Clustering of laser scanner scan points

Abstract

According to a method for recognizing an object (13) in the vicinity of a laser scanner (2) by clustering scan points of the laser scanner (2), a number of consecutive scan points (7) are generated by the laser scanner (2), each of the scan points (7) is characterized by an incidence angle (φ), and a sequence of a plurality of consecutive scan points (7) is defined by the incidence angle (φ). At least one cluster (6a, 6b) of scan points comprising a portion of the number of consecutive scan points (7) is determined by at least one calculation unit (3a, 3b) based on the sequence.

Description

[Technical Field]

[0001] The present invention relates to a method for detecting objects in the vicinity of a laser scanner by clustering scan points of the laser scanner, and also to a method for at least partially automatic guidance of a vehicle comprising a laser scanner and at least one computing unit, a corresponding sensor system for the vehicle, and a computer program product. [Background technology]

[0002] Lidar sensor systems are often installed in automobiles to enable various functions for automated or partially automated driving or driver assistance, including distance measurement, distance control algorithms, lane-keeping assist systems, object tracking, and autonomous driving functions.

[0003] Known designs of lidar sensor systems include so-called laser scanners, which deflect a laser beam using a deflection unit, thereby achieving different deflection angles of the laser beam. For example, the deflection unit can include a rotatably mounted mirror or a mirror element with a tiltable and / or oscillating surface. The mirror element can be designed, for example, as a microelectromechanical system (MEMS). The emitted laser beam is partially reflected by the surroundings, and the reflected components can then be incident on the laser scanner, in particular on the deflection unit, which can direct these reflected components to the detector unit of the laser scanner. Each photodetector of the detector unit generates an associated detector signal, for example, based on the component recorded by the respective photodetector. As a result, the direction of incidence of the detected reflected component can be inferred based on the spatial arrangement of the respective detector and the current position of the deflection unit, in particular the rotational or tilting and / or oscillating position of the deflection unit. The radial distance of a reflecting object can be determined based on a time-of-flight measurement method. Alternatively or additionally, a method for evaluating the phase difference between the emitted light and the detected light can be used to determine the distance.

[0004] Many of the aforementioned functions are performed based on corresponding scan points of a laser scanner, and require the detection of corresponding objects in the surrounding area of ​​the laser scanner from the scan points. This allows for the identification of groups of scan points that are closely spaced and likely belong to a single physical object, known as clusters. Various methods are known for clustering unordered point clouds, such as the k-nearest neighbor algorithm. Summary of the Invention

[0005] The drawback of such an approach lies in the fact that in order to determine whether a point in the point cloud belongs to the same cluster, a very large number of distances between different scan points must be calculated. Assuming there are n points in the point cloud to be clustered, the total number of distances is n*(n-1) / 2, or O(n 2 ) which translates into high demands, especially in embedded systems such as those used in the automotive sector, given the limited computational and storage resources.

[0006] An object of the present invention is to reduce the amount of computation and / or storage requirements needed to detect objects by clustering the scan points of a laser scanner.

[0007] This object is achieved by the subject matter of the respective independent claims. Advantageous refinements and preferred embodiments are the subject matter of the dependent claims.

[0008] The present invention is based on the concept of utilizing the natural sequence of scan points provided by the measurement principle or structural design of the laser scanner to perform a more efficient cluster analysis of the scan points. To this end, at least one cluster of scan points of the laser scanner is determined in a manner that depends on the sequence defined by the respective angles of incidence of the scan points.

[0009] According to one aspect of the present invention, a method for detecting an object in the vicinity of a laser scanner by clustering scan points of the laser scanner is disclosed. For this purpose, the laser scanner is used to generate a number of consecutive scan points, each of which is uniquely characterized, in particular, by an incidence angle. The sequence of the consecutive scan points is defined by the incidence angles of the scan points at the consecutive scan points. At least one computing unit is used to determine at least one cluster of scan points in a manner dependent on the sequence of the consecutive scan points, each cluster of the one or more clusters including a corresponding portion of the multiple scan points. In particular, each cluster of the one or more clusters consists of a corresponding portion of the multiple scan points.

[0010] In the following description, a laser scanner is understood to mean a lidar sensor system designed as a laser scanner. In particular, a laser scanner includes a transmitting unit having one or more laser light sources, e.g., infrared laser diodes, a detector unit having one or more photodetectors, e.g., photodiodes, in particular, avalanche photodiodes (APDs), and a control and evaluation unit configured to control the transmitting unit and the detector unit and to evaluate the detection signals generated by the photodetectors. In this case, the at least one computing unit may, for example, include the control and evaluation unit of the laser scanner.

[0011] The laser scanner also includes a deflection unit arranged and configured to deflect the laser beam generated by the transmission unit around the periphery of the laser scanner, achieving different transmission angles, particularly within the transmission plane. Again, reflected components of the transmitted laser beam are incident on the deflection unit and directed to the detector unit, where they are detected by a suitable photodetector or detectors. For example, the deflection unit may include a mirror rotatably mounted about an axis of rotation perpendicular to the transmission plane. When the reflected components of light are detected by the detector unit, the direction of incidence of the detected components can be determined from the current position of the deflection unit, particularly the current position of the mirror, in combination with the geometrical arrangement of the respective detector. Furthermore, the control and evaluation unit may perform time-of-flight measurements, for example, to determine radial distances.

[0012] Generally, the direction of incidence can be defined by two angles in a polar coordinate system. These angles are usually called the horizontal or azimuthal angle of incidence, and the polar or vertical angle of incidence. The horizontal angle of incidence corresponds to the angle in the plane of transmission, while the polar angle corresponds to the angle perpendicular to the plane of transmission.

[0013] The different polar angles are also called poses. Each pose corresponds to a photodetector, especially when the photodetectors of the detector unit are linearly arranged in a direction parallel to the rotation plane of the deflection mirror. A 360° rotation of the deflection mirror is also called a scan frame. Therefore, each scan frame generally produces multiple scan points for one or more poses, and each scan point at a given pose is uniquely characterized by the corresponding rotational position of the deflection mirror, and thus by a horizontal incidence angle. Therefore, the scan points at a given pose have a naturally given sequence corresponding to a succession of horizontal incidence angles.

[0014] In the context of the present invention, and in particular in the method according to the present invention, or in the following description, when referring to angles of incidence, in particular angles of incidence defining a sequence, the angles of incidence always relate to the horizontal angle of incidence, whereas, where necessary, polar angles are explicitly referred to as vertical angles of incidence, attitudes or attitude indices, etc.

[0015] Therefore, a sequence of multiple scan points generated according to the method of the present invention, whose sequence is defined by an incidence angle, can be understood as a sequence of multiple scan points at a single pose. However, preprocessing of the point cloud may be performed so that multiple poses can be combined and processed together. In any case, in the following description, it can be assumed that the sequence is defined by a vertical incidence angle and not by a pose index.

[0016] Furthermore, it can be assumed that all scan points of a series of multiple scan points have different angles of incidence, i.e., different horizontal angles of incidence. It should be noted that the rotatably mounted mirror of the deflection unit may optionally include multiple mirror surfaces, for example, two opposing mirror surfaces. Reflections from different mirror surfaces can be considered independently of each other. In other words, in the following, it can be assumed that all scan points of a series of multiple scan points are the result of reflections from the same mirror surface.

[0017] Furthermore, the multiple consecutive scan points are not necessarily raw, unfiltered data, but may instead have undergone one or more upstream pre-processing steps, e.g., for noise reduction or other filtering purposes.

[0018] Thus, a sequence of multiple successive scan points can be understood as a uniform increase or decrease, more particularly a gradual increase or decrease, in the angle of incidence, or in other words, the associated rotational position of the rotatably mounted mirror.

[0019] The sequence of consecutive scan points is characterized by the fact that the consecutive scan points include exactly one start point, which has exactly one successor point, and exactly one end point, which has exactly one predecessor point. Furthermore, the consecutive scan points include one or more intermediate points, each of which has exactly one predecessor point and one successor point.

[0020] A cluster can be understood to be a subset of scan points. The number of scan points in a cluster can be 1 or more, with the maximum number in a cluster being given by the total number of consecutive scan points.

[0021] To determine at least one cluster, i.e., to identify which scan points among a number of consecutive scan points belong to at least one cluster or belong to the same cluster, the distance between different scan points can be taken into account. In the following description, distance can always be understood to refer to the geometric distance, particularly the Euclidean distance, between scan points. However, according to the present invention, the at least one cluster is not determined solely in a manner that depends on the distance between different scan points. Rather, the at least one cluster is determined in a manner that depends on the sequence, i.e., the sequence is taken into account when determining the at least one cluster. In particular, when determining whether a scan point belongs to a cluster, the position of the scan point among the number of consecutive scan points is fully taken into account. In other words, the position within the sequence or according to the sequence is taken into account. For example, this can be achieved by analyzing one or more distances of the scan point only in a specific neighborhood within the sequence, rather than in relation to all other scan points in the number of consecutive scan points. For example, only the nearest neighbor, or only the nearest neighbor and one neighbor, or only the nearest neighbor, one neighbor, and two neighbors, etc., can be considered.

[0022] Furthermore, different thresholds for the maximum distance are taken into account in the process depending on whether corresponding scan points are adjacent in sequence, i.e., nearest neighbors, or one next door, two next doors, etc. The sequence direction, i.e., which scan points follow immediately after other scan points in sequence, or which scan points follow immediately before other scan points, is constant, i.e., defined, but in principle arbitrary.

[0023] In particular, taking the sequence into account when determining at least one cluster ensures that the probability that two points out of a number of consecutive points belong to the same cluster increases the closer their respective positions are according to the sequence. Note that the geometric distance of scan points still represents a relative measure for cluster analysis: the close position of two scan points in a sequence may not be sufficient to assign these scan points to the same cluster.

[0024] In this way, the method according to the invention efficiently utilizes the information arising from the constructive design of the laser scanner, and therefore the information defining the sequence, in order to reduce the number of necessary calculation steps, in particular the number of distances between pairs of scan points that need to be calculated, thereby reducing the amount of calculations and / or the storage requirements.

[0025] Clustering scan points, i.e., determining at least one cluster, can be understood as detecting an object in the sense that the probability that scan points belonging to the same cluster correspond to a physical object in the laser scanner's surroundings, i.e., can be traced back to a reflection from the corresponding surface of this object, is increased. In other words, object detection in this sense involves determining with a certain probability the presence or location of an object in the laser scanner's surroundings. In particular, object detection does not necessarily involve object classification, bounding box determination, etc. However, at least one cluster can be used for such purposes, for example, by serving as the basis for an automatic recognition algorithm.

[0026] In other words, at least one cluster may serve as the basis or input for an algorithm for automatic recognition, such as an object tracking algorithm, a classification algorithm, a segmentation algorithm, etc.

[0027] According to at least one embodiment of the method, a first scan point of the multiple scan points is identified as part of a first cluster of one or more clusters, and a distance between the first scan point and a second scan point of the multiple scan points is determined, and if the distance is less than or equal to a predetermined maximum distance, the second scan point is identified as part of the first cluster.

[0028] For example, the first scan point may be determined as the initial point of the first cluster, or similarly may be determined according to an embodiment of the method according to the present invention.

[0029] In particular, the second scan point in the sequence immediately follows the first scan point. In this way, each pair of immediately consecutive scan points in the series of scan points can be considered, their Euclidean distance from each other can be determined, and if the distance is less than a predetermined maximum distance to the nearest neighbor, the two points of the pair can be assigned to the same cluster. According to at least one embodiment, the predetermined maximum distance depends on the position of the first scan point in the sequence relative to the position of the second scan point in the sequence.

[0030] In other words, the maximum distance is determined in a manner that depends on the respective positions of the first and second scan points in the sequence, and in particular, the position of the first scan point relative to the position of the second scan point can be considered to be a position difference.

[0031] In this way, for example, it is possible to allow a greater maximum distance between scan points that are close together in a sequence than between scan points that are far apart in a sequence.

[0032] For example, the maximum distance can be assigned to the nearest neighbors, and also to all pairs of scan points that are not nearest neighbors. The maximum distance for the nearest neighbors can then be greater than the maximum distance for all other pairs of scan points, such that nearest neighbors are more likely to be assigned to the same cluster, and therefore the same object, than points that are spaced apart sequentially.

[0033] Further gradations are implemented in a similar manner, for example by specifying a maximum distance to the nearest neighbor, as well as a maximum distance to the next neighbor, and optionally a maximum distance to the next neighbor, etc.

[0034] According to at least one first embodiment of the method, a first scan point of the consecutive multiple scan points is identified as part of a first cluster of one or more clusters. A second scan point of the consecutive multiple scan points that immediately follows the first scan point in sequence is identified as part of a second cluster of the one or more clusters. A distance is determined between the first scan point and a third scan point of the consecutive multiple scan points that immediately follows the second scan point in sequence. The third scan point is identified as part of the first cluster or a third cluster of the one or more clusters depending on the distance between the first scan point and the third scan point.

[0035] To determine that the second scan point does not belong to the first cluster, for example, it can be determined that the distance between the first scan point and the second scan point is greater than a predetermined maximum distance to the nearest neighbor. For example, the distance between the second scan point and the third scan point can also be greater than the maximum distance to the nearest neighbor, resulting in the third scan point not belonging to the second cluster.

[0036] However, since the sequence of multiple consecutive scan points is taken into account when determining the cluster, it is possible to verify whether the first and third scan points are close to each other, even though both scan points are distant from the second scan point located between them according to the sequence, thereby preventing the third scan point from being erroneously assigned to a different cluster from the first scan point, even though they are reflections from the same object.

[0037] In the following description, when reference is made to the fact that two scanning points are located close to each other or far away from each other, this can be understood to mean, without any need to specify otherwise, that the distance between corresponding points is smaller than, equal to or larger than a corresponding predetermined maximum distance.

[0038] In particular, if the distance between the first scan point and the third scan point is less than or equal to a predetermined maximum distance to its nearest neighbor, the third scan point is determined to be part of the first cluster.

[0039] For example, if the distance between the first scan point and the third scan point is greater than a predetermined maximum distance to its nearest neighbor, the third scan point is determined to be part of the third cluster.

[0040] According to at least one second embodiment of the method, a first scan point of a plurality of consecutive scan points is identified as part of a first cluster of one or more clusters. A distance is determined between a second scan point of the plurality of consecutive scan points that immediately follows the first scan point in sequence and a third scan point of the plurality of consecutive scan points that immediately follows the second scan point in sequence. A distance is determined between the first scan point and the third scan point. The second scan point is identified as part of the first cluster or a second cluster of the one or more clusters depending on the distance between the first scan point and the third scan point and depending on the distance between the second scan point and the third scan point.

[0041] In particular, the distance between the first and second scan points is greater than a predetermined maximum distance to the nearest neighbor in this case, otherwise the second scan point will be part of the first cluster in any case, without the distance between the first and third scan points or the distance between the second and third scan points being decisive.

[0042] Such an embodiment can therefore advantageously handle situations where the second scan point is far away from the first scan point, but the third scan point is close to both the first and second scan points.

[0043] In particular, if the distance between the first scan point and the third scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, and the distance between the second scan point and the third scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, the second scan point is identified as part of the first cluster.

[0044] In this case, the maximum distance between the nearest neighbor and its next neighbor may be different, but they may also be the same.

[0045] In particular, if the distance between the first scan point and the third scan point is greater than a predetermined maximum distance to the nearest neighbor, or if the distance between the second scan point and the third scan point is greater than a predetermined maximum distance to the nearest neighbor, the second scan point is identified as part of the second cluster.

[0046] According to at least one third embodiment of the method, a first scan point of a plurality of consecutive scan points is identified as part of a first cluster of one or more clusters. A distance is determined between a second scan point of the plurality of consecutive scan points that immediately follows the first scan point in sequence and a third scan point of the plurality of consecutive scan points that immediately follows the second scan point in sequence. A distance is determined between the third scan point and a fourth scan point that immediately follows the third scan point in sequence. A distance is determined between the fourth scan point and the first scan point. The second scan point is identified as part of the first cluster or a second cluster of the one or more clusters depending on the distance between the second scan point and the third scan point, the distance between the third scan point and the fourth scan point, and the distance between the fourth scan point and the first scan point.

[0047] Such an embodiment can advantageously and efficiently handle situations where the first and second scan points, and the first and third scan points, are located far apart from each other, but the second and third scan points, and also the third and fourth scan points, are located close together, such as the fourth and first scan points, in each case.

[0048] In particular, if the distance between the second scan point and the third scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, the distance between the third scan point and the fourth scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, and the distance between the fourth scan point and the first scan point is less than or equal to a predetermined maximum distance to the next nearest neighbor.

[0049] In this case, too, the maximum distance to the nearest neighbor and the maximum distance to the next nearest neighbor may be the same or different.

[0050] In particular, if the distance between the second scan point and the third scan point is greater than the maximum distance to the nearest neighbor, or if the distance between the third scan point and the fourth scan point is greater than the maximum distance to the nearest neighbor, or if the distance between the fourth scan point and the first scan point is greater than the maximum distance to the next nearest neighbor, the second scan point is identified as part of the second cluster.

[0051] According to at least one fourth embodiment of the method, a first scan point of a series of scan points is identified as part of a first cluster of one or more clusters. A distance is determined between a second scan point of the series of scan points that immediately follows the first scan point in sequence and a fourth scan point of the series of scan points, where a third scan point of the series of scan points immediately follows the second scan point in sequence, and the fourth scan point immediately follows the third scan point in sequence. A distance is determined between the fourth scan point and a fifth scan point of the series of scan points that immediately follows the fourth scan point in sequence. A distance is determined between the fifth scan point and the first scan point. The second scan point is identified as part of the first cluster or as part of a second cluster of the one or more clusters depending on the distance between the second scan point and the fourth scan point, depending on the distance between the fourth scan point and the fifth scan point, and depending on the distance between the fifth scan point and the first scan point.

[0052] Such an embodiment can advantageously and efficiently handle situations where the first scan point is far away from both the second scan point and the fourth scan point, the second scan point and the fourth scan point are each far away from the third scan point, the second scan point is located near the fourth scan point, the fourth scan point is located near the fifth scan point, and the fifth scan point is located near the first scan point.

[0053] For example, if the distance between the second scan point and the fourth scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, the distance between the fourth scan point and the fifth scan point is less than or equal to a predetermined maximum distance to the nearest neighbor, and the distance between the fifth scan point and the first scan point is less than or equal to a predetermined maximum distance to the nearest three neighbors, the second scan point can be identified as part of the first cluster.

[0054] In contrast, if the distance between the second scan point and the fourth scan point is greater than the maximum distance to the nearest neighbor, or if the distance between the fourth scan point and the fifth scan point is greater than the maximum distance to the nearest neighbor, or if the distance between the fifth scan point and the first scan point is greater than the maximum distance to the nearest three neighbors, the second scan point can be identified as part of the second cluster.

[0055] It is also possible to combine the method variants previously shown as the first, second, third or fourth embodiment above, so that both of the described situations may be contrasted in appropriate configurations of the method.

[0056] According to at least one embodiment of the method, at least one computing unit is used to execute an algorithm of automatic recognition based on a number of consecutive scan points, the algorithm being executed in a manner dependent on at least one cluster.

[0057] A further aspect of the invention provides a method for at least partially automated guidance of a motor vehicle, the motor vehicle comprising a laser scanner and at least one computing unit. The inventive method for detecting objects is particularly performed by the laser scanner and the at least one computing unit, the method comprising the execution of an algorithm for automated recognition. At least one control signal for the at least partially automated guidance of the motor vehicle is generated in response to a result of the algorithm for automated recognition, particularly by a control unit of the motor vehicle, for example a control unit included in the at least one computing unit.

[0058] The vehicle can then be at least partially automatically guided in response to at least one control signal, for example, the at least one control signal can be supplied to one or more actuators of the vehicle, or the one or more actuators can be controlled accordingly in response to the at least one control signal, so as to guide the vehicle in an automated or partially automated manner.

[0059] According to a further aspect of the present invention, a sensor system for a motor vehicle is provided. The sensor system includes a laser scanner configured to generate sensor data representative of objects in a surrounding area of ​​the laser scanner, and thus in particular in a surrounding area of ​​the motor vehicle. The sensor system includes at least one computing unit configured to generate a sequence of multiple consecutive scan points based on the sensor data, each scan point being characterized by an angle of incidence, and a sequence of the multiple consecutive scan points being defined by the angles of incidence. The at least one computing unit is configured to determine at least one cluster of scan points that includes some of the multiple consecutive scan points in a sequence-dependent manner.

[0060] Further embodiments of the sensor system according to the invention follow directly from various configurations of the method for detecting an object according to the invention and from various configurations of the method for at least partially automatic guidance of a motor vehicle according to the invention, and in each case vice versa. In particular, the sensor system according to the invention can be configured to perform the method for detecting an object according to the invention or performs such a method.

[0061] According to a further aspect of the present invention, an electric vehicle guidance system for a motor vehicle is provided. The electric vehicle guidance system includes the sensor system according to the present invention. At least one computing unit is configured to execute an algorithm for automatic recognition based on a number of consecutive scan points and depending on at least one cluster. A control unit of the electric vehicle guidance system, in particular the at least one computing unit, is configured to generate at least one control signal for at least partial automatic guidance of the motor vehicle depending on the result of the algorithm for automatic recognition.

[0062] Further embodiments of the electric vehicle guidance system according to the invention are directly derived from various configurations of the method for detecting objects according to the invention and from the method for at least partially automatic guidance of a vehicle according to the invention. In particular, the electric vehicle guidance system according to the invention can be configured to perform or performs the method for at least partially automatic guidance of a vehicle according to the invention.

[0063] According to a further aspect of the present invention, a first computer program product is provided having first instructions that, when executed by a sensor system according to the present invention, cause the sensor system to perform a method for detecting an object according to the present invention.

[0064] According to a further aspect of the present invention, a second computer program is provided having second instructions that, when executed by an electric vehicle guidance system according to the present invention, prompt the electric vehicle guidance system to perform a method for at least partially automated guidance of a vehicle according to the present invention.

[0065] According to a further aspect of the invention, a computer-readable storage medium is provided, the latter storing a first computer program according to the invention and / or a second computer program according to the invention.

[0066] The first computer program, the second computer program, and the computer-readable storage medium may be considered to be respective computer program products having first and / or second instructions, respectively.

[0067] Within the scope of this disclosure, the term "light" is understood to include electromagnetic waves in the visible, infrared, and / or ultraviolet ranges, and therefore the term "optical" is also understood to relate to light in this sense.

[0068] An algorithm for automatic image recognition, also referred to as a computer vision algorithm, an algorithm for machine vision, or a machine vision algorithm, is considered to be a computer algorithm for automatically performing a visual recognition task. A visual recognition task, also referred to as a computer vision task, is understood to mean, for example, a task related to the extraction of information from image data. In particular, a visual recognition task can, in principle, be performed by a human being who is able to visually recognize an image corresponding to the image data. However, a visual recognition task can also be performed automatically in this context without human assistance.

[0069] For example, the computer vision algorithm may include an image processing algorithm or an algorithm for image analysis, which is or has been trained by machine learning, for example based on an artificial neural network, in particular a convolutional neural network. For example, the computer vision algorithm may include an object detection algorithm, an obstacle detection algorithm, an object tracking algorithm, a classification algorithm and / or a segmentation algorithm.

[0070] The corresponding algorithms may also be implemented based on input data other than images that can be visually recognized by humans. For example, point clouds or images from infrared cameras, lidar systems, etc. may also be evaluated by appropriately adapted computer algorithms. Strictly speaking, the corresponding algorithms are not algorithms for visual recognition, since the corresponding sensors may operate in a range that is not perceptible to the human eye, e.g., in the infrared range. Therefore, within the scope of the present invention, such algorithms are referred to as algorithms for automatic recognition. Algorithms for automatic recognition thus include algorithms for automatic visual recognition, but are not limited to the latter in terms of human recognition. Consequently, algorithms for automatic recognition in this understanding may also include computer algorithms for the automatic execution of recognition tasks, particularly based on artificial neural networks, that are or have been trained, for example, by machine learning. Such generalized algorithms for automatic recognition may include object detection algorithms, object tracking algorithms, classification algorithms, and / or segmentation algorithms, e.g., semantic segmentation algorithms.

[0071] When using artificial neural networks to implement automatic visual recognition algorithms, the architecture frequently adopted is the convolutional neural network (CNN). In particular, 2D CNNs can be applied to corresponding 2D camera images. CNNs can also be used for other algorithms for automatic recognition. For example, 3D CNNs, 2D CNNs, or 1D CNNs can be applied to point clouds, depending on the spatial dimension of the point cloud and the processing details.

[0072] The results or output of an algorithm for automatic recognition depend on the specific underlying recognition task. For example, the output of an object detection algorithm may include one or more bounding boxes defining the spatial location and optionally the orientation of one or more corresponding objects in the surroundings and / or appropriate object classes for one or more objects. A semantic segmentation algorithm applied to camera images may include a pixel-level class for each pixel in the camera image. In a similar manner, a semantic segmentation algorithm applied to point clouds may include a corresponding point-level class for each point. The pixel-level or point-level class may, for example, define the type of object to which each pixel or point belongs.

[0073] Here, an electric vehicle guidance system can be understood as an electronic system configured to guide a vehicle fully automatically or fully autonomously, in particular without driver control intervention. The vehicle automatically performs all required functions, such as steering, braking, and / or accelerating, observing and detecting road traffic, and responding appropriately. In particular, an electric vehicle guidance system can implement a fully automated or fully autonomous driving mode of the vehicle according to Level 5 of the SAE J3016 classification. An electric vehicle guidance system can also be understood as an advanced driver assistance system (ADAS) that assists the driver during partially automated or partially autonomous driving. In particular, an electric vehicle guidance system can implement a partially automated or partially autonomous driving mode according to Levels 1 to 4 of the SAE J3016 classification. In the following description, "SAE J3016" refers to the corresponding standard in its June 2018 version.

[0074] Thus, at least partially automated vehicle guidance can include guiding a vehicle according to a fully automated or fully autonomous driving mode in accordance with Level 5 per SAE J3016. Also, at least partially automated vehicle guidance can include guiding a vehicle according to a partially automated or partially autonomous driving mode in accordance with Levels 1 through 4 per SAE J3016.

[0075] Within the scope of this disclosure, when reference is made to a component of a sensor system according to the present invention, in particular at least one computing unit of the sensor system, being configured, embodied, designed, etc. to perform or implement a particular function, obtain a particular effect, or serve a particular purpose, this may be understood to mean that by appropriate adaptation, appropriate programming, appropriate physical design, etc., the component is able to concretely and actually perform or implement that function, obtain that effect, or serve that purpose, beyond the component's basic or theoretical usefulness or suitability for this function, effect, or purpose.

[0076] In particular, a computation unit may be understood to mean a data processing device, i.e. a computation unit capable of processing data in particular for the purpose of performing computations, optionally including operations for performing directed accesses to data structures, for example look-up tables (LUTs).

[0077] In particular, the computing unit may include one or more computers, one or more microcontrollers, and / or one or more integrated circuits, such as one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), and / or one or more systems-on-chips (SoCs). The computing unit may also include one or more processors, such as one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs), and / or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit may also include a cluster of physical or virtual computers or other types of the aforementioned units.

[0078] The computing unit of various preferred embodiments includes one or more hardware and / or software interfaces and / or one or more storage units.

[0079] The storage unit may be configured as a volatile data memory, such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), or as a non-volatile data memory, such as a read-only memory (ROM), as a programmable read-only memory (PROM), as an erasable read-only memory (EPROM), as an electrically erasable read-only memory (EEPROM), as a flash memory or flash EEPROM, as a ferroelectric random access memory (FRAM), as a magnetoresistive random access memory (MRAM), or as a phase-change random access memory (PCRAM).

[0080] Further features of the present invention can be found in the claims, the drawings, and the description of the drawings. Features and combinations of features described above in this specification, as well as features and combinations of features described below in the description of the drawings and / or shown in the drawings, can be included in the present invention not only in the combination specified in each case, but also in other combinations. In particular, feature embodiments and combinations that do not have all the features of the claims originally written are also included in the present invention. Furthermore, feature embodiments and combinations that exceed or differ from the feature combinations described in the later references of the claims are also included in the present invention.

[0081] In the drawings: [Brief explanation of the drawings]

[0082] [Figure 1] FIG. 1 is a schematic diagram of a vehicle having a preferred embodiment of a sensor system according to the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a further preferred embodiment of a sensor system for an automobile according to the present invention. [Figure 3] FIG. 3 is a schematic diagram showing a number of scan points. [Figure 4] FIG. 4 is a further schematic diagram showing multiple scan points. [Figure 5] FIG. 5 is a further schematic diagram showing multiple scan points. [Figure 6] FIG. 5 is a further schematic diagram showing multiple scan points. [Figure 7] FIG. 7 is a further schematic diagram showing multiple scan points. [Figure 8] FIG. 8 is a further schematic diagram showing multiple scan points. DETAILED DESCRIPTION OF THE INVENTION

[0083] 1 shows schematically a motor vehicle 5 including a preferred embodiment of a sensor system 1 according to the present invention. The sensor system 1 includes a lidar sensor system in the form of a laser scanner 2 and includes a computing unit 3a, for example configured as or part of an electronic control unit, ECU, ECU.

[0084] The laser scanner 2 can emit light in a transmission plane that includes a field of view 4 and is spanned by a vertical axis x and a horizontal axis y. The laser scanner 2 can detect reflected components of the emitted light signal, and the laser scanner 2 and / or the calculation unit 3a can generate a number of scan points 7 based on the detected components.

[0085] In FIG. 2 a preferred embodiment of the sensor system 1 is depicted schematically.

[0086] The laser scanner 2 may include a control and evaluation unit 3b, which is connected to the calculation unit 3a. Alternatively, the calculation unit 3a may adopt the functions of the control and evaluation unit 3b, or vice versa. The laser scanner 2 includes an illumination unit 8, which includes one or more laser diodes and is controllable by the control and evaluation unit 3b. The laser scanner 2 also includes a detector unit 9, which includes one or more photodetectors, such as avalanche photodiodes, and is also connected to the control and evaluation unit 3b. The laser scanner 2 also includes a mirror 10 rotatably mounted about a rotation axis 11. In particular, the rotation axis 11 is perpendicular to the transmission surface. The control and evaluation unit 3b can also control or determine the rotational position of the mirror 10.

[0087] During operation, the illumination unit 8, under the control of the control and evaluation unit 3b, emits laser pulses 12a that are deflected by the mirror 10, allowing them to exit the housing 14 of the laser scanner 2 and the surroundings of the automobile 5. If the laser pulses 12a strike an object 13 in the surroundings of the automobile 5, they may be at least partially reflected by the object. A reflected component 12b enters the laser scanner 2, passes through the housing 14, and strikes the mirror 10, which deflects the reflected component to the detector unit 9. One of the photodetectors in the detector unit 9 detects the reflected component 12b, and the calculation unit 3a or the control and evaluation unit 3b uses it to generate the appropriate scan point 7. Because the laser pulses 12a and the reflected component 12b propagate at the speed of light, the mirror position of the mirror 10 at the time of detection of the reflected component 12 essentially corresponds exactly to the mirror position at the time the laser pulse 12a was emitted. In combination with time-of-flight measurements, the control and evaluation unit 3b can thus determine three-dimensional coordinates, for example in a polar coordinate system, for each scan point. Each scan point is therefore characterized, in particular, by the corresponding rotational position of the mirror 10, the corresponding horizontal angle of incidence (hereinafter referred to as the angle of incidence) in the xy-plane or transmission plane, the polar angle or orientation index, and the radial distance. The orientation index corresponds to the photodetector that detected the reflected component 12b of the corresponding scan point. The photodetectors of the detector unit 9 are, in particular, arranged linearly, parallel to the rotation axis 11, i.e., perpendicular to the transmission plane.

[0088] The mirror 10 may have multiple reflective mirror surfaces on each side. These mirror surfaces may be treated as separate mirrors. A 360° rotation of the mirror 10 around the rotation axis 11 is called a scan frame. In the case of two reflective surfaces, each scan frame includes a scan frame for the first surface and a scan frame for the second surface. The following description can be considered to refer to the scan frame for a single mirror surface. These descriptions also apply to additional mirror surfaces. Thus, each scan frame creates a number of successive scan points 7 for each pose, and these scan points can be assigned an incidence angle in each case and therefore have a sequence defined by the incidence angle. In the following, only one pose of the scan points will be considered. More poses can also be considered as appropriate.

[0089] For example, the illumination unit 8 may generate laser pulses 12a such that one laser pulse is emitted for each rotation of the mirror by a fixed angular increment, for example, the angular increment may be on the order of 0.1° to 1°, e.g., about 0.25°.

[0090] The calculation unit 3a is able to cluster the scan points 7 in order to assign them to one or more objects 13 in the surroundings of the motor vehicle 5. According to the invention, the calculation unit 3a takes into account a sequence of scan points 7 identified by successive angles of incidence at the transmission surface in order to determine the clustering, i.e. at least one cluster 6a, 6b.

[0091] The sensor system 1 is configured to execute the method according to the present invention for detecting objects 13 in the vicinity of the laser scanner 2, in particular in the vicinity of the vehicle 5. The calculation unit 3a thus determines at least one cluster 6a, 6b. Optionally, the calculation unit 3a may be capable of executing an algorithm for automatic recognition, such as an object tracking algorithm, based on the clustered scan points 7. Based on the result of the algorithm for automatic recognition, the calculation unit 3a or another control unit (not shown here) of the vehicle 5 can generate at least one control signal for at least partially automatic guidance of the vehicle. Based on the control signal, the vehicle 5 is guided in an automated or partially automated manner.

[0092] 3 to 7 of the drawings show different situations in which the scan points 7 are spaced apart from one another in different ways. Various embodiments of the method according to the invention will now be explained in more detail with reference to FIGS.

[0093] 3 depicts a number of scan points 7a to 7l, where each scan point is depicted as a circle with a line indicating the direction from the scan point to the rotation axis 11. Therefore, the angle of incidence φ is equal to the angle that the corresponding line makes with the x-axis.

[0094] To cluster the scan points 7a-7l, the calculation unit 3a can verify which scan points 7a-7l are located at a distance from other scan points 7a-7l that is less than a predetermined cluster distance (which may also be referred to as the maximum distance). As follows, when two scan points are considered to be distant from each other, this can be understood to mean that the distance between the two scan points is greater than the cluster distance, and when two scan points are considered to be close to each other, this can be understood to mean that the distance between the two scan points is equal to or less than the cluster distance. Furthermore, it is assumed that only one cluster distance is defined. However, in alternative embodiments, multiple cluster distances can be specified, such as the distance to the nearest neighbor and the distance to the nearest neighbor, according to a sequence given by the angle of incidence.

[0095] To cluster the scan points 7a-7l, the calculation unit 3a could, in principle, calculate all distances between all scan points 7a-7l and compare these distances with the cluster distance. However, this would entail high demands on computational power and memory. Therefore, according to the present invention, the natural sequence of scan points 7a-7l resulting from the generation of scan points described above is utilized.

[0096] For example, in the example of Fig. 3, the first scan point 7a is followed by the second scan point 7b, which is followed by the third scan point 7c, etc. Here, the calculation unit 3a can, for example, limit the distance between adjacent scan points according to the sequence. Thus, for n scan points, the number of distances to be calculated is O(n 2) to O(n). In this embodiment, the calculation unit 3a determines that, for example, all consecutive scan points 7a-7f satisfy the cluster condition in each case, i.e., the scan points immediately following each other are separated by less than the cluster distance in each case. However, scan point 7f and the scan point immediately following it, 7g, are separated from each other, in particular, their distance is greater than the cluster distance. Therefore, the cluster condition is also satisfied for each adjacent pair of scan points 7h-7l, and therefore scan points 7a-7f are determined to be part of the first cluster 6a, and the remaining scan points 7h-7l are determined to be part of the second cluster 6b. In this example, the amount of calculation and memory usage can be reduced by considering the sequence.

[0097] FIG. 4 illustrates a situation in which eight scan points 7a-7h exist. Following the eight scan points 7a-7h, the second scan point 7b is close to the first scan point 7a, the third scan point 7c is close to the second scan point 7b, the fourth scan point 7d is far from the third scan point 7c, the fifth scan point 7e is far from the fourth scan point 7d, and each of the remaining scan points 7f-7h is also close to its predecessor. However, the fifth scan point 7e is also close to the third scan point 7c, i.e., the point immediately adjacent to the previous point or the point immediately adjacent to the previous point. In other words, if the fourth scan point 7d were ignored, all of the remaining scan points 7a-7c and 7e-7h would belong to the same cluster 6a. The fourth scan point 7d would form the basis of a second cluster 6b. To achieve this consistent result, a corresponding embodiment of the method may perform an additional verification step when a scan point along the sequence is determined to be far from its previous scan point.

[0098] In the example of FIG. 4, the verification is as follows: As an initial point, scan point 7a belongs to the first cluster 6a. The second scan point 7b is close to the first scan point 7a, so it also belongs to the first cluster 6a. The third scan point 7c is close to the second scan point 7b, so it also belongs to the first cluster 6a. The fourth scan point 7d is far from the third scan point 7c, so it does not belong to the first cluster 6a, but may belong to the second cluster 6b. To verify this, the distance between the fourth scan point 7d and the point immediately adjacent to its previous point, i.e., the second scan point 7b, is determined. This distance is also greater than the cluster distance, so in this case, the fourth scan point 7d actually belongs to the second cluster 6b. The fifth scan point 7e is far from the second scan point 7b, so it may not belong to the second cluster 6b. For verification purposes, the distance between the fourth scan point 7d and the point immediately adjacent to its previous point, i.e., the third scan point 7c, is determined. Since this distance is smaller than the cluster distance, the fifth scan point 7e also belongs to the first cluster 6a. Continuing in this manner, the remaining scan points 7f to 7h are also assigned to the first cluster 6a.

[0099] FIG. 5 illustrates a further situation, showing four consecutive scan points 7a, 7b, 7c, and 7d. The first scan point 7a establishes a first cluster 6a. The second scan point 7b that follows it is close to the first scan point 7a and therefore also belongs to the first cluster 6a. The third scan point 7c that follows it is farther away from the second scan point 7b and therefore may belong to a different cluster. In this embodiment, the distance between scan points 7a and 7c is also greater than the cluster distance, so verification based on the point immediately adjacent to the previous point, i.e., the first scan point 7a, would not yield a different result. However, the fourth scan point 7d that follows the third scan point 7c is closer than the cluster distance from both the third scan point 7c and its previous point, the second scan point 7b. Therefore, in this situation, all four scan points 7a, 7b, 7c, and 7d can be assigned to the first cluster 6a.

[0100] The concept of transitivity described with reference to FIG. 5 is extended further in FIG. 6. In this case, five consecutive scan points 7a, 7b, 7c, 7d, and 7e are shown. The first scan point 7a establishes a first cluster 6a. The subsequent second scan point 7b is distant from the first scan point 7a. The third scan point 7c is also distant from the second scan point 7b but close to the first scan point 7a. The fourth scan point 7d is also distant from its previous point, the third scan point 7c, and from the first scan point 7a. However, the fourth scan point 7d is close to the second scan point 7b. The fifth scan point 7e is close to its previous point, the fourth scan point 7d, and is close to the third scan point 7c, which is the point next to the previous point, and is also close to the first scan point 7a. Therefore, in this case, all scan points 7a, 7b, 7c, 7d, and 7e can be assigned to the same cluster 6a.

[0101] Additional levels of transitivity can be added as well, which among other things allows us to balance the computational effort with the accuracy of the clustering results.

[0102] Furthermore, the cluster distance can be chosen to be larger, for example, for the nearest neighbors of a scan point than for other pairs of points. As illustrated schematically in Figure 7, if the angle between the laser pulse direction and the reflecting surface is correspondingly flat, the distance between two consecutive scan points can be relatively large even though these points originate from the same object.

[0103] The geometric distance can be calculated as a squared distance in certain implementations. Therefore, there is no need to calculate roots, which also saves computation time. Intermediate distance results must be stored in various embodiments, for example, as described in connection with Figures 5 and 6.

[0104] Figure 8 shows a more typical example. Nine scan points 7a-7i are depicted here. Consecutive scan points in each pair are farther apart than the cluster distance. In contrast, adjacent pairs—scan points 7a and 7c, 7c and 7e, 7e and 7g, 7g and 7i, as well as scan points 7b and 7d, 7d and 7f, and 7f and 7h—are all close together. This situation can arise, for example, when two relatively long objects are placed one after the other. The above method achieves this: the related scan points 7a, 7c, 7e, 7g, and 7i are assigned to the first cluster 6a, and the remaining scan points 7b, 7d, 7f, and 7h are assigned to the second cluster 6b.

Claims

1. A method for recognizing an object (13) in the vicinity of a laser scanner (2) by clustering scan points of the laser scanner (2), comprising: The laser scanner (2) is used to generate a number of successive scan points (7), each scan point (7) being characterized by an angle of incidence (φ), and the sequence of the number of successive scan points (7) being defined by the angle of incidence (φ); at least one calculation unit (3a, 3b) is used to determine, in a sequence-dependent manner, at least one cluster (6a, 6b) of scan points comprising some of said plurality of consecutive scan points (7); a first scan point (7c) of the consecutive plurality of scan points (7) is identified as part of a first cluster (6a) of one or more clusters (6a, 6b); a second scan point (7d) of the plurality of consecutive scan points (7) immediately following the first scan point (7c) according to the sequence is identified as part of a second cluster (6b) of the one or more clusters (6a, 6b); determining a distance between the first scan point (7c) and a third scan point (7e) of the consecutive multiple scan points (7) that immediately follows the second scan point (7d) according to the sequence; the third scanning point (7e) is identified as part of the first cluster (6a) or as part of a third cluster of the one or more clusters (6a, 6b) depending on the distance between the first scanning point (7c) and the third scanning point (7e); the third scan point (7e) is determined to be part of the first cluster (6a) if the distance between the first scan point (7c) and the third scan point (7d) is less than or equal to a predetermined first maximum distance to its nearest neighbor; a first scan point (7b) of the consecutive plurality of scan points (7) is identified as part of a first cluster (6a) of the one or more clusters (6a, 6b); determining a distance between a second scan point (7c) of the consecutive multiple scan points (7) that immediately follows the first scan point (7b) according to the sequence and a third scan point (7d) of the consecutive multiple scan points (7) that immediately follows the second scan point (7c) according to the sequence; A distance between the first scanning point (7b) and the third scanning point (7d) is determined; the second scanning point (7c) is identified as part of the first cluster (6a) or the second cluster (6b) of the one or more clusters (6a, 6b) depending on the distance between the first scanning point (7b) and the third scanning point (7d) and depending on the distance between the second scanning point (7c) and the third scanning point (7d); The second scan point (7c) is identified as part of the first cluster (6a) if the distance between the first scan point (7b) and the third scan point (7d) is less than or equal to the first predetermined maximum distance to their nearest neighbors and the distance between the second scan point (7c) and the third scan point (7d) is less than or equal to a second predetermined maximum distance to their nearest neighbors.

2. a first scan point (7a) of the plurality of consecutive scan points (7) is identified as part of a first cluster (6a) of one or more clusters (6a, 6b); A distance between the first scan point (7a) and the second scan point (7b) of the plurality of consecutive scan points (7) is determined; 2. The method of claim 1, wherein the second scan point (7b) is identified as part of the first cluster (6a) if the distance is less than or equal to a predetermined maximum distance.

3. 3. The method of claim 2, wherein the maximum distance depends on the position of the first scanning point (7a) according to the sequence relative to the position of the second scanning point (7b) according to the sequence.

4. a first scan point of the plurality of consecutive scan points (7) is identified as part of a first cluster (6a) of the one or more clusters (6a, 6b); a distance between a second scan point of the plurality of consecutive scan points (7) that immediately follows the first scan point according to the sequence and a third scan point of the plurality of consecutive scan points (7) that immediately follows the second scan point according to the sequence is determined; determining a distance between the third scan point and a fourth scan point of the plurality of consecutive scan points (7) immediately following the third scan point according to the sequence; a distance between the fourth scan point and the first scan point is determined; 2. The method of claim 1, wherein the second scan point is identified as part of the first cluster (6a) or the second cluster (6b) of the one or more clusters (6a, 6b) depending on the distance between the second scan point and the third scan point, depending on the distance between the third scan point and the fourth scan point, and depending on the distance between the fourth scan point and the first scan point.

5. 5. The method of claim 4, wherein the second scan point is identified as part of the first cluster (6a) if the distance between the second scan point and the third scan point is less than or equal to the second predetermined maximum distance to a nearest neighbor, the distance between the third scan point and the fourth scan point is less than or equal to the second predetermined maximum distance to a nearest neighbor, and the distance between the fourth scan point and the first scan point is less than or equal to a third predetermined maximum distance to a nearest neighbor.

6. a first scan point of the plurality of consecutive scan points (7) is identified as part of a first cluster (6a) of the one or more clusters (6a, 6b); a distance is determined between a second scan point of the consecutive multiple scan points (7) that immediately follows the first scan point (7a) according to the sequence, and a fourth scan point (7d) of the consecutive multiple scan points (7) where a third scan point (7c) of the consecutive multiple scan points (7) immediately follows the second scan point (7b) according to the sequence, and a fourth scan point (7d) of the consecutive multiple scan points (7) where a fourth scan point (7d) of the consecutive multiple scan points (7) immediately follows the third scan point (7c) according to the sequence; determining a distance between the fourth scan point (7d) and a fifth scan point (7e) of the consecutive multiple scan points (7) immediately following the fourth scan point according to the sequence; The distance between the fifth scanning point (7e) and the first scanning point (7a) is determined; 2. The method of claim 1, wherein the second scan point (7b) is identified as part of the first cluster (6a) or as part of a second cluster (6b) of the one or more clusters (6a, 6b) depending on the distance between the second scan point (2b) and the fourth scan point (7d), depending on the distance between the fourth scan point (7d) and the fifth scan point (7e), and depending on the distance between the fifth scan point (7e) and the first scan point (7a).

7. 7. The method of claim 6, wherein the second scan point (7b) is identified as part of a first cluster (6a) if the distance between the second scan point (7b) and the fourth scan point (7d) is less than or equal to the first predetermined maximum distance to the nearest neighbor, the distance between the fourth scan point (7d) and the fifth scan point (7e) is less than or equal to the second predetermined maximum distance to the nearest neighbor, and the distance between the fifth scan point (7e) and the first scan point (7a) is less than or equal to a fourth predetermined maximum distance to the nearest three neighbors.

8. 2. The method according to claim 1, wherein the at least one computing unit (3a, 3b) is used to execute an algorithm for automatic recognition based on the plurality of consecutive scan points (7), the algorithm for automatic recognition being executed in a manner dependent on the at least one cluster (6a, 6b).

9. A method for at least partial automatic guidance of a motor vehicle (5), comprising a laser scanner (2) and at least one calculation unit (3a, 3b), A method (13) for detecting an object according to claim 8 is carried out, A method, wherein depending on the result of said algorithm of automatic recognition, at least one control signal for at least partially automatic guidance of said vehicle (5) is generated.

10. A sensor system (1) for a motor vehicle (5), said sensor system (1) comprising: a laser scanner (2) configured to generate sensor data representative of surrounding objects (13); At least one calculation unit (3a, 3b), said calculation unit comprising: generating the plurality of successive scan points (7) based on the sensor data, each scan point (7) being characterized by an angle of incidence (φ), and the sequence of the plurality of successive scan points (7) being defined by the angle of incidence (φ); determining, in a sequence-dependent manner, at least one cluster (6a, 6b) of scan points comprising some of said plurality of consecutive scan points (7); a first scan point (7c) of the consecutive plurality of scan points (7) is identified as part of a first cluster (6a) of one or more clusters (6a, 6b); a second scan point (7d) of the plurality of consecutive scan points (7) immediately following the first scan point (7c) according to the sequence is identified as part of a second cluster (6b) of the one or more clusters (6a, 6b); determining a distance between the first scan point (7c) and a third scan point (7e) of the consecutive multiple scan points (7) that immediately follows the second scan point (7d) according to the sequence; the third scanning point (7e) is identified as part of the first cluster (6a) or as part of a third cluster of the one or more clusters (6a, 6b) depending on the distance between the first scanning point (7c) and the third scanning point (7e); the third scan point (7e) is determined to be part of the first cluster (6a) if the distance between the first scan point (7c) and the third scan point (7d) is less than or equal to a predetermined first maximum distance to its nearest neighbor; a first scan point (7b) of the consecutive plurality of scan points (7) is identified as part of a first cluster (6a) of the one or more clusters (6a, 6b); determining a distance between a second scan point (7c) of the consecutive multiple scan points (7) that immediately follows the first scan point (7b) according to the sequence and a third scan point (7d) of the consecutive multiple scan points (7) that immediately follows the second scan point (7c) according to the sequence; A distance between the first scanning point (7b) and the third scanning point (7d) is determined; the second scanning point (7c) is identified as part of the first cluster (6a) or the second cluster (6b) of the one or more clusters (6a, 6b) depending on the distance between the first scanning point (7b) and the third scanning point (7d) and depending on the distance between the second scanning point (7c) and the third scanning point (7d); The second scan point (7c) is identified as part of the first cluster (6a) if the distance between the first scan point (7b) and the third scan point (7d) is less than or equal to a predetermined first maximum distance to its nearest neighbor, and the distance between the second scan point (7c) and the third scan point (7d) is less than or equal to a predetermined second maximum distance to its nearest neighbor.

11. A computer program product having instructions which, when executed by a sensor system (1) as described in claim 10, cause the sensor system (1) to perform the method as described in claim 1.

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