JP5270849B2 - Vehicle position calculation method and vehicle position calculation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine highly accurately the present position of a vehicle. <P>SOLUTION: A computer stores in a storage means, a road graphic of a route defined by connecting in due order a section shown by a starting point, an end point, and a line segment defined by a locus from the starting point to the end point; stores in a distance storage part, a traveling distance which is an integrated distance from a reference position on the road graphic to the present position of the vehicle, relative to the vehicle traveling along the route; reads out the traveling distance stored in the distance storage part; and determines the present position of the vehicle by progressing from the reference position along the locus on the road graphic as long as the traveling distance. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a vehicle position calculation method and a vehicle position calculation device.

A navigation cooperative traveling control system has been developed that obtains terrain information from a navigation device and performs vehicle speed control based on the obtained terrain information. In the navigation cooperative traveling control system, it is necessary to determine the current position of the vehicle, and in particular, a method for continuously obtaining the current position has been devised (for example, Patent Document 1).
JP 05-503775 gazette

  In the conventional method, it is difficult to obtain the current position of the vehicle with high accuracy. As a factor that decreases the accuracy of the current position, the accuracy of environmental data around the vehicle and the vehicle, which is input data for calculating the current position, is low. The environmental data is acquired by a sensor provided in the vehicle.

  That is, the sensor performance affects the accuracy of environmental data. For example, the accuracy of GPS radio waves acquired from a GPS (Global Positioning System) antenna decreases due to radio wave blocking by a shielding object such as a building. In addition, the azimuth sensor that detects the azimuth (direction) in which the vehicle travels is generally low in accuracy, and a high-precision sensor is expensive.

  Therefore, the main object of the present invention is to obtain the current position of the vehicle with high accuracy.

In order to solve the above problems, the present invention provides a computer comprising:
Storing the road figure of the route defined by sequentially connecting the sections where the line segment defined by the locus from the start point, the end point, and the trajectory from the start point to the end point is shown as a clothoid curve;
For a vehicle traveling on the route, a travel distance that is an accumulated distance from a reference position on the road graphic to the current position of the vehicle is stored in a distance storage unit,
The following first process is selected until the travel distance exceeds the first threshold, and the following second processing is performed until the travel distance exceeds the first threshold and then exceeds a second threshold greater than the first threshold. A process is selected, and after the travel distance exceeds the second threshold value, the current position of the vehicle calculated by selecting the following third process is obtained as the current position of the vehicle.
When the first process receives an input of information on the current position of the vehicle expressed in latitude and longitude , the first process updates the received current position of the vehicle as the reference position and is stored in the distance storage unit. An initialization process for setting the travel distance to 0 is executed each time the reference position is updated ,
The second process is a process of obtaining a current position of the vehicle by reading a travel distance stored in the distance storage unit and proceeding a trajectory on the road figure corresponding to the travel distance from the reference position ,
The third process is a process for obtaining the current position by integrating the speed of the vehicle and the direction of the vehicle. Other means will be described later.

  According to the present invention, the current position of the vehicle can be obtained with high accuracy.

  FIG. 1 is an explanatory diagram showing an outline of a method for calculating the current position of the vehicle in the present embodiment. The road graphic is a route along which the vehicle travels, and is obtained by sequentially connecting a plurality of sections. The division between the sections is smoothly connected so that the curvature continuously changes. Each section has one type indicating the shape of the road. For example, the vehicle shown in FIG. 1 travels in the order of a straight line → an entrance of a clothoid curve → an arc → an exit of a clothoid curve → a straight line, and the current position exists on the exit of the clothoid curve.

The correspondence between the actual road and the section type on the road map is as follows. The clothoid curve is a shape whose curvature changes according to the distance.
・ Straight figure → Straight road ・ Crossoid curve entrance figure → Pre-curve relaxation section ・ Arc figure → Curve ・ Crosoid curve exit figure → Relaxation section after curve

  Each section corresponds to a figure in geometry. A figure in geometry is a shape determined by a predetermined rule, and the predetermined rule is expressed by a mathematical expression. And in this embodiment, the line segment defined by the locus | trajectory from a start point, an end point, and a start point to an end point is utilized as a figure in geometry. A road figure is defined by inputting parameters of this line segment in advance.

  As a result, the number of sections can be reduced as compared with the broken line link format that connects straight lines used for navigation and the like, so that the memory capacity required for storing road figures can be reduced. Furthermore, since the shape of the road facility constructed in the real world can be accurately reflected, it is effective in calculating the current position with high accuracy.

  The current position of the vehicle is calculated by the travel distance of the vehicle on the road graphic. The travel distance is an integrated distance with respect to the path of the road figure, that is, a road. A current position, which is two-dimensional information, is obtained by advancing on a road figure defined by two-dimensional information by a trajectory corresponding to a travel distance that is a one-dimensional scalar quantity.

  There are two expression methods for the travel distance of the vehicle, depending on the difference in the starting point for measuring the distance. The first is “travel distance from the initialization position” with the initialization position as the start point and the current position as the end point. The second is “travel distance within the section” starting from the start point of the section to which the current position belongs and having the current position as the end point. When the “travel distance within the section” is subtracted from the “travel distance from the initialization position”, the travel distance from the initialization position to the start point of the section to which the current position belongs is obtained.

  FIG. 2 is a configuration diagram of the vehicle position calculation apparatus 1. The vehicle position calculation device 1 calculates and outputs the current position of the vehicle as needed. The vehicle position calculation device 1 is configured as a computer including at least a memory serving as a storage unit used when performing arithmetic processing and an arithmetic processing device that performs the arithmetic processing. The memory is constituted by a RAM (Random Access Memory) or the like. Arithmetic processing is realized by an arithmetic processing unit configured by a CPU (Central Processing Unit) executing a program on a memory.

  The vehicle position calculation device 1 includes a speed detection unit 12, a direction detection unit 14, a GPS detection unit 16, a road graphic 18, a distance storage unit 20, a current position initialization unit 22, an autonomous navigation calculation unit 24, a current position calculation unit 26, The current position selection unit 30, the vehicle control unit 32, and the navigation unit 34 are configured.

  The current position initialization unit 22 inputs information on the current position of the vehicle expressed by latitude and longitude. Specifically, the current position of the vehicle is automatically read from a marker prepared by the user to input the current position of the vehicle or to output the current position in advance. Reading from the marker includes, for example, camera use, magnetic use, and communication use.

  Furthermore, the current position initialization unit 22 may input the current position of the vehicle using GPS radio waves detected by the GPS detection unit 16. Since the GPS itself has an error of more than a dozen meters, it is difficult to obtain an accurate current position with the GPS alone. Therefore, when the GPS signal is interrupted, it may be determined that the reliability has decreased and the vehicle control of the navigation cooperative traveling control system may be stopped.

  The autonomous navigation calculation unit 24 obtains the current vehicle speed of the vehicle detected by the speed detection unit 12 and the current direction of the vehicle detected by the direction detection unit 14 (in other words, the traveling direction), and the two-dimensional vector. Is integrated to find the current position. As the mileage becomes longer, errors in autonomous navigation accumulate.

  Note that when the current position is initialized by the current position initialization unit 22, the autonomous navigation calculation unit 24 continues to obtain the current position as a difference from the initialized current position. Therefore, the accuracy is high immediately after the initialization, but errors continue to accumulate as the vehicle continues running from the initialization.

  The direction detection unit 14 detects the direction such as a gyroscope or a geomagnetic sensor. Errors are accumulated in the detected orientation due to drift or the like. The azimuth detection unit 14 may obtain the azimuth from the difference between the current positions detected by the GPS detection unit 16.

  As described with reference to FIG. 1, the current position calculation unit 26 obtains the current position by tracing the locus on the road figure by the travel distance obtained by integrating the speed detected by the speed detection unit 12. The distance storage unit 20 holds a travel distance. Thereby, since the accuracy of the azimuth obtained by the azimuth detecting unit 14 does not directly affect the current position, the current position can be calculated with high accuracy.

  Note that when the road graphic 18 such as an intersection branches into a plurality, the current position calculation unit 26 determines to which direction the intersection has been bent based on the approximate direction (rough direction) obtained by the direction detection unit 14. The road graphic 18 is uniquely determined. Since only the general orientation is used, the orientation sensor can be replaced with an inexpensive one with high accuracy.

  Alternatively, when the road graphic 18 branches into a plurality of parts, as a map matching method, the shortest distance from the estimated current position to the section element of the road graphic 18 is calculated, and the vehicle moves on the nearest section element. You may judge that you did.

  Alternatively, when the road graphic 18 branches into a plurality, the road graphic 18 is uniquely determined by having the user input a route that has been determined in advance as in regular bus service. Alternatively, as in route search for car navigation, search conditions such as a departure point and a destination may be input as information for specifying a route from the user, and route candidates that match the search condition may be selected.

  The speed detection unit 12 is a vehicle speed detection unit measured from a wheel speed pulse or an acceleration sensor. The error in the vehicle speed can be corrected as follows, and the reliability can be improved. For example, there is a possibility that a parameter when converting from a wheel speed pulse to a vehicle speed varies depending on a vehicle environment such as a passenger. Therefore, when traveling on a predetermined road that is a predetermined reference in the same vehicle environment, an error depending on the vehicle environment can be reduced by correcting the parameter based on the difference compared to the parameter reference value. .

  The current position selection unit 30 selects and outputs which current position is adopted from among the current positions output by the current position initialization unit 22, the autonomous navigation calculation unit 24, and the current position calculation unit 26, respectively. For example, two threshold values are provided for the travel distance from the point initialized by the current position initialization unit 22. The current position of the current position initialization unit 22 is selected until the first threshold value is exceeded, the current position of the current position calculation unit 26 is selected until the second threshold value is exceeded after the first threshold value is exceeded, and the second threshold value is set. After that, the current position of the autonomous navigation calculation unit 24 is selected.

  The vehicle control unit 32 supports vehicle control based on the current position output from the current position selection unit 30. Specifically, the vehicle control unit 32 obtains terrain information such as a curve (curvature information), an intersection, a speed limit, and a stop line from information on the current position and direction on the map, and is associated with the terrain information. Implement each control.

表１は、地形情報およびその地形に対する車両制御の対応を示す表である。例えば、地形「カーブ」が進行先にあるときには、パラメータ「曲率と距離」に着目し、「横加速度が一定値以下になるよう目標速度を求め減速する」旨の車両制御を実施する。

Table 1 is a table showing terrain information and vehicle control correspondence to the terrain. For example, when the terrain “curve” is ahead, paying attention to the parameter “curvature and distance”, vehicle control is executed to “decelerate and obtain a target speed so that the lateral acceleration becomes a certain value or less”.

  The navigation unit 34 displays the current position output from the current position selection unit 30 together with the route on the map, and guides the destination.

  FIG. 3 is a flowchart showing a vehicle control process or a navigation process performed based on the current position of the vehicle.

  The current position selection unit 30 selects the current position of one vehicle from the current positions of the vehicles calculated by the current position initialization unit 22, the autonomous navigation calculation unit 24, and the current position calculation unit 26, respectively. The current position is obtained (S101). The vehicle position calculation apparatus 1 branches by the function of receiving an input of the current position (S102), and performs “vehicle control” or “navigation”. Note that both “vehicle control” and “navigation” may be performed based on the current position of the vehicle obtained in S101.

  When branching to “vehicle control” in S102, the vehicle control unit 32 obtains terrain information (curve, curvature, speed limit, stop line, etc.) of the direction from a map database (not shown) (S103). The vehicle control unit 32 performs vehicle control such as curve deceleration, stop, slowing down, speed limit traveling, etc. based on the acquired terrain information (S104).

  When branching to “navigation” in S102, the navigation unit 34 obtains a map around the current position from a map database (not shown) (S105). The navigation unit 34 displays the current position on the surrounding map based on the obtained surrounding map and guides the traveling direction (S106).

  FIG. 4 is a flowchart showing a process for obtaining the current position of the vehicle. FIG. 4 shows details of S101.

  The vehicle position calculation apparatus 1 checks whether or not there is an initialization input (S201).

  When initialization is input (S201, Yes), the current position initialization unit 22 inputs latitude and longitude information as the current position (S202). The current position initialization unit 22 determines the initial position of the distance storage unit 20 on the road graphic (S203). The current position initialization unit 22 obtains an orientation on the map from the orientation detected by the orientation detection unit 14 (S204). The current position initialization unit 22 clears the distance storage unit 20 by substituting 0 for the travel distance of the distance storage unit 20 (S205).

  When there is no initialization input (S201, No), the current position calculation unit 26 obtains the sum of the previous value of the distance storage unit 20 and the travel distance up to this time, and updates the distance storage unit 20 (S206). The current position calculation unit 26 obtains a distance from the currently running graphic and the graphic start point from the distance storage unit 20 (S207). The current position calculation unit 26 calculates the current position on the road graphic based on the parameters of the graphic being traveled and the distance from the graphic start point (S208). Then, the current position (represented by latitude and longitude) is calculated by replacing the current position on the road graphic with the current position on the map.

  FIG. 5 is a flowchart showing a process for obtaining the distance from the currently running figure and the figure start point. FIG. 5 shows details of S207.

  The current position calculation unit 26 clears the travel distance work and sets 1 to the section number work (S301). The current position calculation unit 26 sets travel distance work = total length of section of section number + travel distance work (S302). The current position calculation unit 26 determines whether or not the travel distance work exceeds the travel distance (S303). When the travel distance work does not exceed the travel distance (S303, No), the section number is incremented (S304), and the process returns to S303.

  When the travel distance is exceeded (S303, Yes), the current position calculation unit 26 obtains a section element (section number work) that is currently traveling (S305). The current position calculation unit 26 determines whether or not the travel distance from the section element start point is small (S306). When the travel distance is small (S306, Yes), the current position calculation unit 26 determines the traveling branch path from the general direction and performs the current travel. The middle section element is updated (S307).

Details of the process for calculating the current position and the current position on the map shown in S208 of FIG. 4 will be described below. A calculation method for obtaining the position on the section based on the section and the travel distance on the section will be described in detail for each section type. Regardless of the type of section, the variables indicating the section are as follows.
・ The start point of the section is the position vector “X ₁ ”
・ The end point of the section is the position vector “X ₂ ”
The current position of the vehicle on the section is the position vector “P”
・ The length of the section is "L"
・ The distance traveled within the section is “l”.

図６（ａ）に示す区間「直線」について、説明する。位置ベクトル「Ｐ」は、走行距離「ｌ」、および、区間を示す各変数を（式１）に代入することにより、計算できる。

The section “straight line” shown in FIG. The position vector “P” can be calculated by substituting the travel distance “l” and each variable indicating the section into (Equation 1).

The section “arc” shown in FIG. 6B will be described. The variables indicating the section “arc” are as follows.
The tangent angle “θ” is the angle of the tangent at the position vector “X ₁ ” in the direction from the start point to the end point, and is, for example, counterclockwise from the east direction.
・ The radius of curvature is "R"
The sign (rotation direction) is positive (1) counterclockwise and negative (-1) clockwise.

以下が円弧を示す変数および円弧上の走行距離をもとに、（式２）によって円弧上の位置を求める計算方法である。回転角度「φ」は、走行距離「ｌ」および曲率半径「Ｒ」から計算する。回転マトリックス「Ｒｏｔ（α）」は、２行２列の行列で表す。接線上の単位ベクトル「Ｉ（θ）」は、位置ベクトル「Ｘ_１」および接線角「θ」から計算する。

The following is a calculation method for obtaining the position on the arc by (Equation 2) based on the variable indicating the arc and the travel distance on the arc. The rotation angle “φ” is calculated from the travel distance “l” and the curvature radius “R”. The rotation matrix “Rot (α)” is represented by a matrix of 2 rows and 2 columns. The unit vector “I (θ)” on the tangent is calculated from the position vector “X ₁ ” and the tangent angle “θ”.

The arc center vector “C” is obtained as the sum of the position vector “X ₁ ” and the vector from the start point to the center of the arc. The vector from the starting point to the center of the arc is calculated by rotating I (θ) by π at right angles and multiplying by the curvature radius R. The current position vector “P” is calculated by adding a vector obtained by rotating the position vector from the center of the arc to the start point by the rotation angle “φ” to the center vector “C” of the arc.

The section “clothoid curve” shown in FIG. 7 will be described. The variables indicating the section “clothoid curve” are as follows.
The tangent angle “θ” is the angle of the tangent at the position vector “X ₁ ” in the direction from the start point to the end point, and is, for example, counterclockwise from the east direction.
The entrance / exit flag is the entrance (1) when entering the curve from the straight line and the exit (-1) when entering the straight line from the curve.
-The clothoid curve constant is [m] and represents the size of the clothoid curve.

図７（ａ）は、クロソイド曲線の入口を示す。まず、入口出口フラグが「１」（入口）であるときを説明する。以下がクロソイド曲線を示す変数およびクロソイド曲線上の走行距離をもとに、（式３）によってクロソイド曲線上の位置を求める計算方法である。距離「ｄ」は、始点側からの距離である。クロソイド曲線上の位置ベクトル「Ｐ_ｃ」は、始点上での接線座標を基準とする。現在位置ベクトル「Ｐ」は、始点ベクトル「Ｘ_１」と、Ｐ_ｃを接線の角度「θ」だけ回転させたベクトルとの和として計算する。

FIG. 7 (a) shows the entrance of the clothoid curve. First, the case where the entrance / exit flag is “1” (entrance) will be described. The following is a calculation method for obtaining the position on the clothoid curve by (Equation 3) based on the variable indicating the clothoid curve and the travel distance on the clothoid curve. The distance “d” is a distance from the start point side. The position vector “P _c ” on the clothoid curve is based on tangent coordinates on the starting point. The current position vector “P” is calculated as the sum of the start point vector “X ₁ ” and the vector obtained by rotating P _c by the tangent angle “θ”.

図７（ｂ）は、クロソイド曲線の出口を示す。次に、入口出口フラグが「−１」（出口）であるときを説明する。（式４）によってクロソイド曲線上の位置を求める。距離「ｄ」は、終点側からの距離である。終点上での接線座標の位置ベクトル「Ｐ_ｃ」は、終点上での接線座標を基準とし、Ｘ軸方位は逆方位（マイナス）となる。現在位置ベクトル「Ｐ」は、終点ベクトル「Ｘ_２」と、Ｐ_ｃを接線の角度「θ」分回転させたベクトルとの和として計算する。

FIG. 7 (b) shows the exit of the clothoid curve. Next, the case where the entrance / exit flag is “−1” (exit) will be described. The position on the clothoid curve is obtained by (Equation 4). The distance “d” is a distance from the end point side. The position vector “P _c ” of the tangent coordinates on the end point is based on the tangent coordinates on the end point, and the X-axis direction is the reverse direction (minus). The current position vector “P” is calculated as the sum of the end point vector “X ₂ ” and a vector obtained by rotating P _c by the tangent angle “θ”.

  For reference, the induction process of the equations of (Equation 3) and (Equation 4) is shown.

（式５）に示すように、接線角「θ」から曲線長に比例して角速度が変化する曲線は「ｄθ／ｄｌ」であり、単位ベクトル「ｕ（θ）」から現在位置ベクトル「Ｐ（ｓ）」を計算する。

As shown in (Expression 5), the curve whose angular velocity changes in proportion to the curve length from the tangent angle “θ” is “dθ / dl”, and the current position vector “P ( s) ".

（式６）に示すように、置換積分を実施して変数「ｌ」を定義すると、現在位置ベクトル「Ｐ（ｌ）」は、Ｆｒｅｓｎｅｌ関数を用いて計算できる。

As shown in (Equation 6), when the variable “l” is defined by performing substitution integration, the current position vector “P (l)” can be calculated using the Fresnel function.

（式７）は、Ｆｒｅｓｎｅｌ関数の級数展開式、つまり、Ｆｒｅｓｎｅｌ積分と級数展開の公式である。

(Expression 7) is a series expansion formula of the Fresnel function, that is, a formula of Fresnel integral and series expansion.

（式８）は、（式６）のＦｒｅｓｎｅｌ関数に（式７）の公式を当てはめてＦｒｅｓｎｅｌ関数の級数展開を行うことにより、現在位置ベクトル「Ｐ（ｌ）」を求める計算式である。具体的には、曲線長「ｓ」から変数「ｄ」を求め、Ｘ座標値「Ｘ（ｄ）」、Ｙ座標値「Ｙ（ｄ）」を求める。

(Expression 8) is a calculation expression for obtaining the current position vector “P (l)” by applying the formula of (Expression 7) to the Fresnel function of (Expression 6) and performing series expansion of the Fresnel function. Specifically, the variable “d” is obtained from the curve length “s”, and the X coordinate value “X (d)” and the Y coordinate value “Y (d)” are obtained.

  According to the embodiment described above, the current position of the vehicle can be obtained with high accuracy by applying the travel distance from which high-accuracy data can be obtained to the road graphic 18 that accurately reflects the constructed road. it can.

It is explanatory drawing which shows the outline | summary of the calculation method of the present position of the vehicle regarding one Embodiment of this invention. It is a lineblock diagram showing a vehicle position calculation device concerning one embodiment of the present invention. It is a flowchart which shows the vehicle control process or navigation process implemented based on the present position of the vehicle regarding one Embodiment of this invention. It is a flowchart which shows the process which calculates | requires the present position of the vehicle regarding one Embodiment of this invention. It is a flowchart which shows the process which calculates | requires the distance from the figure in the present driving | running | working and figure start point regarding one Embodiment of this invention. It is explanatory drawing which shows the calculation method which calculates | requires the present position of a vehicle about the straight line and circular arc regarding one Embodiment of this invention. It is explanatory drawing which shows the calculation method which calculates | requires the present position of a vehicle about the clothoid curve regarding one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle position calculation apparatus 12 Speed detection part 14 Direction detection part 16 GPS detection part 18 Road figure 20 Distance memory | storage part 22 Current position initialization part 24 Autonomous navigation calculation part 26 Current position calculation part 30 Current position selection part 32 Vehicle control part 34 Navigation part

Claims (5)

Computer
Storing the road figure of the route defined by sequentially connecting the sections where the line segment defined by the locus from the start point, the end point, and the trajectory from the start point to the end point is shown as a clothoid curve;
For a vehicle traveling on the route, a travel distance that is an accumulated distance from a reference position on the road graphic to the current position of the vehicle is stored in a distance storage unit,
The following first process is selected until the travel distance exceeds the first threshold, and the following second processing is performed until the travel distance exceeds the first threshold and then exceeds a second threshold greater than the first threshold. The vehicle position is calculated as a current position of the vehicle by selecting a process and selecting the third process below after the travel distance exceeds the second threshold to select the vehicle. Method of calculation.
When the first process receives an input of information on the current position of the vehicle expressed in latitude and longitude , the first process updates the received current position of the vehicle as the reference position and is stored in the distance storage unit. An initialization process for setting the travel distance to 0 is executed each time the reference position is updated ,
The second process is a process of obtaining a current position of the vehicle by reading a travel distance stored in the distance storage unit and proceeding a trajectory on the road figure corresponding to the travel distance from the reference position ,
The third process is a process of obtaining a current position by integrating the orientation of the speed and the vehicle of the vehicle The step of obtaining the current position of the vehicle, when the road figure of the route is branched into a plurality, select the road figure that matches the direction that the vehicle travels detected by the direction sensor of the vehicle, The vehicle position calculation method according to claim 1, further comprising a process of uniquely determining a route. A process for controlling the vehicle is further executed based on the current position obtained by the step of obtaining the current position of the vehicle and the landform information of the destination from the current position.
The vehicle position calculation method according to claim 1 . The present position obtained by the step of obtaining the current position of the vehicle is displayed together with a route on a map, and a process for guiding a destination is further executed.
The vehicle position calculation method according to claim 1 . Storage means for storing a road figure of a route defined by sequentially connecting a section where a line segment defined by a trajectory from the start point, the end point, and the start point to the end point is shown as a clothoid curve;
For a vehicle traveling on the route, a distance storage unit that stores a travel distance that is an accumulated distance from a reference position on the road graphic to a current position of the vehicle;
The following first process is selected until the travel distance exceeds the first threshold, and the following second processing is performed until the travel distance exceeds the first threshold and then exceeds a second threshold greater than the first threshold. A current position selection unit for obtaining a current position of the vehicle calculated as a current position of the vehicle by selecting a process and selecting the following third process after the travel distance exceeds the second threshold ; A vehicle position calculation device comprising:
When the first process receives an input of information on the current position of the vehicle expressed in latitude and longitude , the first process updates the received current position of the vehicle as the reference position and is stored in the distance storage unit. An initialization process for setting the travel distance to 0 is executed each time the reference position is updated ,
The second process is a process of obtaining a current position of the vehicle by reading a travel distance stored in the distance storage unit and proceeding a trajectory on the road figure corresponding to the travel distance from the reference position ,
The third process is a process of obtaining a current position by integrating the orientation of the speed and the vehicle of the vehicle

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