registration, which automatically calculates an exact registration from the rough information of the pre-registration, either based on minimizing 3D pixel distances (ICP) or on assigning existing objects (e.g., surfaces, cylinders) or structures (e.g., corners, edges) in the 3D point clouds to be registered.

[0031] The software, or the handheld device or tablet, is preferably designed so that if the scan cannot be registered or is only registered with errors, an error message is displayed, allowing the scanning process to be repeated, if necessary, or repeated from a different location. The user can also attempt to improve the registration result through manual intervention.

[0032] Such manual interventions can, for example, consist of first setting different registration parameters or performing a manual pre-registration and then carrying out the actual registration again.

[0033] Alternatively, as explained above, a new scan can be taken after changing scan parameters or changing the scanner's position.

[0034] This sequence is repeated until a complete survey of the object is available and all scan data is recorded as required. The laser scanner is therefore moved to a new location each time, with the scan being evaluated on the satellite computer and a subsequent scan being performed simultaneously using the laser scanner.

[0035] The progress of this registration is constantly monitored in the field (on site), so that immediate action can be taken if the survey of the object is incomplete.

[0036] As explained, multiple laser scanners can be assigned to a single handheld device or tablet. In principle, it is also possible to network several such groups (laser scanners and handheld devices or tablets) together.

[0037] For complex measurement tasks, it can be advantageous if the handheld device or tablet is connected to a central server or project management computer, through which the measurement of the object is coordinated.

[0038] It is particularly advantageous if the handheld device or tablet, or its software, is designed in such a way that simpler measurements can be performed using the handheld device or tablet after the scans have been registered. Such simpler measurements could include, for example, the recording of dimensions, areas, volumes, distances, and the like.

[0039] In one variant of the invention, the laser scanner has an integrated computer on which, for example, a registration or evaluation can be carried out in the event of a failure of a radio connection.

[0040] Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. These show: Figure 1 the basic structure of such a scan arrangement; Figure 2 a variant of the scan arrangement according to Figure 1 with multiple laser scanners or similar recording devices and Figure 3 a flowchart to illustrate a scanning process according to the invention.

[0041] Figure 1 Figure 1 shows the basic structure of a scanning arrangement 1. Accordingly, this arrangement has at least one laser scanner 2, such as the one marketed by the patent applicant under the name "Imager®<". This laser scanner 2 has a rotating measuring head 4, which rotates around a horizontal axis (view according to Figure 1The laser scanner 1 rotates and directs a laser beam at the object to be measured. A transmitter and receiver unit of the laser scanner 1 is arranged in a housing 6, which can be pivoted about a vertical pivot axis 8 by at least 180°, so that an object to be measured can be scanned almost completely by pivoting the housing 4 about the pivot axis 8 while the measuring head 2 rotates. Areas of the object located below the measuring head are covered by the housing 6 and therefore cannot be detected. For further details of the construction of such a scanner, reference is made, for example, to DE 101 50 436 B4 or DE 10 2006 024 534 A1.

[0042] Housing 2 can also contain a storage unit for the scan data and an evaluation unit for a first rough evaluation of the scan data, for example a pre-registration in an electronic field book.

[0043] As in Figure 1As indicated, the laser scanner 2 communicates wirelessly with a handheld device or tablet located in the field, which in this case is a tablet 10. This wireless connection can be, for example, a Bluetooth connection or a connection based on the WiFi standard. Data, such as the location and orientation of the laser scanner 2 during scanning and the 3D point cloud of the scan, can be transmitted via this wireless connection to the memory of the tablet 10. To determine the scanner's location and orientation, the laser scanner 2 can be equipped with an integrated navigation system that enables a GNSS (e.g., GPS)-independent determination of the laser scanner's absolute position or at least a relative position to a known location in the field.The structure of such a navigation system is disclosed in the applicant's parallel patent application, so that with regard to further details reference is made to the explanations in that parallel application, the disclosure of which is to be counted as that of the present application.

[0044] As explained, the roughly pre-registered data of, for example, a newly recorded scan is transferred (downloaded) to Tablet 10. This assumes that a member of the measurement crew operates Tablet 10 in the field.

[0045] The software stored in the Tablet 10 (e.g. Lasercontrol "Scout ®< ") then checks and, if necessary, edits the rough registration of the scan in the higher-level coordinate system, whereby this registration is facilitated by the fact that the position of the laser scanner and its orientation are known either relative to a previously known location or even as an absolute position.

[0046] This relative or absolute location is thus determined with sufficient accuracy to serve as a starting value for a targetless registration. However, the tablet software can also decide that a target registration should take place instead of a targetless registration.

[0047] In the field, a registration process (preferably without targets) is initiated using the tablet software, or all targets in the scan are identified manually or automatically. Individual scans or all scans combined with these identified targets can be registered to a tachymeter file (which contains the world coordinates of all target centers measured with a tachymeter or total station).

[0048] If this registration on the tablet fails, the user immediately receives an error message and can repeat the laser scan either at the same location or at another, more suitable location. The laser scanner can be controlled via the tablet.

[0049] Optionally, the tablet software is designed to suggest an optimal location, which is automatically calculated from the recorded point clouds and positions / orientations.

[0050] After the scan is fully registered, laser scanner 2 is moved to the next recording location. This process is repeated until a complete survey of the object is achieved, with all scans registered either relative to each other or within a higher-level coordinate system. This means that the complete registration takes place in the field and not—as with conventional solutions—after all laser scans have been read and evaluated on an office computer.

[0051] Another advantage is that simple measurements can be carried out on site using software, and conclusions can be drawn from these measurements for further scanning processes.

[0052] In the event that the laser scanner 2 is equipped with a color camera, if sufficient computing capacity is available on the handheld device, (HDR) color mapping can even be performed in the background, which in turn saves evaluation time in the office.

[0053] After the survey is complete, a field book containing the respective optimal scanner positions and orientations is stored on the tablet 10. This field book, along with the associated scan data, can then be transferred via Wi-Fi or similar connection to a central server 16 or a project manager's computer. This allows for centralized monitoring by the project management team and, if necessary, instructions to repeat or perform additional scans for the crew still in the survey area. These instructions are then also transmitted to the tablet 10 via Wi-Fi, mobile network, or similar connection.

[0054] Figure 2 Figure 1 shows a variant in which the Tablet 10 is connected via a wireless connection to several laser scanners 2a, 2b that are simultaneously located in the field. As shown in Figure 1. Figure 2As indicated on the right, the tablet 10 can also be connected to a reference measuring device 18, via which reference data is transferred to the tablet 10, which is then included in the registration and evaluation of the scans.

[0055] For very large objects, it may also be possible to use several of the options listed below. Figure 2 The depicted units each consist of a Tablet 10 and several associated laser scanners 2a, 2b in the field, with the Tablets 10 of the individual groups being networked in such a way that the data is always up to date. Especially with such complex systems, data exchange with the central server 16 or a project management computer is important for coordinating the activities of the measurement crews.

[0056] In Figure 3The basic steps of the operation of the scanning arrangement and the method for scanning an object according to the invention are schematically illustrated. As explained, the laser scanner(s) 2 are first located in the field. This location can be determined relative to a known previous location or absolutely. At this location, a scan is acquired, the scanned data is stored in the memory of the laser scanner 2, and optionally, pre-registration takes place on a computer integrated into the laser scanner 2.

[0057] The saved location and the 3D point cloud of the scan are then transmitted wirelessly in the field to the Tablet 10 (handheld) ("Download"), where a pre-registration takes place first (if this has not already been done on the laser scanner), followed by a fine registration.

[0058] If registration is not possible due to faulty measurement data or similar issues, the software will display an error message. The user can then attempt to achieve a better registration through manual intervention (such as manual pre-registration or changing the registration settings).

[0059] Alternatively, the user can perform another laser scan, perhaps with better scan settings or from a more suitable vantage point.

[0060] Since the old location was known, the navigation system can determine the relative position of the new location to the known location or the absolute position.

[0061] If the scan is registered without an error message, the laser scanner is moved to the next position and the scanning process is repeated in the predetermined manner.

[0062] As in Figure 3The results of the registration performed on the tablet 10, such as the (determined by the registration) exact position and orientation of the current standpoint, any target centers found or other information, are transferred back to the laser scanner ("Upload"), so that all data on the laser scanner and tablet always remain consistent.

[0063] This is repeated until the entire object has been measured - the progress of this measurement and the registration of the individual scans in the field book is constantly monitored on Tablet 10, so that intervention can be made in time if the measurement is insufficient.

[0064] Additionally, instructions can be given to the crew in the measurement field via the project management if several crews with different scanners and tablets are working in the field.

[0065] As explained in the parallel application, the navigation system essentially consists of a combination of a magnetometer, barometer, gyroscope, accelerometer, and a GNSS receiver. In the absence of GNSS reception, such a system can relatively correlate the position change of laser scanner 2 from one location to the next, thus providing sufficiently accurate position / orientation estimates of the new location. However, other navigation methods are also conceivable, for example, using the locations of known WLAN points (RSS or time-of-flight analysis) or GSM data (bearing to mobile phone base stations). As explained, this navigation data is stored in the internal memory of laser scanner 2.

[0066] Furthermore, a very fast data connection between the Laser Scanner 2 and the Tablet 10 is advantageous. A very fast WiFi connection from the Laser Scanner 2 to the Tablet 10, using two antennas and utilizing available g / a and n wireless standards, has proven particularly suitable for quickly downloading the scan from the Laser Scanner 2 to the user's Tablet 10.

[0067] The tablet-based software preferably offers full touch operation and includes all the necessary measurement tools to perform the aforementioned simpler measurements. Furthermore, the software incorporates automated registration processes with and without targets, allowing the user to automatically see results or errors and, if necessary, repeat the scan or proceed to the next scan.

[0068] With the previously described connection to project management or a central server, a higher-level authority, such as the project manager at the surveying office, can record the current status of all laser scanners in the field. Depending on requirements, they can then send planning data to the electronic "field books" of the deployed laser scanners, which, for example, mark the areas to be scanned by the field crew. As explained, the acquired data can be transferred online to headquarters or to a cloud. The field crew can also use handheld devices or tablets to take additional photos and create documents that can be assigned to the project data and shared with project management.

[0069] A scanning arrangement and a method for scanning an object are disclosed, wherein a laser scanner is associated with a handheld device or tablet located in the field, via which the registration and / or evaluation of the scans in the field takes place. Reference symbol list:

[0070] 1Scan setup 2Laser scanner 4Measuring head 6Housing 8Swivel axis 10Tablet with recording / evaluation software 12Scanner position 14Scanner orientation 16Server 18Reference measuring device

Claims

1. A scanning arrangement comprising at least one laser scanner (2) for 2D or 3D measurement of objects located in a field, comprising a memory for storing project-related data and a computer integrated into the laser scanner (2), and comprising a navigation unit for detecting a scanner position (12) and / or a scanner position relative to a start position, comprising a satellite computer located in the field, which is configured as a handheld, in particular a tablet (10), and comprising a remote data communication to the satellite computer of the scanning arrangement in the form of a radio communication, and comprising a device for transmitting recorded scans from the laser scanner (2) to the handheld, which is configured to carry out a registration of the relevant scan in the field within a project-specific coordinate system depending on the respective scanner position (12), wherein a software of the handheld is configured such that a fully or semi-automatic registration of the scans is enabled both with and without targets and also the laser scanner (2) can be driven, wherein the handheld is configured to update the results obtained during registration on the integrated computer of the laser scanner (2) by re-transmission, Upload.

2. The scanning arrangement according to claim 1, wherein the satellite computer includes a device for generating a fault message in the event that the registration of a scan fails.

3. The scanning arrangement according to claim 1 or 2, wherein the data are transmitted via Bluetooth connection or according to WIFI standard or mobile radio communication.

4. The scanning arrangement according to any one of the preceding claims, wherein plural laser scanners (2) are assigned to one satellite computer.

5. The scanning arrangement according to any one of the preceding claims, comprising a joint server (16) or a project management computer that is connected with the satellite computer and via which the scanning operations are jointly evaluated and coordinated.

6. The scanning arrangement according to any one of the preceding claims, comprising an interface for driving an automatic positioning system for moving the laser scanner (2) at a location (12) suitable for scanning.

7. The scanning arrangement according to any one of the preceding claims, comprising a color camera for detecting color information.

8. A method for scanning an object located in a field, preferably by means of a scanning arrangement according to any one of the preceding claims, comprising the steps of: a) recording a scan by at least one laser scanner (2); b) determining the location and the orientation of the laser scanner (2); c) transmitting the scanning and navigation data to a local satellite computer in the form of a handheld, especially a tablet (10) and being part of the scanning arrangement, Download; d) registering the scan in response to the scanner location (12) and the scanner orientation (14) in a higher-level coordinate system or relative to a previously recorded scan, or registering the scan in response to targets identified manually or automatically in the scan in a higher-level coordinate system or relative to a previously recorded scan by means of the handheld; wherein e) a software of the handheld is configured such - that a fully or partially automatic registration of the scan is possible both with and without targets, - that also the laser scanner (2) can be driven, - and that the data on the laser scanner (2) are updated by re-transmission ,Upload, of the results obtained during registration / evaluation on the handheld (10); f) shifting the laser scanner (2) to a new location (12) and repeating the steps a) through d), wherein an evaluation of the scan is carried out on the satellite computer and a subsequent scanning operation is carried out in parallel by means of the laser scanner (2), wherein g) it can be detected by way of the satellite computer that a complete measurement of the object is given.

9. The method according to claim 8, comprising the steps of: output of a fault message if the scan cannot be registered or can be registered only incorrectly, and / or manual intervention by the user by - setting different registering parameters or manual pre-registering, or - repeated scanning with different scanning parameters or from a different position.

10. The method according to claim 8 or 9, wherein the data of plural laser scanners can be processed by means of the satellite computer.

11. The method according to any one of the claims 8, 9 or 10, wherein the satellite computer or computers is / are connected to a central server (16) or a project management computer.

12. The method according to any one of the claims 9 to 11, wherein the recorded data are registered and / or evaluated also on a computer integrated in the laser scanner (2).