SURVEYING DEVICE WITH IMAGE EVALUATOR FOR DETERMINING A SPATIAL POSE OF THE TARGET AXIS

Abstract

A surveying device for a coordinative position determination of a spatial point, wherein the surveying device comprises a camera which is fixedly mounted to a transmission unit in a way that its field-of-view moves with a targeting component. The surveying device further comprises an image evaluator, configured for automatically identifying corresponding image features in different images of the camera, wherein the corresponding image features represent reference points within the environment, and for a derivation of a spatial transformation parameter from a motion of the corresponding features, wherein the spatial transformation parameter provides for a determination of a difference of a spatial pose of a target axis of the surveying device between different distance measurements which correspond to different images.

Claims

1. A surveying device for a coordinative position determination of a spatial point, wherein the surveying device comprises a transmission unit having a targeting component that can be rotated about two axes of rotation, wherein the targeting component is configured to provide for a distance measurement, which comprises transmission of measurement radiation by the targeting component, thereby defining a target axis, and reception of returning measurement radiation by the targeting component, the surveying device comprising: a camera which is fixedly mounted to the transmission unit in a way that its field-of-view moves with the targeting component, wherein the camera is configured to capture two images, wherein each of the two images is associated with a different distance measurement, each of which comprises transmission and reception of corresponding measurement radiation, and an image evaluator, configured for automatically identifying corresponding image features that are present in both of the two images, the corresponding image features representing reference points within the environment, and for a derivation of a spatial transformation parameter from a motion of the corresponding image features, wherein the spatial transformation parameter provides for a determination of a difference of a spatial pose of the target axis between the different distance measurements which correspond to the two images.

2. The surveying device according to claim 1, wherein the surveying device comprises a base and a support that is mounted to the base such that it can be moved in a motorized fashion relative to the base about a first axis of rotation, wherein the targeting component is mounted to the support such that it can be moved in a motorized fashion relative to the support about a second axis of rotation, and the camera is mounted at the targeting component and has a field-of-view of 90 degrees, particularly 180 degrees.

3. The surveying device according to claim 2, wherein the camera is arranged that the second axis of rotation intersects the field-of-view of the camera, particularly wherein the camera is arranged that the optical axis of the objective lens of the camera is parallel to the second axis of rotation, more particularly co-axial with the second axis of rotation, and the surveying device comprises a further camera which is fixedly mounted to the transmission unit in a way that its field-of-view moves with the targeting component, wherein the further camera is arranged that the optical axis of the objective lens of the further camera is parallel to the second axis of rotation, particularly co-axial with the second axis of rotation, wherein the camera and the further camera are facing in opposite directions and the further camera is configured to capture two images, wherein each of the two images is associated with a different distance measurement, each of which comprises transmission and reception of corresponding measurement radiation.

4. The surveying device according to claim 2, wherein the optical axis of the objective lens of the camera is perpendicular to the second axis of rotation.

5. The surveying device according to claim 2, wherein the surveying device is configured to use the spatial transformation parameter to determine an angular change of the targeting component's orientation with respect to a rotation around at least one of the first and the second axis of rotation between the different distance measurements which correspond to the two images.

6. The surveying device according to claim 4, wherein the surveying device is configured to use the spatial transformation parameter to determine an angular change of the targeting component's orientation with respect to a rotation around at least one of the first and the second axis of rotation between the different distance measurements which correspond to the two images.

7. The surveying device according to claim 1, wherein the surveying device is configured to use the spatial transformation parameter to determine a change in position of the surveying device between the different distance measurements which correspond to the two images.

8. The surveying device according to claim 1, wherein the surveying device comprises an inertial measuring unit and/or a tilt sensor arranged in the targeting component and the surveying device is configured to determine an absolute alignment to the gravitational field by making use of the inertial measuring unit and/or the tilt sensor.

9. The surveying device according to claim 1, wherein the surveying device is configured to trigger an image capture by the camera, and if applicable the further camera, at each instant when a distance measurement is carried out and to provide an image associated with the image capture to the image evaluator.

10. The surveying device according to claim 1, wherein the surveying device comprises an acceleration sensor configured for measuring a linear and/or angular acceleration, wherein the surveying device is configured to trigger an image capture by the camera, and if applicable the further camera, when the acceleration sensor detects a linear and/or angular acceleration with an absolute value above a threshold value and to provide an image associated with the image capture to the image evaluator, wherein the surveying device is configured to identify a moving state of the targeting component based on the acceleration sensor and the image capture is triggered at a defined frame rate during the moving state.

11. The surveying device according to claim 1, wherein the surveying device comprises a relocation mode, wherein a series of images is captured by the camera during relocation from a first location of the surveying device to a second location of the surveying device, a simultaneous localization and mapping (SLAM) process is carried out using the series of images, and, based thereof, a difference of a spatial pose of the target axis in the first location, particularly corresponding to a distance measurement carried out from the first location, and a spatial pose of the target axis corresponding to a distance measurement carried out from the second location is determined, wherein the surveying device comprises a movement sensor configured to detect a start and a stop of a movement of the surveying device as a whole and the relocation mode is triggered and stopped by the movement sensor.

12. The surveying device according to claim 11, wherein the surveying device comprises an automatic target search functionality configured to automatically find a spatial reference point within the environment, wherein the spatial reference point is a spatial point associated with a known visual attribute, in particular wherein the surveying device is configured that, in the course of a distance measurement of the spatial reference point by means of the measurement radiation, the visual attribute is automatically provided by a visual pickup unit of the surveying device, and the surveying device is configured to carry out a distance measurement to three spatial reference points from the first location and to carry out, automatically based on the target search functionality, a distance measurement to the three spatial reference points from the second location, thereby measuring 3D coordinates of the three different spatial reference points both from the first and second location, and based on a position resection technique to refine the derivation of the spatial transformation parameter by taking into account the 3D coordinates of the three different spatial reference points measured from the first and the second location, wherein a difference of a pose of the target axis in the first location and a pose of the target axis in the second location is determined by means of a SLAM process, wherein from the second location the three spatial reference points are aimed at by taking into account the difference of the pose of the target axis.

13. The surveying device according to claim 1, wherein the surveying device is configured to: access reference data providing an outer coordinate system, recognize an imaged visual attribute of a marker in an image captured by the camera, and by assuming that the visual attribute of the marker provides an indication of a main axis of the outer coordinate system, derive an orientation of the target axis in the outer coordinate system by analyzing the imaged visual attribute of the marker, wherein the reference data further comprises coordinates of the marker in the outer coordinate system and the surveying device is configured to identify the marker and to derive a pose of the target axis in the outer coordinate system by analyzing the imaged visual attribute, more particularly by deriving a position of the marker in a local coordinate system of the surveying device derived by a SLAM process of the surveying device and by comparing the position of the marker in the local coordinate system with the coordinates of the marker in the outer coordinate system.

14. A surveying device for a coordinative position determination of a spatial point, wherein the surveying device comprises: a base, a support that is mounted to the base rotatably about a first axis of rotation, a targeting component that is mounted to the support rotatably about a second axis of rotation and configured to provide for a distance measurement, which comprises transmission of measurement radiation via a beam exit of the targeting component, thereby defining a target axis, and reception of returning measurement radiation via a beam entry of the targeting component, wherein: the support has a leg component that rises from the base in a direction parallel to the first axis of rotation and the leg component is pierced by the second axis of rotation, the targeting component is arranged in a raised position from the base and is pierced by both the first and the second axes of rotation, wherein the targeting component is connected to the leg component via a shaft, which provides rotation of the targeting component about the second axis of rotation, the surveying device comprising a camera which is fixedly mounted on a remote axial end of the shaft, the remote axial end being the axial end remote from the targeting component, the camera is mounted in a way that a camera opening points away from the targeting component and provides such a field-of-view of the camera so that the second axis of rotation intersects the field-of-view of the camera and the field-of-view of the camera moves with a movement of the shaft, wherein the camera is arranged that the optical axis of the objective lens of the camera is parallel to the second axis of rotation, more particularly co-axial with the second axis of rotation.

15. The surveying device according to claim 14, wherein the camera has a field of view with a horizontal aperture angle of at least 90° and a vertical aperture angle of at least 90°, in particular wherein the horizontal aperture angle is at least 180° and the vertical aperture angle is at least 180°, more particularly wherein the camera is a fish-eye camera.

16. The surveying device according to claim 14, wherein the surveying device comprises an inertial measuring unit and/or a tilt sensor arranged in the targeting component and the surveying device is configured to determine an absolute alignment to the gravitational field by making use of the inertial measuring unit and/or the tilt sensor.

17. The surveying device according to claim 15, wherein the surveying device comprises an inertial measuring unit and/or a tilt sensor arranged in the targeting component and the surveying device is configured to determine an absolute alignment to the gravitational field by making use of the inertial measuring unit and/or the tilt sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The surveying device according to the different aspects are described or explained in more detail below, purely by way of example, with reference to working examples shown schematically in the drawing. Identical elements are labelled with the same reference numerals in the figures. The described embodiments are generally not shown true to scale and they are also not to be interpreted as limiting. Specifically,

[0053] FIG. 1: an embodiment of the surveying device from two different perspectives, wherein for feature tracking two cameras are mounted to the targeting component such that the second axis of rotation intersects the field of views of the two cameras;

[0054] FIG. 2 an exemplary workflow with a surveying device, wherein the orientation of the targeting component is determined by tracking image features in a camera image;

[0055] FIG. 3 a further exemplary workflow with a surveying device, wherein the surveying device is relocated, and performs a SLAM process between the first location and the second location and a calibration measurement to three spatial reference points to refine the derivation of the spatial transformation parameter;

[0056] FIG. 4 a further exemplary workflow with a surveying device, wherein dedicated markers are used for referencing measurement points generated from different locations of the surveying device,

[0057] FIG. 5 an exemplary 360° panorama image generated by a surveying device, merged to a full dome panorama image (top part) and merged at one side of the two captured images (bottom part).

DETAILED DESCRIPTION

[0058] FIG. 1 depicts an exemplary embodiment of the surveying device 1 in two different side perspectives. Here, the surveying device 1 is embodied as a total station with a telescope 2, a support 3, and a base 4. A pair of fish-eye cameras 5 is integrated into the telescope 2, e.g. wherein each camera 5 has a field-of-view which is larger than 180° and each of the cameras 5 is rotating together with the telescope 2.

[0059] The telescope 2 can be rotated in a motorized fashion, whereby the support 3 is attached to the base 4 so as to be rotatable about a vertical axis of rotation 6 and the telescope 2 is attached to two opposing leg components 7 of the support 3 so as to be rotatable about a horizontal axis of rotation 8.

[0060] The total station 1 is configured for carrying out a distance measurement by means of a laser beam 9 emitted via a beam exit 10 of the telescope 2, thereby defining a target axis. In the example shown, the beam exit 10 is also the beam entry for reception of returning parts of the laser beam 9.

[0061] By way of example, the telescope 2 is connected to the two opposing leg components 7 via two shafts 11 on opposing sides of the telescope 2, wherein the cameras 5 are mounted on remote axial ends of the shafts 11 and the optical axes 12 of the objective lenses of the cameras are co-axial with the horizontal axis of rotation 8. In combination, the two cameras 5 provide for derivation of a full-dome panorama image.

[0062] FIG. 2 schematically depicts an exemplary workflow with a surveying device 1, which in the example shown is embodied as previously described with reference to FIG. 1. For measuring a spatial point by means of the laser beam 9 (not shown, see FIG. 1), the telescope is moved with respect to the horizontal and vertical axes of rotation 6,8 in order to aim the laser beam onto one or multiple different spatial points (not shown). During the rotation of the telescope about the horizontal and vertical axis point features 13 are tracked in the panorama images captured with the fish-eye cameras 5. The point features 13 are significant points detected with a feature detector, e.g. edges, corners, or high-intensity reflections. From the motion of the features 13 the change of the orientation, e.g. the horizontal and vertical angle with respect to the initial orientation of the telescope are measured.

[0063] Upon triggering a measurement, e.g. upon triggering an electro-optical distance measurement by the laser beam the coordinates of the spatial point to be measured is computed from the measured distance and the determined horizontal and vertical angle changes with respect to the initial orientation of the telescope.

[0064] By way of example, the determination of the change in orientation is based on a “simplified” SLAM process, where only the orientation angles are computed while the position of the telescope is considered as fixed.

[0065] Consequently, no angle encoders or tilt sensors are needed to determine the orientation of the telescope.

[0066] In an alternative setup, the camera data are combined with data from a tilt sensor and/or angle encoders. By way of example, there could be angle encoders for both axes of rotation 6,8 or for only one of the axes of rotation, e.g. there could be one angle sensor measuring the horizontal angle but no angle sensor measuring the vertical angle. The latter would then be determined based on the tracking of the features 13 in the image data of the cameras 5. Moreover, the image data and the data from the angle and tilt sensors can be fused together to determine the orientation of the telescope.

[0067] FIG. 3 schematically depicts the surveying device in a further location, away from the location depicted by FIG. 2. For illustrative purposes, the previous setup is still shown in the figure. Since now also the position of the surveying device (and thus the telescope and support) has changed, not only the orientation but all six degrees of freedom (three coordinates (X, Y, Z) and three orientation angles) of the telescope 2 at the new setup are determined with respect to a previous position and orientation of the telescope at the previous location of the surveying device 1. Again, this is done by performing a SLAM process between the first location and the second location.

[0068] Optionally, at the new setup an automatic measurement procedure is carried out, wherein three spatial reference points with known coordinates are measured to refine the derivation of the spatial transformation parameter.

[0069] The surveying device 1 is identifying based on the image data of the camera 5 a sub-set of points that have been measured at the previous location. Here, for example, it is assumed that the spatial points 13 used for feature tracking were also actual measurement points for which the surveying device determined accurate coordinates by means of the laser beam 9. Thus, these spatial points can be used in a twofold way, namely as features 13 for feature tracking and as spatial reference points 14 to refine the derivation of the spatial transformation parameter.

[0070] The surveying device 1 then automatically aims at these spatial reference points 14, e.g. by using positional information provided by the SLAM process and an automatic target search functionality, and measures the coordinates of these points from the current position by means of the laser beam 9. These coordinates are then used to determine the position and pose of the support 3 at the new setup more accurately.

[0071] FIG. 4 shows a further embodiment, wherein dedicated markers 15 are used to reference measurement points generated from different locations of the surveying device 1. The coordinates of these markers 15 are given in a common coordinate system for the whole site. For example, the coordinates of these markers 15 are measured once, e.g. with a high-end total station.

[0072] The surveying device 1 is configured to recognize an imaged visual attribute 16 of a marker 15 in an image captured by the camera 5. By using the visual attribute 16, here an indication of the horizontal and vertical axes of the common coordinate system, the surveying device derives an orientation of the telescope 2 in the common coordinate system.

[0073] By way of example, it may also be sufficient to have only an indication of the gravity vector in order to provide the surveying device 1 with a reference of the gravity vector. This makes a tilt sensor obsolete.

[0074] The characteristics of the markers 15 are known to the surveying device 1 and the markers are fixedly attached to a surveying site. Targeting of the markers can be performed using an eye-piece or using an opto-electronic image pickup of the surveying device, wherein an targeting image is displayed to the user on a mobile device, e.g. a tablet. Alternatively or in addition, the surveying device is configured to automatically search, identify, and measure the markers 15.

[0075] In order to monitor the construction progress, it might be desirable to survey the construction site multiple times, e.g. every month. Assuming that the markers 15 did not change their position and/or orientation, the surveying device 1 can be set up at different times in different locations on the construction site, while using the markers to reference measurement points into the common coordinate system, e.g. by targeting the same markers again. By way of example, the surveying device 1 is provided with reference data, which comprise the coordinates of the markers 15 in the common coordinate system. Therefore, by performing coordinate measurements of different markers 15 from a current measurement location, the surveying device 1 is able to absolutely reference measurement points from that current location with respect to the common coordinate system.

[0076] FIG. 5 shows an exemplary 360° panorama image generated by a surveying device 1, merged to a full dome panorama image (top part) and merged at one side of the two captured images (bottom part).

[0077] By way of example, the panorama image depicted in the top of the figure is obtained by using two fish-eye cameras, each exhibiting a field of view with a horizontal aperture angle greater than 180° and a vertical aperture angle greater than 180°, wherein the two cameras are mounted to the telescope such that the two cameras have opposing fields of view. Both cameras capture an image at the same moment and from the same position and orientation of the surveying instrument. Since the two cameras exhibit fields of view with overlapping regions in the fringe area of the images, the images of the two cameras can be easily merged, e.g. based on corresponding features found in the fringe area.

[0078] For example, the two cameras are mounted at the remote ends of a shaft providing rotation of the telescope about the horizontal axis, e.g. as depicted by FIG. 1. Another possibility is to mount the two cameras on a main body of the telescope, e.g. in a back to back configuration, wherein the fields of view of the cameras are different by 180 degrees. The panorama image may also be generated by only using one camera.

[0079] The bottom of the figure depicts the same panorama, which is again obtained by using two cameras. However, this image is merged only at one side, in order to provide a better overview for the observer.

[0080] Although aspects are illustrated above, partly with reference to some preferred embodiments, it must be understood that numerous modifications and combinations of different features of the embodiments can be made. All of these modifications lie within the scope of the appended claims.