Patent Publication Number: US-2022219634-A1

Title: Accident determination device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation application of U.S. patent application Ser. No. 16/471,104, which is U.S. National Stage entry of PCT Application No: PCT/JP2017/040035 filed Nov. 7, 2017, which claims priority to Japanese Patent Application No. 2016-246218, filed Dec. 20, 2016, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an accident determination device. 
     There has been proposed an accident notifying system that, if an accident occurs in a moving object such as a vehicle, automatically notifies the occurrence of the accident to a server. In this accident notifying system, for example, a terminal device mounted in a vehicle detects an impact having occurred in the vehicle and determines based on the detected magnitude of the impact (impact value) whether an accident has occurred. And if determining that an accident has occurred, the terminal device notifies the fact of accident occurrence and the site of occurrence of the accident to an external server via radio communication (e.g., Patent Document 1). 
     PRIOR ARTS LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-266294 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the above conventional technique, when an impact having a magnitude greater than or equal to a predetermined threshold is detected, it is determined that an accident has occurred and is notified. However, in reality, even during normal travel, an impact occurs in a moving object, and its magnitude is different depending on irregularities in the road surface, a curve, the condition of inclination, and so on. Hence, there is the problem that it may be difficult to determine whether an accident has occurred, depending on the area where the moving object is located. Especially in parking spaces, accidents with relatively small impact tends to occur. Therefore, there is a problem that an accident cannot be detected if the same threshold is used in the parking space as on the road. 
     The problem that, with an accident determination device that determines whether an accident has occurred based on impacts having occurred in a moving object, it is difficult to appropriately determine according to attributes of the area where the moving object is located can be cited as an example of problems to be solved by the present invention. 
     Means to Solve the Problems 
     The invention according to claim  1  is an accident determination device which determines whether an accident has occurred in a moving object based on impact having occurred in said moving object, comprising: a first sensor that detects an impact having occurred in said moving object; a second sensor that acquires position information indicating a position of said moving object; an area determining unit that determines the area attribute of the area where said moving object is located, based on the position information; and a processor that compares impact value of the impact detected by said first sensor with a determination threshold so as to determine whether an accident has occurred in said moving object, wherein the processor sets said determination threshold according to the area attribute of the area where said moving object is located defined by said area determining unit, wherein, when the area attribute of the area where said moving object is located indicates a parking space, said processor sets said determination threshold to be at a lower value than when said area attribute indicates a road, and wherein the processor determines whether the accident has occurred based on the result of comparing the impact value with said determination threshold. 
     The invention according to claim  4  is an accident determination device which determines whether an accident has occurred in a moving object based on an impact having occurred in said moving object, comprising: a first sensor that detects an impact having occurred in said moving object; a second sensor that acquires position information indicating a position of said moving object; an area determining unit that determines the area attribute of the area where said moving object is located, based on the position information; and a processor that compares impact value of the impact detected by said first sensor with a determination threshold so as to determine whether an accident has occurred in said moving object, wherein processor sets said determination threshold according to the area attribute of the area where said moving object is located defined by said area determining unit, wherein said area attribute includes a primary attribute indicating whether the area is a road or not and a secondary attribute indicating whether the road is an expressway or an ordinary road when said primary attribute indicates a road, and wherein, when said secondary attribute indicates an expressway, said processor sets said determination threshold to be at a higher value than when said secondary attribute indicates an ordinary road; and wherein the processor determines whether the accident has occurred based on the result of comparing the impact value with said determination threshold. 
     The invention according to claim  7  is an accident determination device which determines whether an accident has occurred in a moving object based on an impact having occurred in said moving object, comprising: a first sensor that detects an impact having occurred in said moving object; a second sensor that acquires position information indicating a position of said moving object; an area determining unit that determines the area attribute of the area where said moving object is located, based on the position information; and a processor that compares impact value of the impact detected by said first sensor with a determination threshold so as to determine whether an accident has occurred in said moving object; wherein the processor sets said determination threshold according to the area attribute of the area where said moving object is located defined by said area determining unit, wherein said area attribute includes a primary attribute indicating whether the area is a road or not and a secondary attribute indicating whether the road surface is covered with snow or noncovered with snow when said primary attribute indicates a road, and wherein, when said secondary attribute indicates being covered with snow, said processor sets said determination threshold to be at a higher value than when said secondary attribute indicates being non-covered with snow; and wherein the processor determines whether the accident has occurred based on the result of comparing the impact value with said determination threshold. 
     The invention according to claim  10  is an accident determination device which determines whether an accident has occurred in a moving object based on an impact having occurred in said moving object, comprising: a first sensor that detects an impact having occurred in said moving object; a second sensor that acquires position information indicating a position of said moving object; an area determining unit that determines the area attribute of the area where said moving object is located, based on the position information; and a processor that compares impact value of the impact detected by said first sensor with a determination threshold so as to determine whether an accident has occurred in said moving object; wherein the processor sets said determination threshold according to the area attribute of the area where said moving object is located defined by said area determining unit, wherein said area attribute includes a primary attribute indicating whether the area is a road or not and a secondary attribute indicating whether that road is a low-speed way or an ordinary road when said primary attribute indicates a road, and wherein, when said secondary attribute indicates a low-speed way, said processor sets said determination threshold to be at a lower value than when said secondary attribute indicates an ordinary road; and wherein the processor determines whether the accident has occurred based on the result of comparing the impact value with said determination threshold. 
     The invention according to claim  13  is an accident determination device which determines whether an accident has occurred in a moving object based on an impact having occurred in said moving object, comprising: a first sensor that detects an impact having occurred in said moving object; a second sensor that acquires position information indicating a position of said moving object; an area determining unit that determines the area attribute of the area where said moving object is located, based on the position information; and a processor that that compares impact value of the impact detected by said sensor with a determination threshold so as to determine whether an accident has occurred in said moving object; wherein the processor sets said determination threshold according to the area attribute of the area where said moving object is located defined by said area determining unit, wherein, when the area attribute of the area where said moving object is located indicates a ferry landing, said processor sets said determination threshold to be at a higher value than when said area attribute indicates a road; and wherein the processor determines whether the accident has occurred based on the result of comparing the impact value with said determination threshold. 
     The invention according to claim  16  is an accident determination method which is executed by an accident determination device having a sensor, comprising: a step of acquiring position information indicating a position of a moving object a step of determining an area attribute of an area where said moving object is located based on the position information, a step of setting a determination threshold with which to determine whether an accident has occurred according to the area attribute of the area where said moving object is located; a step of detecting an impact having occurred in said moving object; a step of comparing impact value of said impact detected and said determination threshold to determine whether an accident has occurred in said moving object; a step of determining that the accident has occurred in the moving object based on the result of comparing the impact value with the determination threshold; wherein, in the step of setting the determination threshold, when the area attribute of an area where said moving object is located indicates a parking space, said determination threshold is set to be at a lower value than when said area attribute indicates a road. 
     The invention according to claim  17  is a non-transitory computer-readable storage medium storing a program configured to cause a computer executing: a step of acquiring position information indicating a position of a moving object a step of determining an area attribute of an area where said moving object is located based on the position information, a step of setting a determination threshold with which to determine whether an accident has occurred according to the area attribute of the area where said moving object is located; a step of detecting an impact having occurred in said moving object; a step of comparing impact value of said impact detected and said determination threshold to determine whether an accident has occurred in said moving object; a step of determining that the accident has occurred in the moving object based on the result of comparing the impact value with the determination threshold; wherein, in the step of setting the determination threshold, when the area attribute of an area where said moving object is located indicates a parking space, said determination threshold is set to be at a lower value than when said area attribute indicates a road. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the configurations of an accident determination device and a server of Embodiment 1; 
         FIG. 2  is a flow chart showing the processing operation of an accident determining process of Embodiment 1; 
         FIG. 3  is a block diagram showing the configuration of an accident determination device of Embodiment 2; 
         FIG. 4  is a flow chart showing the processing operation of an accident determining process of Embodiment 2; 
         FIG. 5  is a diagram showing schematically a threshold table of Embodiment 3; 
         FIG. 6  is a block diagram showing the configurations of an accident determination device and a server of Embodiment 4; and 
         FIG. 7  A is a diagram showing schematically a threshold table of Embodiment 4. 
         FIG. 7  B is a diagram showing schematically a threshold table of Embodiment 4. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals are used to denote substantially the same or equivalent parts in the descriptions and accompanying drawings of the embodiments below. 
     Embodiment 1 
       FIG. 1  is a block diagram showing the configuration of an accident notifying system according to Embodiment 1. The accident notifying system is composed of a server  20  and a plurality of terminal devices  10 - 1  to  10 - n  (n is an integer of two or greater). 
     The accident determination device  10 - 1  to  10 - n  is, for example, a navigation device mounted in a moving object (hereinafter simply called a vehicle) such as a vehicle and performs radio communication with the server  20 . The accident determination devices  10 - 1  to  10 - n  each have the same configuration, and hence these are generalized to the accident determination device  10 , and the configuration and operation thereof will be described below. 
     The accident determination device  10  has a communication unit  11 , a position information acquiring unit  12 , an impact detecting unit  13 , a threshold setting unit  14 , a sound pickup unit  15 , an image acquiring unit  16 , and an accident determining unit  17 . 
     The communication unit  11  transmits and receives information to and from the server  20 . For example, the communication unit  11  transmits position information acquired by the position information acquiring unit  12  and receives threshold information that the accident determining unit  17  uses in accident determination. Further, the communication unit  11  may transmit image information of images around the moving object acquired by the image acquiring unit  16  to the server  20 . 
     The position information acquiring unit  12  is constituted by, e.g., a GPS (Global Positioning System) sensor and acquires position information indicating the current position of the vehicle. For example, the position information acquiring unit  12  receives radio waves transmitted from a plurality of GPS satellites and calculates the distance from each GPS satellite based on the received radio waves to acquire position information. 
     The impact detecting unit  13  is constituted by, e.g., an acceleration sensor and detects the magnitude of an impact having occurred in the vehicle impact value G (hereinafter simply called impact value) based on a change in acceleration of the vehicle. 
     The threshold setting unit  14  sets a threshold that the accident determining unit  17  uses in accident determination based on threshold information acquired by the communication unit  11 . The threshold that the accident determining unit  17  uses in accident determination includes a threshold for the magnitude of impact value (an impact threshold) and a threshold for the sound volume of an impact sound (a sound-volume threshold). In the present embodiment, the sound-volume threshold is set at a constant value, and the threshold setting unit  14  changes only the impact threshold based on threshold information transmitted from the server  20 . Thus, in the description below, the impact threshold set by the threshold setting unit  14  (that is, the impact threshold that the accident determining unit  17  uses in accident determination) is called a “determination threshold”. Note that in the present embodiment an impact threshold premised on the case where the moving object is on a road is set as the determination threshold for an initial state (state before changed). 
     The sound pickup unit  15  is constituted by a sound pickup device such as a microphone. The sound pickup unit  15  picks up an impact sound when the impact detecting unit  13  detects an impact. 
     The image acquiring unit  16  is constituted by an image pickup device such as an in-vehicle camera. The image acquiring unit  16  acquires images around the moving object at the time when the impact detecting unit  13  detects an impact. Further, the image acquiring unit  16  performs image recognition on the images around the moving object. By this means, if an obstacle is in the vicinity of the moving object, that obstacle is recognized by image recognition. If the area where the moving object is located is a parking space, signs or character strings placed at the entrance or the like of the parking space are recognized by image recognition. Thus, image information of the images around the moving object is transmitted to the server  20  via the communication unit  11 , so that the server  20  can determine area attributes based on the image information. 
     The accident determining unit  17  determines whether an accident has occurred in the moving object based on the impact value of the impact detected by the impact detecting unit  13 , the impact sound picked up by the sound pickup unit  15 , and the images around the moving object acquired by the image acquiring unit  16 . Specifically, the accident determining unit  17  determines whether the detected impact value is greater than or equal to the determination threshold (impact threshold) set by the threshold setting unit  14 . Further, the accident determining unit  17  determines whether the sound volume of the impact sound is greater than or equal to the sound-volume threshold. Yet further, the accident determining unit  17  determines whether an obstacle such as a vehicle, a person, or a ground object existed in the vicinity of the moving object when an impact was detected based on the result of image recognition of the images around the moving object acquired by the image acquiring unit  16 . 
     The accident determining unit  17  can determine whether an accident has occurred in the moving object using any of the determination based on the impact value, the determination based on the impact sound, and the determination based on the image information. Further, determination may be made by a combination of these. For example, if the impact value is greater than or equal to the determination threshold, and the sound volume of the impact sound is greater than or equal to the sound-volume threshold, or if the impact value is greater than or equal to the determination threshold, and the existence of an obstacle in the vicinity of the moving object is ascertained, then the accident determining unit  17  determines that an accident has occurred in the moving object. 
     The server  20  includes a communication unit  21 , a storage unit  22 , a map information checking unit  23 , an area attribute determining unit  24 , and a threshold information acquiring unit  25 . 
     The communication unit  21  transmits and receives information to and from the accident determination device  10 . For example, the communication unit  21  receives position information of the moving object from the accident determination device  10  and transmits threshold information to the accident determination device  10 . Further, the communication unit  21  may receive image information of the images around the moving object from the accident determination device  10 . 
     The storage unit  22  stores map information including the positions of roads and parking spaces. Further, the storage unit  22  stores information about impact thresholds set according to area attributes, as threshold information. In general, the moving speed of a moving object in a parking space is smaller than the moving speed of the moving object on a road, so that an accident with small impact is likely to occur in the parking place. Thus, the impact threshold in parking spaces is set at a lower value than the impact threshold in roads (that is, such that detection sensitivity is higher in parking spaces) in the threshold information. 
     The map information checking unit  23  reads out map information stored in the storage unit  22  and compares the read-out map information and the position information received by the communication unit  21 . Thereby, the position on the map of the moving object is identified. 
     The area attribute determining unit  24  determines an attribute given to the area (that is, an area attribute of the area) where the moving object is located, based on the result of comparing by the map information checking unit  23 . Specifically, in the present embodiment, the area attribute determining unit  24  determines whether the moving object is located on a road or in a parking space. 
     Further, when the communication unit  21  receives image information of the images around the moving object, the area attribute determining unit  24  can determine whether the moving object is located in a parking space based on the image information. 
     The threshold information acquiring unit  25  reads out corresponding threshold information from the storage unit  22  based on the area attribute determined by the area attribute determining unit  24  and supplies the threshold information to the communication unit  21 . 
     Next, an example operation of an accident determining process executed by the accident determination device  10  and the server  20  will be described with reference to the flow chart of  FIG. 2 . In the following, an example processing operation will be described in which the server  20  determines the area attribute based on the result of comparing the position information of the moving object received from the accident determination device  10  with the map information, and in which the accident determining unit  17  performs accident determination by a combination of the determination based on the impact value, the determination based on the impact sound, and the determination based on the image information. 
     The position information acquiring unit  12  of the accident determination device  10  detects the position of the moving object and acquires position information (step S 101 ). The communication unit  11  transmits the position information to the server  20  (step S 102 ). 
     The communication unit  21  of the server  20  receives the position information of the moving object from the accident determination device  10 . The map information checking unit  23  reads out map information stored in the storage unit  22 , and checks the position information received by the communication unit  21  against the read-out map information (step S 103 ). 
     The area attribute determining unit  24  determines the area attribute of the area where the moving object is located (whether the area is a road or a parking space), based on the result of checking by the map information checking unit  23  (step S 104 ). 
     The threshold information acquiring unit  25  reads out threshold information corresponding to the area attribute determined by the area attribute determining unit  24  from the storage unit  22  to acquire. The communication unit  21  transmits the threshold information acquired by the threshold information acquiring unit  25  to the accident determination device  10  (step S 105 ). 
     The communication unit  11  of the accident determination device  10  receives the threshold information from the server  20 . The threshold setting unit  14  sets (changes) the determination threshold with which the accident determining unit  17  performs accident determination based on the received threshold information (step S 106 ). In the present embodiment, the threshold setting unit  14  sets an impact threshold indicated by the threshold information as the determination threshold. 
     The accident determining unit  17  determines whether the impact detecting unit  13  has detected an impact having impact value greater than or equal to the determination threshold (step S 107 ). If not detected (No at step S 107 ), the accident determining unit  17  waits for an impact being detected by the impact detecting unit  13 . 
     If determining that the impact greater than or equal to the determination threshold has been detected (Yes at step S 107 ), the accident determining unit  17  determines whether an impact sound greater than of equal to the sound-volume threshold has been detected by the sound pickup unit  15  or an obstacle has been detected in the images around the moving object by the image acquiring unit  16  (step S 108 ). If neither has been detected (No at step S 108 ), the process returns to step S 107 , where the accident determining unit  17  waits again for an impact detected by the impact detecting unit  13 . 
     If determining that either an impact sound greater than or equal to the sound-volume threshold or an obstacle has been detected (Yes at step S 108 ), the accident determining unit  17  determines that an accident has occurred in the moving object. The communication unit  11  transmits an accident notification indicating that an accident is determined to have occurred in the moving object to the server  20  to notify the accident (step S 109 ). 
     By the above processing operation, the accident determination device  10  and the server  20  perform the accident determining process. 
     In the accident notifying system of the present embodiment, the accident determination device  10  transmits position information of the moving object or image information of the images around the moving object to the server  20  and receives threshold information corresponding to the area attribute of the area where the moving object is located from the server  20  so as to perform accident determination. Thus, with the accident notifying system of the present embodiment, accident determination can be performed appropriately according to the area attribute of the area where the moving object is located. 
     Further, with the accident notifying system of the present embodiment, in addition to determination of whether the impact value is greater than or equal to the determination threshold, it is possible to determine whether the impact sound greater than or equal to the sound-volume threshold has been detected and whether an obstacle has been detected in the vicinity of the moving object to perform accident determination. Therefore, with the accident notifying system of the present embodiment, accident determination can be performed with the possibility of erroneous determination being reduced. 
     Embodiment 2 
       FIG. 3  is a block diagram showing the configuration of an accident determination device  30  of Embodiment 2. The accident determination device  30  of the present embodiment differs from the accident determination device  10  of Embodiment 1 in that the device  30  does not acquire threshold information by communicating with the server each time in performing accident determination but performs accident determination based on threshold information stored in its own storage unit. 
     The accident determination device  30  has a storage unit  31 , an area attribute determining unit  32 , an impact detecting unit  33 , a threshold setting unit  34 , a sound pickup unit  35 , an image acquiring unit  36 , an accident determining unit  37 , a position information acquiring unit  38 , and a map information checking unit  39 . 
     The storage unit  31  stores information about impact thresholds set according to area attributes, as threshold information. As in Embodiment 1, the impact threshold in parking spaces is set at a lower value than the impact threshold in roads. Also, the storage unit  31  stores map information including the positions of roads and parking spaces. 
     The area attribute determining unit  32  determines whether the area where the moving object is located is a road or a parking space based on the result of image recognition of the images around the moving object acquired by the image acquiring unit  36 . For example, if signs or character strings placed at the entrance of the parking space are recognized by image recognition, the area attribute determining unit  32  determines that the area where the moving object is located is a parking space. The area attribute determining unit  32  may determine whether the area where the moving object is located is a road or a parking space based on the result of checking position information against map information by the map information checking unit  39 . 
     The impact detecting unit  33  is constituted by an acceleration sensor or the like and detects the impact value of the impact having occurred in the vehicle based on a change in acceleration of the vehicle. 
     The threshold setting unit  34  reads out threshold information stored in the storage unit  31  based on the area attribute determined by the area attribute determining unit  32  and sets the impact threshold corresponding to the read-out threshold information as the determination threshold. In the present embodiment, the sound-volume threshold is set at a constant value. Note that in the present embodiment an impact threshold premised on the case where the moving object is on a road is set as the determination threshold for an initial state (state before changed). 
     The sound pickup unit  35  is constituted by a sound pickup device such as a microphone and picks up an impact sound at the time an impact was detected by the impact detecting unit  33 . 
     The image acquiring unit  36  is constituted by an image pickup device such as an in-vehicle camera and acquires images around the moving object at the time the impact was detected by the impact detecting unit  33 . Further, the image acquiring unit  36  performs image recognition on the images around the moving object. On the basis of the result of this image recognition, the accident determining unit  37  determines whether an obstacle exists in the vicinity of the moving object. Further, the area attribute determining unit  32  determines the area attribute of the area where the moving object is located. 
     The accident determining unit  37  determines whether an accident has occurred in the moving object based on the impact value of the impact detected by the impact detecting unit  33 , the impact sound picked up by the sound pickup unit  35 , and the images around the moving object acquired by the image acquiring unit  36 . The accident determining unit  37  may determine using any of the impact value, impact sound, and image information of the images around the moving object, or by a combination of these. For example, if the detected impact value is greater than or equal to the determination threshold (the impact threshold), and the sound volume of the impact sound is greater than or equal to the sound-volume threshold, or if the impact value is greater than or equal to the determination threshold, and the existence of an obstacle in the vicinity of the moving object is recognized by image recognition, then the accident determining unit  37  determines that an accident has occurred in the moving object. 
     The position information acquiring unit  38  acquires position information indicating the current position of the moving object as does the position information acquiring unit  12  of Embodiment 1. 
     The map information checking unit  39  reads out map information stored in the storage unit  31  and compares the read-out map information and the position information acquired by the position information acquiring unit  38 , thereby identifying the position on the map of the moving object. 
     Next, the operation of an accident determining process executed by the accident determination device  30  will be described with reference to the flow chart of  FIG. 4 . In the following, an example processing operation will be described in which the accident determination device  30  determines the area attribute based on the images around the moving object and in which the accident determining unit  37  performs accident determination by a combination of the determination based on the impact value, the determination based on the impact sound, and the determination based on image information. 
     The image acquiring unit  36  acquires the images around the moving object (step S 201 ). The area attribute determining unit  32  determines whether the area where the moving object is located is a road or not based on the result of image recognition of the acquired images around the moving object (step S 202 ). 
     If it is determined that the area where the moving object is located is a road (Yes at step S 202 ), the threshold setting unit  34  maintains the previous determination threshold without changing the determination threshold (step S 203 ). 
     The accident determining unit  37  determines whether an impact greater than or equal to the determination threshold has been detected by the impact detecting unit  33  (step S 204 ). If determining that impact greater than or equal to the determination threshold has not been detected (No at step S 204 ), the accident determining unit  37  waits for an impact being detected by the impact detecting unit  33 . 
     If determining that the impact greater than or equal to the determination threshold has been detected (Yes at step S 204 ), the accident determining unit  37  then determines whether the impact sound greater than or equal to the sound-volume threshold has been detected by the sound pickup unit  35  or whether an obstacle has been detected in the images around the moving object acquired by the image acquiring unit  36  (step S 205 ). If neither has been detected (No at step S 205 ), the process returns to step S 204 , where the accident determining unit  37  waits again for an impact being detected by the impact detecting unit  33 . 
     If determining that either of the detection of an impact sound greater than or equal to the sound-volume threshold and the detection of an obstacle has happened (Yes at step S 205 ), the accident determining unit  37  determines that an accident has occurred in the moving object on a road and notifies the accident (step S 206 ). 
     On the other hand, if determining that the area where the moving object is located is not a road (No at step S 202 ), the area attribute determining unit  32  determines whether the area where the moving object is located is a parking space or not (step S 207 ). 
     If it is determined that the area where the moving object is located is a parking space (Yes at step S 207 ), the threshold setting unit  34  reads out threshold information corresponding to the case where the moving object is located in a parking space from the storage unit  31  and changes the determination threshold set beforehand to an impact threshold corresponding to parking spaces (step S 208 ). 
     The accident determining unit  37  determines whether the impact greater than or equal to the determination threshold has been detected by the impact detecting unit  33  (step S 209 ). If determining not having been detected (No at step S 209 ), the accident determining unit  37  waits for an impact being detected by the impact detecting unit  33 . 
     If determining that the impact greater than or equal to the determination threshold has been detected (Yes at step S 209 ), the accident determining unit  37  determines whether the impact sound greater than or equal to the sound-volume threshold has been detected by the sound pickup unit  35  or whether an obstacle has been detected in the images around the moving object acquired by the image acquiring unit  36  (step S 210 ). If neither has been detected (No at step S 210 ), the process returns to step S 209 , where the accident determining unit  37  waits again for an impact being detected by the impact detecting unit  33 . 
     If determining that either of the detection of an impact sound greater than or equal to the sound-volume threshold and the detection of an obstacle has happened (Yes at step S 210 ), the accident determining unit  37  determines that an accident has occurred in the moving object in a parking space and notifies the accident (step S 211 ). 
     By the above processing operation, the accident determination device  30  performs the accident determining process. 
     The accident determination device  30  of the present embodiment stores impact thresholds corresponding to area attributes, determines the attribute of the area where the moving object is located by image recognition, and sets the corresponding impact threshold as the determination threshold. Therefore, with the accident determination device  30  of the present embodiment, an appropriate determination threshold can be selected according to the attribute of the area where the moving object is located, to perform accident determination. 
     Embodiment 3 
     An accident notifying system of the present embodiment has the same configuration as the accident notifying system of Embodiment 1 and differs from the accident notifying system of Embodiment 1 in threshold information stored in the storage unit  22  of the server  20  and the type of area attribute determined by the area attribute determining unit  24 . 
     The area attribute determining unit  24  determines the primary attribute and secondary attribute of the area where the moving object is located, based on the result of comparing map information and position information by the map information checking unit  23 . For example, the area attribute determining unit  24  determines whether the area where the moving object is located is a road or a place other than a road (a non-road), for the primary attribute of the area. Then the area attribute determining unit  24  determines whether the road is an unpaved road, an expressway, a low-speed way such as a zone  30 , or a road other than those (called an ordinary road), for the secondary attribute. The area attribute determining unit  24  may determine further for the secondary attribute of roads whether a bump exists on the road, whether a difference in level exists between the road and a sidewalk, whether an intersection exists, whether a store entrance exists, whether a sharp curve exists, whether the road slopes and curves, and so on. As to a non-road area, the area attribute determining unit  24  determines whether that area is a parking space, a ferry landing, or another area for the secondary attribute. 
     The storage unit  22  stores map information including locations of low-speed ways, ordinary roads, expressways, unpaved roads, parking spaces, ferry landings, bumps on roads, spots with a difference in level between a road and a sidewalk, intersections, store entrances, sharp curves, spots where the road slopes and curves, so on. Further, the storage unit  22  stores thresholds to be used by the accident determination device  10  in accident determination based on impact values, as threshold information corresponding to area attributes. 
       FIG. 5  presents a threshold table stored in the storage unit  22  that shows an example of the impact threshold for each area attribute. In this table, impact thresholds corresponding to a low-speed way, an ordinary road, an expressway, an unpaved road, a parking space, a ferry landing, and the other non-road areas from among the above plurality of places (area attributes), are extracted and shown. A threshold A for a low-speed way, a threshold B for an ordinary road, a threshold C for an expressway, a threshold D for an unpaved road, a threshold E for a parking space, a threshold F for a ferry landing, and a threshold G for the other non-road areas, are stored as impact thresholds corresponding to the area attributes in the storage unit  22 . 
     The movement speed of a moving object is smaller on a low-speed way than on an ordinary road and greater on an expressway than on an ordinary road. Thus, the impact threshold for a low-speed way is set at a lower value than the impact threshold for an ordinary road (that is, such that the sensitivity of detection is higher), the impact threshold for an expressway is set at a higher value than the impact threshold for an ordinary road (that is, such that the sensitivity of detection is lower) (threshold A&lt;threshold B&lt;threshold C). Since an unpaved road is rougher in road surface than an ordinary road, it is assumed that erroneous detection more often happens. Thus, in order to prevent erroneous detection, the impact threshold for an unpaved road is set at a higher value than the impact threshold for an ordinary road (that is, such that the sensitivity of detection is lower) (threshold D&gt;threshold B). In a parking space, the movement speed of a moving object is smaller than on a road. Thus, the impact threshold for a parking space is set at a lower value than the impact threshold for a road (that is, such that the sensitivity of detection is higher) (threshold E&lt;threshold B). In a ferry landing, the impact that occurs in a moving object while it is getting on or off a ferry is large, and hence it is assumed that erroneous detection more often happens. Thus, in order to prevent erroneous detection, the impact threshold for a ferry landing is set at a higher value than the impact threshold for a road (that is, such that the sensitivity of detection is lower) (threshold F&gt;threshold B). 
     The threshold information acquiring unit  25  acquires threshold information denoting the impact threshold for the corresponding area attribute from among threshold information stored in the storage unit  22  according to the area attribute determined by the area attribute determining unit  24 . The communication unit  21  transmits the threshold information acquired by the threshold information acquiring unit  25  to the accident determination device  10 . 
     The threshold setting unit  14  of the accident determination device  10  sets (or changes) the determination threshold based on the threshold information received from the server  20  via the communication unit  11 . The accident determining unit  17  performs accident determination based on the set determination threshold. 
     The accident notifying system of the present embodiment determines not only whether the area where the moving object is located is a road or a parking space but the area attribute further categorized into details to set the threshold. Therefore, since one of impact thresholds categorized into details can be selected to set the determination threshold, accident determination can be performed more appropriately according to the area where the moving object is located. 
     Further, the present embodiment can be applied to an accident determination device having the same configuration as in Embodiment 2. For example, the storage unit  31  of the accident determination device  30  stores map information including locations of low-speed ways, ordinary roads, expressways, unpaved roads, parking spaces, ferry landings, bumps on roads, spots with a difference in level between a road and a sidewalk, intersections, store entrances, sharp curves, spots where the road slopes and curves, so on, and threshold information corresponding to these locations; the area attribute determining unit  32  determines the area attribute based on the result of comparing position information and the map information; and the threshold setting unit  34  sets the threshold corresponding to the area attribute as the determination threshold, so that the accident determination device  30  of Embodiment 2 can perform accident determination according to the area attribute categorized into details as in the present embodiment. 
     Embodiment 4 
       FIG. 6  is a block diagram showing the configuration of an accident notifying system of Embodiment 4. The accident notifying system of the present embodiment is composed of a server  20  and a plurality of accident determination devices  10 - 1  to  10 - n  (accident determination devices  10 ) as in Embodiment 1. The accident notifying system of the present embodiment differs from the accident notifying system of Embodiment in that the server  20  has a congestion information acquiring unit  26  and a weather information acquiring unit  27  and in the contents of threshold information stored in the storage unit  22  of the server  20 . 
     Further, the accident notifying system of the present embodiment differs from the accident notifying system of Embodiment 1 in that the accident determining unit  17  of the accident determination device  10  changes the sound-volume threshold as well as the impact threshold as the determination threshold according to the area attribute. 
     The congestion information acquiring unit  26  of the server  20  acquires real-time congestion information of each road link for roads contained in the map information stored in the storage unit  22  from an external device (not shown) via the communication unit  21 . 
     The weather information acquiring unit  27  acquires real-time weather information of each area from an external device via the communication unit  21 . The weather information contains information about the strength of wind and rain and the presence/absence of deposited snow. 
     The area attribute determining unit  24  determines the primary attribute and secondary attribute of the area where the moving object is located based on the result of comparing the map information and position information by the map information checking unit  23 , the congestion information acquired by the congestion information acquiring unit  26 , and the weather information acquired by the weather information acquiring unit  27 . 
     Specifically, the area attribute determining unit  24  determines whether the area where the moving object is located is a road or a parking space, for the primary attribute of the area attribute. Further, the area attribute determining unit  24  determines whether the road where the moving object is located is congested, for a congestion attribute that is one secondary attribute of the area attribute. Yet further, the area attribute determining unit  24  determines whether the area where the moving object is located is covered with snow, for a road surface attribute that is one secondary attribute of the area attribute. Still further, the area attribute determining unit  24  determines the strength of wind and rain in the area where the moving object is located, for a weather attribute that is one secondary attribute of the area attribute. 
     The storage unit  22  stores impact thresholds to be used in accident determination by the accident determination device  10  as threshold information corresponding to area attributes including the primary attribute, congestion attribute, road surface attribute, and weather attribute. 
       FIG. 7  A presents a threshold table stored in the storage unit  22  that shows an example of the impact threshold for each area attribute. A threshold H is stored as the impact threshold for the case where the road is congested. As the impact threshold for the case where the road is covered with snow (a snow covered road), a threshold I is stored for the case where wind and rain are weak; a threshold J for the case where wind and rain are intermediate in strength; and a threshold K for the case where wind and rain are strong. As the impact threshold for the case where the road is not covered with snow (a snow non-covered road), a threshold L is stored for the case where wind and rain are weak; a threshold M for the case where wind and rain are intermediate in strength; and a threshold N for the case where wind and rain are strong. As the impact threshold for the case where the parking space is covered with snow (a snow covered parking space), a threshold O is stored for the case where wind and rain are weak; a threshold P for the case where wind and rain are intermediate in strength; and a threshold Q for the case where wind and rain are strong. As the impact threshold for the case where the parking space is not covered with snow (a snow non-covered parking space), a threshold R is stored for the case where wind and rain are weak; a threshold S for the case where wind and rain are intermediate in strength; and a threshold T for the case where wind and rain are strong. 
     In congestion, since the movement speed of a moving object is lower, an accident with a small impact is likely to occur. Thus, in the threshold table, for a congested road, the impact threshold is set at a lower value than the impact threshold for a non-congested road (that is, such that the sensitivity of detection is higher). When covered with snow, since the road surface is rougher than when not covered with snow, it is assumed that erroneous detection often happens. Thus, in order to prevent erroneous detection, for a snow covered road, the impact threshold is set at a higher value than the impact threshold for a snow non-covered road (that is, such that the sensitivity of detection is lower). Likewise, for a snow covered parking space, the impact threshold is set at a higher value than the impact threshold for a snow non-covered parking space. When wind and rain are strong, since the movement speed of a moving object is smaller than when wind and rain are weak, an accident with a small impact is likely to Occur. Thus, for when wind and rain are strong, the impact threshold is set at a lower value than the impact threshold for when wind and rain are weak (threshold I&gt;threshold J&gt;threshold K, threshold L&gt;threshold M&gt;threshold N, threshold O&gt;threshold P&gt;threshold Q, threshold R&gt;threshold S&gt;threshold T). 
     The storage unit  22  stores sound-volume thresholds to be used in accident determination by the accident determination device  10  as threshold information corresponding to the weather attribute that is one secondary attribute of the area attribute. 
       FIG. 7  B presents a threshold table stored in the storage unit  22  that shows an example of the sound-volume threshold for each weather attribute. A threshold (1) is stored as the sound-volume threshold for the case where wind and rain are weak; a threshold (2) as the sound-volume threshold for the case where wind and rain are intermediate in strength; and a threshold (3) as the sound-volume threshold for the case where wind and rain are strong. When wind and rain are strong, since the sound pickup unit  15  picks up more noise, it is assumed that erroneous detection often happens. Thus, in order to prevent erroneous detection, the sound-volume threshold is set at a greater value as wind and rain become stronger (that is, such that the sensitivity of detection becomes lower) (that is, threshold (1)&lt;threshold (2)&lt;threshold (3)). 
     The threshold information acquiring unit  25  acquires threshold information denoting the impact threshold and sound-volume threshold for the corresponding area attribute from among threshold information stored in the storage unit  22  according to determination of the area attribute determining unit  24 . For example, if the area where the moving object is located is a snow covered road, and wind and rain are strong, then threshold information denoting threshold K as the impact threshold and threshold (3) as the sound-volume threshold is acquired. The communication unit  21  transmits the threshold information acquired by the threshold information acquiring unit  25  to the accident determination device  10 . 
     The threshold setting unit  14  of the accident determination device  10  sets (changes) the impact threshold and sound-volume threshold as the determination threshold based on the threshold information acquired by the communication unit  11 . Note that the threshold setting unit  14  can change the impact threshold and the sound-volume threshold independently of each other. The accident determining unit  17  performs accident determination based on the set impact threshold and sound-volume threshold. 
     The accident notifying system of the present embodiment sets the determination threshold based on the congestion attribute indicating whether congestion exists, the road surface attribute indicating whether snow is deposited, and the weather attribute indicating the strength of wind and rain as well as the primary attribute indicating whether the area where the moving object is located is a road or a parking space. Further, not only the impact threshold but also the sound-volume threshold can be changed according to the area attribute. Therefore, a threshold can be selected according to the situation in which the moving object is, to perform accident determination appropriately. 
     Embodiments of the present invention are not limited to what are shown by the above embodiments 1 to 4. For example, the above embodiments 1, 3, and 4 describe the configuration where the accident determination device  10  receives threshold information from the server  20  and sets the determination threshold based on the received threshold information. However, a configuration may be made in which the accident determination device  10  stores pieces of threshold information in the storage unit beforehand, receives information about the area attribute, not threshold information, from the server  20 , and sets the determination threshold based on threshold information stored in its own storage unit. 
     Further, the above embodiment 4 describes the configuration where the sound-volume threshold for an impact sound is changed according to the weather attribute indicating the strength of wind and rain. However, a configuration may be made in which the sound-volume threshold is changed according to an area attribute other than the weather attribute (e.g., whether the area is a road or a parking space). In this case, the impact threshold and the sound-volume threshold as the determination threshold can be changed independently of each other. 
     Yet further, the above embodiment 3 describes the configuration where the road surface state and the congestion situation are determined for the area attribute of the area where the moving object is located so as to change the determination threshold. However, a configuration may be made in which additionally speed information of the moving object is acquired so as to change the threshold according to a combination of the area attribute and the speed information. The speed information can be acquired, for example, by providing a vehicle speed sensor in the accident determination device and acquiring a vehicle speed pulse signal from the ECU (Engine Control Unit) of the vehicle that is the moving object to calculate the vehicle speed. 
     The above embodiments can be used in combination as needed. For example, the above embodiments 3 and 4 may be combined to form a configuration where the area attribute is further determined into details to set the threshold. 
     A series of processes described in the above embodiments can be executed by computer processing according to a program stored in a recording medium such as a ROM.