FIELD OF THE INVENTION

The invention relates to the field of stair lifts, and more specifically to a method and system for obtaining spatial information on a staircase and an environment of the staircase where a stair lift is to be installed.

BACKGROUND OF THE INVENTION

When a stair lift is to be designed for implementation at a particular staircase, a first step to take is to acquire an accurate three-dimensional representation of the staircase and its environment to identify interfaces on which to mount a guide, for example a rail assembly to support a movable carrier of the stair lift. To acquire the three-dimensional representation of the staircase and its environment comprising a floor, walls, a ceiling, railing(s), and possibly other object(s), it is common to place a plurality of optical markers on or at the staircase at points of interest, such as on the steps of the staircase, wherein the optical markers each are optically identifiable. Then, a series of images is taken by a camera, each image showing at least a part of the staircase and the corresponding optical markers. Next, the images are analyzed to generate, using e.g. photogrammetry software, a three- dimensional representation of the staircase using the structural and dimensional information in the images provided by the markers showing therein. In particular, the relative positions of the markers may be determined with a high accuracy, permitting an accurate three- dimensional representation of the staircase and its environment in case the markers have been properly placed. This method may be referred to as a variant of optical positional tracking.

However, an issue of relying on markers is that placing markers on or at all places that are relevant to obtain an accurate three-dimensional representation is not always possible or practical, and may be time-consuming.

To avoid the use of optical markers WO 2016/028146 A1 discloses a method and system of designing a stair lift rail assembly to be mounted on a three-dimensional structure, a light beam comprising an optical pattern on at least part of the structure is projected from a reference location relative to the structure. Light from said structure is detected. Image data of said structure are generated based on said detected light. The image data are processed to generate a set of map data of said structure, the set of map data representing a three- dimensional map of said structure. A spatial path of the stair lift rail and locations of support interfaces for the stair lift rail assembly in the three-dimensional map are determined. A design of the stair lift rail assembly is generated based on the spatial path of the stair lift rail and the locations of the support interfaces for the stair lift rail assembly.

However, the acquired three-dimensional representation, based on the

aforementioned detection of the optical pattern may in some cases lack a required accuracy to adequately design a stair lift. Also, the measurement may consist of more than several hundred thousand points, making it challenging to extract a few relevant dimensions for the design of a stair lift.

In view of the above, there is a need for further improvement of methods and devices for obtaining an accurate three-dimensional representation of a staircase and its

environment.

SUMMARY OF THE INVENTION

It would be desirable to provide means to acquire an accurate three-dimensional representation of the staircase and its environment without the need to place markers on all points of interest.

To better address one or more of these concerns, in a first aspect of the invention a staircase measuring method for obtaining spatial information on a staircase and an environment of the staircase is provided. The staircase measuring method comprises:

(a) determining, based on positional tracking, a position of a device point located on a distance measuring device, with respect to a position of a staircase reference point located on the staircase or in the environment of the staircase;

(b) determining, based on measuring a distance in a predetermined direction using the distance measuring device, a position of a staircase point with respect to a position of the device point, wherein the staircase point is located on the staircase or on a surface in an environment of the staircase; and

(c) determining, based on: o the position of the staircase point with respect to the position of the device point, and

o the position of the device point with respect to the position of the staircase reference point,

the position of the staircase point with respect to the position of the staircase reference point.

The staircase measuring method according to the first aspect of the invention may be used to obtain accurate spatial information on a staircase and an environment of the staircase.

The spatial information may refer to coordinates of a staircase point located on a staircase or on a surface in an environment of the staircase. The surface may be a material surface. Examples of relevant staircase points may include points on the edges of steps, points at the beginning and end of the stairs, points on a wall adjacent to the stairs, points on a handrail, and other points. Also, the staircase point may be a point on the surface of an object that resides in the environment of the staircase. In general, the staircase point is a point of interest for making a stair lift comprising a guide which is installed on the staircase and along which a frame on which a person can be seated can move. Examples of objects are posts, (wall) decorations, fences, doors, etc. However, more points, depending on the specific stair case and its environment, may be relevant and those are generally easy to identify by a person skilled in designing stair guides or rails or stair lifts.

In a step of the staircase measuring method, the position of the device point with respect to a position of a staircase reference point located on the staircase or in the environment of the staircase is determined using known position tracking techniques.

Positional tracking refers to a plurality of technologies that allows to determine the position of the distance measuring device and its associated device point relative to the environment around it, in particular to the staircase reference point. Positional tracking may use a combination of hardware and software. The tracking of the position of the device point may be performed substantially continuous in time or at substantially separate time instances.

The positional tracking may be used to track movement of the distance measuring device with six degrees of freedom, comprising the 3D position and the 3D orientation.

Many positional tracking technologies are available, and the invention works independent of the specific tracking technology. It is within the capabilities of the skilled person to determine a positional tracking methodology to determine the position of the device point with respect to the staircase reference point. A non-exclusive list of known technologies that may be used for positional tracking are Arkit, Arcore, Constellation, Lighthouse and WorldSense. A positional tracking method may be an optical positional tracking method comprising the use of computer vision algorithms and imaging devices such as a camera of visible or infrared range, a stereo camera and/or a depth camera. There are two common approaches to optical positional tracking:

• Inside-out tracking: a camera is fixed to the distance measuring device and markers are placed in stationary locations on the staircase and/or in the environment of the staircase.

• Outside-in tracking: the camera or several cameras is/are placed in a stationary

location on the staircase and/or in the environment of the staircase. Markers are placed on the distance measuring device. Outside-in approach implies the presence of an external observer, such as the camera, that determines the position of a movable object by the characteristic markers.

In another embodiment the optical positional tracking is performed without the use of markers, wherein image data comprising information of the staircase and/or the environment of the staircase are compared with predetermined 3D representations of objects such as 3D representations of parts of staircases or objects that are commonly located in the

environment of the staircase. Also, the method disclosed in WO 2016/028146 A1 may be used to perform optical tracking.

In another embodiment the optical positional tracking is performed with natural features, wherein distinctive optical points related to the natural features are detected in recorded images. Corresponding observations of an optical point in other images can be determined by tracking in a sequence of images, or by feature matching techniques. By applying various photogrammetry techniques, the position of the optical points and the position where the images were recorded can be retrieved.

In another embodiment the position tracking is performed with the usage of depth cameras, wherein the relative position of the depth camera can be retrieved by comparing a recorded depth image with another recorded depth image or with a combined point cloud.

In another embodiment acoustic tracking, inertial tracking or magnetic tracking may be utilized to localize the device point. Also, various tracking techniques may be combined using for example sensor fusion techniques.

In a step of the staircase measuring method, a position of a staircase point with respect to a position of a device point associated with a distance measuring device is determined. The device point may be a point on the distance measuring device and functions as a point of reference to which a distance is determined by the distance measuring device. To determine the position of the staircase point with respect to the device point, also the orientation of the distance measuring device with respect to the device point is predetermined or determinable. Based on the distance of the staircase point to the device point and based on the orientation of the distance measuring device with respect to the device point, the distance in a predetermined direction is determinable.

Based on the position of the staircase point with respect to the position of the device point, and based on the position of the device point with respect to the position of the staircase reference point, the position of the staircase point with respect to the position of the staircase reference point is determinable.

The obtained spatial information on the staircase point may be used to localize, in three dimensions, the staircase point in a coordinate system. The spatial information may enable localizing the staircase point with respect to other points on the staircase and/or in the environment of the staircase.

In an embodiment of the staircase measuring method, the distance measuring device comprises a measuring arm having a tip, wherein the device point has a predetermined distance to the tip, and step (b) further comprises:

• touching the staircase point with the tip of the measuring arm.

In case the distance measuring device comprises a measuring arm of which the tip of the measuring arm has a determinable position with respect to the position of the device point, an efficient method to determine the distance between the staircase point and the position of the device point, is to touch the staircase point with the tip of the measuring arm. By touching the staircase point, the position of the tip of the measuring arm coincides with the position of the staircase point.

In an embodiment of the staircase measuring method, the distance measuring device comprises a light pulse emitting and receiving device, and step (b) further comprises:

• emitting, by the light pulse emitting and receiving device, a light pulse to the staircase point;

• receiving, by the light pulse emitting and receiving device, the light pulse from the staircase point; and • determining a distance between the device point and the staircase point from the light pulse emitted and measured by the light pulse emitting and receiving device.

Using a light pulse emitting and receiving device to determine a distance is a well- established way to determine the distance to a point, such as the staircase point.

Determining the distance to a point may be based on a measured time of flight, the measured phases or triangularization. The emitted light illuminates the staircase point of interest such that it is easy to decide for an operator, handling the distance measuring device, whether the distance is the distance to the correct staircase point.

In an embodiment of the staircase measuring method, wherein the staircase reference point is associated with a marker located on the staircase or in the environment of the staircase, step (a) further comprises:

(a1) capturing, by an imaging device, at least one image comprising image data associated with the marker;

(a2) determining, based on analysing the at least one image using

photogrammetry techniques, a position of the imaging device with respect to a position of the staircase reference point; and

(a3) determining the position of the imaging device with respect to the position of the device point, wherein determining the position of the staircase point with respect to the position of the device point in step (c), is based on

• the position of the imaging device with respect to the position of the staircase reference point, determined in step (a2), and

• the position of the imaging device with respect to the device point, determined in step (a3).

It may be efficient to obtain a staircase reference point by associating the staircase reference point with a marker. In particular, a marker may be used to indicate a point of which a position or a relative position is determinable. The marker may refer to a movable object that has a shape such that it has a characteristic appearance, which can be accurately detected in an image. It may be efficient to place the marker on the staircase or in the environment of the staircase. The marker may have a part unambiguously indicating a staircase reference point. Preferably, the markers each have their own unique, detectable ID.

Alternatively, the marker may be a natural feature on the staircase or in the environment of the staircase that may be detected in an image. The position of this type of marker may be determined by applying matching techniques, matching image data associated with the natural feature with predetermined image data comprising sizes and shapes of a plurality of objects that may be commonly present at a staircase or in the environment of the staircase.

In step (a2), the position of a marker with respect to the position of the imaging device may be determined using photogrammetry comprising image analysis techniques. First an image of the marker is captured by the imaging device. With the aid of

photogrammetry, the image is further analysed to exactly determine the position of the marker with respect to the imaging device.

The image analysis techniques may comprise a marker tracking algorithm and a simultaneous localisation and mapping, SLAM, algorithm.

In step (a3), the position of the imaging device with respect to the device point is determined. In an embodiment of the staircase measuring method, the position of the imaging device with respect to the device point is predetermined.

In an embodiment of the staircase measuring method, wherein the distance measuring device comprises a measuring arm, the measuring arm is fixed to the imaging device, and the imaging device has a predetermined position with respect to the position of the device point.

It may be convenient to fix the measuring arm to the imaging device, such that determining the position of the imaging device with respect to the position of the device point may be performed before measuring the staircase. It may be efficient to additionally fix the measuring arm at a predetermined orientation with respect to the imaging device. The measuring arm may be able to hinge in two or three dimensions for this purpose, before it is fixed.

In an embodiment of the staircase measuring method, the position of the staircase point with respect to the position of the device point during step (a) is substantially equal to the position of the staircase point with respect to the position of the device point determined in step (b).

When step (a) and step (b) are performed substantially at the same time, the position of the device point during step (a) is substantially equal to the position of the staircase point with respect to the position of the device point determined in step (b). In particular, this may make it easier to relate the various relative positions to each other in step (c) to determine the position of the staircase point with respect to the position of the staircase reference point.

In an embodiment of the staircase measuring method, the at least one image captured by the imaging device does not contain image data on the staircase point.

The staircase measuring method allows to determine the position or relative position of the staircase point without the need of image data on the staircase point. This is, in particular, possible because the distance measuring device does not rely on image data to determine the position of the staircase point with respect to the device point.

In an embodiment of the staircase measuring method, the staircase measuring method further comprises:

• constructing a virtual wireframe, based on the position of the staircase point with respect to the position of the staircase reference point.

By constructing a wireframe based on the position information on a plurality of points, a better representation of an object associated to the plurality of points can be obtained. In an embodiment, the staircase measuring method further comprises:

• associating a description indicating a type of object with the virtual wireframe.

In a second aspect of the invention, a staircase measuring system for obtaining spatial information on a staircase and an environment of the staircase is provided. The staircase measuring system comprises:

• a positional tracking system, configured to determine a position of a device point, associated with a distance measuring device, with respect to a position of a reference point located on the staircase or in the environment of the staircase; • a distance measuring device, configured to measure a distance in a predetermined direction and to determine a position of a staircase point with respect to a position of the device point, wherein the staircase point is located on the staircase or on a surface in the environment of the staircase; and

• a processing system configured to be operatively connected to the positional tracking system and the distance measuring device, and configured to determine the position of the staircase point with respect to the position of the staircase reference point, based on:

• the position of the staircase point with respect to the position of the device point, and

• the position of the device point with respect to the position of the

staircase reference point.

Accordingly, the staircase measuring system may carry out the method according to the first aspect of the invention.

In an embodiment of the staircase measuring system, the distance measuring device comprises a measuring arm having a tip, wherein the device point has a predetermined distance to the tip, and wherein the tip of the measuring arm is suitable for touching the staircase point. In an embodiment of such staircase measuring system, the distance of the device point to the tip is adjustable and/or the orientation of the measuring arm with respect to the device point is adjustable.

In an embodiment of the staircase measuring system, the distance measuring device comprises a light pulse emitting and receiving device with a determinable orientation with respect to the device point. The light pulse emitting and receiving device is configured to determine a distance between the device point and the staircase point, based on a light pulse emitted and received by the light pulse emitting and receiving device.

In an embodiment of the staircase measuring system,

• the positional tracking system further comprises an imaging device configured to capture at least one image comprising image data associated with a marker located on the staircase or in the environment of the staircase; • the processing system further is configured to associate the position of the marker with the position of the staircase reference point and to determine, based on analysing the image data using image processing and photogrammetry techniques, a position of the imaging device with respect to the position of the staircase reference point; and

• the position of the device point with respect to the position of the imaging device is predetermined, or the staircase measuring system further comprises a position measuring device configured to determine the position of the device point with respect to the position of imaging device.

In an embodiment of the staircase measuring system, the marker is associated with the distance measuring device.

These and other aspects of the invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically depicts a perspective view of a staircase and part of its environment.

Figure 2 illustrates how the positions of a device point, a staircase point and a staircase reference point are related.

Figure 3 illustrates how the positions of the device point, the staircase point, the staircase reference point and the position of an imaging device are related.

Figure 4 schematically depicts a perspective view, partially in diagram, of a first embodiment of a staircase measuring system according to the invention.

Figure 5 schematically depicts a perspective view, partially in diagram, of a second embodiment of a staircase measuring system according to the invention.

Figure 6 schematically depicts a perspective view, partially in diagram, of a third embodiment of a staircase measuring system according to the invention.

Figure 7 depicts a first flow diagram of steps associated with the staircase measuring method according to invention.

Figure 8 depicts a second flow diagram of steps associated with staircase measuring method according to the invention. DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 schematically depicts a perspective view of a staircase 800 and part of its environment. The staircase 800 comprises steps 813. In Figure 1 , only three steps 813 are shown. However, the staircase 800 can have less than three, or more than three steps 813. The staircase 800 may slope up along a straight line, as indicated in figure 1. However, the staircase 800 may also slope up along a curved line, or partially along a straight line and partially along a curved line. Different steps 813 may have equal or different widths and/or heights. The staircase 800 may comprise a schematically indicated wall 811 adjacent to the staircase 800. At least one of another wall, a floor, a ceiling, and a railing structure may be present adjacent to the steps 813 of the staircase 800 in a staircase environment.

One or more staircase reference points 801 are present on the steps 813. The staircase reference points 801 may be indicated by optical markers or associated with optical markers 810 that are placed on the steps 813 of the staircase 800. Alternatively, staircase reference points 801 may be natural features of the staircase and its environment that comprise distinctive optically identifiable points. In Figure 1 , three staircase reference points 801 are depicted. However, also less or more staircase reference points 801 may be present on the staircase 800 or in the environment of the staircase.

A well-known approach to measure the staircase and its environment is to put markers 810 or identify staircase reference points 801 at all relevant positions and to capture images comprising the markers 810 or staircase reference points 801 and to determine the relative distances to each other using photogrammetry and image processing, to construct a 3D representation of the staircase and its environment.

However, the wall 811 comprises a staircase point 803 having a position which is of importance for the design of a stair lift and where no marker can be easily placed.

As illustrated in Figure 2, the position of a staircase point 803 with respect to a position of a staircase reference point 801 may be determined indirectly, by determining the position of the staircase point 803 with respect to a device point 805, and determining the position of the staircase reference point 801 with respect to the device point 805. The device point 805 is located on a distance measuring device. Examples of distance measuring devices are provided below with reference to Figures 4 to 6.

Figure 2 illustrates how the positions of the device point 805, the staircase point 803 and the staircase reference point 801 are related. First, a first distance vector 311 may be determined, using a distance measuring device that indicates the position of the staircase point 803 with respect to the position of device point 805. Also, a second distance vector 301 may be determined, using positional tracking, that indicates the position of the device point 805 with respect to the position of the staircase reference point 801. Using positional tracking is well-established method to determine the relative position of two points to each other in case both points are clearly identifiable.

Based on the first distance vector 311 and second distance vector 301 , a third distance vector 321 may be determined, for example by adding the first distance vector 311 to the second distance vector 301 , or by subtracting the first distance vector 311 from the second distance vector 301. The third distance vector 321 then indicates the position of a staircase point 803 with respect to a position of a staircase reference point 801.

It may be that the position of the device point 805 with respect to the staircase reference point 801 is not determinable directly. This is for example the case when an imaging device is used to capture images comprising image data associated to the staircase reference point 801 , such that relative positions with respect to the imaging device have to be determined as well.

Figure 3 illustrates how the position of the device point 805, the position of the staircase point 803, the position of the staircase reference point 801 and the position 820 of the image device may be related. To determine the position of a staircase point 803 with respect to a position of a staircase reference point 801 , a first distance vector 311 may be determined, using a distance measuring device, that indicates the position of the staircase point 803 with respect to the position of device point 805 located on the distance measuring device. Also, a fourth distance vector 401 may be determined, using positional tracking, wherein the fourth distance vector indicates the position of the staircase reference point 801 with respect to the position 820 of the imaging device. Furthermore, a fifth distance vector 431 is determined. The fifth distance vector 431 is either predetermined or determinable by known techniques, and indicates the position of the position of the device point 805 with respect to the position 820 of the imaging device. Based on the first distance vector 311 , the fourth distance vector 401 and the fifth distance vector 431 , a third distance vector 321 may be determined. The third distance vector 321 indicates the position of a staircase point 803 with respect to a position of a staircase reference point 801.

Figure 4 depicts a perspective view, partially schematic, of a first embodiment of a staircase measuring system 900. The staircase measuring system 900 is portable. The staircase measuring system 900 is located in an environment of the staircase depicted in Figure 1. The staircase measuring system 900 comprises a positional tracking system 901. The positional tracking system 901 comprises an imaging device 902 and a processing system 904. The imaging device 902 may comprise one or more cameras that are configured to capture images of the staircase 800 and the environment of the staircase. For illustration purposes, the area visible for the imaging device 902 is, for example, between a first line of sight 911 and a second line of sight 913. Two upper staircase reference points 801 are within the visible area for the imaging device 902. A lower staircase reference point 801 and a staircase point 803 are outside the visible area for the imaging device 902. The positional tracking system 901 may further comprise additional components that, based on received signals generated by the imaging device 902, allow, utilizing photogrammetry and images processing techniques, to determine the position of the imaging device 902 with respect to the positions of the staircase reference points 801 that are in the visible area of the imaging device 902. The position of a device point 805 with respect to the imaging device 902 is predetermined, such that the positional tracking system 901 comprising the imaging device 902 is configured to determine a position of the device point 805 with respect to a position of a staircase reference point 801.

The staircase measuring system 900 has a distance measuring device 907 comprising a measuring arm 908. The measuring arm 908 is fixed to the staircase measuring system 900. The measuring arm 908 may be fixable in a predetermined orientation with respect to the imaging device 902. When not fixed in the predetermined orientation, the measuring arm 908 may be able to hinge in two or three dimensions. The ability to hinge may allow to stow away the measuring arm 908 when then staircase measuring system 900 is not in use. The distance measuring device 907 is used to determine the position of the staircase point 803 with respect to a position of the device point 805 by touching the staircase point 803 with a tip 909 of the measuring arm 908, by determining the length of the measuring arm 908 and by determining the orientation of the measuring arm 908 with respect to the device point 805. The tip 909 of the measuring arm 908 may have a predetermined distance to device point 805, and the tip 909 of the measuring arm 908 is suitable for touching the staircase point 803. The distance of the device point 805 to the tip 909 may also be adjustable and/or the orientation of the measuring arm 908 with respect to the device point 805 may be adjustable.

The processing system 904 is configured to be operatively connected to the positional tracking system 901 and the distance measuring device 907, and configured to determine the position of the staircase point 803 with respect to the position of the staircase reference point 801 , based on the position of the staircase point 803 with respect to the position of the device point 805, and the position of the device point 805 with respect to the position of the staircase reference point 801 , as explained above with reference to Figure 2.

The staircase measuring system 900 comprises a display 905 for providing information to an operator. Figure 5 depicts a perspective view, partially schematic, of a second embodiment of a staircase measuring system according to the invention. The staircase measuring system comprises a portable distance measuring device 503 that is configured to determine a position of a staircase point 803 with respect to a position of a device point 805 associated with the distance measuring device 503. The distance measuring device 503 comprises a light pulse emitting and receiving device with a determinable orientation with respect to the device point 805. The light pulse emitting and receiving device is configured to emit light pulses that travel along a path of the light pulse 501 , causing a light spot 511 on the staircase point 803. The light pulse emitting and receiving device is also configured to receive light pulses reflected from the staircase point 803. The light pulse emitting and receiving device is further configured to determine a distance between the device point 805 and the staircase point 803, based on a light pulse emitted and measured by the light pulse emitting and receiving device.

The staircase measuring system further comprises a positional tracking system 901. The positional tracking system 901 comprises a device marker 505 located on the distance measuring device 503, wherein the device marker 505 has a predetermined position with respect to the position of the device point 805.

The positional tracking system 901 further comprises an imaging device 902 configured to capture an image of the staircase 800 and its environment, the image comprising image data associated with the device marker 505. The device marker 505 is in a field of view of the imaging device 902. For illustration purposes, the field of view of the imaging device 902 is between a first line of sight 911 and a second line of sight 913. The imaging device 902 is located on pole 601 , having a predetermined length, the pole having a lower end at a staircase reference point 801. Alternatively, a point on the imaging device 902 may also serve as a staircase reference point.

The positional tracking system 901 is configured to determine a position of a device point 805 with respect to a position of a reference point 801 located on the staircase 800 or in the environment of the staircase.

The staircase measuring system further comprises a processing system 904 that is operatively connected to the positional tracking system 901 , as schematically indicated by the dashed lines 509, and the distance measuring device 503, as schematically indicated by the dashed line 510. The operative connections 509, 510 may be adapted for wired or wireless communication.

The processing system 904 may be located at the distance measuring device 503 and/or the imaging device 902. The processing system 904 may be wirelessly connected to the distance measuring device 503 or the imaging device 902. The processing system 904 may be located in the environment of the staircase or may be located remotely. The processing system 904 further is configured to associate the position of the imaging device 902 with the staircase reference point 801 , and to determine, based on analysing the image data using image processing and photogrammetry techniques, a position of the device marker 505 with respect to the position of the imaging device 902.

The processing system 904 is configured to determine the position of the staircase point 803 with respect to the position of the staircase reference point 801 , based on the position of the device point 805 with respect to the position of the device marker 505, the position of the imaging device 902 with respect to the position of the staircase reference point 801 , the position of the staircase point 803 with respect to the position of the device point 805, and the position of the device marker 505 with respect to the position of the imaging device 902, as explained above with reference to Figure 3.

Figure 6 depicts a perspective view, partially in diagram, of a third embodiment of a staircase measuring system. The embodiment depicted in Figure 6 is a variation to the embodiments depicted in Figures 4 and 5. In particular, Figure 6 depicts a distance measuring device 907 comprising a measuring arm 908 that is not fixed to an imaging device 902. To determine the position of a device point 805 of the distance measuring device 907 with respect to the position of the imaging device 902, a position measuring system 610 is utilized, that is operatively connected to the imaging device 902 through a first antenna 609 which is configured to connect via communication signal 607 to a second antenna 605 located on the distance measuring device 907. The position measuring system 610 is configured to determine, using known positioning technologies, the position of the device point 805 with respect to the position of the imaging device 902.

The embodiments of the staircase measurement system depicted in Figures 4 to 6 use a common method to determine the position of a staircase point 803 with respect to a position of the staircase reference point 801. Figure 7 depicts a first flow diagram of steps associated with the staircase measuring method, wherein the arrows indicate an efficient order to perform the plurality of steps. In particular, the first flow diagram illustrates how the position of a staircase point 803 with respect to a position of the staircase reference point 801 may be determined.

Figures 4 to 6 illustrate embodiments of staircase measuring devices, wherein the steps of the first flow diagram are applicable. It is however within the capabilities of the skilled person to apply the steps of the first flow diagram to other embodiments of staircase measuring devices as well.

In step 101 , a position of a device point 805 located on a distance measuring device 907, 503 with respect to a position of the staircase reference point 801 located on the staircase 800 or in the environment of the staircase is determined by using positional tracking techniques. In an embodiment, the positional tracking techniques comprise the use of an imaging device 902. Examples of such embodiments are provided in Figures 4 to 6. The staircase reference point 801 may be associated with a marker. The imaging device 902 captures an image comprising image data associated with the marker indicating the staircase reference point 801. Based on analysing the image using image processing and photogrammetry techniques a position of the imaging device 902 with respect to a position of the staircase reference point 801 is determined. Also, the position of the imaging device 902 with respect to the position of the device point 805 is determined. The position of the staircase point 803 with respect to the position of the device point 805 is determined based on the position of the imaging device 902 with respect to the position of the staircase reference point 801 , and the position of the imaging device 902 with respect to the device point 805.

In an embodiment, the captured image does not contain image data on the staircase point 803.

In step 111 , a position of a staircase point 803 with respect to a position of the device point 805 is determined, based on measuring a distance in a predetermined direction using the distance measuring device 907, 503. The distance measuring device 907, 503 may be any device configured to measure a distance.

For example, the distance measuring device 907 comprises a measuring arm 908 having a tip 909, wherein the device point 805 has a predetermined distance to the tip 909. To determine the distance between the device point 805 and the staircase point 803, the staircase point 803 is touched with the tip 909 of the measuring arm 908. The measuring arm 908 may be fixed to the imaging device 902 as shown in figure 4, wherein the imaging device 902 has a predetermined position with respect to the position of the device point 805.

Alternatively, the distance measuring device 503 comprises a light pulse emitting and receiving device. Then, the distance between the device point 805 and the staircase point 803 is determined by: emitting, by the light pulse emitting and receiving device 503, a light pulse to the staircase point 803 causing a light spot 511 on the staircase point 803;

receiving, by the light pulse emitting and receiving device 503, a light pulse from the staircase point 803; and analysing the light pulse emitted and received by the light pulse emitting and receiving device.

In step 121 , the position of the staircase point 803 with respect to the position of the staircase reference point 801 is determined, based on the position of the staircase point 803 with respect to the position of the device point 805, and the position of the device point 805 with respect to the position of the staircase reference point 801. Step 101 and step 111 may be performed in either order or at substantially the same time. Preferably, the position of the staircase point 803 with respect to the position of the device point 805 during step 101 is substantially equal to the position of the staircase point 803 with respect to the position of the device point 805 determined during step 111.

The staircase measuring system 900 may comprise a button 903 that upon activation performs the steps according to the first flow diagram in Figure 1.

Figure 8 depicts a second flow diagram of steps associated with the staircase measuring method, wherein the arrows indicate an efficient order to perform the plurality of steps. Some steps of the second flow diagram are similar to steps of the first flow diagram depicted in Figure 7, but the flow diagram of Figure 8 comprises a few modifications and additional steps as described in the following.

Step 101 , step 111 and step 121 are described with reference to Figure 7. In Figure 8, step 111 is performed after step 101. However, step 111 may also be performed before step 101 , or at substantially the same time as step 101.

In step 231 , the position of the staircase point 803 with respect to the staircase reference point 801 is stored in a storage medium operatively connected to the staircase measuring system. The storage medium may be part of the staircase measuring system or may be external to the staircase measuring system.

In step 241 , it is determined whether a position of another staircase point 803 with respect to the staircase reference point 801 should be determined.

If in step 241 it is determined that a position of another staircase point 803 with respect to the staircase reference point 801 should be determined, the flow continues with step 101.

If in step 241 it is determined that no position of another staircase point 803 with respect to the staircase reference point 801 should be determined, the flow continues with step 251.

In step 251 , a virtual wireframe is constructed, based on the position of the one or more staircase points 803 with respect to the position of the one or more staircase reference points 801.

In step 261 , a description indicating a type of object is associated with the virtual wireframe.

Accordingly, a three-dimensional representation of a staircase and its environment is constructed. As explained in detail above, a staircase measuring method and system for obtaining spatial information on a staircase and an environment of the staircase are based on the steps of

(a) determining, based on positional tracking, a device point on a distance measuring device, with respect to a staircase reference point on the staircase or in the environment thereof;

(b) determining, based on measuring a distance in a predetermined direction using the distance measuring device, a staircase point with respect to the device point, wherein the staircase point is on the staircase or on a surface in an environment of the staircase; and

(c) determining a vector between the staircase point and the staircase reference point, based on a vector between the staircase point and the device point, and a vector between the device point and the staircase reference point.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a"/"an", as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e. , open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

The term position, as used herein, refers to a location in three dimensions, i.e. a spatial location. A vector, as used herein, has a spatial orientation as determined by the spatial locations of the starting point and the end point thereof.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically (e.g. magnetically). A single processor or other unit may fulfil the functions of several items recited in the claims. Additionally, some of the functions recited in the claims may be fulfilled by software that may run locally, remotely or distributed on one or more processors or other units.

LIST OF REFERENCE SIGNS

101 , 111 , 121 , 231 , 241 , 251 , 261 flow diagram steps

311 first distance vector

301 second distance vector

321 third distance vector

401 fourth distance vector

431 fifth distance vector

501 path of light pulse

503 distance measuring device comprising a light pulse emitting and receiving device 505 device marker

509 communication signal

510 communication signal

511 light spot

601 pole

605 second antenna

607 communication signal

609 first antenna

610 position measuring system

800 staircase

801 staircase reference point

803 staircase point

805 device point

810 optical marker

811 wall

813 step

820 position of imaging device

900 staircase measuring system

901 positional tracking system

902 imaging device

903 button

904 processing system

905 display 907 distance measuring device

908 measuring arm

909 tip

911 first line of sight

913 second line of sight