METHOD FOR DETECTING PARKING SPACES USING ULTRASONIC SENSORS

Description

[0001] The invention relates to a method for detecting parking spaces using one or more ultrasonic sensors.

[0002] It is known to collect environmental information in the area of ​​a vehicle using ultrasonic sensors, for example to determine the distance to other objects when parking.

[0003] It is also known to perform parking space detection based on information from multiple ultrasonic sensors using trilateration. Using trilateration, it is possible to determine not only the distance to an object but also the spatial direction in which the object is located.

[0004] The disadvantage of the known methods for parking space detection is that they are computationally intensive and that parking space detection is prone to errors due to inaccuracies in the odometry system and noise.

[0005] It is also known from DE 10 2019 111569 A1 to cluster object points detected in a vehicle environment using DBSCAN over a radius around the respective object point.

[0006] Based on this, it is the object of the invention to provide a method for detecting parking spaces by means of one or more ultrasonic sensors, which requires little computing and memory effort and is low in error.

[0007] This object is achieved by a method having the features of independent patent claim 1. Preferred embodiments are the subject of the dependent claims. A system for detecting parking spaces using one or more ultrasonic sensors is the subject of independent patent claim 7, and a vehicle with such a system is the subject of independent patent claim 12.

[0008] According to a first aspect, the invention relates to a method for detecting parking spaces using at least one ultrasonic sensor provided on a vehicle. The method comprises the following steps: First, a detection list is created in a storage unit, wherein the detection list for received reflected signal components of ultrasonic signals (hereinafter also referred to as echo or ultrasonic echo) has a list area relating to the location at which the echo occurred and a list area for a neighborhood indicator, wherein the neighborhood indicator provides information relating to the number of neighboring echoes that occurred in a defined neighborhood area of ​​the echo. The locations to be entered in the detection list thus indicate the local position at which the reflection that caused the echo occurred.

[0009] An ultrasonic signal is emitted by an ultrasonic sensor on the vehicle. This can be either a single ultrasonic sensor transmitting an ultrasonic signal, or multiple ultrasonic sensors can transmit ultrasonic signals simultaneously or sequentially.

[0010] A reflected portion of the ultrasonic signal is then received by the ultrasonic sensor. This reflected portion can be received either by the same ultrasonic sensor that transmitted the ultrasonic signal or by a different ultrasonic sensor (a so-called cross-echo).

[0011] The azimuth angle from which the echo was received is then determined. The azimuth angle is an angle measured in a horizontal plane between the vehicle's longitudinal axis or a line parallel to this longitudinal axis and the straight line connecting the ultrasonic sensor and the reflection point where the reflection that generated the ultrasonic echo occurred. The azimuth angle preferably opens toward the front of the vehicle.

[0012] After determining the azimuth angle, the local position at which the reflection generating the echo occurred is determined based on the travel time of the ultrasonic signal between the transmission of the ultrasonic signal and reception of the echo and the azimuth angle.

[0013] The detection list is then modified. Neighboring echoes of the received echo contained in the detection list are determined based on a neighborhood rule. For each detected neighboring echo, the neighborhood indicator of the respective detected neighboring echo is increased by an incremental value.

[0014] In addition, an entry relating to the received echo is added to the detection list, the entry containing information relating to the local position at which the reflection generating the echo occurred and having a proximity indicator, the proximity indicator having a value corresponding to the number of neighboring echoes detected based on the proximity rule.

[0015] Finally, the values ​​of the neighborhood indicators of the detection list are compared with a threshold and parking space detection is performed based on those echoes whose neighborhood indicator is greater than the threshold.

[0016] It is understood that the steps described above are carried out at least partially iteratively in order to obtain a sufficient number of echoes from objects in the vicinity of the vehicle and to carry out reliable parking space detection based thereon.

[0017] The technical advantage of the method according to the invention is that it enables improved detection of areas in the vehicle's surroundings that are free for parking, with respect to computing power and memory requirements. The method is insensitive to ultrasonic sensor noise, and the false positive rate can be minimized by filtering the detections based on the neighboring echoes already detected.

[0018] According to one embodiment, the azimuth angle is determined based on the radial velocity of the vehicle relative to an object at which the reflection occurs. The difference between the radial velocity of the vehicle in the direction of the object (radial in relation to the circular propagation of the ultrasonic signal emanating from the ultrasonic sensor) and the vehicle speed in the direction of movement of the vehicle is a measure of the azimuth angle, which extends between the line connecting the ultrasonic sensor and the reflecting object and a line running parallel to the direction of movement of the vehicle. This allows the azimuth angle to be inferred from the radial velocity.

[0019] According to one embodiment, the vehicle's radial velocity is determined based on the frequency change of the received echo due to the Doppler effect. The Doppler frequency change is a measure of the vehicle's radial velocity relative to the reflecting object. The greater the radial velocity, the greater the frequency change.

[0020] According to another embodiment, the radial velocity of the vehicle is determined by tracking multiple echoes over time. This tracking of the echoes can be performed, for example, using a Kalman filter. The temporal change in the location of the reflection relative to the vehicle position allows a conclusion to be drawn about the radial velocity.

[0021] According to a further embodiment, the local position at which the reflection that generates the echo occurred is specified by coordinates that refer to a stationary position that does not move with the vehicle. The coordinates of the local position of the echo are thus geographical coordinates that indicate a fixed point on the Earth's surface in the area surrounding the vehicle. Information from the vehicle's odometry system can be used to determine these stationary coordinates. Using this odometry information, it is possible to convert position information that refers to the vehicle and thus moves with the vehicle into stationary position information or coordinates.

[0022] According to a further embodiment, the neighborhood area is defined by a circle with a predetermined radius around the local position where the reflection generating the echo occurred. This allows a neighborhood rule to be provided in a geometrically simple manner, based on which it can be determined whether or which echoes are in a neighborhood relationship with the respective currently received echo.

[0023] According to the invention, the proximity indicator is incremented by a variable value for each neighboring echo located in the vicinity of a received echo. The variable value depends on the distance of the received echo from the respective neighboring echo and / or the amplitude of the echo. This makes it possible to weight the neighborhood relationship, for example, to assign a higher weight to neighboring echoes that are closer to the currently received echo.

[0024] According to a further aspect, the invention relates to a system for detecting parking spaces, comprising at least one ultrasonic sensor and a computing unit configured to evaluate the information provided by the ultrasonic sensor. The system is configured to perform the following steps: a) Creating a detection list in a storage unit, wherein the detection list for received echoes has a list area for the location where the echo occurred and a list area for a neighborhood indicator, wherein the neighborhood indicator provides information regarding the number of neighboring echoes that occurred in a defined neighborhood area of ​​the echo; b) Emitting an ultrasonic signal by an ultrasonic sensor of the vehicle; c) Receiving an echo in the form of a reflected signal component of the ultrasonic signal by the ultrasonic sensor; d) Determining the azimuth angle from which the echo was received; e) Determining the local position at which the reflection generating the echo occurred, based on the propagation time of the ultrasonic signal between the emission of the ultrasonic signal and the reception of the echo and the azimuth angle;f) modifying the detection list by: determining the neighboring echoes of the received echo contained in the detection list based on a neighborhood rule; for each detected neighboring echo, increasing the neighborhood indicator of the respective detected neighboring echo by an incremental value; adding an entry relating to the received echo to the detection list, wherein the entry contains information relating to the local position at which the reflection generating the echo occurred and has a neighborhood indicator, wherein the neighborhood indicator has a value corresponding to the number of neighboring echoes detected based on the neighborhood rule; g) comparing the values ​​of the neighborhood indicators of the detection list with a threshold value and performing parking space detection based on those echoes whose neighborhood indicator is greater than the threshold value.

[0025] According to one embodiment of the system, the computing unit is configured to determine the azimuth angle based on the radial velocity of the vehicle relative to an object at which the reflection generating the echo occurs. The difference between the radial velocity of the vehicle in the direction of the object (radial in relation to the circular propagation of the ultrasonic signal emanating from the ultrasonic sensor) and the vehicle speed in the direction of movement of the vehicle is a measure of the azimuth angle, which extends between the line connecting the ultrasonic sensor and the reflecting object and a line running parallel to the direction of movement of the vehicle. The azimuth angle can thus be inferred from the radial velocity.

[0026] According to one embodiment of the system, the computing unit is configured to determine the radial velocity of the vehicle based on the frequency change of the received echo due to the Doppler effect. The Doppler frequency change is a measure of the radial velocity of the vehicle relative to the reflecting object. The greater the radial velocity, the greater the frequency change.

[0027] According to one embodiment of the system, the computing unit is configured to determine the radial velocity of the vehicle by tracking multiple echoes over time. This tracking of the echoes can be performed, for example, using a Kalman filter. The temporal change in the location of the reflection relative to the vehicle position allows a conclusion to be drawn about the radial velocity.

[0028] According to one embodiment of the system, the computing unit is configured to specify the local position at which the reflection generating the echo occurred using coordinates that refer to a stationary position that does not move with the vehicle. The coordinates of the local position of the echo are thus geographical coordinates that indicate a fixed point on the Earth's surface in the area surrounding the vehicle. Information from the vehicle's odometry system can be used to determine these stationary coordinates. Using this odometry information, it is possible to convert position information that refers to the vehicle and is therefore position information that moves with the vehicle into stationary position information or coordinates.

[0029] According to one embodiment of the system, the computing unit is configured to increase the proximity indicator by a variable value for each neighboring echo located in the neighborhood of a received echo. The variable value depends on the distance of the received echo from the respective neighboring echo and / or the amplitude of the echo. Increasing the value by a variable value allows for weighting of the neighborhood relationship, for example, assigning a higher weight to neighboring echoes that are closer to the currently received echo.

[0030] According to yet another aspect, the invention relates to a vehicle with a system for detecting parking spaces according to one of the previously described embodiments.

[0031] The terms "approximately", "substantially" or "about" mean, in the sense of the invention, deviations from the exact value by + / - 10%, preferably by + / - 5% and / or deviations in the form of changes that are insignificant for the function.

[0032] Further developments, advantages and possible applications of the invention will also become apparent from the following description of embodiments and from the figures.

[0033] The invention is explained in more detail below with reference to exemplary embodiments and the figures. They show: Fig. 1 shows an exemplary and schematic representation of a vehicle with several ultrasonic sensors when driving past a parallel parking situation; Fig. 2 shows an exemplary representation of a plurality of received, non-filtered ultrasonic echoes in the surrounding area of ​​a vehicle, wherein the echoes are plotted in a two-dimensional map according to their position; Fig. 3 shows an exemplary representation analogous to Fig. 2, wherein the ultrasonic echoes were subjected to filtering based on neighborhood relationships; Fig. 4 shows an example of a flowchart of a method for filtering ultrasonic echoes based on neighborhood relationships; Fig. 5 shows an example of a representation of received echoes and a neighborhood rule (represented by the dashed circle) by means of which some of the echoes can be classified as neighboring echoes; and Fig. 6 shows an example of a flowchart illustrating the steps of a method for detecting parking spaces in the surrounding area of ​​the vehicle.

[0034] Figure 1shows an example of a parking situation in which, as indicated by the direction arrow, a vehicle 1 is driving past several parallel parking spaces. A parking space located between two vehicles is free. It is understood that the present invention is not limited to parallel parking situations, but can also be applied to perpendicular parking situations.

[0035] The vehicle 1 has a plurality of ultrasonic sensors 2, by means of which environmental information can be acquired. In the illustrated embodiment, two ultrasonic sensors 2 are shown. It is understood that more than two ultrasonic sensors can be provided on the vehicle 1. In particular, the ultrasonic sensors 2 can be arranged such that environmental information in front of and behind the vehicle 1 and to both sides of the vehicle 1 can be determined. In particular, the ultrasonic sensors 2 are designed to emit an ultrasonic signal in a transmission cycle and, in a subsequent reception cycle, to receive signal components of the ultrasonic signal that have been reflected by objects in the vicinity of the vehicle 1. The time interval between the emission of the ultrasonic signal and the reception of the reflected signal component is a measure of the distance of the object from the ultrasonic sensor 2.This allows information about objects in the surrounding area of ​​vehicle 1 to be determined.

[0036] In addition to the distance, the information provided by the ultrasonic sensors 2 can also be used to determine the azimuth angle of an echo, ie the angle at which the reflection leading to the received echo occurs.

[0037] The azimuth angle can be determined, for example, based on the radial velocity of the vehicle relative to the object at which the reflection of the ultrasonic signal occurs. The radial velocity can be determined, for example, based on the Doppler frequency shift of the ultrasonic signal. For example, the ultrasonic sensor 2 can provide information regarding the Doppler frequency shift. Alternatively, the radial velocity can be calculated by tracking ultrasonic echoes over a certain period of time. The tracking of ultrasonic echoes can be performed, for example, using a Kalman filter.

[0038] The azimuth angle can be calculated, for example, as follows: α = cos − 1 V r V s where: α: azimuth angle; vr: radial velocity; vs: sensor velocity / vehicle velocity.

[0039] The vector of the radial velocity vr is directed with a vector component in the direction of the vector of the sensor speed or vehicle speed vs, so that the angle extends between the vehicle's longitudinal axis and the object at which the reflection occurs and opens towards the front of the vehicle.

[0040] If the Doppler frequency shift is provided by the sensor, the radial velocity vr can be calculated as follows: v r = c ∗ f D f 0 where: c: propagation velocity of the ultrasonic signal; fd : Doppler frequency; f 0 : carrier frequency of the ultrasonic signal.

[0041] Based on the azimuth angle and the distance of the reflection point from ultrasonic sensor 2, the xy coordinate at which the reflection occurred can be determined with the aid of information from the vehicle odometry system. The xy coordinates are, in particular, fixed, stationary location coordinates that do not move with the vehicle.

[0042] Figure 2 shows an xy diagram of the surrounding area of ​​the vehicle, in which detections determined by the ultrasonic sensors 2 of the vehicle 1 are entered using the individual points. The respective xy coordinates refer to fixed, stationary location coordinates that do not move with the vehicle.

[0043] As in Fig. 2As can be seen, the image contains a large number of false-positive echoes, i.e., those caused by noise or false detections. These false-positive echoes are particularly characterized by the fact that they are located in locations with fewer or no other echoes nearby (so-called "outliers").

[0044] Fig. 3 however, shows an xy diagram of the surrounding area of ​​vehicle 1 analogous to Fig. 2 , whereby a filtering was carried out which leads to a significant reduction in the number of false positive echoes and thus the contours of the objects on which the reflections occurred can be seen more clearly.

[0045] The method for filtering the echoes in order to reduce the number of false positive echoes is described in more detail below using an exemplary embodiment.

[0046] Fig. 4shows an example flowchart of a filter algorithm. The filter algorithm is described below based on the flowchart.

[0047] After starting the algorithm, a detection list is first initialized and a threshold is set. The detection list is preferably configured to include entries for the coordinates at which a reflection generating the echo occurred, as well as an entry for a neighborhood indicator (NI).

[0048] An ultrasonic echo is then received (S10). The ultrasonic echo results from an emitted ultrasonic signal being reflected by an object, thereby sending a signal component back toward ultrasonic sensor 2.

[0049] The coordinates of the reflection location of the ultrasonic echo are then calculated (S11). These coordinates are preferably two-dimensional coordinates that refer to a horizontal plane in which the vehicle is moving. In other words, the coordinates indicate a position in the horizontal longitudinal and transverse directions, but not in the vertical direction. The coordinates are calculated, for example, based on the radial velocity vr, which is determined, for example, as described above, by determining the azimuth angle between the line connecting the ultrasonic sensor and the reflection location and the vehicle's direction of movement. The azimuth angle is an angle that opens towards the front of the vehicle or in the direction of movement of vehicle 1.

[0050] Alternatively, three-dimensional coordinates of the reflection location are calculated, meaning the method can be applied not only in two-dimensional but also in three-dimensional space. Additional information can also be recorded that allows conclusions to be drawn about the reflection location, such as amplitude, Doppler frequency, etc.

[0051] After calculating the reflection location, the neighboring echoes (NE) of the received ultrasonic echo are determined (S12). Neighboring echoes (NE) are, for example, those echoes that satisfy a specific neighborhood rule with respect to the currently received ultrasonic echo. The neighborhood rule specifies, for example, the area within which an echo must lie to be considered a neighboring echo (NE).

[0052] Fig. 5For example, illustrates a neighborhood rule using a circle with a predefined radius, at the center of which is a recently received and located ultrasonic echo. The circle defines that the neighboring echoes NE1 and NE2 satisfy the neighborhood rule, meaning that the neighboring echoes NE1 and NE2 lie within the circle. Echoes E3 and E4, however, do not satisfy the neighborhood rule and are therefore not considered neighboring echoes.

[0053] It goes without saying that Figure 5merely illustrates one embodiment. As previously described, different neighborhood rules can be used to define neighboring echoes. For example, a different neighborhood rule can define an elliptical region that is used to determine neighboring echoes. The definition of the neighborhood rule can be determined depending on the ultrasonic sensor used and its specific properties.

[0054] After all neighboring echoes to the currently received echo have been determined, the neighborhood indicator NI is increased by an incremental value for each detected neighboring echo, for example, in a loop (S13). According to the invention, the incremental value is a variable value that depends on the distance between the currently received echo and the neighboring echo NE and / or on the signal strength of the received echo.

[0055] Subsequently, for each neighboring echo NE, it is checked whether its neighborhood indicator NI has exceeded the threshold SW (S14).

[0056] If the neighborhood indicator NI of the respective neighboring echo NE exceeds the threshold SW, the neighboring echo NE is output and, for example, written into a final detection list (S15).

[0057] After increasing the neighborhood indicators NI of the neighboring echoes NE, the neighborhood indicator NI of the received ultrasonic echo (i.e., the ultrasonic echo that triggered the routine) is set (S16).

[0058] Subsequently, it is checked whether the set neighborhood indicator NI is greater than the threshold SW (S17). If the neighborhood indicator NI exceeds the threshold SW, the echo is output and, for example, written to a final detection list (S18).

[0059] Regardless of whether the proximity indicator NI exceeds the threshold SW or not, the received ultrasonic echo (i.e., the ultrasonic echo that triggered the routine) is added to the detection list (S19). This allows this echo to subsequently be checked for its proximity relationship to a newly received echo.

[0060] Parking space detection can then be performed based on the final detection list, which only contains echoes filtered according to the neighborhood relationships.

[0061] The algorithm described above is preferably executed iteratively after each reception of a reflected ultrasonic signal. Received signals from multiple ultrasonic sensors 2 can be used to populate the detection list and / or the final detection list. It is also possible for cross-echoes between multiple ultrasonic sensors 2 to be used to populate the detection list and / or the final detection list. This means that a reflected signal component of an ultrasonic signal received by an ultrasonic sensor other than the transmitting ultrasonic sensor is also used to populate the detection list and / or the final detection list.

[0062] Fig. 6 shows a schematic representation of the steps of a method according to the invention for detecting parking spaces by means of at least one ultrasonic sensor 2 of a vehicle 1.

[0063] First, a detection list is created or initialized (S20). This detection list can contain entries related to echoes, such as coordinates of the echo origin (location of the reflection that causes the echo), a proximity indicator, etc. Subsequently, an ultrasonic signal is emitted by an ultrasonic sensor 2 of vehicle 1 (S21).

[0064] A reflected signal component of the ultrasonic signal (ie, ultrasonic echo) is then received by the ultrasonic sensor 2 (S22). The receiving ultrasonic sensor may be the same as or different from the transmitting ultrasonic sensor 2.

[0065] After receiving the reflected signal portion of the ultrasonic signal, the azimuth angle from which the ultrasonic echo is received is determined (S23).

[0066] Based on this azimuth angle, the local position at which the reflection occurred is calculated using the distance between the sensor and the location of the reflection of the ultrasonic signal (determined by the propagation time of the ultrasonic signal between transmission and reception) (S24).

[0067] The detection list is then modified (S25). The neighboring echoes NE of the received echo contained in the detection list are determined based on a neighborhood rule. Subsequently, for each detected neighboring echo, the neighborhood indicator NI of the respective detected neighboring echo NE is increased by an incremental value.

[0068] Then, an entry relating to the received echo is added to the detection list, the entry containing information relating to the local position at which the reflection generating the echo occurred and having a proximity indicator, the proximity indicator NI having a value corresponding to the number of neighboring echoes detected based on the proximity rule.

[0069] Finally, the values ​​of the neighborhood indicators of the detection list are compared with a threshold and parking space detection is performed based on those echoes whose neighborhood indicator is greater than the threshold (S26).

[0070] The above-described steps of transmitting the ultrasonic signal (S21), receiving the echo of the ultrasonic signal (S22), determining the azimuth angle of the echo (S23), determining the local position of the echo (S24), modifying the detection list (S25) and comparing the neighborhood indicators of the detection list with a threshold value can preferably be repeated several times in order to generate a plurality of entries in the detection list, based on which a reliable parking space detection is possible. List of reference symbols

[0071] 1Vehicle 2Ultrasonic sensor αAzimuth angle NENeighbor echo NINeighborhood indicator SWThreshold

Claims

1. Method for identifying parking spaces by means of at least one ultrasonic sensor (2) of a vehicle (1), comprising the following steps: a) creation of a detection list in a memory unit, wherein the detection list for received echoes in each case has a list region for the location at which the echo has occurred and a list region for an adjacency indicator (NI), wherein the adjacency indicator (NI) provides (S20) information regarding the number of adjacent echoes (NE) that have occurred in a defined adjacent region of the echo; b) emission of an ultrasonic signal by the ultrasonic sensor (2) of the vehicle (1) (S21); c) reception of an echo in the form of a reflected signal component of the ultrasonic signal by the ultrasonic sensor (2) (S22); d) determination of the azimuth angle from which the echo was received (S23); e) determination of the local position at which the reflection that generates the echo took place, based on the propagation time of the ultrasonic signal between the emission of the ultrasonic signal and the reception of the echo and the azimuth angle (S24); f) modification of the detection list (S25) by:

1. determination of the adjacent echoes (NE) of the received echo contained in the detection list based on an adjacency rule; 2. for each detected adjacent echo (NE), increasing of the adjacency indicator (NI) of the respective identified adjacent echo (NE) by an incremental value, with the adjacency indicator (NI) being increased by a variable value for each adjacent echo (NE) located in the adjacent region of a received echo, wherein the variable value depends on the distance between the received echo and the corresponding adjacent echo and / or on the amplitude of the echo; 3. adding an entry regarding the received echo to the detection list, where the entry contains information regarding the local position at which the reflection that generates the echo took place and has an adjacency indicator, wherein the adjacency indicator (NI) has a value equal to the number of adjacent echoes identified by the adjacency rule; g) comparison of the values of the adjacency indicators in the detection list with a threshold value and performance of parking gap identification based on those echoes whose adjacency indicator is greater than the threshold value (S26).

2. Method according to Claim 1, characterized in that the azimuth angle is determined based on the radial velocity of the vehicle (1) relative to an object at which the reflection occurs.

3. Method according to Claim 2, characterized in that the radial velocity of the vehicle (1) is ascertained based on the change in frequency of the received echo due to the Doppler effect.

4. Method according to Claim 2, characterized in that the radial velocity of the vehicle (1) is ascertained by chronologically tracking multiple echoes.

5. Method according to any one of the preceding claims, characterized in that the local position at which the reflection that the echo generates took place is indicated by coordinates that refer to a stationary position that is not moved together with the vehicle (1).

6. Method according to any one of the preceding claims, characterized in that the adjacent region is defined by a circle having a predetermined radius around the local position at which the reflection that the echo generates took place.

7. System for identifying parking spaces, comprising at least one ultrasonic sensor (2), a computation unit and a memory unit that is configured to evaluate the information provided by the ultrasonic sensor (2), wherein the system is configured to execute the following steps: a) creation of a detection list in a memory unit, wherein the detection list for received echoes in each case has a list region for the location at which the echo has occurred and a list region for an adjacency indicator (NI), wherein the adjacency indicator (NI) provides (S20) information regarding the number of adjacent echoes (NE) that have occurred in a defined adjacent region of the echo; b) emission of an ultrasonic signal by an ultrasonic sensor (2) of the vehicle (1) (S21); c) reception of an echo in the form of a reflected signal component of the ultrasonic signal by the ultrasonic sensor (2) (S22); d) determination of the azimuth angle from which the echo was received (S23); e) determination of the local position at which the reflection that generates the echo took place, based on the propagation time of the ultrasonic signal between the emission of the ultrasonic signal and the reception of the echo and the azimuth angle (S24); f) modification of the detection list (S25) by:

1. determination of the adjacent echoes (NE) of the received echo contained in the detection list based on an adjacency rule; 2. for each detected adjacent echo (NE), increasing of the adjacency indicator (NI) of the respective identified adjacent echo (NE) by an incremental value, with the adjacency indicator (NI) being increased by a variable value for each adjacent echo (NE) located in the adjacent region of a received echo, wherein the variable value depends on the distance between the received echo and the corresponding adjacent echo and / or on the amplitude of the echo; 3. adding an entry regarding the received echo to the detection list, where the entry contains information regarding the local position at which the reflection that generates the echo took place and has an adjacency indicator (NI), wherein the adjacency indicator (NI) has a value equal to the number of adjacent echoes (NE) identified by the adjacency rule; g) comparison of the values of the adjacency indicators (NI) in the detection list with a threshold value (SW) and performance of parking gap identification based on those echoes whose adjacency indicator (NI) is greater than the threshold value (SW) (S26).

8. System according to Claim 7, characterized in that the computation unit is designed to determine the azimuth angle based on the radial velocity of the vehicle (1) relative to an object at which the reflection that generates the echo occurs.

9. System according to Claim 7 or 8, characterized in that the computation unit is designed to ascertain the radial velocity of the vehicle (1) based on the change in frequency of the received echo due to the Doppler effect.

10. System according to Claim 7 or 8, characterized in that the computation unit is designed to ascertain the radial velocity of the vehicle (1) by chronologically tracking multiple echoes.

11. System according to any one of Claims 7-10, characterized in that the computation unit is designed to use coordinates that refer to a stationary position that is not moved together with the vehicle (1) to indicate the local position at which the reflection that the echo generates has taken place.

12. Vehicle comprising a system according to any one of Claims 7-11.