Patent Publication Number: US-2018054709-A1

Title: Estimation device, estimation method, and non-transitory computer readable storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2016-160875 filed in Japan on Aug. 18, 2016. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an estimation device, an estimation method, and a non-transitory computer readable storage medium having stored therein an estimation program. 
     2. Description of the Related Art 
     Conventionally, car navigation (hereinafter, also referred to as “guidance”) techniques to guide a vehicle on which a user is riding to a destination using a portable terminal device such as a smartphone have been known. A terminal device that performs such guidance uses a satellite positioning system such as a global positioning system (GPS) to specify a current location of a vehicle and displays a screen representing a map or an induced route and the specified current location in a superimposed manner. 
     Meanwhile, the terminal device is incapable of displaying the current location in a place where it is difficult to receive a signal from a satellite such as the inside of a tunnel. The same problem is common generally in positioning techniques using an outside signal (for example, a radio wave from a mobile phone (cellular) base station, a wireless LAN radio wave, or the like) without being limited to the GPS. In this regard, a technique of autonomous positioning to estimate a current location of a vehicle using acceleration measured by an accelerometer is conceivable. For example, proposed is a technique in which a device including an accelerometer is fixed in a vehicle in a predetermined posture, and a traveling state of the vehicle is estimated based on acceleration detected by the device (see the publication of Japanese Patent No. 4736866). 
     However, installation postures of the terminal device such as the smartphone inside a car are different each time depending on a type of the car on which a user rides, a use state of a holder holding the terminal device, and the like. Thus, it may be difficult to estimate the traveling state of a vehicle. 
     For example, the terminal device includes the accelerometer that detects the acceleration in an axial direction having the terminal device as a reference, and thus, converts a direction of the detected acceleration into a direction having a movement direction of the vehicle as a reference based on the installation posture of the terminal device. In addition, the terminal device estimates the movement direction and speed of the vehicle using the acceleration whose direction has been converted and specifies a current location of the vehicle based on the estimated movement direction and speed. However, when the installation posture is unknown or when the installation posture changes, the terminal device is incapable of converting the direction of acceleration, and accuracy in estimation of the traveling state deteriorates. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     An estimation device includes a detection unit that detects acceleration in a moving object, an acquisition unit that acquires speed of the moving object, and an estimation unit that estimates a movement direction of the moving object based on a direction of the acceleration detected by the detection unit when the speed acquired by the acquisition unit changes. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view for describing an example of an operational effect exerted by a terminal device according to an embodiment; 
         FIG. 2  is a diagram describing an example of a functional configuration of the terminal device according to the embodiment; 
         FIG. 3  is a view illustrating an example of information registered in a GPS speed database according to the embodiment; 
         FIG. 4  is a view illustrating an example of information registered in an acceleration database according to the embodiment; 
         FIG. 5  is a view illustrating an example of information registered in an average value database according to the embodiment; 
         FIG. 6  is a flowchart describing an example of flow of a guidance process executed by the terminal device according to the embodiment; 
         FIG. 7  is a flowchart describing an example of flow of an acquisition process executed by the terminal device according to the embodiment; 
         FIG. 8  is a flowchart describing an example of flow of a detection process executed by the terminal device according to the embodiment; 
         FIG. 9  is a flowchart describing an example of flow of an estimation process executed by the terminal device according to the embodiment; 
         FIG. 10  is a view illustrating an example of acceleration acquired by the terminal device according to the embodiment; 
         FIG. 11  is a view illustrating an example of a process of processing in which the terminal device according to the embodiment estimates a movement direction; and 
         FIG. 12  is a view illustrating an example of a process of detecting a change of an installation posture by the terminal device according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, modes (hereinafter, referred to as “embodiments”) for carrying out an estimation device, an estimation method, and a non-transitory computer readable storage medium having stored therein an estimation program according to the present application will be described in detail with reference to the drawings. Incidentally, the estimation device, the estimation method, and the non-transitory computer readable storage medium having stored therein the estimation program according to the present application are not limited by the embodiment. In addition, the same parts and processes in the following respective embodiments will be denoted by the same reference numerals, and the redundant descriptions thereof will be omitted. 
     In addition, an example of car navigation, which guides a vehicle on which a user rides to a destination will be described as a process executed by the estimation device in the following description, but the embodiment is not limited thereto. For example, the estimation device may execute the process of guiding the user to the destination by executing a process to be described hereinafter even in a case where the user is walking or in the case of using a transportation means other than a vehicle, such as a train. 
     1. Overview of Movement State 
     First, a concept of a movement mode determined by a terminal device  10  which is an example of the estimation device will be described with reference to  FIG. 1 .  FIG. 1  is a view for describing an example of an operational effect exerted by a terminal device according to an embodiment. For example, a terminal device  10  is a terminal device such as a smart phone, a tablet terminal, a mobile terminal such as a personal digital assistant (PDA), and a laptop personal computer (PC), and is a terminal device capable of communicating with an arbitrary server via a network N such as a mobile communication network and a wireless local area network (LAN). 
     In addition, the terminal device  10  has a car navigation function of guiding a vehicle C 10  on which a user rides to a destination. For example, when receiving input of the destination from the user, the terminal device  10  acquires route information, configured to induce the user to the destination, from a server (not illustrated) or the like. For example, the route information includes a route to the destination that can be used by the vehicle C 10 , information on expressway included in the route, traffic congestion information on the route, a facility serving as a landmark of guidance, information on a map displayed on a screen, and data such as a sound to be output at the time of guidance and an image such as the map. 
     In addition, the terminal device  10  has a positioning function of specifying a position of the terminal device  10  (hereinafter referred to as a “current location”) at predetermined time intervals using a satellite positioning system such as a global positioning system (GPS). Further, the terminal device  10  displays the image such as the map included in the route information on a liquid crystal screen, an electroluminescence or light emitting diode (LED) screen (hereinafter, simply referred to as the “screen”), and further, displays the specified current location on the map each time. In addition, the terminal device  10  displays a left turn, a right turn, a change of a lane to be used, an expected arrival time to a destination, and the like according to the specified current location, or outputs these types of information using voice from a speaker or the like of the terminal device  10  and the vehicle C 10 . 
     Here, signals transmitted from a plurality of satellites are received in the satellite positioning system, and the current location of the terminal device  10  is specified using the received signals. Thus, when it is difficult to appropriately receive the signal transmitted from the satellite, such as in a tunnel or a place between buildings, the terminal device  10  is incapable of specifying the current location. In addition, an application or the like that implements guidance in the terminal device  10  does not have a function of acquiring information such as speed, a movement direction, and the like from the vehicle C 10 . Thus, it is possible to conceive a technique in which an acceleration sensor to measure acceleration is installed on the terminal device  10  and the current position of the terminal device  10  is estimated based on the acceleration measured by the acceleration sensor. For example, it is possible to conceive a technique to perform an estimation process of estimating movement speed, a movement direction, and the like of the terminal device  10  and stop determination in which whether the terminal device  10  is moving or stopped based on the acceleration measured by the acceleration sensor. 
     A more specific example will be described. For example, when it is difficult to appropriately receive the signal transmitted from the satellite, the terminal device  10  determines that the vehicle C 10  has entered a tunnel or the like and advances an estimated position without any change with vehicle speed and a movement direction specified last. In addition, the terminal device  10  determines whether or not the vehicle C 10  is stopped based on the measured acceleration, and stops movement of the estimated position when it is determined that the vehicle C 10  is stopped. On the other hand, when it is determined that the vehicle C 10  is not stopped, the terminal device  10  estimates the movement speed of the vehicle C 10  as the moving object using the measured acceleration and continues guidance assuming movement at the estimated movement speed. 
     1-1. Example of Speed Estimation Technique 
     Here, an example of a speed estimation technique to estimate the movement speed of the vehicle C 10  will be described. Incidentally, the technique illustrated herein is an example of a technique that is a preliminary step of the present embodiments, and does not belong to the original related art. That is, the technique illustrated herein is a technique that the present applicant confidentially performs for the purpose of development, testing, research, and the like, and is not a technique departing from secrets such as what is so-called public knowledge, public use, or public knowledge from the literature. 
     For example, as illustrated in (A) of  FIG. 1 , the terminal device  10  sets a short-length direction of the screen as an x axis, a long-length direction of the screen as a y axis, and a direction perpendicular to the screen as a z axis, and measures acceleration in each of x axis, y axis, and z axis directions. For example, when the screen is set as the front, the terminal device  10  sets the front side to a +z axis direction and the back side to a −z axis direction, and measures acceleration in a terminal coordinate system in which an upper side of the screen at the time of using the terminal device  10  is set as a +x axis direction, a lower side of the screen is set as a −x axis direction, a left side of the screen is set as a +y axis direction, and a right side of the screen is set as a −y axis direction. 
     On the other hand, the movement direction and speed of the vehicle C 10  used by the user are expressed in a vehicle coordinate system in which a progressing direction of the vehicle C 10  is set as a Z axis, and on a plane perpendicular to the Z axis, a direction in which the vehicle C 10  turns right or left at the time of progressing is set as a Y axis direction, and an up-and-down direction of the vehicle C 10  is set as an X axis direction as illustrated in (B) of  FIG. 1 . For example, the movement direction and the speed of the vehicle C 10  are expressed in the vehicle coordinate system in which an up direction of the vehicle C 10  is set as +X axis direction, a down direction (for example, a ground side) is set as a −X axis direction, a left-turning direction is set as a +Y axis direction, a right-turning direction is set as a −Y axis direction, a rear direction of the vehicle C 10  is set as a +Z axis direction, and a front direction thereof is set as a −Z axis direction. 
     Here, the vehicle coordinate system and the terminal coordinate system have deviations depending on an installation posture and the like of the terminal device  10 . Thus, for example, the terminal device  10  estimates a direction of gravity, that is, the −X axis direction of the vehicle coordinate system using the acceleration measured in the terminal coordinate system, specifies the movement direction of the vehicle C 10  using a variance of the acceleration generated when the vehicle C 10  accelerates or decelerates, or changes the movement direction, and obtains a rotation matrix to convert the acceleration measured in the terminal coordinate system into the vehicle coordinate system based on an estimated reference direction and the movement direction. Further, the terminal device  10  converts the acceleration in the terminal coordinate system into the acceleration in the vehicle coordinate system using the rotation matrix, and executes stop determination on whether or not the vehicle C 10  is stopped, and estimation of the movement speed of the vehicle C 10  using a converted acceleration. 
     For example, the terminal device  10  collects information on an amplitude, a frequency, an average value, a standard deviation, a maximum value, a minimum value, and the like in each axis direction of the converted acceleration as a feature amount. In addition, the terminal device  10  accumulates a feature amount acquired when the speed of the vehicle C 10  is equal to or higher than a predetermined threshold as a feature amount during traveling, and accumulates a feature amount acquired when the speed of the vehicle C 10  is equal to or lower than the predetermined threshold as a feature amount during stop. 
     Further, the terminal device  10  learns a stop determination model (for example, obtained by a support vector machine (SVM) or the like) to determine whether or not the vehicle C 10  is stopped using the accumulated feature amount, and determines whether or not the vehicle C 10  is stopped using the learned stop determination model in a case where it is difficult to use the satellite positioning system, such as in the tunnel. Further, when determining that the vehicle C 10  is not stopped, the terminal device  10  estimates the movement speed of the vehicle C 10  based on an integrated value of acceleration values on a plane including the movement direction among accelerations acquired in the vehicle coordinate system. 
     However, the movement direction of the vehicle C 10  is specified using the variance of the acceleration generated when the vehicle C 10  moves in such a technique, and thus, it is necessary for the vehicle C 10  to accelerate or decelerate plural times in order to obtain the rotation matrix so that it takes time to obtain the rotation matrix. As a result, when the vehicle C 10  enters the tunnel before obtaining the rotation matrix after start of guidance, for example, there is a problem that it is difficult to obtain the rotation matrix and to start the stop determination. In addition, data obtained for a certain period is used at the time of determining the movement direction of the vehicle C 10  in such a technique. Thus, there is a possibility that it is difficult to accurately determine the movement direction depending on the quality of data used to determine the movement direction. 
     In addition, there is a case where the user gets off a car possessing the terminal device  10  in a service area or the like. As a result, it is necessary to specify the movement direction again and to obtain the rotation matrix again based on the specified movement direction and the reference direction because the rotation matrix changes when the posture of the terminal device  10  changes. However, even when such a process is executed, it is difficult to start the stop determination until the movement direction is specified. In addition, a deviation occurs between the terminal coordinate system and the vehicle coordinate system when a road is inclined, and thus, an error is likely to occur. 
     Incidentally, it is also possible to conceive a technique in which an average value of accelerations is calculated without coordinate conversion of the acceleration measured in the terminal coordinate system and the stop determination model is learned from a feature amount of the calculated average value. In such a technique, however, the installation posture of the terminal device  10  is unknown, and thus, it is necessary to unconditionally learn the stop determination model every time the guidance is started. In addition, even when such a technique is used, it is necessary to learn the stop determination model again if the installation posture of the terminal device  10  changes, and further, the error is likely to occur when the road is inclined. 
     2. Regarding Determination Process Executed by Terminal Device  10  According to Embodiment 
     Then, the terminal device  10  executes the following determination process. For example, the terminal device  10  detects acceleration of a moving object in which the terminal device  10  is installed, such as the vehicle C 10 . In addition, the terminal device  10  acquires speed of the moving object. Further, the terminal device  10  estimates a movement direction of the moving object based on a direction of the acceleration detected when the acquired speed changes. 
     Hereinafter, an example of a functional configuration and operational effects of the terminal device  10  that implements the above-described determination process will be described with reference to the drawings. 
     2-1. Example of Functional Configuration 
       FIG. 2  is a diagram describing an example of the functional configuration of the terminal device according to the embodiment. As illustrated in  FIG. 2 , the terminal device  10  includes a communication unit  11 , a storage unit  12 , a plurality of acceleration sensors  13   a  to  13   c  (hereinafter, collectively referred to as an “acceleration sensor  13 ” in some cases), a GPS reception antenna  14 , an output unit  15 , and a control unit  16 . The communication unit  11  is implemented using, for example, a network interface card (NIC) or the like. Further, the communication unit  11  is connected to a network N in a wired or wireless manner, and performs transmission and reception of information between the terminal device  10  and a distribution server, which distributes route information indicating a route to a destination when receiving the destination from the terminal device  10 . 
     The storage unit  12  is implemented using, for example, a semiconductor memory element such as a random access memory (RAM) and a flash memory or a storage device such as a hard disk and an optical disk. In addition, the storage unit  12  includes a guidance information database  12   a , a GPS speed database  12   b , an acceleration database  12   c , and an average value database  12   d  which are various types of data used to execute guidance. 
     Various types of data used when the terminal device  10  performs guidance are registered in the guidance information database  12   a . For example, the route information to the destination received from the server (not illustrated) or the like is stored in the guidance information database  12   a . In addition, various types of images, voice data and the like output for guidance are stored in the guidance information database  12   a.    
     In the GPS speed database  12   b , GPS speed, which is the speed of the vehicle C 10  acquired using an arbitrary positioning system such as the GPS is registered. More specifically, the GPS speed calculated from a difference between positions of the vehicle C 10  acquired at predetermined time intervals (for example, one second) using the GPS is registered in the GPS speed database  12   b . Incidentally, a description will be given regarding an example in which the terminal device  10  acquires the GPS speed from the difference between positions of the vehicle C 10  in the following description, but the embodiment is not limited thereto. For example, the terminal device  10  may acquire the speed of the vehicle C 10  from a signal received from a GPS satellite using the Doppler effect. For example, the terminal device  10  may acquire the speed of the vehicle C 10  based on a wave number change of a signal (carrier wave) received from the GPS satellite. 
     For example,  FIG. 3  is a view illustrating an example of information registered in the GPS speed database according to the embodiment. As illustrated in  FIG. 3 , information having items such as “date and time”, “speed”, and “change amount” is registered in the GPS speed database  12   b . Here, “date and time” is information indicating the estimated date and time when the vehicle C 10  moves at the associated “speed”. More specifically, the “date and time” is the date and time when one of two GPS signals, used at the time of calculating the GPS speed indicated by the associated “speed”, is received or a median of dates and times of the two GPS signals. This “date and time” is information indicating the date and time when the vehicle C 10  moves at the speed indicated by the associated “speed”. 
     In addition, “speed” is information indicating the GPS speed, and for example, the movement speed of the vehicle C 10 , calculated by dividing a distance between a position indicated by a GPS signal received at a certain date and time and a position indicated by a GPS signal received immediately before the GPS signal, by an interval between times when the respective GPS signals are received is registered. In addition, “change amount” is information indicating a difference between the associated “speed” and the previously acquired “speed”, that is, a change amount of the GPS speed. 
     For example, a date and time “2016/10/1/10:00:15”, speed “30 km/h”, and a change amount “N/A” are registered in the GPS speed database  12   b  in association with each other in the example illustrated in  FIG. 3 . Such information indicates that the speed “30 km/h” is acquired as the GPS speed of the vehicle C 10  in the date and time “2016/10/1/10:00:15”. In addition, a date and time “2016/10/1/10:00:16”, speed “32 km/h”, and a change amount “2 km/h/s” are registered in the GPS speed database  12   b  in association with each other in the example illustrated in  FIG. 3 . Such information indicates that the speed “32 km/h” is acquired as the GPS speed of the vehicle C 10  in the date and time “2016/10/1/10:00:16”, and a difference from the previously acquired speed, that is, the speed “30 km/h” in the date and time “2016/10/1/10:00:15” is the change amount “2 km/h/s”. Here, the change amount “2 km/h/s” indicates that acceleration is performed at a rate of 2 km/h per second. 
     The acceleration measured by the acceleration sensor  13  of the terminal device  10  is assumed in the acceleration database  12   c . More specifically, the acceleration measured by the acceleration sensor  13  at a predetermined time interval (for example, 0.02 seconds) is held in the acceleration database  12   c  during a predetermined period. 
     For example,  FIG. 4  is a view illustrating an example of information registered in the acceleration database according to the embodiment. As illustrated in  FIG. 4 , information having items such as “date and time”, “acceleration”, and “average value” is registered in the acceleration database  12   c . Here, “date and time” illustrated in  FIG. 4  is information indicating a date and time when acceleration associated therewith is measured at a predetermined interval. In addition, “acceleration” is information indicating acceleration detected at a date and time associated therewith. In addition, “average value” is an average value of associated accelerations, that is, an average value of accelerations detected at a date and time indicated by the associated “date and time”. 
     For example, when the acceleration sensor  13  measures acceleration at a rate of 50 times per second (that is, an interval of 0.02 seconds),  50  accelerations measured during an arbitrary one second and an average value of the accelerations, and a median of the dates and times when the respective accelerations are measured are registered in the acceleration database  12   c  in the state of being associated with each other. More specifically, a date and time “2016/10/1/10:00:15”, accelerations “acceleration #1-1” to “acceleration #1-3”, and an average value “average value #1” are registered in the acceleration database  12   c  in association with each other in the example illustrated in  FIG. 4 . Such information indicates that a median of dates and times when the accelerations “acceleration #1-1” to “acceleration #1-3” are measured is the date and time “2016/10/1/10:00:15” and an average value of the accelerations “acceleration #1-1 “to” acceleration #1-3” is the average value “average value #1”. Although conceptual values such as “acceleration #1-1” and “average value #1” are described in  FIG. 4 , in practice, values indicating acceleration and an average value are registered. 
     A collected average value, which is an average value collected from the acceleration database  12   c  by a process to be described later, is registered in the average value database  12   d . For example,  FIG. 5  is a view illustrating an example of information registered in the average value database according to the embodiment. As illustrated in  FIG. 5 , information having items such as “collection average value identifier (ID)” and “collection average value” is registered in the average value database  12   d . Here, “collected average value ID” is an identifier to identify a collected average value, and “collected average value” is a collected average value which is an average value collected from the acceleration database  12   c.    
     For example, a collected average value ID “1” and a collected average value “average value #1” are registered in association with each other in the average value database  12   d  in the example illustrated in  FIG. 5 . Such information indicates that the average value “average value #1” is collected from the acceleration database  12   c  as the collected average value. 
     Returning to  FIG. 2 , the description will be continued. The acceleration sensor  13  measures a magnitude and a direction of acceleration according to the terminal device  10  at a predetermined time interval. For example, the acceleration sensor  13   a  measures acceleration in the x axis direction in the terminal coordinate system. The acceleration sensor  13   b  measures acceleration in the y axis direction in the terminal coordinate system. The acceleration sensor  13   c  measures acceleration in the z axis direction in the terminal coordinate system. That is, the terminal device  10  can acquire a vector indicating the direction and the magnitude of the acceleration with respect to the terminal device  10  by setting the acceleration measured by each of the acceleration sensors  13   a  to  13   c  as the acceleration in each axis direction of the terminal coordinate system. 
     The GPS reception antenna  14  is an antenna configured to receive a signal used in the satellite positioning system such as the GPS from a satellite. In addition, the output unit  15  is a screen configured to display a map and a current location at the time of performing guidance or a speaker configured to output sound. Incidentally, the acceleration sensor  13  and the GPS reception antenna  14  are implemented by predetermined hardware. 
     The control unit  16  is implemented, for example, as various programs, stored in the storage device inside the terminal device  10  are executed by a central processing unit (CPU), a micro processing unit (MPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like using a storage area such as a RAM as a work area. In the example illustrated in  FIG. 2 , the control unit  16  includes a guidance execution unit  17 , a sound output unit  18 , an image output unit  19 , and a movement state determination unit  20  (hereinafter, collectively referred to as processors  17  to  20  in some cases). In addition, the movement state determination unit  20  includes a detection unit  21 , a specifying unit  22 , a conversion unit  23 , an acquisition unit  24 , an estimation unit  25 , and a determination unit  26 . 
     Incidentally, a connection relationship among the processors  17  to  20  provided in the control unit  16  is not limited to the connection relationship illustrated in  FIG. 2 , but may be other connection relationships. In addition, although each of the processors  17  to  20  implements and executes functions and operations (for example,  FIG. 1 ) of the guidance process as will be described hereinafter, these are functional units organized for the sake of description, and do not necessarily matches actual hardware elements or software modules. That is, the terminal device  10  may implement and execute the guidance process in arbitrary functional units as long as the functions and operations of the following guidance process can be implemented and executed. 
     2-2. Example of Operational Effect of Guide Process 
     Hereinafter, a content of the guidance process to be executed and implemented by each of the processors  17  to  20  will be described with reference to a flowchart illustrated in  FIG. 6 .  FIG. 6  is the flowchart describing an example of flow of the guidance process executed by the terminal device according to the embodiment. 
     First, the guidance execution unit  17  determines whether or not a destination has been input from the user (Step S 101 ). Further, when the destination is input (Step S 101 : Yes), the guidance execution unit  17  acquires route information from an external server (not illustrated) (Step S 102 ). Here, the guidance execution unit  17  determines whether or not the GPS is available (Step S 103 ). 
     For example, the guidance execution unit  17  determines that the GPS is not available (Step S 103 : Yes), for example, when it is difficult for the GPS reception antenna  14  to receive a signal from a satellite or when the number of satellites from which signals have been received is smaller than a predetermined threshold, and acquires a current position from a movement direction and speed of the vehicle C 10  estimated by the movement state determination unit  20  (Step S 104 ). For example, the guidance execution unit  17  acquires the current location estimated by the movement state determination unit  20 . Incidentally, a specific content of a process of estimating the current location of the vehicle C 10  executed by the movement state determination unit  20  will be described later. 
     On the other hand, when determining that the GPS is available (Step S 103 : No), the guidance execution unit  17  specifies a current location using the GPS (Step S 105 ). Further, the guidance execution unit  17  controls the sound output unit  18  and the image output unit  19 , and outputs guidance using the current location obtained using the GPS or the estimated current location (Step S 106 ). For example, the sound output unit  18  outputs sound indicating the current location, a direction in which the vehicle C 10  is to travel, and the like from the output unit  15  in accordance with the control by the guidance execution unit  17 . In addition, the image output unit  19  outputs an image in which a current location and a surrounding map are superimposed on each other, and an image indicating the direction in which the vehicle C 10  is to travel, and the like from the output unit  15  in accordance with the control by the guidance execution unit  17 . 
     Subsequently, the guidance execution unit  17  determines whether or not the current location is around the destination (Step S 107 ). Further, when determining that the current location is around the destination (Step S 107 : Yes), the guidance execution unit  17  controls the sound output unit  18  and the image output unit  19  to output end guidance indicating end of guidance (Step S 108 ), and ends the process. On the other hand, when determining that the current location is not around the destination (Step S 107 : No), the guidance execution unit  17  executes Step S 103 . Incidentally, when the destination is not input (Step S 101 : No), the guidance execution unit  17  waits until input is made. 
     2-3. Example of Operational Effect of Acquisition Process 
     Next, a content of an acquisition process executed and implemented by the acquisition unit  24  will be described with reference to a flowchart illustrated in  FIG. 7 .  FIG. 7  is the flowchart describing an example of flow of the acquisition process executed by the terminal device according to the embodiment. 
     For example, the acquisition unit  24  executes the acquisition process illustrated in  FIG. 7  at a predetermined time interval (for example, one second). First, the acquisition unit  24  specifies a position of the terminal device  10 , that is, a position of the vehicle C 10  using the GPS (Step S 201 ). Further, the acquisition unit  24  calculates GPS speed based on a difference between a position previously specified using the GPS and the position specified in Step S 201  (Step S 202 ). 
     In addition, the acquisition unit  24  calculates a difference between the previously calculated GPS speed and a newly calculated GPS speed as a change amount (Step S 203 ). Incidentally, for example, when calculating the GPS speed every t seconds, the acquisition unit  24  may use a value obtained by dividing the difference between the previously calculated GPS speed and the newly calculated GPS speed by t as the change amount. Further, the acquisition unit  24  registers a date and time when the position of the vehicle C 10  is specified in Step S 201 , the calculated GPS speed, and the calculated change amount in the GPS speed database  12   b  in association with each other (Step S 204 ). That is, the acquisition unit  24  executes processes of specifying a position of the vehicle C 10 , which is the moving object, at a predetermined time interval using a predetermined position positioning system, and acquiring speed of the vehicle C 10  as the moving object based on a change in the specified position. 
     For example, as illustrated in (D) in  FIG. 1 , the acquisition unit  24  acquires GPS information at an interval of one second, and acquires GPS speed #1, GPS speed #2, and GPS speed #3 at an interval of one second based on a difference between positions indicated by the acquired pieces of GPS information. Further, the acquisition unit  24  calculates a change amount #1 from the GPS speed #1 and the GPS speed #2, and calculates a change amount #2 from the GPS speed #2 and the GPS speed #3. 
     Incidentally, the acquisition unit  24  may acquire the speed of the vehicle C 10  via a general standard configured to acquire information from a control device of an information system or a control system provided in the vehicle C 10  such as an on-board diagnostics (OBD) terminal. In addition, the acquisition unit  24  may acquire the movement speed of the vehicle C 10  from the control device of the information system or the control system provided in the vehicle C 10  using a short-range wireless communication technology such as Bluetooth (registered trademark). When the speed is directly acquired from the control device provided in the vehicle C 10  in this manner, the accuracy of speed is improved and a delay can be suppressed as compared with the case where the movement speed is estimated using the GPS. Thus, the terminal device  10  can improve accuracy in estimation of the movement direction of the vehicle C 10  in an estimation process to be described later. 
     2-4. Example of Operational Effect in Detection Process 
     Next, an example of flow of a detection process executed by the detection unit  21 , the specifying unit  22 , and the conversion unit  23  will be described with reference to a flowchart illustrated in  FIG. 8 .  FIG. 8  is the flowchart describing the example of the flow of the detection process executed by the terminal device according to the embodiment. 
     For example, the detection unit  21  acquires acceleration from the acceleration sensor  13  (Step S 301 ). Specifically, the acceleration sensor  13  acquires a magnitude of the acceleration measured for each (x, y, z) axis direction of the terminal coordinate system at a predetermined time interval. In addition, the detection unit  21  calculates an average value of the magnitudes of the accelerations measured by the acceleration sensor  13  during a predetermined period for each axis direction of the terminal coordinate system (Step S 302 ). For example, the detection unit  21  collects the accelerations of the terminal coordinate system detected by the acceleration sensor  13  every 20 milliseconds (that is, at a rate of 50 times during one second) for one second. Further, the detection unit  21  calculates an average value x m  of values in the x axis direction, an average value y m  of values in the y axis direction, and an average value z m  of values in the z axis direction of the respective collected accelerations, respectively, and sets a vector (x m , y m , z m ) formed of the calculated average values in the respective axial directions as an average vector G. 
     Subsequently, the specifying unit  22  specifies a reference direction based on the acceleration calculated by the detection unit  21  (Step S 303 ). More specifically, as illustrated in (C) in  FIG. 1 , the specifying unit  22  sets a direction of the average vector G, formed of the average values of the accelerations calculated by the detection unit  21 , as the reference direction. 
     Subsequently, the conversion unit  23  calculates a rotation matrix that causes a predetermined axial direction of the terminal coordinate system to match the reference direction set by the specifying unit  22  (Step S 304 ). Further, the conversion unit  23  converts each component of the acceleration, acquired in the terminal coordinate system by the detection unit  21 , using the calculated rotation matrix (Step S 305 ). That is, the conversion unit  23  converts the acceleration acquired by the detection unit  21  into acceleration of a coordinate system having the reference direction as a reference instead of the vehicle coordinate system. 
     For example, the specifying unit  22  sets the direction of the average vector G of the acceleration as the reference direction. Further, the conversion unit  23  calculates a rotation matrix as a C 1  conversion formula such that the −x axis direction of the terminal coordinate system and the direction of the average vector G match each other. Here, when the vehicle C 10  is stopped or the like, it is predicted that the direction of the average vector G matches the direction of a gravitational acceleration. Thus, the conversion unit  23  matches the −x axis direction of the terminal coordinate system and the X axis direction of the vehicle coordinate system by matching the −x axis direction of the terminal coordinate system and the direction of the average vector G. 
     Incidentally, the conversion unit  23  may determine whether or not the vehicle C 10  is stopped using the SVM, the GPS speed, or the like, and set the direction of the average vector G of the acceleration acquired by the acceleration sensor  13  as the reference direction when it is determined that the vehicle C 10  is stopped. In addition, the conversion unit  23  may adopt an arbitrary rotation matrix as long as the rotation matrix enables the −x axis direction of the terminal coordinate system and the direction of the average vector G to match each other. That is, the conversion unit  23  may adopt a rotation matrix that causes the y axis direction or the z axis direction to be rotated into an arbitrary direction. In addition, a process of converting the coordinate system of the acceleration measured by the acceleration sensor  13  using the C 1  conversion formula that causes the −x axis direction of the terminal coordinate system and the direction of the average vector G to match each other will be sometimes described as C 1  conversion in the following description. 
     Further, the conversion unit  23  calculates an average value on a YZ plane of accelerations subjected to the C 1  conversion, and holds the calculated average value together with a date and time when the acceleration has been measured during a predetermined period (Step S 306 ). For example, the conversion unit  23  performs the C 1  conversion of the acceleration acquired by the detection unit  21  into acceleration of a coordinate system in which the y axis does not match the Y axis and the z axis does not match the Z axis (the coordinate system having the reference direction as the reference). In addition, the conversion unit  23  extracts accelerations on the YZ plane, that is, a plane perpendicular to the x axis direction among the accelerations detected during a predetermined period (for example, one second). 
     Further, the conversion unit  23  registers the extracted accelerations, the date and time when each acceleration is detected, and an average value of the extracted accelerations in the acceleration database  12   c  in association with each other. For example, the conversion unit  23  registers a date and time serving as a start point, an end point, or a midpoint during one second, accelerations on the YZ plane of the accelerations measured during the one second, and an average value of the accelerations in the acceleration database  12   c  in association with each other. 
     In this manner, the conversion unit  23  applies the rotation matrix to the measured accelerations and acquires the average value #1, the average value #2, and the average value #3 of the accelerations on the YZ plane as illustrated in (E) in  FIG. 1 . That is, the terminal device  10  calculates the GPS speed from the GPS information and calculates the change amount, and further, calculates the average value of the accelerations detected by the acceleration sensor  13  at a predetermined time interval. 
     Incidentally, when the above-described C 1  conversion is performed on the acceleration measured by the acceleration sensor  13 , the x axis of the terminal coordinate system and the X axis of the vehicle coordinate system can be made to match each other, but, it is not always possible to make the y axis or the z axis of the terminal coordinate system match the Y axis or the Z axis of the vehicle coordinate system. Thus, the terminal device  10  estimates the movement direction of the vehicle C 10  based on the acceleration by the estimation process to be described later, and calculates a rotation matrix that causes the y axis or the z axis of the terminal coordinate system to match the Y axis or the Z axis of the vehicle coordinate system as a C 2  conversion formula. 
     2-5. Example of Operational Effect in Estimation Process 
     Next, an example of flow of the estimation process executed by the estimation unit  25  and the determination unit  26  will be described with reference to a flowchart illustrated in  FIG. 9 .  FIG. 9  is the flowchart describing the example of the flow of the estimation process executed by the terminal device according to the embodiment. 
     For example, the estimation unit  25  refers to the GPS speed database  12   b  and specifies a date and time when a change amount exceeds a predetermined threshold (Step S 401 ). That is, the estimation unit  25  specifies the date and time when it is estimated that acceleration greater than a predetermined threshold is applied to the vehicle C 10  by acceleration, deceleration, or the like, using the GPS speed. It is predicted that information on the acceleration detected at such timing includes information indicating a magnitude or a direction of acceleration caused by acceleration or deceleration, that is, information indicating a movement direction of the vehicle C 10 . Thus, the estimation unit  25  estimates the movement direction of the vehicle C 10  by executing the following process using the acceleration detected at the specified date and time. More specifically, the estimation unit  25  estimates the movement direction of the vehicle C 10  based on the direction of the acceleration detected when the acquired change amount in speed exceeds the predetermined threshold. 
     For example, the estimation unit  25  extracts an average value of the accelerations measured a predetermined period before the specified date and time from the acceleration database  12   c  (Step S 402 ). That is, the estimation unit  25  estimates the movement direction of the vehicle C 10  as the moving object based on the direction of the acceleration detected when the acquired speed changes. Here, there is a case where a predetermined delay (for example, about two seconds) occurs when the movement speed of the vehicle C 10  is acquired using the GPS. For example, when the movement speed of the vehicle C 10  is acquired using the GPS in a case where the vehicle C 10  is moving at speed “B” in a date and time “A”, the speed “B” is measured as the speed of the vehicle C 10  in a date and time that is delayed by about two seconds from the date and time “A”. Thus, the estimation unit  25  extracts an average value calculated from accelerations measured a predetermined period before the specified date and time from the acceleration database  12   c.    
     For example, as illustrated in (F) in  FIG. 1 , the estimation unit  25  extracts an average value of accelerations detected earlier by the time obtained by considering the delay of the GPS speed than the time when a value of the change amount exceeds the predetermined threshold. For example, when a value of the change amount #2 exceeds the predetermined threshold, the estimation unit  25  specifies a date and time when the change amount #2 is acquired, for example, a median of dates and times when the GPS speed #2 and the GPS speed #3 are acquired, and specifies that an average value calculated from acceleration acquired two seconds before the specified median is the average value #1. In such a case, the estimation unit  25  extracts the average value #1 from the acceleration database  12   c.    
     To give a more specific example, the estimation unit  25  refers to the GPS speed database  12   b  and specifies a date and time associated with a change amount of 2 km/h/s or more, or −2 km/h/s or less, that is, the date and time when acceleration or deceleration is performed by the predetermined threshold or more. For example, when information illustrated in  FIG. 3  is registered in the GPS speed database  12   b , the estimation unit  25  specifies a date and time “2016/10/1/10:00:17” associated with a change amount “18 km/h/s”. In such a case, the estimation unit  25  calculates a date and time “2016/10/1/10:00:15” two seconds before “2016/10/1/10:00:17” in consideration of the delay of the GPS, and extracts an average value of accelerations associated with the calculated date and time “2016/10/1/10:00:15” from the acceleration database  12   c . For example, when information illustrated in  FIG. 4  is registered in the acceleration database  12   c , the estimation unit  25  extracts the average value “average value #1” of the acceleration associated with the date and time “2016/10/1/10:00:15”. That is, the estimation unit  25  extracts the acceleration associated with the date and time “2016/10/1/10:00:15” as the average value of accelerations caused by acceleration or deceleration in which the GPS speed is greatly changed. 
     Incidentally, when acquiring the movement speed of the vehicle C 10  from the control device of the information system or the control system provided in the vehicle C 10 , the terminal device  10  can acquire the movement speed of the vehicle C 10  substantially in real time. Thus, when the movement speed of the vehicle C 10  has been acquired from the control device of the information system or the control system provided in the vehicle C 10 , the estimation unit  25  may extract an average value of acceleration detected at the same time as the time when the change amount in speed of the vehicle C 10  exceeds the predetermined threshold and acceleration detected in a same period as the time when the change amount in speed of the vehicle C 10  exceeds the predetermined threshold. 
     Here, it is considered that acceleration in the Z axis direction is detected in the vehicle coordinate system when the vehicle C 10  is accelerated, and acceleration in the −Z axis direction is detected in the vehicle coordinate system when the vehicle C 10  is decelerated. Thus, the estimation unit  25  specifies whether the vehicle C 10  as the moving object is accelerated or decelerated based on the acquired change in speed, and estimates the movement direction of the moving object based on a direction of the detected acceleration and whether the moving object is accelerated or decelerated. More specifically, when the GPS speed indicates deceleration (for example, when a value of the change amount is negative), the estimation unit  25  reverses the sign of the extracted average value (Step S 403 ) to align the direction of the acceleration extracted from the acceleration database  12   c . That is, the estimation unit  25  sets the direction of the detected acceleration as a direction opposite to the movement direction of the moving object when it is determined that the vehicle C 10  is accelerated, and sets the direction of the detected acceleration as the movement direction of the moving object when it is determined that the vehicle C 10  is decelerated. 
     Further, the estimation unit  25  registers the extracted average value in the average value database  12   d  (Step S 404 ). That is, the estimation unit  25  registers acceleration on a plane perpendicular to a gravity direction, that is, the acceleration estimated when the vehicle C 10  is accelerated or decelerated by a predetermined threshold or more in the average value database  12   d  as a collected average value. Incidentally, when a predetermined number of collected average values are registered in the average value database  12   d , the estimation unit  25  may eliminate a collected average value with the oldest registered date and time or date and time when acceleration as a calculation source has been measured, and register a newly extracted average value as the collected average value in the average value database  12   d . In addition, the estimation unit  25  may execute the above-described process every time when the change amount of the GPS speed whose absolute value is larger than a predetermined threshold is measured. 
     Further, the estimation unit  25  estimates the movement direction of the vehicle C 10  based on an average value of the average values registered in the average value database  12   d  (Step S 405 ). Here, the average value registered in the acceleration database  12   c  is the acceleration on the plane perpendicular to the direction of gravity, that is, the average value on the YZ plane. Thus, the estimation unit  25  calculates a further average value of the average values registered in the average value database  12   d  to specify the direction of the acceleration generated when the vehicle C 10  performs linear acceleration, that is, the direction of the acceleration in the Z axis in the vehicle coordinate system. 
     That is, the estimation unit  25  estimates the direction on the plane perpendicular to the direction of gravity as the movement direction of the vehicle C 10 . More specifically, the conversion unit  23  performs the C 1  conversion of the direction of the detected acceleration in the direction on the plane perpendicular to the direction of gravity. Further, the estimation unit  25  estimates the movement direction of the vehicle C 10  on the plane perpendicular to the direction of gravity based on an average value of the converted accelerations. Further, the estimation unit  25  calculates a coordinate conversion formula to convert the terminal coordinate system to the vehicle coordinate system (that is, a coordinate conversion formula to convert the acceleration subjected to the C 1  conversion into the vehicle coordinate system) based on the estimated movement direction of the vehicle C 10  as the C 2  conversion formula (Step S 406 ). Thereafter, the determination unit  26  converts the acceleration measured by the acceleration sensor from the terminal coordinate system into the vehicle coordinate system using the C 2  conversion formula, and estimates the movement state of the vehicle C 10  based on the converted acceleration (Step S 407 ). 
     For example, the estimation unit  25  corrects a direction of the average value depending on acceleration or deceleration, and continues to collect the average value as illustrated in (G) in  FIG. 1 . In addition, the estimation unit  25  further calculates an average value of the collected average values, that is, the average value of the average values registered in the average value database  12   d , estimates the movement direction of the vehicle C 10  based on the calculated average value, and calculates the C 2  conversion formula based on the estimated movement direction of the vehicle C 10  as illustrated in (H) in  FIG. 1 . 
     For example,  FIG. 10  is a view illustrating an example of acceleration acquired by the terminal device according to the embodiment. Incidentally, as illustrated in (A) to (C) in  FIG. 10 , the drawing obtained by plotting the acceleration subjected to the C 1  conversion on the YZ plane is described in the example illustrated in  FIG. 10 . For example, the drawing illustrated in (A) in  FIG. 10  is the drawing obtained by performing the C 1  conversion on a plurality of accelerations estimated to have been generated during a period (for example, one second) in which the change amount of the GPS speed exceeds the predetermined threshold and plotting the accelerations subjected to the C 1  conversion on the YZ plane. Here, since the movement direction of the vehicle C 10  is unknown in the C 1  conversion, a direction of rotation about the Z axis is not accurate. Thus, when the acceleration generated at the time of acceleration or deceleration of the vehicle C 10  is subjected to the C 1  conversion and plotted on the YZ plane as illustrated in (A) in  FIG. 10 , a deviation is caused between the acceleration and the Z axis, and it is unclear which one between the −Z axis direction and the Z axis direction is the movement direction. 
     Thus, the terminal device  10  specifies the movement direction of the vehicle C 10  using the average value of the accelerations subjected to the C 1  conversion on the YZ plane. For example, the terminal device  10  calculates an average value of accelerations subjected to the C 1  conversion for each period during which the accelerations are measured as illustrated in (B) in  FIG. 10 . Then, the terminal device  10  can obtain an average value of directions of accelerations generated by acceleration and an average value of directions of accelerations generated by deceleration as illustrated in (B) in  FIG. 10 . 
     Further, the terminal device  10  reverses the direction of acceleration generated by deceleration among the averages of the accelerations illustrated in (B) in  FIG. 10  on the YZ plane. For example, the terminal device  10  rotates a direction of the average value of the acceleration estimated to have been generated when the change amount of the GPS speed is negative by  7   c  on the YZ plane using the X axis as the center thereof as illustrated in (C) in  FIG. 10 . Further, the terminal device  10  calculates the average value of the directions of the respective accelerations and sets a direction of the calculated average value as the direction of the acceleration generated by acceleration of the vehicle C 10 , that is, the +Z axis direction as illustrated in (D) in  FIG. 10 . As a result, the terminal device  10  can obtain an angle α between the Z axis and the z axis using the X axis direction as the center thereof. Incidentally, the terminal device  10  may calculate angles between the average values illustrated in (C) in  FIG. 10  and the +Z axis direction, respectively, and set an average value of the calculated angles as the angle α between the Z axis and the z axis using the X axis direction as the center thereof. 
     Further, the determination unit  26  calculates the movement direction and speed of the vehicle C 10  based on the acceleration measured by the acceleration sensor  13  using the C 2  conversion formula. For example, the estimation unit  25  performs the C 1  conversion of the acceleration measured by the acceleration sensor  13 , and generates a C 2  conversion formula so as to convert the acceleration measured by the acceleration sensor from the terminal coordinate system into the vehicle coordinate system when the C 2  conversion formula is applied to the acceleration after being subjected to the C 1  conversion. 
     Further, the determination unit  26  estimates the movement direction of the vehicle C 10  using the acceleration after being subjected to the C 2  conversion. For example, the determination unit  26  determines that the vehicle C 10  is accelerating when the acceleration in the +Z axis direction is measured, and determines that the vehicle C 10  is decelerating when the acceleration in the −Z axis direction is detected. In addition, the determination unit  26  determines that the vehicle C 10  has turned right when the acceleration in the +Y axis direction perpendicular to the −Z axis direction as the movement direction is measured, and determines that the vehicle C 10  has turned left when the acceleration in the −Y axis direction is measured. 
     In addition, the determination unit  26  calculates the movement speed of the vehicle C 10  using the converted acceleration. Specifically, the determination unit  26  sets an integral value of Z axis components of acceleration as the movement speed of the vehicle C 10  with an average value of the Z axis components of the acceleration at the time of stop of the vehicle C 10  as an origin (0) thereof. Incidentally, the determination unit  26  may correct the integral value to zero when it is determined that the vehicle C 10  is not moving in order to eliminate accumulation of errors caused by adopting the integral value. For example, the determination unit  26  may determine whether or not the vehicle C 10  is stopped using the SVM that has learned the feature amount of the acceleration at the time of stop of the vehicle C 10 , and correct the integral value to zero when it is determined that the vehicle C 10  is stopped. In this manner, the determination unit  26  performs estimation of the movement speed and the movement direction of the vehicle C 10  using the acceleration measured by the acceleration sensor  13 . 
     2-6. Example of Flow of Processing 
     Next, an example of a process of processing in which the terminal device  10  estimates the movement direction will be described with reference to  FIG. 11 .  FIG. 11  is a view illustrating the example of the process of the processing in which the terminal device according to the embodiment estimates the movement direction. For example, the terminal device  10  performs measurement of GPS information at an interval of one second as illustrated in (A) in  FIG. 11 , and performs measurement of acceleration according to the terminal coordinate system with a rate of about 50 times during one second as illustrated in (B) in  FIG. 11 . 
     In such a case, the terminal device  10  calculates the average value of the accelerations at the predetermined time interval, and derives the C 1  conversion formula (rotation matrix) to perform the C 1  conversion to convert the x axis direction of the terminal coordinate system into the X axis direction of the vehicle coordinate system at a predetermined time interval by considering the direction of the average value of the calculated accelerations as the reference direction as illustrated in (C) in  FIG. 11 . Further, the terminal device  10  executes the C 1  conversion to covert the measured acceleration using the C 1  conversion formula as illustrated in (D) in  FIG. 11 . 
     Subsequently, the terminal device  10  calculates an average value on the YZ plane from the accelerations after being subjected to the C 1  conversion as illustrated in (E) in  FIG. 11 . In addition, the terminal device  10  extracts an average value estimated to have been acquired when the change amount of the GPS speed calculated based on the GPS information exceeds the predetermined threshold as illustrated in (F) in  FIG. 11 . For example, as illustrated in (G) in  FIG. 11 , the terminal device  10  extracts the average value calculated from the acceleration a predetermined period (for example, two seconds) before the time when it is determined that the change amount of the GPS speed exceeds the predetermined threshold in consideration of a delay amount relating to the acquisition of the GPS speed. 
     Further, the terminal device  10  derives the C 2  conversion formula for conversion from the terminal coordinate system into the vehicle coordinate system using the extracted average value as illustrated in (H) in  FIG. 11 . More specifically, the terminal device  10  derives a new C 2  conversion formula every time when the change amount of the GPS speed exceeds the predetermined threshold. As a result, at the time of initial setting, the terminal device  10  promptly estimates the movement direction of the vehicle C 10 , derives the C 1  conversion formula and the C 2  conversion formula, and updates the C 1  conversion formula and the C 2  conversion formula at a certain time interval, and thus, the estimation accuracy can be maintained. 
     2-7. Example of Mathematical Expression 
     Next, an example of a process of calculating the C 2  conversion formula to convert the terminal coordinate system to the vehicle coordinate system by the estimation unit  25  will be described using mathematical expressions. Incidentally, the process executed by the estimation unit  25  is not limited to the process indicated by the following mathematical expressions. For example, the estimation unit  25  may perform coordinate conversion from the terminal coordinate system to the vehicle coordinate system using a mathematical expression expressing the primary conversion. 
     For example, the respective axes of the terminal coordinate system are set as the x axis, the y axis, and the z axis, and the respective axes of the vehicle coordinate system are set as the X axis, the Y axis, and the Z axis. In such a case, a process of converting the vehicle coordinate system into the terminal coordinate system is expressed by the following Formula (1). Incidentally, a rotation angle about the x axis is α, a rotation angle about the γ axis is β, a rotation angle about the z axis is γ, a rotation matrix to perform coordinate conversion by rotation about the x axis is R x (α), a rotation matrix to perform coordinate conversion by rotation about the y axis is R y (β), and a rotation matrix to perform coordinate conversion by rotation about the z axis is R z (γ) in Formula (1). 
     
       
         
           
             
               
                 
                   
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     In addition, the rotation matrix R x (α), the rotation matrix R y (β), and the rotation matrix R z (γ) (hereinafter, collectively referred to as “the respective rotation matrices” in some cases) can be expressed by the following Formulas (2) to (4). 
     
       
         
           
             
               
                 
                   
                     
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     Here, the direction of the average vector G is the acceleration in the −X axis direction, and thus, can be expressed by the following Formula (5) in the vehicle coordinate system. 
     
       
         
           
             
               
                 
                   
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     On the other hand, the average vector G in the respective axis directions detected in the terminal coordinate system is described as (a x , a y , a z ). In such a case, a x , a y , and a z  are values obtained by converting the average vector G expressed by the Formula (5) with the respective rotation matrices, and thus, the following Formula (6) is established. 
     
       
         
           
             
               
                 
                   
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                                
                               sin 
                                
                               
                                   
                               
                                
                               β 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     As a result, Formula (7) is obtained from a value in the z axis direction in Formula (6). 
     
       
         
           
             
               
                 
                   
                     sin 
                      
                     
                         
                     
                      
                     β 
                   
                   = 
                   
                     
                       a 
                       z 
                     
                     G 
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
     In addition, since the Formula (8) is established by standardization in consideration of the magnitude of the average vector G, the Formula (9) is obtained from values in the x axis direction and the y axis direction in the Formula (6). As a result, the terminal device  10  can specify the rotation angle β around the y axis from the Formulas (7) and (9). 
     
       
         
           
             
               
                 
                   
                     G 
                     2 
                   
                   = 
                   
                     
                       a 
                       x 
                       2 
                     
                     + 
                     
                       a 
                       y 
                       2 
                     
                     + 
                     
                       a 
                       z 
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
             
               
                 
                   
                     cos 
                      
                     
                         
                     
                      
                     β 
                   
                   = 
                   
                     
                       ± 
                       
                         
                           1 
                           - 
                           
                             
                               ( 
                               
                                 
                                   a 
                                   z 
                                 
                                 G 
                               
                               ) 
                             
                             2 
                           
                         
                       
                     
                     = 
                     
                       ± 
                       
                         
                           
                             
                               a 
                               x 
                               2 
                             
                             + 
                             
                               a 
                               y 
                               2 
                             
                           
                         
                         G 
                       
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
     
     Here, if cases are divided depending on a sign of a value expressed in the Formula (9), the following Formulas (10) to (13) can be obtained as solutions of Formula (6). 
     
       
         
           
             
               
                 
                   
                     sin 
                      
                     
                         
                     
                      
                     β 
                   
                   = 
                   
                     
                       a 
                       z 
                     
                     G 
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
             
               
                 
                   
                     cos 
                      
                     
                         
                     
                      
                     β 
                   
                   = 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             
                               a 
                               z 
                             
                             G 
                           
                           ) 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   ( 
                   11 
                   ) 
                 
               
             
             
               
                 
                   
                     sin 
                      
                     
                         
                     
                      
                     γ 
                   
                   = 
                   
                     - 
                     
                       
                         a 
                         y 
                       
                       
                         
                           
                             a 
                             x 
                             2 
                           
                           + 
                           
                             a 
                             y 
                             2 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   12 
                   ) 
                 
               
             
             
               
                 
                   
                     cos 
                      
                     
                         
                     
                      
                     γ 
                   
                   = 
                   
                     - 
                     
                       
                         a 
                         x 
                       
                       
                         
                           
                             a 
                             x 
                             2 
                           
                           + 
                           
                             a 
                             y 
                             2 
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   13 
                   ) 
                 
               
             
           
         
       
     
     On the other hand, a process of converting the terminal coordinate system into the vehicle coordinate system is inverse conversion of the coordinate conversion expressed in the Formula (1), and thus, is expressed by the following Formula (14). 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           X 
                         
                       
                       
                         
                           Y 
                         
                       
                       
                         
                           Z 
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       
                         R 
                         x 
                       
                        
                       
                         ( 
                         
                           - 
                           α 
                         
                         ) 
                       
                     
                      
                     
                       
                         R 
                         y 
                       
                        
                       
                         ( 
                         
                           - 
                           β 
                         
                         ) 
                       
                     
                      
                     
                       
                         R 
                         z 
                       
                        
                       
                         ( 
                         
                           - 
                           γ 
                         
                         ) 
                       
                     
                      
                     
                       ( 
                       
                         
                           
                             x 
                           
                         
                         
                           
                             y 
                           
                         
                         
                           
                             z 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   14 
                   ) 
                 
               
             
           
         
       
     
     In addition, the values of β and γ have been already derived from Formulas (10) to (13), and thus, the C 1  conversion, which causes only the y axis and the z axis among the accelerations a x , a y , and a z  in the terminal coordinate system to be rotated and the x axis of the terminal coordinate system to match the X axis of the vehicle coordinate system can be expressed by Formula (15). 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           x 
                         
                       
                       
                         
                           y 
                         
                       
                       
                         
                           z 
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       
                         R 
                         y 
                       
                        
                       
                         ( 
                         
                           - 
                           β 
                         
                         ) 
                       
                     
                      
                     
                       
                         R 
                         z 
                       
                        
                       
                         ( 
                         
                           - 
                           γ 
                         
                         ) 
                       
                     
                      
                     
                       ( 
                       
                         
                           
                             
                               a 
                               x 
                             
                           
                         
                         
                           
                             
                               a 
                               y 
                             
                           
                         
                         
                           
                             
                               a 
                               z 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   15 
                   ) 
                 
               
             
           
         
       
     
     Here, the terminal device  10  may calculate the direction on the YZ plane of the acceleration determining the movement direction, that is, the acceleration estimated to have been generated when the GPS speed greatly changes, and calculate the rotation angle α about the x axis (the same as the X axis after being subjected to C 1  conversion) such that the calculated direction matches the Z axis direction. For example, in a case where the acceleration estimated to have been generated when the GPS speed greatly changes is taken as a sample, Formula (16) is obtained when a sample of the acceleration in the y axis direction is set as y, a sample of the acceleration in the z axis direction is set as z, and components of samples of the accelerations projected on the YZ plane are set as y′ and z′. 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           
                             y 
                             ′ 
                           
                         
                       
                       
                         
                           
                             z 
                             ′ 
                           
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             
                               cos 
                                
                               
                                   
                               
                                
                               α 
                             
                           
                           
                             
                               sin 
                                
                               
                                   
                               
                                
                               α 
                             
                           
                         
                         
                           
                             
                               
                                 - 
                                 sin 
                               
                                
                               
                                   
                               
                                
                               α 
                             
                           
                           
                             
                               cos 
                                
                               
                                   
                               
                                
                               α 
                             
                           
                         
                       
                       ) 
                     
                      
                     
                       ( 
                       
                         
                           
                             y 
                           
                         
                         
                           
                             z 
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   16 
                   ) 
                 
               
             
           
         
       
     
     Here, when a rotation angle between the y axis direction and the z′ axis direction is set as θ, α can be expressed by the following Formula (17), and the sine and the cosine of θ are expressed by the following Formulas (18) and (19), respectively. 
     
       
         
           
             
               
                 
                   α 
                   = 
                   
                     θ 
                     - 
                     
                       π 
                       2 
                     
                   
                 
               
               
                 
                   ( 
                   17 
                   ) 
                 
               
             
             
               
                 
                   
                     sin 
                      
                     
                         
                     
                      
                     θ 
                   
                   = 
                   
                     z 
                     
                       
                         
                           y 
                           2 
                         
                         + 
                         
                           z 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   18 
                   ) 
                 
               
             
             
               
                 
                   
                     cos 
                      
                     
                         
                     
                      
                     θ 
                   
                   = 
                   
                     y 
                     
                       
                         
                           y 
                           2 
                         
                         + 
                         
                           z 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   19 
                   ) 
                 
               
             
           
         
       
     
     Here, from the Formulas (17) to (19), a value of y′ becomes zero as expressed in the following Formula (20). More specifically, the following Formulas (21) and (22) are established from Formula (17). As a result, Formula (20) is established by converting each left side of the Formulas (18) and (19) into the equation of a using Formulas (21) and (22) and substituting Formula (16) with the result. 
         y′= 0  (20)
 
       cos α=sin θ  (21)
 
       sin α=−cos θ  (22)
 
     To summarize the above-described calculation results, the C 1  conversion formula represented by the following Formula (23) can be expressed by the following Formula (24). 
     
       
         
           
             
               
                 
                   
                       
                   
                    
                   
                     
                       ( 
                       
                         
                           
                             
                               x 
                               ′ 
                             
                           
                         
                         
                           
                             
                               y 
                               ′ 
                             
                           
                         
                         
                           
                             
                               z 
                               ′ 
                             
                           
                         
                       
                       ) 
                     
                     = 
                     
                       
                         
                           R 
                           y 
                         
                          
                         
                           ( 
                           
                             - 
                             β 
                           
                           ) 
                         
                       
                        
                       
                         
                           R 
                           z 
                         
                          
                         
                           ( 
                           
                             - 
                             γ 
                           
                           ) 
                         
                       
                        
                       
                         ( 
                         
                           
                             
                               x 
                             
                           
                           
                             
                               y 
                             
                           
                           
                             
                               z 
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   23 
                   ) 
                 
               
             
             
               
                 
                   
                     ( 
                     
                       
                         
                           
                             x 
                             ′ 
                           
                         
                       
                       
                         
                           
                             y 
                             ′ 
                           
                         
                       
                       
                         
                           
                             z 
                             ′ 
                           
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       
                         
                           R 
                           y 
                         
                          
                         
                           ( 
                           
                             - 
                             β 
                           
                           ) 
                         
                       
                        
                       
                         ( 
                         
                           
                             
                               
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                             
                             
                               
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                             
                             
                               0 
                             
                           
                           
                             
                               
                                 
                                   - 
                                   sin 
                                 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                             
                             
                               
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                             
                             
                               0 
                             
                           
                           
                             
                               0 
                             
                             
                               0 
                             
                             
                               1 
                             
                           
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           
                             
                               x 
                             
                           
                           
                             
                               y 
                             
                           
                           
                             
                               z 
                             
                           
                         
                         ) 
                       
                     
                     = 
                     
                       ( 
                       
                         
                           
                             
                               
                                 
                                   ( 
                                   
                                     
                                       x 
                                        
                                       
                                           
                                       
                                        
                                       cos 
                                        
                                       
                                           
                                       
                                        
                                       γ 
                                     
                                     + 
                                     
                                       y 
                                        
                                       
                                           
                                       
                                        
                                       sin 
                                        
                                       
                                           
                                       
                                        
                                       γ 
                                     
                                   
                                   ) 
                                 
                                  
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 β 
                               
                               - 
                               
                                 z 
                                  
                                 
                                     
                                 
                                  
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 β 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   - 
                                   x 
                                 
                                  
                                 
                                     
                                 
                                  
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                               + 
                               
                                 y 
                                  
                                 
                                     
                                 
                                  
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 γ 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   ( 
                                   
                                     
                                       x 
                                        
                                       
                                           
                                       
                                        
                                       cos 
                                        
                                       
                                           
                                       
                                        
                                       γ 
                                     
                                     + 
                                     
                                       y 
                                        
                                       
                                           
                                       
                                        
                                       sin 
                                        
                                       
                                           
                                       
                                        
                                       γ 
                                     
                                   
                                   ) 
                                 
                                  
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 β 
                               
                               + 
                               
                                 z 
                                  
                                 
                                     
                                 
                                  
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 β 
                               
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   24 
                   ) 
                 
               
             
           
         
       
     
     In addition, the C 2  conversion formula to perform the C 2  conversion can be expressed by the following Formula (25) by rotating the acceleration subjected to the C 1  conversion about the X axis. 
     
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         
                           X 
                         
                       
                       
                         
                           Y 
                         
                       
                       
                         
                           Z 
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                               1 
                             
                             
                               0 
                             
                             
                               0 
                             
                           
                           
                             
                               0 
                             
                             
                               
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                             
                               
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                           
                           
                             
                               0 
                             
                             
                               
                                 
                                   - 
                                   sin 
                                 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                             
                               
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                           
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           
                             
                               
                                 x 
                                 ′ 
                               
                             
                           
                           
                             
                               
                                 y 
                                 ′ 
                               
                             
                           
                           
                             
                               
                                 z 
                                 ′ 
                               
                             
                           
                         
                         ) 
                       
                     
                     = 
                     
                       ( 
                       
                         
                           
                             
                               x 
                               ′ 
                             
                           
                         
                         
                           
                             
                               
                                 
                                   y 
                                   ′ 
                                 
                                  
                                 
                                     
                                 
                                  
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                               + 
                               
                                 
                                   z 
                                   ′ 
                                 
                                  
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                           
                         
                         
                           
                             
                               
                                 
                                   - 
                                   
                                     y 
                                     ′ 
                                   
                                 
                                  
                                 
                                     
                                 
                                  
                                 sin 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                               + 
                               
                                 
                                   z 
                                   ′ 
                                 
                                  
                                 
                                     
                                 
                                  
                                 cos 
                                  
                                 
                                     
                                 
                                  
                                 α 
                               
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   25 
                   ) 
                 
               
             
           
         
       
     
     3. Modified Example 
     The terminal device  10  according to the above-described embodiment may be implemented in various different modes other than the above-described embodiment. Thus, another embodiment of the above-described terminal device  10  will be described hereinafter. 
     3-1. Regarding Weighting 
     Here, the movement direction of the vehicle C 10  is estimated based on the direction of the acceleration in the estimation process described above. However, the embodiment is not limited thereto. For example, the terminal device  10  may estimate the movement direction of the vehicle C 10  in consideration of the magnitude of the acceleration. For example, when great acceleration or deceleration occurs during traveling of the vehicle C 10 , it is predicted that the vehicle C 10  has traveled straight. For example, it is predicted that great acceleration or deceleration, and a high acceleration in turn, is to be measured when the vehicle stops at a signal intersection and then accelerates or when sudden braking is performed. In such a state, the vehicle C 10  is predicted to be in a straight traveling state. Thus, acceleration higher than a predetermined threshold becomes more reliable data at the time of estimating the movement direction of the vehicle C 10  than acceleration lower than the predetermined threshold. 
     Thus, the terminal device  10  may estimate the movement direction of the vehicle C 10  as the moving object using a plurality of detected accelerations in the state of considering weighting based on each magnitude of the accelerations. More specifically, the terminal device  10  may estimate the movement direction of the vehicle C 10  by performing the weighting with respect to each acceleration such that a weight increases as the magnitude of the acceleration increases. 
     For example, the terminal device  10  may perform the weighting according to the magnitude of the acceleration when calculating an average value of accelerations used at the time of estimating the movement direction of the vehicle C 10 , that is, when performing the C 1  conversion on the accelerations detected by the acceleration sensor  13  and calculating the average value of the accelerations after being subjected to the C 1  conversion. To give a more specific example, for example, when a vector of the acceleration subjected to the C 1  conversion is described as a i  (in the mathematical expression, a is indicated by a bold letter, which is similarly applied hereinafter), the terminal device  10  may calculate an average value using a value obtained by integrating the |a i | which is a norm of the vector a i  and the predetermined weighting coefficient w with the vector a i  as expressed in the following Formula (26) as a value of the vector a i . 
         a   i   →w·|a   i   |·a   i   (26)
 
     In addition, the terminal device  10  may estimate the movement direction of the vehicle C 10  as the moving object based on an average value of directions of a plurality of accelerations in consideration of the weighting based on the magnitude of each acceleration. That is, the terminal device  10  may consider the weighting based on a magnitude of each average value at the time of calculating the rotation direction about the X axis from the average value of the accelerations acquired when the change amount of the GPS speed becomes larger than the predetermined threshold, that is, the average value registered in the average value database  12   d . For example, when the vector of the average value registered in the average value database  12   d  is set as the vector a i  and an angle between a direction of the vector a i  and the −Z axis direction is set as θi, the terminal device  10  may calculate an average value of angles between the −Z axis direction and the respective average values using a formula represented by the following Formula (27) and estimate the movement direction of the vehicle C 10 . 
     
       
         
           
             
               
                 
                   
                     
                       ∑ 
                       
                         θ 
                         i 
                       
                     
                     
                       ∑ 
                       1 
                     
                   
                   → 
                   
                     
                       ∑ 
                       
                         w 
                         · 
                         
                            
                           
                             a 
                             i 
                           
                            
                         
                         · 
                         
                           θ 
                           i 
                         
                       
                     
                     
                       ∑ 
                       
                         w 
                         · 
                         
                            
                           
                             a 
                             i 
                           
                            
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   27 
                   ) 
                 
               
             
           
         
       
     
     Incidentally, the above-described Formulas (26) and (27) are merely examples, and the terminal device  10  may adopt an arbitrary formula in consideration of the weighting based on the magnitude of the acceleration as long as the movement direction of the vehicle C 10  is estimated. In addition, the weighting process described above is implemented by the estimation unit  25  illustrated in  FIG. 2 , for example. 
     3-2. Regarding Posture Detection Function 
     Here, when the terminal device  10  is implemented by a mobile terminal device such as a smart device or the like, it is predicted that the user conducts behavior such as performing search processing using the terminal device  10  and leaving the vehicle C 10  directly possessing the terminal device  10 . Thus, there is a risk that the installation posture of the terminal device  10  may change. However, when the terminal device  10  estimates the movement direction and the movement speed of the vehicle C 10  using the C 1  conversion formula and the C 2  conversion formula obtained before the installation posture changes despite the change of the installation posture, the accuracy in estimation of the movement direction and the movement speed deteriorates. 
     Therefore, the terminal device  10  may include a means for detecting the change of the installation posture, calculate the C 1  conversion formula and the C 2  conversion formula again in the case of detecting the change of the installation posture, and convert the acceleration in the terminal coordinate system into the acceleration in the vehicle coordinate system using the C 1  conversion formula and the C 2  conversion formula that have been calculated again. More specifically, the terminal device  10  calculates a first average value, which is an average value of accelerations before a lapse of a predetermined time after detection, and a second average value which is an average value of accelerations before a lapse of a time shorter than the predetermined time. For example, the terminal device  10  calculates a long-term average acceleration (hereinafter, referred to as a “long-term average”) which is continuously calculated while the installation posture does not change and an acceleration average (hereinafter, referred to as a “short-term average”) calculated at a certain interval (for example, one second). 
     Further, the terminal device  10  may determine whether or not the installation posture of the terminal device  10  has changed based on a difference between the first average value and the second average value, that is, a difference between the long-term average and the short-term average. For example,  FIG. 12  is a view illustrating an example of a process of detecting the change of the installation posture by the terminal device according to the embodiment. For example, as illustrated in (A) in  FIG. 12 , when there is no change in the installation posture during a predetermined period, it is predicted that directions of the long-term average indicated by the dotted arrow and the short-term average indicated by the solid arrow substantially match each other. On the other hand, when the installation posture of the terminal device  10  changes as illustrated in (B) in  FIG. 12 , it is predicted that the directions of the long-term average indicated by the dotted arrow and the short-term average indicated by the solid arrow are divergent. 
     Thus, as illustrated in (C) in  FIG. 12 , when a value of an angle θ between a long-term average vector and a short-term average vector exceeds a predetermined threshold, the terminal device  10  determines that the posture has changed. For example, when a state where a value of a cosine product of the first average value and the second average value exceeds “0.8” continues during a predetermined period, the terminal device  10  may determine that the installation posture of the terminal device  10  has changed. For example, when the long-term average vector is set as a L , the short-term average vector is set as a S , and the angle between the long-term average and the short-term average is set as θ, the terminal device  10  may calculate the value of the cosine product (that is, an inner product) of the long-term average and the short-term average using the following Formula (28) and determine that the installation posture of the terminal device  10  has changed when the calculated value is equal to or less than a predetermined threshold. 
       | a   L   |·|a   S |·cos θ= a   L   ·a   S   (28)
 
     Incidentally, for example, when determining that the installation posture of the terminal device  10  has changed, the terminal device  10  erases the information registered in the GPS speed database  12   b , the acceleration database  12   c , and the average value database  12   d , and newly collects GPS speed, a change amount of the GPS speed, acceleration detected by the acceleration sensor  13 , and the like. In addition, the terminal device  10  estimates a direction of gravity from an average value of the collected accelerations, and calculates a new C 1  conversion formula according to the estimated direction of gravity. Further, the terminal device  10  may estimate a movement direction of the vehicle C 10  based on the acceleration when the change amount of the GPS speed exceeds the predetermined threshold, and calculate a new C 2  conversion formula based on the estimated movement direction. 
     In this manner, the terminal device  10  detects the acceleration in the moving object, and calculates the first average value, which is the average value of accelerations before the lapse of the predetermined time after the detection, and the second average value which is the average value of accelerations before the lapse of the time shorter than the predetermined time. Further, the terminal device  10  determines whether or not the posture of the terminal device  10  has changed based on the first average value and the second average value. Thus, the terminal device  10  can easily determine whether or not the installation posture of the terminal device  10  has changed. Incidentally, the process of detecting the change of the installation posture described above may be implemented by the determination unit  26  illustrated in  FIG. 2 , or implemented by a functional configuration such as a calculation unit and a posture determination unit that is provided separately from the respective units  21  to  26  illustrated in  FIG. 2 , for example. When the terminal device  10  has such a functional configuration, the calculation unit calculates the first average value and the second average value. Further, the posture determination unit determines whether or not the posture of the terminal device  10  has changed based on the first average value and the second average value calculated by the calculation unit. 
     3-3. Discrimination Between Curve and Right or Left Turn 
     Here, the terminal device  10  converts the acceleration in the terminal coordinate system to the acceleration in the vehicle coordinate system using the C 2  conversion formula, and estimates the movement direction of the vehicle C 10  based on the acceleration in the vehicle coordinate system. For example, the terminal device  10  can estimate that the vehicle C 10  has turned to the right or left based on the acceleration in the Y axis direction. However, it is difficult to distinguish whether the vehicle turns a curve at a constant speed, or whether or not the vehicle turns at the intersection only with the acceleration in the Y axis direction. 
     Here, in the case of performing not only the guidance process but also diagnosis on whether or not driving is appropriate (hereinafter, referred to as “driving ability diagnosis”) using the terminal device  10 , it is desirable that the terminal device  10  perform detailed analysis by distinguishing whether the vehicle turns the curve or turns at the intersection. Here, when turning at the intersection, it is predicted that deceleration greater than a predetermined threshold is performed before the right turn or left turn, and acceleration greater than a predetermined threshold is performed after the right turn or left turn. On the other hand, it is considered that great deceleration or acceleration is not performed when the vehicle turns the curve. 
     Thus, when acceleration in a direction different from the movement direction of the moving object is detected after the speed of the vehicle C 10  decelerates, and thereafter, the speed of the vehicle C 10  accelerates, the terminal device  10  may determine that the vehicle C 10  as the moving object has made a right turn or a left turn. In addition, the terminal device  10  may determine that the vehicle C 10  as the moving object is traveling along a curved road when the speed of the terminal device  10  has not decelerated before detection of the acceleration in the direction different from the movement direction of the moving object, or when the speed does not accelerate after detection of the acceleration in the direction different from the movement direction of the moving object. 
     For example, the terminal device  10  specifies the acceleration in the Y axis direction from the acceleration after being subjected to the C 2  conversion. Subsequently, when the acceleration in the Y axis direction exceeds a predetermined threshold, the terminal device  10  specifies a date and time when the acceleration in the Y axis direction exceeds the predetermined threshold as a reference date and time, and sets a few seconds immediately before the reference date and time as an immediately preceding period and a few seconds immediately after the reference date and time as an immediate following period. Further, the terminal device  10  calculates a change amount of speed of the vehicle C 10  in the immediately preceding period or the immediately following period using the GPS speed. Incidentally, the terminal device  10  may take into consideration the delay caused at the time of acquiring the GPS speed when performing such calculation. In addition, the terminal device  10  may acquire speed of the vehicle C 10  through the general standard configured to acquire information from the control device of the information system or the control system provided in the vehicle C 10 , and calculate the change amount of the speed of the vehicle C 10  in the immediately preceding period or in the immediately following period based on the acquired speed, using OBD or the like. 
     Further, when the speed of the vehicle C 10  decelerates below a predetermined threshold in the immediately preceding period and the speed of the vehicle C 10  accelerates above a predetermined threshold in the immediately following period, the terminal device  10  determines that the vehicle C 10  has made a right turn or a left turn. On the other hand, when the speed of the vehicle C 10  does not decelerate below the predetermined threshold in the immediately preceding period and the speed of the vehicle C 10  does not accelerate above the predetermined threshold in the immediately following period, the terminal device  10  determines that the vehicle C 10  has turned a curve. 
     Further, the terminal device  10  may perform the driving ability diagnosis depending on whether or not the vehicle C 10  has made a right turn or a left turn, or whether or not the vehicle C 10  has turned a curve. For example, in a case where a value of the acceleration measured in the reference date and time is greater than a predetermined threshold when it is determined that the vehicle C 10  has made a right turn or a left turn, the terminal device  10  may output a message for calling attention to the user assuming that a sudden right turn or left turn has been made. In addition, in a case where acceleration in the immediate following period is greater than a predetermined threshold when it is determined that the vehicle C 10  has made a right turn or a left turn, the terminal device  10  may output the message for calling attention to the user 
     In this manner, the terminal device  10  detects the acceleration in the moving object. In addition, the terminal device  10  acquires speed of the moving object. Further, the terminal device  10  determines that the moving object has made a right turn or a left turn when the acceleration in the direction different from the movement direction of the moving object is detected after deceleration of the acquired speed, and thereafter, the acquired speed accelerates. The terminal device  10  determines that the moving object is traveling on a curved road when the acquired speed does not decelerate before detection of the acceleration in the direction different from the movement direction of the moving object or when the acquired speed does not accelerate after detection of the acceleration in the direction different from the movement direction of the moving object. 
     Incidentally, it is possible to consider a case where a certain deceleration or acceleration is hardly detected due to congestion or the like. However, it is possible to consider that such a case may be ignored since there is no problematic driving operation in the case in the first place. Thus, the terminal device  10  may determine whether or not the vehicle C 10  is caught in congestion based on information of a road traffic information communication system such as the vehicle information and communication system (VICS) (registered trademark), and does not necessarily perform the determination process on whether or not the vehicle C 10  has made a right turn or a left turn or whether or not the vehicle C 10  has turned the curve in the case of being caught in congestion. Incidentally, the above-described process of detecting the change in the installation posture may be implemented by the determination unit  26  illustrated in  FIG. 2 , for example, and may be implemented by a functional configuration such as a movement determination unit provided separately from the respective units  21  to  26  illustrated in  FIG. 2 , for example. 
     3-4. Regarding Sudden Braking 
     In addition, since sudden acceleration and sudden deceleration are one of dangerous driving operations, it is desirable to enable detection of such sudden acceleration and sudden deceleration in the driving ability diagnosis. However, there is a case where sudden acceleration occurs at the time of joining to an expressway when switching from an ordinary road to the expressway. Thus, the accuracy of the driving ability diagnosis deteriorates in a case where it is determined that the dangerous driving operation is performed simply when the sudden acceleration or the sudden deceleration is performed. 
     Here, when switching from a general road to an expressway, it is predicted that the speed after acceleration will continue for a certain time (for example, 10 minutes) or more after a sudden acceleration. Thus, the terminal device  10  determines whether or not there is acceleration equal to or more than a predetermined threshold, that is, whether or not sudden acceleration has occurred based on the acceleration measured by the acceleration sensor  13 , the change amount of the GPS speed, the speed acquired from the control device of the information system or the control system provided in the vehicle C 10 , and the like. Further, when determining that sudden acceleration has occurred, the terminal device  10  determines whether or not a predetermined speed (for example, 80 km/h or more) has continued during a predetermined period (for example, for 10 minutes) after the sudden acceleration based on the acceleration measured by the acceleration sensor  13 , the change amount of the GPS speed, the speed acquired from the control device of the information system or the control system provided in the vehicle C 10 . Further, when the predetermined speed has continued during the predetermined period after the sudden acceleration, the terminal device  10  may determine that the dangerous driving operation is not performed. 
     In addition, it is possible to consider a case where it is difficult to acquire GPS speed at the time of sudden acceleration in a tunnel and the like. Thus, when it is difficult to acquire the GPS speed, the terminal device  10  may determine whether or not a certain deceleration has been generated during a predetermined period based on the acceleration detected by the acceleration sensor  13  and determine that the dangerous driving operation is not performed in a case where the certain deceleration has not been generated during the predetermined period. 
     In this manner, when the speed exceeding the predetermined threshold has not been acquired over the predetermined period after the acceleration exceeding the predetermined threshold is detected by the acceleration sensor  13 , the terminal device  10  may determine that the dangerous operation is performed. In addition, when it is difficult to acquire the speed of the moving object such as the GPS speed, the terminal device  10  may determine whether or not the moving body is decelerated based on the acceleration detected by the acceleration sensor  13 , and determine that the dangerous operation is performed in a case where the moving body is decelerated during a lapse of the predetermined period. Further, when the speed exceeding the predetermined threshold has been acquired over the predetermined period after detection of the acceleration exceeding the predetermined threshold is detected, the terminal device  10  may determine that the moving object is traveling on a road for high-speed movement. 
     In this manner, the terminal device  10  acquires the speed of the vehicle C 10  using an arbitrary technique such as the acceleration, the GPS speed, or the speed acquired from the control device of the information system or the control system provided in the vehicle C 10 . In addition, when the change amount of the speed of the vehicle C 10  exceeds the predetermined threshold, the terminal device  10  determines whether or not the vehicle C 10  is decelerated during the predetermined period. Further, the terminal device  10  determines that the dangerous driving operation is not performed when the vehicle C 10  has not decelerated during the predetermined period, and determines that the dangerous driving operation is performed when the vehicle C 10  has decelerated during the predetermined period. Incidentally, the above-described process of detecting the change in the installation posture may be implemented by the determination unit  26  illustrated in  FIG. 2 , for example, and may be implemented by a functional configuration such as an operation determination unit provided separately from the respective units  21  to  26  illustrated in  FIG. 2 , for example. 
     3-5. Regarding Processing Interval 
     In addition, the above-described terminal device  10  may execute the acquisition process, the estimation process, the guidance process, and the like described above at arbitrary time intervals. In addition, the terminal device  10  may divide the acquisition process, the estimation process, and the guidance process into arbitrary processes and independently execute the respective divided processes at arbitrary time intervals. For example, the terminal device  10  may execute acquisition of the acceleration, acquisition of the GPS speed, calculation of a change rate, the C 1  conversion and C 2  conversion of the acceleration, calculation of the average value of the acceleration, estimation of the movement direction of the vehicle C 10 , and the like at independent timings. 
     3-6. Other Embodiments 
     Incidentally, the above-described embodiment is merely an example, and the present embodiments also include other embodiments exemplified hereinafter and other than the exemplified ones. For example, the functional configuration, the data structure, the order and content of the processing illustrated in the flowchart, and the like in the present application are merely examples, and presence or absence of each element, arrangement thereof, the order of execution of the process and the like, the specific content thereof, and the like can be appropriately changed. For example, the guidance process and the determination process described above can be implemented as devices, methods, or programs in a terminal implemented by an application of a smartphone or the like, instead of being implemented by the terminal device  10  as exemplified in the above-described embodiment. 
     In addition, a configuration in which the respective processors  17  to  20  forming the terminal device  10  are implemented by independent devices, respectively is general. In addition, it may be configured such that the respective units  21  to  26  forming the movement state determination unit  20  are implemented by independent devices. Similarly, the configuration of the present embodiments can be flexibly changed by implementing each means illustrated in the above-described embodiment by calling an external platform or the like with an application program interface (API) or network computing (a so-called cloud, and the like). Further, each element such as a means relating to the present embodiments may be implemented not only by an arithmetic control unit of a computer but also by another information processing mechanism such as a physical electronic circuit. 
     For example, the terminal device  10  may execute the above-described guidance process in cooperation of a distribution server communicable with the terminal device  10 . For example, the distribution server may include the respective units  21  to  26 , execute the detection process, the acquisition process, the estimation process, and the like described above using the acceleration and the GPS speed detected by the terminal device  10 , distribute estimation of the movement direction of the vehicle C 10 , estimation of the movement speed of the vehicle C 10 , and the like to the terminal device  10 , and cause the terminal device  10  to execute guidance of the user. 
     4. Effects 
     As described above, the terminal device  10  detects the acceleration in the moving object. In addition, the terminal device  10  acquires speed of the moving object. Further, the terminal device  10  estimates a movement direction of the moving object based on a direction of the acceleration detected when the acquired speed changes. For example, the terminal device  10  estimates the movement direction of the moving object based on the direction of the acceleration detected when the acquired change amount in speed exceeds the predetermined threshold. 
     In this manner, the terminal device  10  estimates the movement direction of the vehicle C 10  using the acceleration measured by the acceleration sensor  13  when acceleration or deceleration is performed, and thus, it is possible to accurately estimate the movement direction of the vehicle C 10  in a short period of time. In addition, since the terminal device  10  can accurately specify the movement direction of the vehicle C 10 , it is possible to promptly and accurately perform the determination of acceleration, deceleration, and a right or left turn, and further the estimation (also including stop determination) of speed of the vehicle C 10 . In addition, the terminal device  10  can promptly and accurately perform the estimation of the installation posture of the terminal device  10 . In addition, since the terminal device  10  repeatedly performs estimation of the movement direction of the vehicle C 10  using the acceleration measured by the acceleration sensor  13  when acceleration or deceleration is performed, it is possible to reduce an error accompanying a deviation between the terminal coordinate system and the vehicle coordinate system. 
     In addition, the terminal device  10  can estimate the movement direction of the vehicle C 10  in a stand-alone manner using the acceleration and the GPS signal measured by the acceleration sensor  13  installed in the own device. As a result, the terminal device  10  does not necessarily acquire the movement direction of the vehicle C 10  from, for example, a server device that estimates the movement direction of the vehicle C 10  and the own control device of the vehicle C 10 , and thus, it is possible to reduce the amount of data to be communicated with these server device and control device. 
     In addition, since the terminal device  10  can accurately estimate the movement direction of the vehicle C 10  without installing the terminal device  10  in the vehicle C 10  with a predetermined installation posture, it is possible to make a holder to hold the terminal device  10  with the predetermined installation posture unnecessary. In addition, the terminal device  10  can make manufacturing of the holder or fixing of a direction of the holder unnecessary. 
     In addition, the terminal device  10  specifies the position of the moving object using the predetermined position positioning system, and acquires the speed of the moving object based on the change of the specified position. For example, the terminal device  10  specifies positions of the moving object at predetermined time intervals, and acquires the speed of the moving object based on a difference between a newly specified position and a previously specified position. Thus, the terminal device  10  can estimate the movement direction of the vehicle C 10  in a stand-alone manner without having a function of acquiring the speed from the control device or the like of the vehicle C 10 . 
     Here, a GPS for civilian use or the like sometimes contains a predetermined error in advance. Thus, when the movement direction of the vehicle C 10  is estimated directly using a position indicated by the GPS, the estimation accuracy deteriorates if the vehicle C 10  does not move much more than the error of the GPS. However, the terminal device  10  calculates the GPS speed based on the position indicated by the GPS, and determines acceleration or deceleration of the vehicle C 10  based on the calculated change amount of the GPS speed. Further, the terminal device  10  estimates the movement direction of the vehicle C 10  based on acceleration accompanying the acceleration or deceleration of the vehicle C 10 , and thus, it is possible to shorten the time for initial adjustment performed at the start of the guidance process, for example, and to accurately estimate the movement direction of the vehicle C 10 . 
     In addition, the terminal device  10  estimates the movement direction of the moving object based on the direction of the acceleration detected the predetermined period before the date and time when the acquired speed changes. That is, the terminal device  10  estimates the movement direction of the moving object based on the direction of the acceleration detected when the speed exceeds the predetermined threshold considering the delay of the GPS speed. Thus, the terminal device  10  can accurately estimate the movement direction of the vehicle C 10  even in the case of using the GPS speed. 
     In addition, the terminal device  10  specifies whether the moving object is accelerated or decelerated based on the acquired change in speed, and estimates the movement direction of the moving object based on the direction of the detected acceleration and whether the moving object is accelerated or decelerated. For example, the terminal device  10  sets the direction of the detected acceleration as a direction opposite to the movement direction of the moving object when determining that the moving object is accelerated, and sets the direction of the detected acceleration as the movement direction of the moving object when determining that the moving object is decelerated. Thus, since the terminal device  10  can estimate the movement direction of the vehicle C 10  based on not only the acceleration caused by acceleration of the vehicle C 10  but also the acceleration caused by deceleration of the vehicle C 10 , it is possible to accurately estimate the movement direction of the vehicle C 10 . 
     In addition, the terminal device  10  specifies the direction of gravity using the average value of accelerations detected in a predetermined state. Further, the terminal device  10  estimates the direction on the plane perpendicular to the direction of gravity as the movement direction of the moving object. For example, the terminal device  10  converts the direction of the detected acceleration into the direction on the plane perpendicular to the direction of gravity, that is, the YZ plane, and estimates the movement direction of the moving object on the YZ plane based on the average value of the converted accelerations. Thus, since the terminal device  10  can specify the direction of gravity without measuring the acceleration of the vehicle C 10  for a long period of time, it is possible to promptly estimate the movement direction of the vehicle C 10  with the direction of gravity as the reference. 
     In addition, the terminal device  10  estimates the movement direction of the moving object using the plurality of detected accelerations in the state of considering the weighting based on the magnitude of the acceleration. For example, the terminal device  10  performs the weighting such that the weight increases as the magnitude of the acceleration increases. In addition, the terminal device  10  estimates the movement direction of the moving object based on the average value of directions of the plurality of detected accelerations in the state of considering the weighting based on each magnitude of the accelerations. As a result, the terminal device  10  can accurately estimate the movement direction of the vehicle C 10 . 
     In addition, the terminal device  10  is installed in the moving object and calculates the first average value (that is, the long-term average), which is the average value of accelerations before the lapse of the predetermined time after the detection, and the second average value (that is, the short-term average) which is the average value of accelerations before the lapse of the time shorter than the predetermined time. Further, the terminal device  10  determines whether or not the installation posture of the terminal device  10  has changed based on the first average value and the second average value. Specifically, when the value of the cosine product of the first average value and the second average value is equal to or less than the predetermined threshold during the predetermined period, the terminal device  10  determines that the installation posture has changed. As a result, the terminal device  10  can promptly detect the change of the installation posture, and thus, it is possible to promptly update the C 1  conversion formula and the C 2  conversion formula, and as a result, it is possible to accurately estimate the movement state of the vehicle C 10 . 
     In addition, when the acceleration in the direction different from the estimated movement direction of the moving object is detected after deceleration of the acquired speed, and thereafter, the acquired speed accelerates, the terminal device  10  determines that the moving object has made a right turn or a left turn. In addition, when the speed has not decelerated before detection of the acceleration in the direction different from the estimated movement direction of the moving object, or when the speed has not accelerated after detection of the acceleration, the terminal device  10  determines that the moving object is traveling along the curved road. Thus, the terminal device  10  can separate the case where the vehicle C 10  turns right or left and the case where the vehicle C 10  is traveling on the curved road in the driving ability diagnosis. 
     In addition, when the speed exceeding the predetermined threshold has not been acquired over the predetermined period after detection of the acceleration exceeding the predetermined threshold, the terminal device  10  determines that the dangerous operation is performed. As a result, the terminal device  10  can appropriately determine whether or not the vehicle C 10  has performed acceleration in order to get on the expressway in the driving ability diagnosis. 
     In addition, the terminal device  10  determines whether or not the moving object is decelerated based on the detected acceleration when it is difficult to acquire the speed of the moving object, and determines that the dangerous operation is performed when the moving object is decelerated before the lapse of the predetermined period. In addition, when the speed exceeding the predetermined threshold has been acquired over the predetermined period after detection of the acceleration exceeding the predetermined threshold, the terminal device  10  determines that the moving object is traveling on the road for high-speed movement. Thus, the terminal device  10  can implement the driving ability diagnosis in a stand-alone manner even when it is difficult to use the GPS or the like. In addition, the terminal device  10  can reduce the amount of communication with the external server or the like that performs driving ability diagnosis. 
     In addition, the above-described “unit (section, module, unit)” can be rewritten as a “means”, a “circuit”, or the like. For example, the movement state determination unit can be rewritten as a movement state determination means or a movement state determination circuit. 
     According to one aspect of the embodiment, an effect that it is possible to estimate the traveling state of the vehicle regardless of the installation posture of the terminal device is obtained. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.