System, method and apparatus for transmitting and receiving position information of a digital map

Procedure and device for transmitting position information for digital map

5 Technical field

The present invention relates to a method for transmitting position information on a digital map and an apparatus for performing the procedure, and in particular a method and apparatus for accurately transmitting position information on a digital map using only a small amount of data.

Background of the invention

In recent years, the number of vehicles carrying a navigation device on board has rapidly increased. The on-board navigation device maintains a digital map database and is capable of presenting on screen

fifteen traffic congestion and traffic accident positions on the map based on traffic congestion information and traffic accident information provided by a traffic information center, as well as perform a route search using conditions that include such information.

In Japan, several companies prepare digital map databases. The problem is that the map data contains errors due to different base maps and scanning technologies. The error depends on the digital map of each editor.

In the traffic information, for example, in the case that the latitude / longitude data of the position is presented only to indicate, for example, a traffic accident position, the on-board navigation apparatus may

25 Identify a different point on the road as a traffic accident position depending on the type of digital database carried by the device.

To compensate for such incorrect information transmission, in the related art, node numbers are defined for nodes, such as intersections in a road network, and link numbers are defined for links representing roads connecting nodes. The digital map database of each editor stores intersections and roads in correspondence with node numbers and link numbers. For traffic information, a road number is identified by a link number and a point on the road is presented in a representation in which the road is XX meters from where the link begins.

35 However, node numbers and link numbers defined in a road network must be changed to new numbers in case a road is built or modified. When a node number or link number is changed, the digital map database of each editor must be updated. Thus, the procedure for transmitting position information on a digital map requires a very high maintenance cost.

To solve such problems, the author of the invention proposed, in Japanese Patent Application No. 214068/1999, a system where one side of information provision transmits road shape data including a coordinate chain showing the shape of the road in the road section of a predetermined length including the road position, and relative position data showing the road position in the road section represented by the road shape data to indicate the position in

Four. Five road, and a receiving side uses the road shape data to map, identifies the road section on a digital map, and uses the relative position data to identify the road position in the road section. The inventor proposed, in Japanese Patent Application number 242166/1999, a system where additional information is also transmitted including the type of road, the number of roads, the number of crossings in the road section, the angles of the links of crossing and the names of the intersections, and a system where the amount of road shape data to be transmitted is reduced without producing erroneous correspondence on the receiving side.

In this case, map correspondence on the receiving side is done, for example, as follows:

55 As shown in Figure 21, when the longitude / latitude data of the point P0 (x0, y0), P1 (x1, y1), ..., pk (xk, yk) are transmitted as (x0, y0) ( x1, y1), ..., (xk, yk), the receiving side uses as candidates the map data read from its digital map database to select roads included in the error range around point P0 (x0 , and 0), and reduce the candidates using the complementary information transmitted. When a single candidate is finally selected, a position closer to point P0 (x0, y0) and point Pk (xk, yk) on the road is obtained, and the section is taken as a road section represented by the data of road shape.

When the final candidate is not selected, but the roads Q, R are selected as candidates, the points Q0, R0 are obtained on the candidate roads closest to the point P0 (x0, y0) to calculate the distance between P0 and Q0 and the distance between P0 and R0. This operation is repeated for each point P1 (x1, y1), ..., Pk (xk, yk) and a road section is obtained where the sum of the quadratic mean of the distances from each point P0, P1,. .., pk is smaller. This section is taken as a road section represented by the shape data of

road to identify the road section.

The traffic congestion section AB is identified based on relative data transmitted from the starting point of the road section obtained from the road form data. 5 EP-A-0932134 can be consulted in relation to what is characterized by the present invention.

Description of the invention

Aspects of the invention are defined in the claims.

The invention can solve the important problem, in a system where road data is transmitted, of how to reduce the amount of transmission data without degrading the accuracy of the information. The inventor, in order to reduce the amount of data, proposed a system by which data can be reduced in the form of

fifteen Road linear sections and a system where the curve shape of a road is represented by Fourier coefficients, is approximated by arcs, or represented by a piecewise polynomial function to compress the amount of data. In the case that, as shown in Figure 23, the density of roads is low, but the road shape is complicated and the interval between nodes is longer, as in mountain roads, the use of such a system still It requires a large amount of data to represent the road shape.

The invention solves such problems of the related art and is intended to facilitate a method of transmitting position information to accurately transmit a position and form on a digital map using a small amount of data, and an apparatus for implementing the procedure. .

25 In a preferred embodiment of the invention, a position information transmission method where the transmitting side transmits road shape information to specify the desired road section in a digital map and event information to specify an event position using a position relative in the desired road section, and the receiving side maps map based on the road shape information to identify the desired road section and identifies the event position in the desired road section based on the event information, characterized in that the transmitting side intermittently select nodes included in the desired road section to include the coordinate data of the nodes in the road form information for transmission, and because the receiving side maps on the map to determine the positions of the nodes included in the road form information and obtains the road that connects the nodes by means of a route search to identify the section

35 of desired road.

The transmitting side evaluates the potential for incorrect correspondence of the nodes in the desired road section on the receiving side, and determines the length of the desired road section or the number of nodes to be included in the road shape information.

The preferred embodiment also provides a position information transmission apparatus for transmitting road shape information to specify the desired road section in a digital map and event information to specify an event position using a relative position in the road section. desired. The transmission apparatus is characterized in that the apparatus includes information conversion means

Four. Five position to select a desired road section that has the event position and transmission node extraction means to intermittently select from the nodes arranged in the desired road section the nodes to be included in the road shape information.

The preferred embodiment further provides a position information receiving apparatus for receiving road shape information to specify the desired road section in a digital map and event information to specify an event position using a relative position in the desired road section. , characterized in that the apparatus includes map correspondence means to carry out map correspondence to determine the positions of the nodes included in the road form information and route search means to obtain the road connecting the nodes determined for

55 Play the desired road section.

This makes it possible to efficiently and accurately transmit event positions on a digital map with a small amount of data, thus improving the efficiency of data transmission.

Brief description of the drawings

Figure 1 is a schematic view of a method of transmitting position information according to the first embodiment. Figure 1 (1) shows the processing in the transmission apparatus, and Figures 1 (2), (3) and (5) show the processing in the receiving apparatus. Figure 1 (1) is a schematic view of a process of selecting desired roads, (2) selecting nodes to be transmitted, (3) representing the nodes received on the map of the receiving device, (4) calculating the road position in the local map, and (5) connect

the nodes calculated with the shortest path search to determine the desired road or section. Figure 2 is a block diagram depicting the configuration of the information receiving apparatus. on position according to the first embodiment of the invention. Figure 3 is a flowchart depicting a method of transmitting information about

5 position according to the first embodiment. Figures 4 (a), (b), (c), (d) and (e) show an example of data configuration in the method of transmitting position information according to the first embodiment. Figure 4 (a) represents form vector data string information to identify roads and sections. Figure 4 (b) represents various road information represented by a relative distance of each node after identifying

10 The road section. Figure 4 (c) shows a representation of absolute latitude / longitude, (c) shows a representation of lot normalization coordinates, and (e) shows a representation of curvature function. Figure 4 (f) explains the angle of deflection in the curvature function representation. Figures 5 (a) and (b) show other examples of data configuration of a method of transmitting position information according to the first embodiment. Figure 5 (a) shows chain information of

fifteen Shape vector data with the type or number of road to identify roads and sections. Figure 5 (b) shows complementary information to facilitate the identification of nodes. Figure 6 explains a connection link angle. Figure 7 shows a route search with reference to complementary information by means of a procedure for transmitting position information according to the first embodiment.

twenty Figure 8 shows an interception azimuth to be transmitted from the transmitter side by means of a position information transmission method according to the second embodiment. Figure 9 explains the map correspondence on the receiving side in a method of transmitting position information according to the second embodiment. Figure 10 explains how to obtain the interception azimuth.

25 Figure 11 shows a processing flow on the transmitter side in a position information transmission procedure according to the second embodiment. Figure 12 shows a map correspondence flow on the receiving side in a method of transmitting position information according to the second embodiment. Figure 13 shows an example of data configuration of a transmission procedure of

30 position information according to the second embodiment and illustrates vector data string information to identify roads and sections. Figures 14 (1), (2), (3), (4) and (5) are schematic views of a method of transmitting position information according to the third embodiment. Figures 14 (1) and (2) show the processing in the transmission apparatus, and (3), (4) and (5) show the processing in the receiving apparatus. Figure 14 (1) is a

35 schematic view of a process of selecting desired roads, (2) selecting nodes to be transmitted, (3) representing nodes received on the map of the receiving device, (4) calculating the road position on the local map, and (5) connecting the Knots calculated with the shortest path search to determine the desired road or section. Figure 15 shows an example of data configuration of a transmission procedure of

40 position information according to the third embodiment and illustrates vector data string information to identify roads and sections. Figure 16 explains the distance to an adjacent road and the difference in the interception azimuth angle used for decision in the position information transmission procedure according to the third embodiment.

Four. Five Figure 17 shows a processing flow in a position information transmission procedure according to the third embodiment. Figure 18 shows a processing flow in the transmission apparatus in a position information transmission procedure according to the fourth embodiment. Figure 19 shows a processing flow in the receiving apparatus in a transmission process of

fifty position information according to the fourth embodiment. Figure 20 shows an example of data configuration of a position information transmission method according to the fourth embodiment and illustrates vector data chain information to identify roads and sections. Figure 21 explains an example map correspondence.

55 Figure 22 explains road shape data and relative position information. Figure 23 is a printed photograph of a map showing the shape of mountain roads.

In the figures, the numbers 10, 20 represent position transmitter / receiver apparatus, 11, 22 a position information receiver, 12 a map correspondence section, 13 a section of

60 route search, 14 a digital map database, 15 a digital map display section, 16 an event information input section, 17 a position information converter, 18 a node group extraction section of transmission / complementary information, and 19, 21 a transmitter of position information.

Best way to put the invention into practice

First realization

5 According to a method of transmitting position information of the invention, a transmitting side selects a small number of nodes (which can be two points, starting point and end point) of the nodes included in a section of road to be transmitted, and transmits the knot information A receiving side maps the map to determine the positions of the received nodes and sequentially searches for the shortest routes that connect the nodes, and then links the shortest routes to identify the road section.

Figure 2 shows the configuration of the transmitting / receiving position information apparatus 10 that exchanges event information that occurs in the jurisdiction with another apparatus 20.

The apparatus 10 includes a position information receiver 11 to receive information on the sent position

fifteen from the information transmitter on position 21 of the other apparatus 20, a digital map database 14 to accumulate digital map data, a map map section 12 to identify the corresponding node position from the included node information in the information received using a map correspondence, a route search section to find the shortest routes that connect nodes, a digital map display section 15 for displaying the event position on a map, an event information input section 16 for entering event information, a position information converter 17 for displaying the event position using the relative position of the desired road section represented by road shape data, a section for extracting group of transmission nodes / complementary information 18 to select nodes in the desired road section whose node information has to be transmitted and complementary information to be transmitted, and a position information transmitter 19 to send the

25 position information of the selected nodes together with the complementary information selected to the receiver of position information 22 of the other apparatus 20.

The digital map database 14 includes node data and link data in a digital map. The node data includes the latitude / longitude coordinate data of the nodes, node type data (identification information such as intersections, entry and exit of a tunnel, toll barriers on links, change points of the attributes of road, province boundaries, secondary network boundaries, and signals), names, number of connection links to connect to nodes, and connection link angle representing the angle of the connection link. Link data includes data such as road number, road type (national highway identification information, provincial roads, and municipal roads), link type 35 (main line identification information, entry / exit of exchange, links at an intersection, shortcuts, connection roads and interconnection roads), presence / absence of prohibited traffic and prohibited traffic direction, various costs of each link represented by distance or travel time, as well as interpolation point coordinate data representing a link form. Interpolation points are points established to represent a road shape between nodes. Here, unless otherwise specified, the nodes and interpolation points where coordinate data is maintained are called nodes. Node data and link data on a digital map include rivers, administrative boundaries, contour lines and houses. Node data and link data other than road node data have an inherent code of type and attribute, although the configuration is the same as on roads. Thus, the system can be applied to node data and link data other than road data. Coordinate data includes data

Four. Five represented by latitude and longitude, the representation of relative latitude / longitude with respect to the previous / next node, the normalized representation of coordinates in a predetermined section number and the representation of the curvature function (representation of polar relative coordinates with respect to to the previous / next knot).

Figure 3 shows individually the process of processing on the transmitter side and receiver side. Figures 1 (1), (2), (3), (4), and (5) are schematic views of the individual details of the processing on a map.

Step 1: When entering information to indicate an event, such as a traffic congestion and a traffic accident, from the event information entry section 16, the information converter on

55 position 17 selects a road section including the event position as a desired road section based on the data from the digital map database 14 and generates traffic information that displays the event position on the screen using the relative distance from the reference point of the desired road section. Figure 1 (1) shows the desired road section selected. The solid circles in the desired embodiment show the nodes whose coordinate data is maintained in the digital map database 14.

Step 2: The section of extraction of group of transmission nodes / complementary information 18 selects from the nodes in the desired road section the nodes whose node information is to be transmitted. As shown in Figure 1 (2), the nodes at the starting point (p1) and the end point (p3) of the desired road section must be selected. The selected nodes can be these two, but they can include the selected ones

65 intermittently, that is, at intervals of several hundred meters to several kilometers. In this example, an intermediate node p2 is also selected.

Step 3: Information that improves map correspondence accuracy and a route search as required as complementary information of the node data of the selected nodes and link data of the desired road section is extracted.

5 Step 4: The position information transmitter sends form vector data string information including coordinate data of the selected nodes and complementary information selected to represent the desired road section and traffic information to represent the event position by the relative distance from the reference point of the desired road section.

Figures 4 (a), (b), (c) and (d) show vector data string information in a form without complementary information. Figure 4 (b) shows traffic information including event information on position represented by the relative distance from the reference point of the desired road section and detailed event information. The shape vector data string information can be represented by various coordinate data, as mentioned above, but it can be any data as regards the

fifteen present request In the representation of the curvature function of Figure 4 (e), a deflection angle represented in Figure 4 (f) is used. The following description uses the example in Figure 4 (a). In the representation of relative coordinates of Figure 4 (a), the coordinates of the initial node are represented by absolute coordinates (longitude / latitude) and the coordinates of the remaining nodes by relative coordinates with respect to the initial node (or previous node in the knot line) to reduce the amount of data. A reference point of the desired road section in the traffic information may be the knot p2 halfway in the desired road section instead of the starting point (p1) and the end point (p3).

Figure 5 (a) shows vector data string information as complementary information including link data, such as road type, road number and link type. The figure

25 5 (b) shows vector data string information as complementary information including node data, such as node type, node name, number of connection links of the node, and the angle between links of Connection. The angle between connection links is presented by the angle θ1 to θ4 with respect to the absolute azimuth of the true north (dashed line) at the node (node ​​type = intersection, name = 4 cho-me, Tsunashima).

On the receiving side,

Step 5: The position information receiver 11 receives the shape vector data string information and the traffic information.

35 Step 6: The map correspondence section 12 uses the data from the digital map database 14 to map and determine the position of the nodes included in the shape vector data string information. In case the shape vector data string information includes complementary information, the map correspondence section 12 uses the complementary information to execute map correspondence.

Figure 1 (3) shows the result of the representation of the nodes received p1, p2 and p3 on the map of the receiving side. In case the publisher of the digital map data possessing the transmitting side differs from the editor of the digital map data possessing the receiving side, such an arrangement occurs frequently.

Four. Five Figure 1 (4) shows a state where the position of the nodes p1 ', p2' and p3 'corresponding to the nodes p1, p2 and p3 on the map of the receiving side is determined. Even if there is a nearby intersection that may produce erroneous correspondence with p1 around node p1 as shown in Figure 7, correspondence with a correct node position is possible by reference to the complementary information, such as the name of knot

Step 7: The route search section 13 uses the link cost represented by the distance of the link data in the digital map database 14 to sequentially search the shortest route between the nodes determined in step 6. In If the form vector data string information includes the

55 complementary information on link data, the route search section 13 uses the complementary information to execute a route search.

Step 8: The shortest routes obtained in step 7 are sequentially linked to reproduce the desired road section.

Figure 1 (5) shows a state where the shortest route between nodes p1 'and p2' is searched, and the shortest route between nodes p2 'and p3' is searched; These routes are then joined to determine the desired road section from node p1 'to node p3'. In case there is the provincial highway 123 (dashed line) that leaves the national highway 256 (thick continuous line) as shown in Figure 7, thus easily causing an error

65 In the search for the shortest routes, it is possible to reproduce the correct desired road section by reference to the complementary information, such as the type of road and the road number.

When the desired road section is reproduced, the event position is calculated from the reference point of the desired road section based on the traffic information received. The event position on the map is then displayed on the screen by the digital map display section 15.

5 When the nodes are selected intermittently from the desired road section, the nodes must be selected so that the positions of the nodes do not produce an error when identifying the node positions or the calculation of the routes on the receiving side. For example, in Figure 7, a point where the type of road changes from the national highway to the main local road is selected as the node p2. This makes it possible to incorporate separately complementary information between nodes p1 and p2 (road type, road number = national highway, 256) and complementary information between nodes p2 and p3 (road type, road number = main local road, 923) to the shape vector data string, thus facilitating the reproduction of the desired road section on the receiving side.

In this way, only the transmission of information on the selected nodes is required

fifteen intermittently from the desired road section as road shape data to identify the desired road section in this position information transmission procedure. This considerably reduces the amount of transmission data compared to the case in which coordinate line information is transmitted at each node in the desired road section.

Including complementary information to facilitate node identification and complementary information to facilitate route identification in road form data, the receiving side can carry out map correspondence to accurately determine node positions and accurately calculate routes shorter between the nodes, thus faithfully reproducing the desired road section transmitted on its own digital map.

25 This method of transmitting position information is especially advantageous in transmitting a road form, such as mountain roads with low road density, fewer intersections and complicated layout.

Although an example of a position information transmitter / receiver apparatus that constitutes a traffic information provision system, is represented as an apparatus for performing the position information transmission procedure, the receiver device of this apparatus can be implemented in a car navigation apparatus so as to provide the car navigation apparatus with the feature of receiving position information by this procedure.

35 Second embodiment

The second embodiment explains a procedure for including as complementary information the interception azimuth information in the node position in the vector data string information so as to improve the accuracy of correspondence on the receiving side when implementing a transmission procedure of information on position of the first embodiment.

The interception azimuth in the node position is the azimuth of a tangent to the road curve in the px node as represented by the dashed line arrow in Figure 8, and is presented to the right within the range

Four. Five from 0 to 360 degrees, assuming the absolute azimuth of true north as 0 degrees. The interception azimuth of the px node is obtained by averaging the azimuth θx-1 of a line connecting the px-1 node and the px-1 node and the azimuth θx of a straight line connecting the px node and the px + 1 node where px-1 is a node located up next to the px node and px + 1 is a node located down next to the px node as shown in Figure 10:

(θx-1 + θx) / 2 (formula 1)

Figure 11 shows the procedure for the transmitting side to obtain the interception azimuth of a node selected from the desired road section.

55 Step 11: The transmitting side obtains the coordinate data of a selected node and its adjacent nodes located up and down from the digital map database.

Step 12: The transmitting side calculates the azimuths of straight lines connecting the nodes and uses (formula 1) to obtain the interception azimuth of the selected node.

Figure 13 shows form vector data string information including the information on the interception azimuths of the nodes selected from the desired road section as complementary information. Here, the interception azimuth of the initial node (p1) is presented in absolute azimuth and the interception azimuths of the remaining nodes in relative azimuth with respect to the immediately preceding nodes

65 included in the form vector data string information, to reduce the amount of data.

The receiving side receives the shape vector data string and uses the information on the interception azimuth to map. Figure 12 shows the map correspondence procedure.

5 Step 13: The receiving side uses the data from the digital map database of the receiving side to extract positions on the road near the longitude / latitude data of the px node as candidates for correspondence in the increasing order of the distance to the node px

Step 14: The receiving side obtains the coordinates of the adjacent node of the candidate position of the database

10 of digital map to calculate the interception azimuth of the candidate position. Then, the receiving side obtains the difference between the calculated interception azimuth and the interception azimuth of the px node sent in the complementary information. In case the difference is less than the regulated value, the receiving side determines the candidate position as a selected node.

fifteen In case the difference is greater than the regulated value, the receiving side excludes the candidate position of the correspondence candidates. The execution returns to step 13 and the receiving side extracts the next closest position as a correspondence candidate and proceeds to step 14.

In this way, it is possible to avoid erroneous correspondence by reference to the azimuth information about the 20 node position.

In Figure 8, the px node on the road 1 is likely to be erroneously mapped with the road 1 that passes near the px point and crosses the road 1. Correspondingly, as shown in Figure 9, the receiving side could set the point on road 2 closest to the px point as a candidate point 1 for

25 correspondence and the point on the next road 2 closest to the px point as a candidate point 2 for correspondence. The candidate point 1 is excluded from the corresponding candidates because the difference between the interception azimuth of the candidate point 1 and that of the px node exceeds the regulated value. The candidate point 2 is determined as a selected node because the difference between the interception azimuth of the candidate point 2 and that of the px node is less than the regulated value.

30 In this practice, the erroneous correspondence of the candidate point 1 on a different road as a selected node results in an error in the calculation of routes in the following route search, thus making it impossible to reproduce the desired road section.

35 A method of transmitting position information of this embodiment includes as complementary information the information about the interception azimuth at the node position in the shape vector data string information. This avoids the inadvertent establishment of a knot point on a road that crosses the desired road, thus improving the accuracy of the correspondence.

40 Third embodiment

The third embodiment explains a procedure for increasing the number of transmission nodes at road points where it is likely that the receiving side will make an erroneous correspondence, thus improving the accuracy of the correspondence on the receiving side when implementing a procedure for transmitting information about

Four. Five position of the first embodiment.

Figures 14 (1), (2), (3), (4), and (5) are schematic views of the processing details in the procedure for transmitting position information on the map.

fifty The transmitting side, as shown in Figure 14 (1), selects a desired road section, and then the nodes to be transmitted from the nodes in the desired road section. In this practice, the transmitting side selects a plurality of nodes (group of nodes) for easy identification of the different shape of the adjacent road in the sections, where it is likely that the receiving side will make an erroneous correspondence due to the presence of a road adjacent, which is parallel to the desired road.

55 The transmitting side transmits vector data string information in a manner including the coordinate data of the selected nodes and complementary information along with traffic information.

Figure 15 illustrates the shape vector data string information. In this example, a transmission node

60 It includes n groups of knots, the group of knots 1 has m knots, ..., the group of knots n has s knots. Although the coordinate data of the nodes included in each node group are arranged in order in this shape vector data string information, the road shape represented by a plurality of nodes in the individual node groups can be represented by Fourier coefficients, be approached by arcs and straight lines, or represented by a piecewise polynomial function to compress the amount of

65 data.

Meanwhile, the receiving side that has received the node node positions in each group of nodes included in the shape vector data string information on the map of the receiving side as shown in Figure 14 (3), Then make a map correspondence to calculate the position of each node on the map of the receiving side as shown in Figure 14 (4).

5 In this practice, by making the correspondence between the shape represented by the arrangement of a plurality of knots in a group of knots and the road shape on the map of the receiving side, it is possible to accurately obtain the position of each knot on the map of the receiving side

When the node position is determined, the receiving side sequentially searches for the shortest routes that connect the intermittently located nodes, then links the shorter routes to reproduce the desired road section, as shown in Figure 14 (5).

In this procedure for transmitting position information, the transmitting side selects the nodes to be included in a group of nodes based on the following criteria:

(1) As shown in Figure 16, when the distance Lj from the node pj to the closest position pj 'is short and the difference (Δθj = θj -θj') between the interception azimuth angle θj at the node pj and the interception azimuth angle θj 'in the node pj' is small, the node pj is determined as a node in which erroneous correspondence is probably made on the receiving side.

For example, the decision value εj is defined as

εj = α x Lj + β x | Δθj | (formula 2) 25 (where α and β are predetermined coefficients)

and when εj is less than the regulated value ε0, the node pj is determined as a node in which erroneous correspondence will probably be made on the receiving side.

(2) When the pj node is a node in which erroneous correspondence is likely to be made, it is determined whether the nodes before and after the pj node are nodes in which erroneous correspondence will probably be made on the receiving side based on the criteria according to ( 1) and the range of nodes to be determined is expanded sequentially until a node is found in which there will probably be no wrong correspondence on the receiving side. When

35 it finds a node in which probably no wrong correspondence will be made on the receiving side, that is, a node that meets εj≥ ε0, it is assumed that a shape that is identified from the adjacent road shape is obtained, and the node as well as the knots that meet εj <ε0 are used as elements of a group of knots.

Figure 17 shows an example of a procedure to select nodes to include in a group of nodes.

Step 21: The desired road section is selected.

Step 22: Select the node pj to transmit.

Four. Five Step 23: Assume m = 0.

Step 24: The distance Lj ± m to the adjacent road and the difference of the interception azimuth angle Δθj ± m are calculated.

Step 25: The decision value εj ± m is calculated using (formula 2).

Step 26: When εj-m and εj + m are less than the regulated value ε0,

Step 28: The procedure of step 24 is repeated assuming m = m + 1. 55 When one of εj-m or εj + m is greater than the regulated value ε0,

Step 27: Pj-m, ..., Pj, ..., Pj + m are used as elements of a group of knots around Pj.

In this way, this procedure evaluates the potential for erroneous correspondence of the nodes on the receiving side based on the distance of a knot from an adjacent road and the difference between the interception azimuth in the node and the interception azimuth at the point closest to the adjacent road, and select the nodes to include in a group of nodes depending on the evaluation value.

65 The transmitting side evaluates the potential for erroneous correspondence of nodes on the receiving side. The transmitting side transmits more knots at road points where the receiving side is likely to make a wrong correspondence, thereby improving the accuracy of the correspondence on the receiving side and faithfully reproducing the desired road section.

5 The approach of assessing the potential for erroneous correspondence of nodes on the receiving side based on the distance of a knot to an adjacent road and the difference of the interception azimuth can be applied to a procedure for transmitting road shape data including chains of shape vector data, as mentioned in Background of the invention. It is possible to determine the length of the road shape specified by shape vector data chains and the number of nodes to be included in the shape vector data chains depending on the evaluation value.

Fourth realization

The fourth embodiment explains a procedure to support a case in which the digital map data maintained by the receiving side is from an earlier version.

In a procedure for transmitting position information according to the first to third embodiments, the receiving side obtains the shortest routes between nodes by means of a route search to reproduce the desired road section. Thus, roads not included in the digital map database on the receiving side cannot be reproduced. For example, if the digital map data on the receiving side is from an earlier version and does not include data from a recently opened road to traffic, it is impossible to connect intermittent nodes specified by the transmitting side using this road. As a result, the desired road section provided by the transmitting side differs from that reproduced by the receiving side. This will cause the receiving side to mistakenly assume that an event is present on another road.

25 In fact, such a problem frequently occurs if the transmitting side is a means of providing information of a traffic information provisioning system and the receiving side is a car navigation apparatus provided with traffic information.

The fourth embodiment explains a procedure for transmitting position information to avoid such a situation.

In this procedure, the transmitting side identifies the date on which the digital map data of the desired road was established, and selects the type of the procedure for transmitting position information used depending on the date of establishment. Put the date in a digital road map database

35 substantially overlaps the road opening period. For example, when the desired road has just been opened to traffic, the number of car navigation devices that have the digital map database including the new road data is very small. In this case, the transmitting side employs a position information transmission procedure that will avoid confusion that an event is present on a road other than the desired road, if not identify the desired road, even when the navigation device of Car have a digital map database that does not include the data of the new road, to provide traffic information.

In case the data establishment date for the road is defined on each road link in the digital map database, the transmitting side uses the date. Otherwise, the transmitting side compares the

Four. Five versions of the digital map data and calculates the date of establishment from the revision date of the version that first has the road link.

The transmitting side includes the information representing the date of data establishment of the desired road and the information about the distance between nodes in the shape vector data string information.

The receiving side references the date of data establishment of the desired road in the vector data string information received. When the receiving side has determined that the desired road data is not included in its own digital map database, it stops playing the desired road section.

55 In case the distance of the shortest route between nodes is extremely different from the distance between nodes included in the shape vector data, the receiving side determines that the desired road data is not included in its own digital map database, and stop playing the desired road section.

The flow chart of Figure 18 shows the procedure on the transmitter side.

Step 30: The transmitter side selects the desired road section.

Step 31: The transmitter side selects the nodes to transmit.

65 Step 32: When the date of establishment of the road data connecting the selected nodes is equal to or earlier than the reference date (regulated value),

Step 33: The transmitting side employs a position information transmission procedure according to the first to third embodiments.

5 In the event that the date of establishment of the road data connecting the selected nodes is later than the reference date,

Step 35: The transmitting side employs a position information transmission procedure to transmit data that directly represents the road shape of the desired road section (such as the coordinate data chain at each node to identify the road shape) .

Step 36: The transmitting side transmits the position information based on the selected procedure.

fifteen Figure 20 illustrates vector data string information of form to be transmitted using a method of the invention.

This information includes the data establishment date of the roads that connect nodes and searches for distance data.

The flowchart of Figure 19 shows the procedure on the receiving side that has received the shape vector data string information.

Step 40: The receiving side receives the information.

25 Step 41: The receiving side references the complementary information to determine the coordinates of each node by means of map correspondence.

Step 42: The receiving side identifies whether the date of establishment of the data between nodes included in the received data is earlier than the date of creation of the map data of the local device, and if it is earlier,

Step 43: The receiving side references the complementary information to perform a route search between nodes and determine the desired road section.

35 Step 44: The receiving side identifies whether the difference between the distance of the desired desired road section and the search distance between nodes included in the received data is within the regulated error, and if it is within the regulated error,

Step 45: The receiving side reproduces the entire shape of the desired road section.

In case the date of establishment of data is not earlier than the date of creation of map data of the local device in Step 42, or in case the difference between the distance of the desired desired road section and the distance Search between nodes included in the received data is not within the regulated error, the receiving side discards the information between the nodes.

Four. Five By following this procedure, it is possible to avoid the transmission of information on erroneous position produced by different versions of the digital map data maintained by the transmitter side and the receiver side when a position information transmission method according to the invention is applied.

Although the above description includes the date of establishment of the road data connecting nodes and the search distance data in the shape vector data string, any data can be included.

Although the invention has been described in detail with reference to particular embodiments, those skilled in the art

55 they will appreciate that the invention can be modified or corrected in several ways without departing from the spirit and scope of the invention.

This application is based on Japanese Patent Application number 020082/2001 filed on January 29, 2001, which is incorporated herein by reference.

Industrial applicability

As understood by the above description, according to a procedure for transmitting position information on a digital map and an apparatus for performing the procedure, it is possible to efficiently and accurately transmit the

65 information on the shape and position on a digital map using a small amount of data, thereby improving the efficiency of data transmission.