Method for parking a vehicle in a perpendicular parking space with recognition of the orientation of the adjacent vehicle using a test sticker, as well as parking assistance system

Abstract

Method for parking a vehicle (1) in a first transverse parking space (2), in which a further vehicle (5, 6) is parked in at least one second transverse parking space (3, 4) which is adjacent to the first transverse parking space (2), wherein the position and / or orientation of the further vehicle (5, 6) in the second transverse parking space (3, 4) is determined and, depending thereon, the target position and / or target orientation of the vehicle (1) in the first transverse parking space (2) is determined, wherein at least one image (9) of the at least one further vehicle (5, 6) is generated by an optical detection unit (7) of the vehicle (1) before the vehicle (1) is parked in the first transverse parking space (2), and the image (9) is evaluated to determine whether the image (9) contains an official license plate (10, 11) of the further vehicle (5, 6), wherein an existing official license plate (10, 11) is detected with regard to at least a characteristic feature is evaluated and, depending on this, is recognized,whether it is a front-side license plate or a rear-side license plate and, depending thereon, at least the orientation of the further vehicle (5, 6) in the second transverse parking space (3, 4) is determined, characterized in that, if at least two license plates (10, 11) are present in the image (9), vehicle coordinates of the vehicle (1) and / or of the at least one further vehicle (5, 6) and / or intrinsic and / or extrinsic parameters of the optical detection unit (7) are taken into account and, depending thereon, it is recognized which license plate (10, 11) belongs to the further vehicle (5, 6) that is parked in the immediately adjacent second transverse parking space (3, 4).

Description

One aspect of the invention relates to a method for parking a vehicle in a first perpendicular parking space. In at least one second perpendicular parking space adjoining the first perpendicular parking space, a further vehicle is parked. The position and / or the orientation of the further vehicle in the second perpendicular parking space is determined. Depending on this, the target position and / or the target orientation of the vehicle in the first perpendicular parking space is determined. A further aspect of the invention relates to a parking assistance system for a vehicle.GB 2496905 A discloses a method for parking a vehicle in a transverse parking space. Adjacently parked vehicles can be detected and recognized on the basis of specific features, how they are parked there. Depending on this information, the parking situation of the vehicle to be parked can be judged.DE 10 2010 033 212 A1 discloses a method and a device for determining a distance of a vehicle from an adjacent vehicle during a current traffic flow.Furthermore, DE 10 2012 212 091 A1 discloses a system and a method for improving image recognition. Furthermore, DE 103 24 895 A1 discloses a method and a device for object locating for motor vehicles.Methods as mentioned above are known from the prior art. For example, DE 10 2011 077 173 A1 describes a method for determining a parking trajectory. The vehicle to be parked can be brought into the transverse parking space to be parked depending on an orientation and / or a position of vehicles which are parked in adjacent transverse parking spaces. In this case, an off-center parking position in the transverse parking space can be assumed. The orientation of the vehicle to be parked in the perpendicular parking space and thus whether the vehicle is to be parked forwards or backwards in the perpendicular parking space can also be effected depending on the position and / or orientation of the adjacently parked vehicles.Furthermore, DE 10 2014 210 043 A1 discloses a method for carrying out a parking process of a vehicle into a transverse parking space. There too, depending on the position and / or the orientation of adjacently parked vehicles, an advantageous position and / or orientation of the vehicle to be parked in the transverse parking space can be determined. To determine the orientation of the adjacently parked vehicles, a steering wheel of the other parked vehicles may be determined with respect to its position and detected depending on whether the adjacently parked vehicle is parked forward or backward.In this prior art, therefore, it is stated concretely on the basis of which information the orientation of the adjacently parked vehicles is to be determined. However, these components, as provided by a steering wheel, are relatively concealed and therefore can only be detected with difficulty. Moreover, they are arranged inside the motor vehicle and therefore they can be detected from the outside only for this reason with difficulty. The orientation of the vehicles parked in adjacent perpendicular parking spaces is therefore insufficiently possible in the prior art.It is the object of the present invention to provide a method in which adjacent vehicles can be detected in an improved manner in a parking process of a vehicle into a transverse parking space to be carried out. It is likewise an object to provide a parking assistance system for a vehicle.This object is achieved by a method and a parking assist system according to the independent claims.One aspect of the invention relates to a method for parking a vehicle in a first perpendicular parking space. In at least one second perpendicular parking space directly adjoining the first perpendicular parking space, a further vehicle is parked. The position and / or orientation of the further vehicle in the second perpendicular parking space is determined. Depending on this, the target position to be reached and / or the target orientation to be reached of the vehicle in the first perpendicular parking space into which the vehicle is to be parked is determined, in particular before the parking in the first perpendicular parking space. By means of an optical detection unit of the vehicle, at least one image of the further vehicle is generated before the vehicle is parked in the first perpendicular parking space. The image is evaluated to determine whether an official license plate of the further vehicle is contained on the image. An existing official license plate or license plate is evaluated with regard to characteristic features. Depending on this, it is recognized whether the official license plate is a front-side official license plate or a rear-side official license plate. Depending on this, at least the orientation of the further vehicle in the second perpendicular parking space is determined. This means that when a license plate at the front is recognized on the image, it is recognized that the further vehicle has been parked backward into the second perpendicular parking space. If a rear-end official license plate of this further vehicle is detected, it is detected that this further vehicle has been parked forward into the second perpendicular parking space. Since the detection of the further vehicle takes place before the vehicle is parked in the first perpendicular parking space, this generation of the at least one image is carried out outside the first perpendicular parking space. This image recording is therefore also carried out in particular when the vehicle is located on the roadway which adjoins the perpendicular parking spaces. As a result, recording of the at least one further vehicle in the image can take place in an advantageous manner. The evaluation with regard to the official license plate with at least one characteristic feature is therefore made possible in a very advantageous manner.By virtue of such a configuration, it is made possible more quickly and more precisely to capture the further vehicle, with regard to its orientation in the second perpendicular parking space. Characteristic components of this further vehicle are evaluated in the context. These characteristic components are those which are arranged on the outside of the further vehicle. These components are therefore easier and more clear to identify. This makes it possible to achieve an improved and more accurate determination of the orientation of the further vehicle in the second perpendicular parking space. In addition, it is precisely these specific external characteristic features of an external official license plate that are particularly preferred to determine an orientation of the further vehicle. Since, for example, a steering wheel, as evaluated in the prior art, can also be covered on the periphery by a dashboard or the like, detection is difficult in this respect. In addition, a steering wheel can also be at a plurality of positions, for example in the case of a left-hand-controlled or a right-hand-controlled vehicle. A clear determination of the orientation of the vehicle on the basis of the steering wheel is therefore not possible in the prior art.The official license plate is preferably evaluated with regard to the presence of an applied test badge for a main examination of the further vehicle as a characteristic feature for the further vehicle. In the presence of such a test badge, the official license plate is recognized as a rear-side official license plate. Since such a test badge is present in many countries and is attached as prescribed only to an official license plate, namely the rear official license plate, such a recognition of a test badge in the image is a unique criterion in order to be able to decide which of the two official license plates was detected on the image. This also allows a clear decision to be made as to whether the further vehicle has parked in the reverse or forward direction. In this context, a test plate string is in particular also a characteristic feature which is arranged unambiguously with respect to its configuration and position. This is a characteristic feature that is present only once, so that it can also be sought and optionally recognized in a very targeted manner. In addition, such a test plate string also has a size and / or shape which advantageously enables a corresponding detection and search. In particular, confusion with other symbols on the official license plate is minimal in this respect.Preferably, a search field is generated locally in the image in the official license plate, in which search field a characteristic feature is sought which, in the event of a presence, must be applied as prescribed in this zone of the official license plate. Thus, if an official license plate is basically recognized in the image, characteristic features are sought only in a specific reduced area or in a specific zone of this official license plate. In particular, if this characteristic feature is a test plate string, this zone is arranged in a very specific area of the official license plate. It is therefore advantageous if in this respect a search field is generated in this zone of the official license plate in which the test tag can only be. The search effort and the evaluation effort for the image evaluation are thus significantly reduced. Moreover, the accuracy of the evaluation is increased.In an advantageous embodiment, it is provided that the characteristic feature is recognized as not present if the search field has a surface region having essentially only one color in a region between two characterizing symbols, which surface region has a height greater than or equal to one third of the height of the official license plate. This is advantageous in particular if the characteristic feature is a test tag which is sought after. Since the test plate string, in particular in the case of specific official country licenses in which letters and numbers are used, is arranged in a quite specific surface area or a zone if it is not arranged there, otherwise no further symbol or emblem or the like is attached thereto, it is possible to distinguish very unambiguously whether only a color area which is homogeneous in this respect is present or the test plate string is present in this zone. Since this surface region has a certain size, in particular a certain height, it is also possible in this context to identify simply not only on the basis of the coloring but also with respect to the size whether or not the test plate chain is present in this surface region. This in turn makes it possible to identify very easily and nevertheless highly accurately whether the official license plate is a rear-side official license plate or a front-side official license plate. For example, in the case of official license plates in Germany, it is the case that the test plate chain is arranged in a surface region which is formed between the letter identifier, which defines the respective country circle or city and is then separated therefrom, and in particular by a hyphen, and an at least further letter. In particular, this surface region is formed above this hyphen between the at least one letter in each case.Preferably, it is provided that a characteristic, end-side pointer field of the date label is sought in the image and the search field is generated in the width direction of the date label subsequent to the characteristic pointer field. This characteristic field of information can be, for example, an EU country map. This is usually colored blue and extends over the entire height of the official license plate. Since no test plate chain can be arranged or allowed to be arranged in this area of the official license plate, the search in this area can be ignored. Since it is also known that a possible test plate chain must be in a surface area adjacent thereto, if it is present, the position and also the size of this search field can be formed precisely in the official license plate. This also allows the search for the test plate string to be carried out more quickly and nevertheless also more precisely. The search effort is thus likewise reduced.In particular, this end pointer field is, as already explained above, an EU (European Union) pointer field.Preferably, a recorded image is equalized and the license plate is searched for in the equalized image. Such equalization may be advantageous in at least some situations. For example, if the detection of the further vehicle takes place at a very oblique angle. By such an equalization, the detection evaluation can be improved, in particular more accurately, with regard to the presence of a characteristic feature.If at least two official indicators are present in the image, vehicle coordinates of the vehicle and / or vehicle coordinates of further vehicles and / or intrinsic parameters of the optical detection unit and / or extrinsic parameters of the optical detection unit are taken into account. Depending on at least one of these characteristic variables, it is detected which official license plate is associated with that further vehicle which is parked in the second perpendicular parking space. The further detected official identifiers are then sorted out and not evaluated in more detail. By means of such a configuration, it is possible, in the case of a plurality of recorded official characteristics in the image, to first unambiguously decide which of the official characteristics is of interest at all and which has to be taken into account with regard to an analysis of a characteristic feature. As a result, misinterpretations can be reduced. In particular, a background color of the area of the official license plate is evaluated as a characteristic feature of the official license plate. In addition or instead, letters and / or numbers and / or symbols on the official license plate are evaluated as a characteristic feature. Depending on at least one of the aforementioned criteria, it can be recognized whether the official license plate is a front-side or rear-side official license plate.It is also known that in specific countries the coloring and / or the geometry and / or the area size of a front official license plate is different from a rear official license plate.Since different official characteristics are given in different countries, this aspect can also be taken into account. In an advantageous embodiment, it is provided that in a first step, the official license plate that was recorded in the image is evaluated to which country or which state it is associated. Depending on characteristic data which are known about an official license plate in this state or country, an individual search can then be made for a characteristic feature of an official license plate of such a state. These identifiers can be stored, for example, in a control unit of the parking assistance system. However, these can also be interrogated externally by a database, for example. It is thus also possible that a characteristic feature is present in particular only in a state-specific manner and that such a state-specific characteristic feature of an official license plate is sought if it is known to which state the official license plate which was detected in the image belongs. By such a procedure, an analysis can be performed even more accurately.A further aspect of the invention relates to an electronic parking assistance system for a vehicle for parking the vehicle in a perpendicular parking space. The parking assistance system has at least one detection unit and at least one evaluation unit or control unit. The parking assistance system is designed to carry out a method according to the above-mentioned aspect and an advantageous configuration thereof. In particular, the method is carried out using the parking assistance system.The invention also includes the combinations of the features of the described embodiments.Exemplary embodiments of the invention are described below. The following shows: FIG. 1 shows a simplified top view of a first parking situation; FIG. 2 shows a simplified top view of a second parking situation; FIG. 3 shows a simplified top view of a third parking situation; FIG. 4 shows a simplified top view of a fourth parking situation; FIG. 5 shows a perspective illustration for determining an orientation of a further vehicle which is parked in a parking space adjacent to that parking space into which a vehicle is to be parked; and FIG. 6 is an enlarged view of the official license plate in FIG. 5.The exemplary embodiment explained below is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual features of the invention that are to be considered independently of one another and that develop the invention in each case also independently of one another and are therefore also to be considered as part of the invention individually or in a combination other than the combination shown. Furthermore, the described embodiment can also be supplemented by further features of the invention that have already been described.In the figures, identical or functionally identical elements are provided with the same reference numerals.FIG. 1 shows a plan view of a parking scenario in which a vehicle 1 has already been parked in a specific target position and / or a specific target orientation in the perpendicular parking space 2. Adjacent to this transverse parking space 2, a first further transverse parking space 3 is formed and opposite a second further transverse parking space 4. Another vehicle 5 is parked in the first further perpendicular parking space 3. The further vehicle 5 is parked forward here. This means that a rear end 5 afaces a roadway 6 which opens out at the transverse parking spaces 2, 3, 4. A front 5 bof the further vehicle 5 faces away from this roadway 6. In the scenario shown in FIG. 1, a further vehicle 6 is parked in the second further perpendicular parking space 4. This further vehicle 6 is also parked forward in this second further transverse parking space 4.With regard to advantageous getting out, in particular of a driver, the vehicle 1 has been parked in reverse in the perpendicular parking space 2 in the exemplary embodiment shown. In addition, the vehicle 1 has been positioned on the outside in the middle of a central longitudinal axis M of the transverse parking space 2. In particular, this vehicle 1 is positioned in this outwardly central position closer to that further transverse parking space 3 which is facing a passenger door of the vehicle 1. This makes it possible for at least one driver to find a larger exit area in his perpendicular parking space 2 via the driver door of the vehicle 1.In this constellation, the vehicle 1 has been parked in the opposite orientation to the further vehicles 5 and 6 that have already been parked beforehand. Moreover, this orientation makes it possible for all three drivers of the vehicles 1, 5 and 6 to keep the largest possible boarding area ready via the respective driver door. The vehicle 1 was parked in the first transverse parking space 2 at a point in time at which the further vehicles 5 and / or 6 had already been parked in the further second transverse parking space 3, 4.The same applies to the parking scenario according to FIG. 2 This simplified plan view also shows a constellation in which, in contrast to FIG. 1, the two further vehicles 5 and 6 are each parked backwards in the further transverse parking spaces 3 and 4. In this configuration, it is advantageous if the vehicle 1 to be parked subsequently in this regard has been parked forwards into the transverse parking space 2 and likewise has again been parked therein eccentrically with respect to the central longitudinal axis M. In particular, it is advantageous in this configuration if the vehicle 1 is positioned with its passenger door closer to the further transverse parking space 4. Thus, in this case as well, a largest possible exit area is made possible via the driver door of the vehicle 1. Likewise, the largest possible access area for the drivers of the vehicles 1 and 5 is made possible via the respective driver doors. The same then applies to an access for a driver via the driver door of the vehicle 6.If, for example, due to regulations in a transverse parking space, it is only allowed in a specific orientation, namely, for example, only forward, as shown in FIG. 3, or only backward, as shown in FIG. 4, in this respect, a best possible position for the vehicle 1 to be parked can likewise be determined depending on the position and / or the orientation of the vehicles 5 and 6 already parked adjacent. In particular, in these parking scenarios according to FIGS. 3 and 4, it may be provided that vehicle 1 is parked centrally in transverse parking space 2 and assumes the same orientation as neighboring further vehicles 5 and 6.In order to determine an orientation of a further, adjacently parked vehicle 5 and / or 6, it is generally provided in all exemplary embodiments that the environment is detected by a detection unit, in particular an optical detection unit 7. This at least one optical detection unit 7 is in particular a camera. By means of this at least one optical detection unit 7 of the vehicle 1, at least one image 9, in particular a plurality of images, of the at least one further already parked vehicle 5, 6 is generated before the vehicle 1 is parked in the perpendicular parking space 2. The image 9 is evaluated to determine whether an official license plate of this further vehicle 5 and / or 6 can be identified on this image 9.FIG. 5 shows an exemplary image 9 recorded with the optical detection unit 7 of the vehicle 1 before parking in the perpendicular parking space 2. The vehicle 1 is still located on the roadway 6 during this recording of the image 9. The further vehicle 5 is detected in the image 9. In the image 9, a search is first made for the presence of an official license plate. In this connection, it is recognized in the illustration in FIG. 5 that two official identifiers 10 and 11 are contained. The official license plate 11 originates in the context of yet another vehicle, which is parked on the left side of the other vehicle 5 in the plan view according to FIG. 2 and is no longer illustrated in FIG. 2. In particular, in such a situation, it is first judged which of the two official license plates 10 and 11 is associated with that further vehicle 5 which is parked in the further second perpendicular parking space 3 which directly adjoins the first perpendicular parking space 2 to be parked. In particular, this analysis is carried out as a function of vehicle coordinates of the vehicle 1 and / or as a function of vehicle coordinates of the further vehicle 5 and / or as a function of intrinsic and / or extrinsic parameters of the optical detection unit 7. It is thus possible to detect which of the two official license plates 10 or 11 is associated with the further vehicle 5.If only the further vehicle 5 with its official license plate 10 is contained in the image 9, this analysis step is not necessary.In a preceding step, an equalization of the image 9 can be carried out. This equalization can, however, also be carried out, for example, after the step as explained above, if at least two different official identifiers 10 and 11 have been detected in the image 9. By detecting official indicators 9 and 10 in the image, a detector model can be used. This can be stored in a control unit of the parking assistance system. In particular, if a characteristic feature, in particular a test tag for a main examination of the further vehicle 5, is sought in an official license plate, a detector model based on OpenALPR (Automatic License Plate Recognition) can be used.With regard to the detection of which of the official license plates 10 or 11 is assigned to the further vehicle 5, it is also possible, for example, to carry out a localization of a "genuine" license plate center using the position of the optical detection unit 7 and / or of the license plate center with respect to an equalizing projection plane. Radar-based object detection can also be carried out here.The official license plate 10, which is a license plate, is then further evaluated. A characteristic feature is sought in the official license plate 10. The characteristic feature is generally a criterion which uniquely individualizes the tag 10 with respect to its position. Depending on whether this characteristic feature is detected, it can be concluded whether the official license plate 10 is a front-side official license plate or a rear-side official license plate. Depending on this, it can then be detected again whether the further vehicle 1 has been parked forwards or backwards in the further second perpendicular parking space 3.In the present situation shown in FIG. 5, a test tag for a main examination is searched for as a characteristic feature in the official license plate 10. In particular, a characteristic end information field 12 is also sought in this context, as is shown in the enlarged representation of the official license plate 10 in FIG. 6. This end-side information field is in particular an EU identifier field. In the official license plate 10, a search field 13 is generated or formed in which the characteristic feature, in particular the test plate string, is sought. The search field 13 is generated in the width direction of the official license plate 10 following, in particular directly following, the end-side pointer field 12. The search field 13 is generated smaller than the remaining surface area of the official license plate 10 without the end-side pointer field 12. In this regard, the search field 13 also comprises a surface region 13 a(FIG. 6 ) between two characterizing symbols 8, in particular letters. If this surface region 13 ais only of single-color design and has a height greater than or equal to one third of the height of the official license plate 10, it can be concluded that no test badge is attached to this official license plate 10. This is the case in FIGS. 5 and 6. This is because this specific surface area 13 ais only a single-colored surface, in this case in particular a white surface, in the present embodiment.Such a test plate chain, which is arranged, for example, in the case of a German official license plate, between the letter combination which characterizes the country circle and a subsequent letter combination spaced apart therefrom by a hyphen or at least one letter, can be recognized in this respect according to the illustration in FIG. 6. Here, in the example, no element is attached in this specific surface area 13a between the two characterizing symbols. In this case, it can thereby be concluded that this official license plate 10 is a front official license plate. This is because no test badge is present only in the case of front official license plates 10. A test plate string is, for example, attached in accordance with regulations only to the rear-end official license plate in the case of German official license plates. It can thus be detected that the further vehicle 5 has been parked backwards in the further second perpendicular parking space 3 and thus faces the roadway 6 with the front 5 b. In particular, it can be provided that before searching for the characteristic feature in the official license plate 10, it is first analyzed which official license plate 10 is present with regard to a state membership or country membership. Depending on this, it is then possible to search for again state-specific characteristic features in this then state-specific official license plate 10. In this way, further vehicles that are permitted in a wide variety of different states and can therefore have a wide variety of state-specific official license plates can be evaluated. In this context, at least one characteristic feature can also be, for example, an individual coloring of the base area of the official license plate, on which a numerical and / or letter and / or symbol representation is then specified, which characterizes the individual license plate. Other characteristic features, such as, for example, an individual coloring of the letters and / or numbers and / or symbols, can also be evaluated. These exemplary details of characteristic features are not to be understood as exhaustive. Rather, all characteristic features of predetermined or prescribed characteristic features of individual state-specific official characteristics are possible and can be evaluated.In addition or instead, it may be provided that vehicle 1 has at least one radar sensor 14 (FIG. 1 ). This radar sensor 14 is designed with a height measurement function. This radar sensor 14 can be used to determine a transition 15 (FIG. 1 ) between a body region and a roof of the further vehicle 5. Depending on a position of the transition to an end, in particular a front 5 band / or a rear 5 a, it is detected whether this further vehicle 5 is parked in this further perpendicular parking space 3 oriented forwards or backwards.The explanations presented here for the further vehicle 5 apply circumferentially and correspondingly also for the further vehicle 6.In particular, the vehicle 7 has a parking assist system 16. This has in particular at least one detection unit, in particular the optical detection unit 7. The parking assistance system 16 preferably also has at least one evaluation unit 16 a. This can also be a control unit. It may have a memory. In addition, the parking assistance system 16, in particular the evaluation unit 16 a, has a computer program product. This has commands which, when stored on a computer, in particular the evaluation unit 16 a, are designed to carry out the method as has been mentioned.List of reference characters1 Vehicle 2 First Perpendicular Parking Gap 3 Second Perpendicular Parking Gap 4 Second Perpendicular Parking Gap 5 Further Vehicle 6 Further Vehicle 7 Detection unit 8 Symbol 9 Image 10 Official License Plate 11 Official License Plate 12 End-side Indicator field 13 Search field 13 a Surface region 14 Radar sensor 15 Transition 16 Parking assistance system 16 a Evaluation Unit

Claims

Method for parking a vehicle (1) in a first transverse parking space (2), in which a further vehicle (5, 6) is parked in at least one second transverse parking space (3, 4) which adjoins the first transverse parking space (2), wherein the position and / or orientation of the further vehicle (5, 6) in the second transverse parking space (3, 4) is determined and, as a function thereof, the target position and / or target orientation of the vehicle (1) in the first transverse parking space (2) is determined, wherein at least one image (9) of the at least one further vehicle (5, 6) is generated by an optical detection unit (7) of the vehicle (1) before the vehicle (1) is parked in the first transverse parking space (2), and the image (9) is evaluated to determine whether an official license plate (10, 11) of the further vehicle (5, in the image (9), A vehicle parking space in which a present official license plate (10, 11) is evaluated with respect to at least one characteristic feature, and it is detected as a function of whether it is a front official license plate or a rear official license plate, and as a function of which at least the orientation of the further vehicle (5, 6) in the second transverse parking space (3, 4) is determined, characterized in that, in the event of at least two official license plates (10, 11) being present in the image (9), vehicle coordinates of the vehicle (1) and / or of the at least one further vehicle (5, 6) and / or intrinsic and / or extrinsic parameters of the optical detection unit (7) are taken into account and as a function of which official license plate (10, 11) is associated with that further vehicle (5, 6) which is parked in the directly adjacent second transverse parking space (3, 4).Method according to Claim 1, characterized in that the official license plate (10, 11) is evaluated with respect to the presence of an applied test plate chain for a main examination as a characteristic feature for the further vehicle (5, 6), and, in the case of the presence of such a test plate chain, the official license plate (10, 11) is recognized as a rear-side official license plate.Method according to Claim 1 or 2, characterized in that a search field (13) is generated locally in the official license plate (10, 11) in the image (9), in which search field a characteristic feature is sought which, in the event of a presence, must be arranged as prescribed in that zone of the official license plate in which the search field (13) is generated.Method according to Claim 3, characterized in that the characteristic feature is detected as not present if the search field (13) has, in a region between two license plate symbols, a surface region (13a) which has substantially only one colour and has a height greater than or equal to one third of the height of the official license plate (10, 11).Method according to Claim 3 or 4, characterized in that a characteristic end-side information field (12) of the date license plate (10, 11) is sought in the image (9), and the search field (13) is generated in the width direction following the characteristic information field (12).Method according to Claim 5, characterized in that the end-side information field (12) is an EU identification field.Method according to one of the preceding claims, characterized in that a recorded image (9) is equalized and the official license plate (10, 11) is sought in the equalized image.Method according to one of the preceding claims, characterized in that a background colour of the area of the official license plate (10, 11) and / or letters and / or numbers and / or symbols on the official license plate (10, 11) is evaluated as a characteristic feature of the official license plate (10, 11) and is detected as a function of whether the official license plate (10, 11) is a front-side or rear-side official license plate.Parking assistance system (16) for a vehicle (1) for parking in a perpendicular parking space (2), which has at least one detection unit (7) and an evaluation unit (16a), wherein the parking assistance system (16) is designed to carry out a method according to one of the preceding claims.

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