Patent Publication Number: US-2021182581-A1

Title: Method and system for recognizing sign

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a bypass continuation application of currently pending international application No. PCT/JP2019/33315 filed on Aug. 26, 2019 designating the United States of America, the entire disclosure of which is incorporated herein by reference. 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2018-163075 filed on Aug. 31, 2018 and Japanese Patent Application No. 2019-136947 filed on Jul. 25, 2019, the entire disclosure of each of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to methods and systems for recognizing signs. 
     BACKGROUND 
     Vehicles, such as automobiles, have each been recently designed to capture images of a forward view thereof using a vehicular camera installed in the corresponding vehicle, and to use the captured images to for example assist driving of the corresponding vehicle. 
     SUMMARY 
     A sign recognition system according to an exemplary aspect of the present disclosure is configured to, when image data of a sign is captured by a vehicular camera, recognize one or more characters, which are included in the sign and belong to at least one specified character type, from the image data, thus extracting, from the image data, the recognized one or more characters. The sign recognition system is also configured to store a sign dataset in a sign database; the sign dataset includes (i) an installation-position information item indicative of the installation position of the sign, and (ii) an attribute information item about the sign. The attribute information item about the sign includes a string of the one or more characters extracted by the extraction unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The object, other objects, features, and benefits regarding the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings in which: 
         FIG. 1  is a block diagram schematically illustrating an overall configuration of a system according to the first embodiment; 
         FIG. 2  is a flowchart schematically illustrating a procedure of an information-sign dataset registering routine carried out by a control unit and a processing unit according to the first embodiment; 
         FIG. 3A  is a view illustrating a specific first example of an information sign according to the first embodiment; 
         FIG. 3B  is a view illustrating a specific second example of an information sign according to the first embodiment; 
         FIG. 3C  is a view illustrating a specific third example of an information sign according to the first embodiment; 
         FIG. 3D  is a view illustrating a specific fourth example of an information sign according to the first embodiment; 
         FIG. 3E  is a view illustrating a specific fifth example of an information sign according to the first embodiment; 
         FIG. 4  is a diagram schematically illustrating a process of extracting only numerals from captured image data according to the first embodiment; 
         FIG. 5  is a diagram schematically illustrating how to update and register an installation position item about an information-sign dataset according to the first embodiment; 
         FIG. 6  is a block diagram schematically illustrating an overall configuration of a system according to the second embodiment; 
         FIG. 7  is a flowchart schematically illustrating a procedure of an information-sign dataset checking routine carried out by a control unit and a processing unit according to the second embodiment; 
         FIG. 8  is a diagram schematically illustrating how to perform checking according to the first embodiment; 
         FIG. 9  is a block diagram schematically illustrating an overall configuration of a system according to the third embodiment; 
         FIG. 10  is a flowchart schematically illustrating a procedure of an information-sign dataset checking routine carried out by a control unit according to the third embodiment; 
         FIG. 11  is a flowchart schematically illustrating a procedure of an information-sign dataset checking routine carried out by a control unit according to the fourth embodiment; 
         FIG. 12  is a view illustrating a specific example of an information sign according to the fifth embodiment; and 
         FIG. 13  is a diagram schematically illustrating a process of extracting, from captured image data, numerals with positional information according to the sixth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Methods and systems for recognizing signs, which will also be referred to as sign recognition methods and systems, are each capable of capturing an image of a sign, such an information sign for road guidance or a signboard using a vehicular camera installed in a vehicle. Then, these sign recognition methods and systems are each capable of recognizing the sign in accordance with data of the captured image, which will also be referred to as a captured image data item. 
     For example, Japanese Patent Application Publication No. 2010-266383 discloses the following technology. The disclosed technology detects, from a forward image captured by a camera installed in a vehicle, an information sign located in a forward portion of a road. Then, the disclosed technology analyzes data of a portion of the captured forward image; the portion corresponds to the information sign. 
     In accordance with a result of the analysis, the disclosed technology recognizes the string of characters written in the information sign, indicative of, for example, one or more destination names, one or more directions, one or more distances, or an intersection to thereby display simplified presentation of the recognized string of characters on a monitor installed in the camera. 
     The implementation of autonomous driving of vehicles has been gained momentum recently. This has resulted in many requests for creating high-accuracy road map data. From this viewpoint, a road map creating system is known, which (i) captures, for example, forward images from a vehicle using a camera installed in the vehicle while the vehicle is traveling, and (ii) generates, based on captured image data items, i.e. probe data items, a road map 
     In addition, a vehicle position detection system is known, which checks images captured by a camera installed in a vehicle against road map data to thereby detect a position of the vehicle. 
     Information signs over roads have different pieces of information displayed thereon. Information signs are typically installed on or over each principal road at suitable intervals. For these characteristics of information signs, superimposing data of each of the information signs on road map data as a corresponding landmark is expected as an effective measure. 
     Unfortunately, analyzing the whole of each of captured image data items for identifying, i.e. recognizing, many information signs included in the captured image data items may result in an increase in the amount of data that should be analyzed, resulting in an increase in time required for (i) communications of the captured image data items and/or (ii) analyzing of the captured image data items. 
     For this reason, more simple identification and/or recognition of one or more information signs may therefore be needed. 
     From this viewpoint, the present disclosure seeks to provide methods and systems for recognizing signs, each of which is capable of simply performing a task of identifying a sign captured by a vehicular camera as one of sign data items in a database. Note that signs according to the present disclosure include, for example, information signs for road guidance and/or signboards 
     A sign recognition system according to a first aspect of the present disclosure for recognizing a sign in accordance with image data of the sign captured by a vehicular camera installed in a vehicle includes an extraction unit. The extraction unit is configured to recognize, in the image data, one or more characters that are included in the sign and belong to at least one specified character type, and extract, from the image data, the recognized one or more characters. The sign recognition system includes a sign database configured to store a sign dataset. The sign dataset includes (i) an installation-position information item indicative of an installation position of the sign, and an attribute information item about the sign. The attribute information item about the sign includes a string of the one or more characters extracted by the extraction unit. 
     When the image data of the sign is captured by the vehicular camera, the extraction unit recognizes one or more characters, which are included in the sign and belong to at least one specified character type, from the image data, thus extracting, from the image data, the recognized one or more characters. 
     In the sign database, the sign dataset is stored; the sign dataset includes (i) the installation-position information item indicative of the installation position of the sign, and (ii) the attribute information item about the sign. 
     The first aspect uses, as the attribute information item about the sign, information about the string of the one or more characters extracted by the extraction unit for identification of the sign. This therefore drastically lowers the amount of data processed for identification of the sign, resulting in both shorter time of communications of the attribute information item and shorter time required to perform processing, such as image processing, of the attribute information item. The above configuration also limits recognition target characters of the sign to characters belonging to the at least one specified character type. This makes it possible to reduce the size of a dictionary used for recognition of the sign, thus enabling the recognition of the sign to be carried out faster. This results in more simple execution of a task of identifying that the sign captured by the vehicular camera matches which of signs stored in the sign database. 
     The following describes embodiments with reference to the accompanying drawings. Components of each embodiment, which correspond to those of one or more already-described embodiments, are denoted by the same reference characters or numerals, and therefore new or duplicated descriptions of the components of each embodiment may be omitted. 
     In the following descriptions, information signs are signs installed at predetermined respective locations linked to roads by road managers, which serve as at least one of route guidance, destination guidance, and adjunct facility guidance. Each information sign is installed for a corresponding road in accordance with predetermined rules, so that the corresponding information sign has a predetermined shape, at least one predetermined color, and a predetermined size of each character used therein. 
     Additionally, in the following descriptions, signboards are produced for mainly commercial purposes, such as advertising purposes, and installed, for example, at shopfronts and/or along roads in order to show the signboards to people passing through the roads. For example, each signboard is comprised of a board on which the name of at least one commercial facility, the direction to at least one commercial facility, and/or the location of at least one commercial facility, which includes a distance thereto. Signs represent a broader concept of such information signs and signboards. 
     First Embodiment 
     The following describes the first embodiment with reference to  FIGS. 1 to 5 . 
       FIG. 1  schematically illustrates an overall configuration of an information sign recognition system  1  serving as a sign recognition system according to the first embodiment. The information sign recognition system  1  is comprised of a data center  2  and vehicular devices  3 . The data center  2  collects data items and analyzes the collected data items to accordingly generate an information sign database as a high-accuracy sign database. 
     The vehicular devices  3  are installed in respective vehicles including passenger vehicles and/or trucks, which travel on roads.  FIG. 1  schematically illustrates one vehicular device  3  for simple illustration. 
     The vehicular device  3  installed in each vehicle includes a vehicular camera  4 , a position detector  5 , various vehicular sensors  6 , a map data storage unit  7 , a communication unit  8 , a detection data storage unit  9 , an operation display unit  10 , and a control unit  11 . 
     The vehicular camera  4  is mounted to, for example, the front end of the corresponding vehicle, and configured to capture at least a forward road situation of the corresponding vehicle in its traveling direction. 
     The position detector  5  includes a known configuration that is provided with a GPS receiver for receiving position data, and detects the current position of the corresponding vehicle in accordance with the position data received by the GPS receiver. 
     The various vehicular sensors  6  include one or more sensors for measuring speed information indicative of the speed of the corresponding vehicle, and one or more sensors for measuring direction information indicative of the traveling direction, i.e. the direction of the body, of the corresponding vehicle. 
     The map data storage unit  7  stores road map information indicative of a road map across the corresponding nation. The communication unit  8  communicates with the data center  2  using a mobile communication network and/or road-to-vehicle communications. The communication unit  8  serves as both a transmitter  8   a  as a transmitter unit, and a receiver  8   b  as a receiver unit. 
     As described later, in the detection data storage unit  9 , detection data items for respective information signs are stored; each of the detection data items includes an estimated capture-position information item and an obtained attribute information item about a corresponding one of the information signs. 
     The operation display unit  10  includes, for example, unillustrated switches, a touch screen, and a display. The operation display unit  10  enables a user, such as a driver, of the vehicular device  3  to operate the operation display unit  10 , and displays information required for a user, such as navigation frame images. 
     The control unit  11  is configured to include a computer, and operative to control overall operations of the vehicular device  3 . 
     Specifically, the control unit  11  instructs the vehicular camera  4  to capture a forward road situation of the corresponding vehicle while the corresponding vehicle is traveling. Then, the control unit  11  determines whether there is at least one information sign as at least one sign in captured image data. 
     In response to determination that there is at least one information sign as at least one sign in the captured image data, the control unit  11  recognizes, from captured image data of the at least one information sign, each of selected characters included in a character set written in the at least one information sign using a known OCR technology to thereby extract the recognized characters from the captured image data; the selected characters included in the character string belong to at least one specified type of characters, i.e. at least one specified character type. 
     After extraction of the recognized characters of the at least one information sign, the control unit  11  recognizes the string of the extracted characters of the at least one information sign as an attribute information item for identifying the at least one information sign. That is, the control unit  11  serves as an extraction unit. The detailed information about such an attribute information item will be described later. 
     In addition to the extraction, the control unit  11  estimates the position of the at least one information sign where the at least one information sign is placed in accordance with, for example, 
     (i) The position of the corresponding vehicle at the timing of capturing the at least one information sign detected by the position detector  5   
     (ii) The traveling speed of the corresponding vehicle at the timing of capturing the at least one information sign 
     (iii) The traveling direction of the corresponding vehicle at the timing of capturing the at least one information sign 
     Then, the control unit  11  recognizes the estimated position as a capture-position information item, and stores a detection data item in the detection date storage unit  9  while an additional data item, such as captured date and time, is attached to the corresponding detection data item; the detection data item is comprised of (i) the attribute information item about the at least one information sign, and (ii) the capture-position information item about the at least one information sign. 
     The communication unit  8  transmits the detection data items stored in the detection data storage unit  9  to the data center  2 . 
     The data center  2  includes a communication unit  12 , an input operation unit  13 , a processing unit  14 , a detection data storage unit  15 , a road map database  16 , and an information sign database  17  serving as a sign database. The communication unit  12  communicates with the communication unit  8  of each vehicle to thereby receive the detection data items from the corresponding vehicle. The communication unit  12  serves as both a receiver  12   a  as a receiver unit and a transmitter  12   b  as a transmitter unit. The input operation unit  13  enables an operator to perform necessary input operations. 
     The processing unit  14  is mainly comprised of a computer, and is operative to control overall operations of the data center  2 . In addition to the overall control, the processing unit  14  performs, for example, 
     1. A task of generating road map data 
     2. A task of generating information-sign datasets (see  FIG. 5 ) as sign datasets 
     3. A task of updating at least one of the information-sign datasets 
     These tasks will be described later. 
     In the detection date storage unit  15 , the detection-date items transmitted from each vehicle are temporarily stored. This enables an enormous number of detection data items to be collected from many vehicles traveling in, for example, all over Japan. 
     In the road map database  16 , high-accuracy road map data generated by the processing unit  14  is stored. In the information sign database  17 , the information-sign datasets are stored as the sign datasets; each information-sign dataset can be used as landmark information. 
     As partially illustrated in  FIG. 5 , the information-sign dataset about a selected sign includes 
     (1) An installation position information item, i.e. a coordinate information item including corresponding coordinates of longitude and latitude, about the selected sign 
     (2) An attribute information item about the selected sign 
     The signs include information signs installed for each of main roads throughout Japan, and signboards installed along roads 
     In the road map database  16 , the information sign database  17  can be incorporated. In the road map data, the sign data items can be included as landmarks, and the attribute information items can be included in the respective sign data items. 
     As described in the later explanation of how the control unit  11  works using a flowchart, the control unit  11  of each vehicular device  3  according to the first embodiment performs an extraction step of 
     1. Recognizing, from at least one information sign, which is an example of signs, of the first embodiment, in image data captured by the vehicular camera  3 , at least one numeral included in the range of 0 to 9 as the at least one specified character type 
     2. Extracting the recognized at least one numeral from the captured image data 
     The extracted at least one numeral, i.e. at least one numeric character, of at least one information sign is recognized as an attribute information item about the at least one information sign. 
     As a specific process in the extraction step, the control unit  11  performs a search of the at least one information sign in the captured image data for numerals from left to right, and repeats the search from top to bottom of the at least one information sign to thereby extract numerals from the at least one information sign. Then, the control unit  11  arranges the extracted numerals in the order of extraction, thus obtaining the string of the arranged numerals, i.e. numeric characters, as an attribute information item. 
     Then, the processing unit  14  of the data center  2  receives the detection data items transmitted from the vehicular device  3  of each vehicle to thereby collect them, and stores the collected detection data items in the detection data storage unit  15 . In addition to the data collection, the processing unit  14  of the data center  2  performs a sign data storing step of 
     1. Generating, based on the collected detection data items, information-sign datasets 
     2. Registering the generated information-sign datasets in the information-sign database  17  and/or 
     3. Updating the information-sign database  17  based on the generated information-sign datasets 
     Thus, the processing unit  14  serves as both a collector  14   a , which is a collection unit, and a register  14   b , which is a register unit. 
     As a specific process in the sign data storing step, for register of a generated information-sign dataset in the information-sign database  17 . the processing unit  14  is configured to 
     1. Select, from the detection data storage unit  15 , some detection data items that have the attribute information item identical to the attribute information item about the generated information-sign dataset 
     2. Perform statistical processing of the capture-position information items of the respective selected detection data items to thereby determine the installation position information item about the generated information-sign dataset, thus registering, in the information-sign database  17 , the generated information-sign dataset with the determined installation position information item 
       FIGS. 3A to 3E  illustrate captured images that respectively include information signs A 1  to A 5  installed for, for example, an expressway; the information signs A 1  to A 5  are an example of information signs as signs. Each of the information signs A 1  to A 5  guides the name of the corresponding direction of the expressway and/or the name of the corresponding upcoming interchange exit of the expressway. Each of the information signs A 1  to A 5  is comprised of a rectangular board with a green-colored major surface on which white characters are written. 
     Specifically, the information sign A 1  illustrated in  FIG. 3A  shows the upcoming interchange exit “  (Yatomi)” at the interchange number “26”, and the distance of 2 km thereto. 
     The information sign A 2  illustrated in  FIG. 3B  shows the upcoming interchange exit to the direction of “  (Yatomi)” and “  (Tsushima)”, the distance of 1 km thereto, and National highway  1  to which the exit accesses. 
     The information sign A 3  illustrated in  FIG. 3C  shows the upcoming interchange exit to the direction of “  (Yatomi)” and “  (Tsushima)”, and the distance of 550 m thereto. 
     The information sign A 4  illustrated in  FIG. 3D  shows the upcoming interchange exit to the direction of “  (Yatomi)” and “  (Tsushima)”. 
     The information sign A 5  illustrated in  FIG. 3E  shows that Highway radio at 1620 kHz is available from the point of the expressway posted with the information sign A 5 . 
     Next, the following describes how the information sign recognition system  1  configured set forth above operates with reference to  FIGS. 2 to 5  in addition to  FIG. 1 . 
       FIG. 2  illustrates a flowchart representing a procedure of an information-sign dataset registering routine carried out by the control unit  11  of each vehicular unit  3  and the processing unit  14  of the data center  2 ; the procedure of the information-sign dataset registration routine corresponds to a sign recognition method of the first embodiment. 
     In  FIG. 2 , operations in respective steps S 1  to S 3  are carried out by the control unit  11  of each vehicular device  3  while the corresponding vehicle is traveling. 
     Specifically, the control unit  11  causes the vehicular camera  4  to capture an image of a forward region of the corresponding traveling vehicle in its traveling direction, and continuously monitor whether there is an information sign included in an image captured by the vehicular camera  4  in step S 1 . 
     In response to determination that there is an information sign included in an image, i.e. a frame image, currently captured by the vehicular camera  4  in step S 1 , the control unit  11  performs, as the extraction step, a step of 
     1. Recognizing, from the information sign included in the frame image as captured image data, numerals as the at least one specified character type 
     2. Extracting the recognized numerals from the frame image in step S 2   
     As the specific process described above, the control unit  11  performs a search of the information sign in the captured image data for numerals from left to right, and repeats the search from top to bottom of the information sign in step S 2 . Then, the control unit  11  arranges numerals extracted from the information sign in the order of extraction, thus obtaining the string of the arranged numerals, i.e. numeric characters, as an attribute information item in step S 2 . 
       FIG. 4  schematically illustrates the specific process of extracting only numerals from the information sign A 2  illustrated in  FIG. 3B , which is an example of an information sign, included in the captured image data. 
     Specifically, the control unit  11  traces a top first block of the captured image data from left to right to thereby recognize numerals “155”, thus extracting, from the captured image data, the numerals “155”. Next, although the control unit  11  traces each of second and third blocks of the captured image data from left to right, the control unit  11  does not recognize numerals. 
     The control unit  11  traces a bottom block of the captured image data from left to right to thereby recognize numerals “26” first, and thereafter recognize a numeral “1”. Thus, the control unit  11  extracts, from the captured image data, the numerals “261”. 
     This results in the string of numerals “155261” being obtained as an attribute data item of the information sign A 2 . 
     Similarly, it is possible to obtain, from the information sign A 1  illustrated in  FIG. 3A , the string of numerals “262” as an attribute data item of the information sign A 1 , and obtain, from the information sign A 3  illustrated in  FIG. 3C , the string of numerals “155265502 as an attribute data item of the information sign A 3 . Additionally, it is possible to obtain, from the information sign A 4  illustrated in  FIG. 3D , the string of numerals “15526” as an attribute data item of the information sign A 4 , and obtain, from the information sign A 5  illustrated in  FIG. 3E , the string of numerals “1620” as an attribute data item of the information sign A 5 . 
     Returning to  FIG. 2 , the control unit  11  identifies the position of the information sign captured by the vehicular camera  4 , that is, a capture-position information item about the captured information sign in step S 3 . 
     Then, the control unit  11  instructs the communication unit  8  to transmit, to the data center  2 , the set of the capture-position information item and the attribute information item about the information sign as a detection data item in step S 3 . 
     Specifically, in step S 3 , the control unit  11  obtains, based on the position and/or size of the information sign in the captured image data, a distance to the information sign, and estimates the capture-position information item about the information sign in accordance with 
     (i) The position of the corresponding vehicle at the timing of capturing the information sign detected by the position detector  5   
     (ii) The obtained distance to the information sign 
     Operations in respective steps S 4  and S 5  are carried out by the processing unit  14  of the data center  2 . 
     Specifically, the processing unit  14  receives, via the communication unit  12  of the data center  2 , the detection data items transmitted from each vehicular device  3 , and the processing unit  14  writes the received detection data items in the detection data storage unit  15  in step S 4 . 
     Next, the processing unit  14  of the data center  2  performs statistical processing of a large number of the received detection data items to thereby identify a location of each of information signs in step S 5 . 
     Then, the processing unit  14  generates information-sign datasets, each of which includes (i) an information item about position coordinates of the installation position of a corresponding one of the information signs, and (ii) the attribute information item about the corresponding one of the information signs in step S 5 . Thereafter, the processing unit  14  registers the information-sign datasets in the information sign database  17  in step S 5 . The operation in step S 5  serves as a sign dataset storage step. The registering operation includes a new registration operation and an updating registration operation. 
     For registering of a target information-sign dataset, the processing unit  14  selects, from the detection data storage unit  15 , some detection data items that have the attribute information item, i.e. the string of numerals, identical to the attribute information item about the target information-sign dataset to be registered. 
     Then, the processing unit  14  performs statistical processing of the position coordinates, which are the capture-position information items, of the respective selected detection data items to thereby determine statistically derived position coordinates as an installation position information item about the target information-sign dataset, thus registering, in the information-sign database  17 , the target information-sign dataset with the determined installation position information item. 
     For example, the processing unit  14  performs, as the statical processing, 
     (1) Elimination of at least one outlier detection data item having an outlier capture-position information item from the selected detection data items 
     (2) Obtain an average, a median, or a mode of the selected detection data items, from which the at least one outlier detection data item has been eliminated 
       FIG. 5  illustrates an example where the updating registration operation is carried out. Specifically, the installation position coordinates (X1, Y1) of an information sign having identification No. 1 and the attribute information item “155261” stored in the information-sign database  17  is updated to new installation position coordinates (X2, Y2). 
     The information sign recognition system  1  and an information sign recognition method according to the first embodiment achieve the following benefits. 
     Specifically, the vehicular camera  4  of each vehicular device  3  captures an information sign while the corresponding vehicle is traveling. The control unit  11  of each vehicular device  3  performs the extraction step of 
     1. Recognizing, from captured image data of the information sign, at least one character that is included in the information sign and belongs to the at least one specified character type 
     2. Extracting the recognized at least one character from the captured image data 
     The communication unit  8  transmits, to the data center  2 , the detection data item including (i) the attribute information item about the information sign, and (ii) the capture-position information item about the information sign. 
     At that time, the processing unit  14  of the data center  2  receives the detection data items transmitted from the vehicular devices  3  of the vehicles to accordingly collect the detection data items. Then, the processing unit  14  performs the sign strong step of 
     1. Generating, based on the collected detection data items, information-sign datasets, each of which includes an installation position information item and an attribute information item about the corresponding one of the information signs 
     2. Registering the generated information-sign datasets in the information-sign database  17   
     Because the attribute information about each information sign for identifying the corresponding information sign is comprised of the string of characters, which belong to the at least one specified character type, extracted from the corresponding information sign, this configuration of the information sign recognition system  1  drastically lowers the amount of data transmitted from each vehicular device  3  to the data center  2 . This therefore results in both shorter time of communications between the data center  2  and each vehicular device  3  and shorter time required to manipulate the detection data items, making it possible to 
     (i) Reduce the amount of the information-sign datasets stored in the road map database  16  to accordingly reduce the storage capacity of the information-sign datasets 
     (ii) Make easier manipulation of the information-sign datasets 
     As described above, each of the information sign recognition system  1  and the information sign recognition method according to the first embodiment causes the vehicular camera  4  of each vehicular device  3  to capture an information sign for road guidance as a sign, and recognizes, based on captured image data of the information sign, the information sign. That is, each of the information sign recognition system  1  and the information sign recognition method makes it possible to easily identify that the information sign captured by the vehicular camera  5  matches which of information signs stored in the information-sign database  17 . 
     The processing unit  14  of the data center  2  according to the first embodiment selects, from the received detection data items, some detection data items that have the attribute information item identical to the attribute information item about a target information-sign dataset. Then, the processing unit  14  performs statistical processing of the capture-position information items of the respective selected detection data items to thereby determine the installation position information item about the target information-sign dataset. This makes it possible to generate the information-sign datasets each having more accurate installation position information item, thus establishing the information sign database  17  with higher accuracy. 
     The first embodiment utilizes, as the at least one specified character type constituting an attribute information item, one or more numerals. This enables recognition of the type of characters included in an information sign to be carried out with a sufficient degree of accuracy and a shorter time. In addition, because the first embodiment extracts and recognizes only ten numerical characters of 0 to 9, the first embodiment can perform extremely simple recognition of characters included in an information sign while making easier data processing of the characters. 
     In particular, the first embodiment utilizes a rule that 
     1. Performs a search of captured image data of an information sign for numerals from left to right of the information sign 
     2. Repeats the search from top to bottom of the information sign 
     3. Arrange numerals extracted from the information sign in the order of extraction, thus obtaining the string of the arranged numerals, i.e. numeric characters, as an attribute information item 
     This makes it easier to extract the attribute information item from an information sign. 
     Note that the vehicular camera  4  is configured to capture an image data frame for example every 100 msec, which is not described in the first embodiment, and therefore it is necessary to determine, from the image data frames, one image data frame captured at which point of time to be used for the above recognition processing. 
     In terms of higher recognition accuracy, it is preferable to use a captured image data frame in which a sign maximally appears just before disappearance thereof from the captured image frame. However, for performing a localization task, which will be described later, from far, it is beneficial to recognize an information sign using an image data frame captured relatively earlier. For example, it is possible to perform processing of an image-data frame captured at a timing when the vehicle is located 50 meters away from a sign. Note that the localization task is to analyze captured image data to thereby localize the position coordinates of an own vehicle in accordance with a relative position of a recognized sign relative to the own vehicle and position coordinates of the sign registered in the map data. 
     Second Embodiment 
     The following describes the second embodiment with reference to  FIGS. 6 to 8 . 
     Referring to  FIG. 6 , an information sign recognition system  1  serving as a sign recognition system according to the second embodiment is comprised of a data center  22  and vehicular devices  23  installed in respective vehicles; the data center  22  and the vehicular systems  23  are communicably connectable with each other. 
     The vehicular device  23  installed in each vehicle includes the vehicular camera  4 , the position detector  5 , the various vehicular sensors  6 , the map data storage unit  7 , a communication unit  24 , the operation display unit  10 , and a control unit  25  serving as an extraction apparatus. 
     The communication unit  24  serves as both a transmitter  24   a  as a transmitter unit, and a receiver  24   b  as a receiver unit. 
     The control unit  25  instructs the vehicular camera  4  to capture a forward road situation of the corresponding vehicle while the corresponding vehicle is traveling. Then, the control unit  25  determines whether there is at least one information sign as at least one sign in captured image data. 
     In response to determination that there is at least one information sign as at least one sign in the captured image data, the control unit  25  recognizes, from the captured image data of the at least one information sign, a string of characters that are included in the at least one information sign and belong to the at least one specified character type. Then, the control unit  25  extracts the recognized string of characters from the captured image data. 
     Thereafter, the control unit  25  determines the extracted string of characters as an attribute information item about the at least one information sign for identifying the at least one information sign. Then, the control unit  25  instructs the communication unit  24  to transmit, to the data center  22 , the set of the capture-position information item and the attribute information item about the at least one information sign as a detection data item. 
     In addition, the communication unit  24  of the vehicular device  23  receives data indicative of the position of the corresponding vehicle transmitted from the communication unit  26  of the data center  22  as vehicle position data. 
     The data center  22  includes a communication unit  26 , the input operation unit  13 , a processing unit  27 , the road map database  16 , and an information sign database  28  serving as a sign database. The communication unit  26  receives the detection data items from each vehicular device  23 . The communication unit  26  also transmits data indicative of each vehicle to the corresponding vehicular device as the vehicle position data. Thus, the communication device  26  serves as both a receiver  26   a  as a receiver unit and a transmitter  26   b  as a transmitter unit. 
     In the information sign database  28 , the information sign datasets are stored; each of the information sign datasets is comprised of 
     (1) An installation position information item about a corresponding information sign as a sign 
     (2) An attribute information item about the corresponding information sign 
     When receiving a detection data item from the vehicular device  3  of a target vehicle via the communication unit  26 , the processing unit  27  checks the attribute information item of the received detection data item against the information-sign datasets stored in the information sign database  28  to thereby determine whether there is an information-sign dataset with the attribute information item that matches the attribute information item about the received detection data item. 
     In response to determination that there is an information-sign dataset with the attribute information item that matches the attribute information item about the received detection data item, the processing unit  27  determines the position of the target vehicle in accordance with (i) the installation position information item about the information-sign dataset, and (ii) a result of referring to the road map database  16 . 
     This therefore enables the processing unit  27  to serve as both a checking unit  27   a  as a checking module and a vehicle position determination unit  27   b  as a vehicle position determination module. 
     For checking of the attribute information item about a target detection data item against the information-sign datasets stored in the information sign database  28 , the processing unit  27  performs the following task. 
     Specifically, the processing unit  27  selects, from the information-sign datasets stored in the information sign database  28 , some information-sign datasets whose capture-position information items are located within a predetermined range around the capture position indicted by the capture-position information item about the target detection data item. For example, the processing unit  27  selects, from the information-sign datasets stored in the information sign database  28 , some information-sign datasets whose capture-position information items are located within a predetermined circular range with radius 100 meters around the capture position indicted by the capture-position information item about the target detection data item. 
     Then, the processing unit  27  searches the selected information-sign datasets for an information-sign dataset whose attribute information item matches the attribute information item about the target detection data item, thus checking the attribute information item about the target detection data item against the selected information-sign datasets. 
     Additionally, the processing unit  27  of the second embodiment instructs the communication unit  26  to transmit the determined position of the target vehicle to the vehicular device  23  of the target vehicle as the vehicle position data. 
     In response to receiving the vehicle position data, the vehicular device  23  of the target vehicle is capable of recognizing the position of the own target vehicle and/or updating the own target vehicle on navigation information. 
       FIG. 7  illustrates a flowchart representing a procedure of a vehicle position determination routine including capturing of an information sign carried out by the control unit  25  of each vehicular unit  23  and the processing unit  27  of the data center  22 . 
     In  FIG. 7 , operations in respective steps S 11  to S 13  are carried out by the control unit  25  of each vehicular device  23  while the corresponding vehicle is traveling. 
     Like the first embodiment, the control unit  25  causes the vehicular camera  4  to capture an image of an information sign in step S 11 . Next, the control unit  25  performs a step of 
     1. Recognizing, from captured image data about the information sign, numerals as the at least one specified character type 
     2. Extracting the recognized numerals from the captured image data to thereby obtain an attribute information item in step S 12   
     Then, the control unit  25  instructs the communication unit  24  to transmit, to the data center  22 , the set of a capture-position information item and the attribute information item about the information sign as a detection data item in step S 13 . 
     Operations in respective steps S 14  to S 16  are carried out by the processing unit  27  of the data center  22 . 
     Specifically, the processing unit  27  of the data center  22  receives, via the communication unit  26  of the data center  22 , the detection data items transmitted from each vehicular device  23  in step S 14 . 
     Next, the processing unit  27  checks the attribute information item about each received each detection data item against the attribute information items of the respective information-sign datasets stored in the information sign database  28  to thereby identify an information-sign dataset for each received detection data item; the at information-sign dataset for the corresponding received detection data item has the attribute information item that matches the attribute information item about the corresponding received detection data item in step S 15 . 
     Subsequently, the processing unit  27  determines, based on the installation position information item about the information-sign dataset identified for each received detection data item, the position of the vehicle identified for the corresponding received detection data item in step S 16 . Then, the processing unit  27  transmits, as the vehicle position data, the position of each vehicle determined based on the corresponding information-sign dataset to the corresponding vehicle in step S 16 . Thereafter, the processing unit  27  terminates the vehicle position determination routine. 
       FIG. 8  illustrates an example representing how the processing unit  27  performs the checking operation.  FIG. 8  illustrates an example situation where the capture-position information item included in a target detection data item has, for example, coordinates (X0, Y0), and the attribute information item included in the target detection data item is “155261”. 
     In this situation, the processing unit  27  draws a circular range R with radius 100 meters around the capture-position information item (X0, Y0), and extracts, from the information sign database  28 , one or more information-sign datasets located within the circular range R. In this example, the processing unit  27  extracts, from the information sign database  28 , three information-sign datasets respectively assigned with identification Nos. 1, 2, and 3 located within the circular range R. 
     Then, the processing unit  27  deter mines whether the attribute information item about the target detection data item matches that about each of the three information-sign datasets respectively assigned with the identification Nos. 1, 2, and 3. In response to determination that the attribute information item about the target detection data item matches that about one of the three information-sign datasets respectively assigned with the identification Nos. 1, 2, and 3, the processing unit  27  identifies that the captured information sign corresponds to an information sign linked to the one of the three information-sign datasets. 
     For example, in  FIG. 8 , because the attribute information item “155261” about the target detection data item matches the attribute information item “155261” about the information-sign dataset assigned with the identification No. 1, the processing unit  27  identifies that the captured information sign corresponds to an information sign linked to the information-sign dataset assigned with the identification No. 1. 
     Otherwise, in response to determination that the attribute information item about the target detection data item does not match that about any of the extracted information-sign datasets or matches two or more of the extracted information-sign datasets, the processing unit  27  determines a failure of identification of the target detection data item. 
     As described above, the information sign recognition system  1  according to the second embodiment is configured such that a detection data item is transmitted from a target vehicular device  23  to the data center  22 , and the processing unit  27  of the data center  22  receives the detection data item, and checks the attribute information item included in the received detection data item against the attribute information items about the respective information-sign datasets stored in the information sign database  28 . This enables one of the information-sign datasets, which corresponds to the received detection data item to be identified, making it possible to identify the position of the vehicle corresponding to the target vehicular device  23 . 
     Additionally, the processing unit  27  is capable of transmitting information about the identified position of the vehicle to the corresponding target vehicular device  23 , making it possible for the target vehicular device  23  to recognize a more accurate position of the corresponding own vehicle. 
     The attribute information about each information sign for identifying the corresponding information sign in the information sign recognition system  1  according to the second embodiment is comprised of the string of characters, such as numerals, which belong to the at least one specified character type, extracted from the corresponding information sign. This therefore lowers the amount of data transmitted from each vehicular device  23  to the data center  22 . 
     This therefore results in 
     1. Shorter time of communications between the data center  22  and each vehicular device  23   
     2. Shorter time required to manipulate the detection data items 
     3. Simpler execution of the checking operation by the processing unit  27  with shorter time because of the lowered amount of data transmitted from each vehicular device  23  to the data center  22   
     Additionally, the processing unit  27  is configured to search information-sign datasets, which are located within a predetermined range around the captured-position information item about a target detection data item, for an information-sign dataset whose attribute information item matches the attribute information item about the target detection data item. This configuration therefore makes it possible to more easily check a captured information sign with the information-sign datasets stored in the information sign database  28  with sufficient accuracy. 
     Third Embodiment 
     The following describes the third embodiment with reference to  FIGS. 9 and 10 . 
     Referring to  FIG. 9 , an information sign recognition system  31  serving as a sign recognition system according to the third embodiment is comprised of a vehicular device  32  installed in a vehicle. 
     The vehicular device  32  installed in the vehicle includes the vehicular camera  4 , the position detector  5 , the various vehicular sensors  6 , the map data storage unit  7 , an information sign database  33  serving as a sign database, the operation display unit  10 , and a control unit  34 . 
     In the information sign database  33 , the information sign datasets are stored, each of which serves as a new high-accuracy sign dataset. Each of the information-sign datasets for example is generated by, for example, the data center  2  described in the first embodiment to have a high accuracy, and the information-sign datasets are transmitted from the data center  2  to each vehicular device  31 . 
     The control unit  34  instructs the vehicular camera  4  to capture a forward road situation of the corresponding vehicle while the corresponding vehicle is traveling. Then, the control unit  25  determines whether there is an information sign as a sign in captured image data. 
     In response to determination that there is an information sign as a sign in the captured image data, the control unit  34  recognizes, from the captured image data of the information sign, a string of characters that are included in the information sign and belong to the at least one specified character type. Then, the control unit  34  extracts the recognized string of characters from the captured image data. 
     Thereafter, the control unit  34  determines the extracted string of characters as an attribute information item about the information sign for identifying the information sign, and generates the set of a capture-position information item and the attribute information item about the information sign as a detection data item. 
     Additionally, the control unit  34  checks the attribute information item about the generated detection data item against the information-sign datasets stored in the information sign database  33  to thereby determine whether there is an information-sign dataset with the attribute information item that matches the attribute information item about the generated detection data item. 
     In response to determination that there is an information-sign dataset with the attribute information item that matches the attribute information item about the generated detection data item, the control unit  34  performs localization of the corresponding own vehicle in accordance with the installation position information item about the information-sign dataset to accordingly determine the position of the corresponding own vehicle. 
     This therefore enables the control unit  34  to serve as an extraction unit  34   a  as an extraction module, a checking unit  34   b  as a checking module, and a vehicle position determination unit  34   c  as a vehicle position determination module. 
       FIG. 10  illustrates a flowchart representing a procedure of a vehicle position determination routine including capturing of an information sign carried out by the control unit  34  of each vehicular unit  32 . 
     Specifically, the control unit  34  causes the vehicular camera  4  to capture an image of an information sign as a sign in step S 21 . Next, the control unit  34  performs a step of 
     1. Recognizing, from captured image data about the information sign, numerals as the at least one specified character type 
     2. Extracting the recognized numerals from the captured image data to thereby obtain an attribute information item in step S 21   
     Then, the control unit  34  generates the set of a capture-position information item and the attribute information item about the information sign as a detection data item in step S 21 . 
     Next, the control unit  34  checks the attribute information item about the generated detection data item against the attribute information items of the respective information-sign datasets stored in the information sign database  33  to thereby identify an information-sign dataset for the generated detection data item; the information-sign dataset for the generated detection data item has the attribute information item that matches the attribute information item about the generated detection data item in step S 23 . 
     In step S 23 , the control unit  34  determines the position of the corresponding own vehicle in accordance with the installation position information item about the information-sign dataset identified for the generated detection data item, and thereafter terminates the vehicle position determination routine. 
     The control unit  34  of the third embodiment can perform the checking operation, which is identical to the checking operation performed by the processing unit  27  of the second embodiment. 
     Specifically, the control unit  34  extracts, from the information sign database  28 , information-sign datasets located within a circular range with radius 100 meters around the capture-position information item about the generated detection data item. 
     Then, the control unit  34  determines whether the attribute information item about the generated detection data item matches that about each of the extracted information-sign datasets. In response to determination that the attribute information item about the generated detection data item matches that about one of the extracted information-sign datasets, the control unit  34  identifies that the captured information sign corresponds to an information sign linked to the one of the extracted information-sign datasets. 
     The vehicular device  32  according to the third embodiment causes the vehicular camera  4  to capture an information sign for road guidance as a sign while the corresponding own vehicle is traveling, and extracts, from captured image data of the information sign, numerals as the at least one specified character type to thereby obtain an attribute information item about the information sign. 
     Then, the vehicular device  32  generates the set of a capture-position information item and the attribute information item about the information sign as a detection data item. Next, the vehicular device  32  checks the attribute information item about the generated detection data item against the attribute information items of the respective information-sign datasets stored in the information sign database  33  to thereby identify an information-sign dataset for the generated detection data item; the information-sign dataset for the generated detection data item has the attribute information item that matches the attribute information item about the generated detection data item. 
     The vehicular device  32  localizes the corresponding own vehicle in accordance with the installation position information item about the information-sign dataset identified for the generated detection data item. 
     That is, the information sign recognition system  31  of the third embodiment enables only the vehicular device  32  to perform localization of the corresponding own vehicle to thereby obtain the position of the corresponding own vehicle with higher accuracy without communications with the data center  2 . This therefore enables the vehicular device  32  to localize the corresponding own vehicle with higher accuracy without confusion of the signs even under a situation where similar signs, such as similar information signs or similar signboards appear successively while, for example, the corresponding own vehicle is traveling on an expressway or a general road in an urban area. 
     The attribute information about each information sign for identifying the corresponding information sign in the information sign recognition system  31  according to the third embodiment is comprised of the string of characters, such as numerals, which belong to the at least one specified character type, extracted from the corresponding information sign. This therefore extremely lowers the amount of data to be checked by the vehicular device  32 , resulting in simpler execution of the checking operation with shorter time. This also enables the amount of the information-sign datasets stored in the information sign database  33  to be smaller, making it possible to obtain the position of the corresponding own vehicle with higher accuracy while maintaining small the storage capacity of the information-sign datasets. 
     Note that a vehicular device installable in a vehicle can include a function of collecting probe data items, each of which includes information about a current position of the vehicle and information about an image captured by a camera while the vehicle is traveling. The probe data items collected by each of the vehicular devices are transmitted to a center of a map data generation system, so that the center collects a lot of the probe data items. Then, the center integrates the probe data items with one another to thereby generate high-accuracy map data while updating it, which can be applied for autonomous driving. 
     In this example, it is possible to use position data items about signs, such as information signs as landmarks, to thereby perform alignment of each probe data with the map data and/or alignment of the probe data items with one another. This makes it possible to perform high-accuracy alignment of landmarks with one another to thereby generate high-accuracy map data. 
     Fourth Embodiment 
     The following describes the fourth embodiment with reference to  FIG. 11 . The following describes features of the fourth embodiment, which is different from those of the third embodiment. 
     Like the third embodiment, a vehicular device installed in a vehicle includes the vehicular camera, the position detector, the various vehicular sensors, the map data storage unit, the information sign database serving as a sign database, the operation display unit, and the control unit. 
     The control unit of the fourth embodiment serves as the extraction module, the checking module, and the vehicle position determination module. That is, the control unit is configured to extract, from captured image data of an information sign as a sign captured by the vehicular camera, the at least one specified character type to thereby obtain an attribute information item about the information sign. 
     The fourth embodiment utilizes kanji characters (Chinese characters) in addition to numerals as the specified types of characters in addition to numerals (numeric characters). 
     The fourth embodiment is configured such that the number of kanji characters in the specified types of characters to be recognized by the control unit is determined to a predetermined limited number. In addition, the control unit is configured to dynamically change recognition target characters included in at least one of the specified types of characters in accordance with the position of the corresponding own vehicle detected by the position detector. 
     For example, signs located in respective intersections include information signs, each of which shows the name of the corresponding intersection, the name of the corresponding traffic spot, or the name of the corresponding facility. Such information signs include many information signs in each of which the name of a corresponding intersection is written by kanji characters, such as “  (kari)”, “  (ya)”, and “  (eki)”, or “  (kari)”, “  (ya)”, “  (eki)”, and “  (nishi)”. 
     It is unfortunately difficult to recognize all kanji characters. 
     From this viewpoint, the control unit of the fourth embodiment determines, based on the current position and the current traveling direction of the corresponding own vehicle, limited kanji characters as the recognition target characters; the limited kanji characters are predicted to be used by an information sign. For example, the number of the limited kanji characters is preferably set to a value selected from the range of approximately ten characters to a few dozen characters. 
       FIG. 11  illustrates a flowchart representing a procedure of a character recognition routine carried out by the control unit of each vehicular unit installed in the corresponding own vehicle. 
     Specifically, the control unit obtains an approximate current position of the corresponding own vehicle based on information measured by the position detector in step S 31 . 
     Next, the control unit determines, based on the current position and current traveling direction of the corresponding own vehicle, recognition target characters in step S 32 . In the above example, the control unit determines limited kanji characters of “  (kari)”, “  (ya)”, “  (eki)”, and “  (nishi)” as the recognition target characters, and adds the limited kanji characters to a prepared recognition dictionary. The recognition target characters can be configured to be transmitted to the control unit of each vehicular device from the data center or the control unit of each vehicular device can extract the recognition target characters from all characters recognizable thereby. 
     Subsequently, the control unit causes the vehicular camera to capture an image of an information sign as a sign to thereby obtain captured image data of the information sign in step S 33 . 
     Following the operation in step S 33 , the control unit performs, as a recognition step, a step of 
     1. Recognizing, from the captured image data of the information sign, numerals and kanji characters belonging to the recognition target characters 
     2. Extracting the recognized numerals and kanji characters from the captured image data of the information sign in step S 34   
     When recognizing kanji characters, the control unit makes it possible to easily perform the recognition step in a shorter time, because the number of kanji characters to be recognized by the control unit is set to a smaller number of characters determined by the limited number of kanji characters. 
     After the corresponding own vehicle passes a location where the captured information sign is installed, the control unit repeats the character recognition routine from step S 31  for the next upcoming information sign. 
     Like the first to third embodiments, the fourth embodiment achieves a benefit of more simply performing a task of identifying that the information sign captured by the vehicular camera  5  as a sign matches which of information signs stored in the information-sign database. In particular, the fourth embodiment utilizes kanji characters as the specified types of characters to be recognized in addition to numerals, making it possible to expand the applicability of the information sign recognition system of the fourth embodiment. 
     Although the fourth embodiment describes an embodied configuration that dynamically changes recognition target kanji-characters in accordance with the position of the corresponding own vehicle, but the present disclosure is not limited to this embodied configuration. 
     Specifically, plural types of characters can be determined as the recognition target characters in accordance with the position of the vehicle. For example, hiragana characters, katakana characters, and kanji characters can be determined as the recognition target characters to be recognized by the control unit. The control unit of each vehicle can dynamically change one or more types of characters determined as the recognition target characters in accordance with the position of the corresponding vehicle. 
     For example, the control unit of each vehicle can be configured to dynamically set 
     1. Numerals (numeric characters) as the recognition target characters in response to determination that the corresponding vehicle is traveling on a limited highway, such as an expressway 
     2. Numerals and alphabets (alphabet characters) as the recognition target characters in response determination that the corresponding vehicle is traveling on a general road 
     Limiting, from all types of characters, one or several types of characters to be determined as the recognition target characters enables the processing road of the CPU of the control unit to be reduced, which is similar to each of the first to thirds embodiment. 
     Fifth and Sixth Embodiments and Other Embodiments 
       FIG. 12  schematically illustrates an example of information signs and signboards according to the fifth embodiment. As illustrated in  FIG. 5 , information signs A 6  and A 7  are juxtaposed to each other as left and right signs. The information signs A 6  and A 7  are very similar to each other, so that, for recognition of numerals in each of the information signs A 6  and A 7 , the numerals “26½” are recognized to be extracted. That is, a result of the recognition of the information sign A 6  is identical to a result of recognition of the information sign A 7 . 
     In addition, in this example, at the upper side of the information sign A 6 , a signboard A 8  in which numerals “95” are written is located, and at the upper side of the information sign A 7 , a signboard A 9  in which numerals “20” are written is located. Inherently, the information sign A 6  and the signboard A 8  are processed as individually separated signs, and similarly, the information sign A 7  and the signboard A 9  are processed as individually separated signs. 
     The information sign A 6  and the signboard A 8  can however be processed as an integrated sign, and similarly the information sign A 7  and the signboard A 9  can however be processed as an integrated sign. 
     This enables the string of characters, i.e. the string of “95 26½”, extracted as an attribute information item from the integrated sign of A 6  and A 8  to be easily distinguished from the string of characters, i.e. the string of “20 26½”, extracted as an attribute information item from the integrated sign of A 7  and A 9 . 
     That is, two information signs, two signboards, or a pair of an information sign and a signboard, which are arranged in a vertical direction corresponding to a Z-axis direction, can be processed as an integrated sign. This achieves a benefit of more easily distinguishing the attribute information item of the integrated sign from another sign. It is also possible to add priority information to each of the string of numerals “95” and the string of numerals “20”; the string of numerals with the priority information being added thereto has a higher priority than another string of numerals with no priority information. 
       FIG. 13  schematically illustrates the sixth embodiment. 
     The sixth embodiment is configured to 
     1. Extract, from captured image data of the information sign A 2  as a sign, a first set of numerals “155”, a second set of numerals “26”, and a third set of a numeral “1”, each of which belongs to a at least one specified character type 
     2. Add coordinate information about the position of each of the first to third sets to an assignment information item of the information sign 
     The coordinate information about each of the first to third sets is comprised of (X,Y); X represents a coordinate of the corresponding one of the first to third sets in the horizontal direction corresponding to an X direction, and Y represents a coordinate of the corresponding one of the first to third sets in the vertical direction corresponding to a Y direction. 
     This enables plural signs which have similar characters in a specified type to be likely to be distinguished from each other, making it possible to more accurately recognize information signs in a shorter time. 
     The sixth embodiment can be modified to 
     1. Add rough positional information about a position of a first set of numerals, such as an upper left position, to an assignment information item of the information sign 
     2. Add rough positional information about the position of a second set of numerals, such as a center position, to the assignment information item of the information sign 
     3. Add rough positional information about the position of a third set of numerals, such as a right end position, to the assignment information item of the information sign 
     For determination of an assignment information item about a single sign using a string of plural characters, it is possible to determine, as the assignment information about the single sign, (i) all the characters, or (ii) a selected character with the largest size in all the characters. 
     If a single sign includes plural sets of characters, it is possible to individually extract a string of the plural sets of characters with a separator, such as a comma, a colon, or a slash, between each adjacent pair of the plural sets. 
     The attribute information about each information sign can include numerals and characters of a unit attached thereto, such as a kanji character of “  (fun)”, alphabetic characters of “min”, “km”, or “m”, which belong to the at least one specified character type. The position information about characters included in each sign can be plotted on the corresponding sign on the map data. The position information about each sign can be efficiently used to perform localization of a corresponding vehicle. Similarly, information about the font size of characters included in each sign can be plotted on the corresponding sign on the map data. The font size information about each sign can also be efficiently used to perform localization of a corresponding vehicle. 
     As at least one specified character type in each embodiment, numeric characters and/or kanji characters are utilized, but capital alphabetic characters, lowercase alphabetic characters, hiragana characters, or katakana characters can be utilized as at least one specified character type. Systematically classified plural types of characters, such as kanji characters and numerals or capital alphabetic characters and numerals, can also be utilized as at least one specified character type. 
     A combination of particular numerals, such as 1, 2, 3, 4, 5, 6, 7, 8, and 9, selected from all numerals and particular alphabetic characters, such as A, B, C, D, E, F, G, H, I, J, K, L, M, and N, can be used as at least one specified character type. At least one type of characters for recognition of signs can be changed depending on types of the signs and/or their landmarks. For example, numerals can be used as the at least one type of characters if a sign is a direction signboard. If a sign is a signboard of a large-scale commercial facility, characters of the name of the large-scale commercial facility written in the signboard can be used as the at least one type of characters. Additionally, if a sign is a signboard indicative of the name of a corresponding intersection, a combination of numerals and kanji characters, or numerals and alphabetic characters can be used as the at least one type of characters. 
     Each embodiment is implemented for recognition of information signs installed mainly for an expressway, but can be implemented for recognition of information signs installed for a general road. 
     The processing unit  27  according to the second embodiment can be programmed to determine, based on the installation position information item about the information-sign dataset identified for each received detection data item, the position of the vehicle identified for the corresponding received detection data item in step S 15 , and thereafter, terminate the vehicle position determination routine without executing the operation in step S 16 . 
     Each embodiment is implemented for recognition of information signs as an example of signs, but each embodiment can be implemented for recognition of signboards as an example of signs. In this modification, signboards can include 
     1. A signboard in which the name of a large-scale shopping center and the distance to the large-scale shopping center are written 
     2. A signboard in which the name of a building is written 
     3. A signboard in which the name of a facility is written 
     4. A signboard in which the name and/or the logo of a shop, such as a gas station, a restaurant, or a fast-food restaurant with a drive-through 
     That is, each embodiment can be implemented for recognition of signboards that are installed for mainly commercial purpose. 
     The hardware configuration and/or the software configuration of each of the vehicular devices, the vehicles, and the data centers can be freely modified. The present disclosure has been described based on the above embodiments, but the present disclosure is understood not to be limited to the embodiments and the above configurations. The present disclosure can include various modifications within the scope of their equivalents. Various combinations or embodiments to which one or more components will be added or from which one or more components will be eliminated are included within the scope of the present disclosure or within the inventive concept of the present disclosure. 
     The control units and methods described in the present disclosure can be implemented by a dedicated computer including a memory and a processor programmed to perform one or more functions embodied by one or more computer programs. 
     The control units and methods described in the present disclosure can also be implemented by a dedicated computer including a processor comprised of one or more dedicated hardware logic circuits. 
     The control units and methods described in the present disclosure can further be implemented by a processor system comprised of a memory, a processor programmed to perform one or more functions embodied by one or more computer programs, and one or more hardware logic circuits. 
     The one or more programs can be stored in a non-transitory storage medium as instructions to be carried out by a computer or a processor.