WO2006042689A1

WO2006042689A1 - Method of establishing a sinuosity index for a digital mapping system

Info

Publication number: WO2006042689A1
Application number: PCT/EP2005/011008
Authority: WO
Inventors: Michel Raynaud
Original assignee: Societe De Technologie Michelin
Priority date: 2004-10-18
Filing date: 2005-10-13
Publication date: 2006-04-27

Abstract

The invention relates to a method of evaluating the sinuosity index of at least one road segment for a digital road mapping system. The inventive method comprises a first step consisting in identifying at least one road segment for which an index is to be established. Subsequently, a calculator and initial data relating to the network-modelling elements are used in order to: determine the number of intermediate points for the segment; determine the length of each path used by said road segment; establish a ratio corresponding to the number of intermediate points in relation to the length of the road segment, said ratio providing a sinuosity for the road segment; and store the data which are linked to corresponding road segments. The inventive method can be used to provide modelling systems with data relating to sinuosity and to perform more precise route calculations.

Description

METHOD FOR ESTABLISHING SINUOSITY INDEX FOR SYSTEM

OF DIGITAL MAPPING

The present invention relates to a method for establishing a sinuosity index of at least a road portion for a digital road mapping system. Thanks to this method, it is possible to take into account that some roads or itineraries take less direct or more sinuous paths than others. Since this first aspect often has a direct impact on the travel time, the invention also provides a method for evaluating the real time of travel of a section, or a plurality of sections, depending on the sinuosity in the presence.

In digital mapping systems, especially those used to perform route calculations and waybills or navigation, the digitized data do not contain most of the time no indications relating to the sinuosity of the sections. Thus, these data make it possible to establish the theoretical speed of a vehicle with reference most of the time to the speed limits associated with the sections of the route or to the average speed indicated by the user during his request. However, in many cases, the actual speeds actually achieved during the execution of the route can vary considerably, especially in the case of journeys on winding routes.

In the past, the cartographer provided, from a paper map, data relating to the sinuosity of certain roads or sections of road. Thus, some databases used for the modeling of road networks still include ¹ such indications. However, this information having been obtained from a paper map, they are not precise because of the generalization of the representation on the map. and subjective. In addition, the maintenance of such data, because of the change in the road network, is very tedious and very expensive. On the other hand, current data sources, mostly on a large scale (ie a scale with a very high level of detail), do not include such indications. Considering the huge size that this would represent, given the number of objects in the current road databases, it is unimaginable to manually update (or update) these databases in order to provide them with data on the sinuosity .

However, the assessment of the sinuosity index implies that one can take into account all the details of the layout of all the sections. Indeed, the simplification of the representation of certain laces, or loops or other turns, in small-scale models (ie a scale with a low level of detail), produces errors that are often important for the evaluation of the sinuosity and consequently of the resulting journey time. Thus, neither manual techniques nor conventional digital technologies currently make it possible to accurately evaluate the sinuosity index of given sections or paths, in particular very sinuous and long paths, where the real speed of the vehicle can vary from considerably compared to that calculated.

To overcome these various disadvantages, the invention provides a method for evaluating a sinuosity index of at least a road portion for a digital road mapping system consisting of digital modeling elements of a road network comprising a set sections representative of said road network, and comprising the following steps:

-identify at least a portion of road for which one wishes to establish an index;

using a calculator and from the initial data relating to the modeling elements of said network:

for this portion, the number of intermediate points is determined; the length of the path traversed by this portion of the road is determined; a ratio is established corresponding to the number of intermediate points relative to the length of the portion of the road, this ratio providing a sinuosity index for said portion of road;

the final data obtained is stored by linking them to the corresponding road sections so that the digital system contains the final data relating to the sinuosity.

The evaluation of this index makes it possible to supplement or enrich the numerical data or parameters made available to perform more precisely or more realistically calculations such as the evaluation of the travel time of a given route or the speed vehicle at a given point along the route.

This particularly simple method is very advantageous for today's digital mapping systems, which can easily count tens of millions of objects in memory. Indeed, the processing of such amounts of data can be done quickly if the basic algorithm is simple and allows high processing speeds.

The intermediate points are the points strictly necessary for drawing curves, given the accuracy of the database used. The endpoints corresponding to the end nodes of each section are preferably ignored.

Advantageously, the sinuosity index of a section is established by evaluating the density d of intermediate points over a given reference distance.

By proceeding in this way, it is possible to establish a plurality of indices for the sections whose effective sinuosity varies according to the different portions of the section. By using a rather short reference distance DRef, such as 100 m for example, one obtains a great precision at the local level. This can be very useful in cases where the actual sinuosity rate of a given sector is sought rather than an average rate. Preferably, sections or portions of sections are considered starting from a given minimum length, for example 50 m.

Preferably, only sections or portions of sections having a minimum number of intermediate points as a function of the given minimum length are considered. According to an advantageous embodiment, this threshold is 5 points for a minimum length of 50m. Using this type of limitation avoids calculating sinuosity index values that may prove to be inconsistent.

According to an advantageous embodiment, the density of intermediate points is established using the relation: d = rounded value of (((nbrepoints - 2) * DRef) / (long)) where: "nbrepoints" corresponds to the number intermediate points; "DRef" is the reference distance used; "Long" is the length of the section.

According to another aspect, the present invention also relates to a method for evaluating the travel time of a given route for a digital road mapping system consisting of digital elements for modeling a road network including in particular data relating to the sections representative of said network, in which, on the one hand, data relating to the density d obtained by the previously described method, and on the other hand digital data relating to a pre-established route represented by a series of sections allowing connecting a starting point and an end point, the travel time between these two points is determined using a calculator, by adding the respective travel times of each of the sections or portions of sections, taking into account the standard times of the section route, to which the following penalties are assigned:

-if there is no impact on the length of the section; if ni <= d <n2, the length of the section is increased by p1; -if d> = n2, the length of the section is increased by p2.

According to an advantageous embodiment, n is equal to 3. According to another advantageous embodiment, n2 is equal to 5.

According to an advantageous embodiment, p1 is 10%. According to another advantageous embodiment, p2 is 20%.

Preferably, obtaining the data relating to the route further comprises the following substeps:

-a) we explore the sections adjacent to the node (or point) of departure or the selected node so as to determine the cost of each node to which these sections lead; -b) among these nodes, we select the one whose cost is the most favorable according to the criteria established (the shortest, the fastest, the most economical, favoring highways, etc., or a combination of these criteria); (c) taking up step "a" and continuing said exploration until the node whose cost is the most favorable corresponds to the arrival point.

The nodes can be either nodes corresponding to points or actual data of the modeling elements, or virtual nodes, corresponding to intersections of sections.

During this exploration phase, the multiplicity of valued nodes implies that a multiplicity of alternative routes are actually evaluated or considered. At the end of the process, one or more routes that satisfy the criteria of the request are retained. Advantageously, the exploration of the nodes is carried out using the Dijkstra algorithm. According to another advantageous embodiment, the exploration of the nodes is carried out using the FORD algorithm.

The preferred route is the one for which the sum of the odds or costs between the starting point and the arrival point is optimal. Of course, the establishment of the rating or overall cost can be done taking into account a number of parameters more or less important, as appropriate. For example, we can consider the sinuosity index alone, or with other parameters such as distance traveled, tolls, travel time, fuel economy, etc. Each of these different parameters may take on a more or less determining importance, by associating with each of the more or less important weightings, as the case may be, for example according to one or more wishes of the user. Depending on the type of user, you may want a route through a rather winding road, very winding, for example to favor a diversified driving, or on the contrary little or no winding, to favor a restful route, with a minimum of difficulties.

The invention also provides software comprising code elements programmed for the implementation of the previously described method, when said software is loaded into a computer system and executed by said computer system.

This software can be in the form of a product recorded on a support readable by a computer system, including programmed code elements as stated above.

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 to 3 in which:

FIG. 1 shows an example of sections on which the intermediate points (from 1 to 9) are indicated. FIG. 2 illustrates a representation of a portion of a road network in the Lachaux area, with the right of each section of the database, its sinuosity index;

FIG. 3 shows a representation of a portion of a road network with three possibilities of routes between Vinça and Amélie-les-Bains, having three sinuosity indices which differ significantly.

In the present description, the following terms are used in particular with the following meanings:

A "node" is a point of intersection between a first map or road network element (or other network) and a second element of such a network, in particular the intersection between a plurality of roadways. A node also designates a point of physical or qualitative change of a section, as for example a passage from two to three lanes, a change of the speed limit, a zone (even temporary) being the subject of work, a point breaking like a boundary, etc.

The term "section" refers to a portion of a track between two nodes.

"Crossroads" is an intersection of several roads at the same level.

A "route" is a subset of points derived from the modeling elements of a road network, creating a link between data in such a way as to enable them to model or represent a route or route on the road network that connects a road network. starting point and a point of arrival. This subset is constituted by the data relating to the sections making it possible to connect the departure and the arrival. Data relating to sections refers to the identifications, the lengths of the sections and the spatial coordinates. This subset may be used to represent said route in different forms, for example by means of a graphic representation, preferably in the form of a map comprising the starting point, the arrival point, and the sections forming said route, or in the form of a "waybill" or list of instructions, comprising an enumeration or sequence of written instructions or pictograms, explaining to a possible driver of a vehicle, the various steps to follow to make said route.

According to the preferred embodiment, the density of intermediate points for 100m of each section measuring more than 50m and having more than 5 intermediate points is calculated. Depending on this density, it subsequently applies penalty factors affecting the travel time (and of course the speed) of the different sections. FIG. 1 shows an example of a section on which the intermediate points (from 1 to 9 in this example) are represented. An intermediate point makes it possible to represent a change of orientation between two sections or between two portions of the same sections. Thus, a section representing a straight road has few intermediate points, while a section representing a winding road has a plurality of intermediate points.

According to the preferred embodiment, the penalty levels are then applied as follows: if d <3, no impact is applied on the duration of the section; if 3 <= d <5, the length of the section is increased by 10% (reduction of 10% of the speed); if d> = 5, increase the length of the section by 20% (20% reduction in speed).

The following table presents an example of data obtained using the method according to the invention. This table includes the different sections to connect Chateldon to Vignolle-Basse. The table includes the identifiers of each section, their lengths, the calculated sinuosity indices, the travel time standard (regardless of the sinuosity), and the time or duration of travel obtained taking into account the sinuosity. This example shows that the travel times of sections with high sinuosity index are likely to be strongly corrected by the method according to the invention.

The route presented in the table is also shown in Figure 2. This figure illustrates an example of modeling elements presented in the form of a map, for a given sector, namely the surroundings of Lachaux. The sinuosity indices of the sections, obtained by means of the method according to the invention, are indicated on the map. It is noted that the sections with a high index are numerous. The possibility of taking into account the impact of this sinuosity on the routes is therefore particularly important for sectors such as the one illustrated in this example.

Finally, the following table (below) and Figure 3 show an example of using sinuosity data to perform iti calculations and course in a very precise way. Three different routes, each linking Amélie-les-Bains to Vinça, have been established. According to a specific request from the user, it is possible to provide the best corresponding route, namely with a sinuosity index the highest or the lowest, or even an intermediate index. Otherwise, several routes, with different sinuosity indices, may be suggested. The user has the possibility of retaining the one of his choice. Figure 3 illustrates very well the impact that sinuosity can have on a route between two given points.

Itinerary of Amélie-les-Bains to Vinça iti N ° distance time index of km minutes sinuosity

Variant 1 (Prunet) 43.6 51 4.57

Variant 2 (Llauro) 46.2 52 3.14

Variant 3 (The Bully) 53.2 53 1, 99

The method according to the invention enables users to take into account the type of situation by making it possible to generate precise routes and to calculate precisely the travel time.

In general, the routes are established by identifying a plurality of routes. This is done by selecting a first road network modeling element, preferably a node, near the starting point (α) and a second road network modeling element, preferably a node, near the end point. (β), identifying a plurality of routes, each consisting of a plurality of related modeling elements from the first element to the second element, and searching for at least one intermediate element for each of said roads in said set of modeling elements of road network.

For example, an algorithm of known type, such as that of Dijkstra or Ford, is used to identify the routes likely to fulfill the criteria of the request.

Claims

A method for evaluating a sinuosity index of at least a road portion for a digital road mapping system consisting of digital road network modeling elements comprising a set of sections representative of said road network, and comprising the following steps:

for this portion, the number of intermediate points is determined;

the length of the path traversed by this portion of the road is determined;

a ratio is established corresponding to the number of intermediate points relative to the length of the portion of the road, this ratio providing a sinuosity index for said portion of road;

2. A method of evaluating a sinuosity index according to claim 1, wherein the sinuosity index of a section is established by evaluating the density d of intermediate points over a given reference distance DRef.

The method of evaluating a sinuosity index according to claim 2, wherein said reference distance DRef is 100 m.

4. A method of evaluating a sinuosity index according to one of claims 1 to 3, wherein one considers the sections or portions of sections from a given minimum length.

5. A method of evaluating a sinuosity index according to one of claims 1 to 4, wherein only sections or portions of sections comprising a minimum number of intermediate points as a function of the given minimum length are considered.

6. A method of evaluating a sinuosity index according to claim 5, wherein the threshold is 5 points for a minimum length of 50m.

7. A method of evaluating a sinuosity index according to one of claims 1 to 6, wherein, the density of intermediate points is established using the relation: d = rounded value of (((nbrepoints - 2) ^* DRef) / (long)) where:

"Nbrepoints" is the number of intermediate points; "DRef" is the reference distance used; "Long" is the length of the section.

8. Software comprising code elements programmed for the implementation of the method according to one of claims 1 to 7, when said software is loaded into a computer system and executed by said informatic system.

9. Software in the form of a product recorded on a computer-readable medium, comprising programmed code elements according to claim 8.

10. A method for evaluating the travel time of a given route for a digital road mapping system consisting of digital road network modeling elements including data relating to the representative sections of said network, in which, starting from part of the density data obtained by the method according to one of claims 1 to 7, and secondly digital data relating to a pre-established route represented by a series of sections connecting a point departure and arrival point, we determines, using a calculator, the travel time between these two points, by adding the respective travel times of each of the sections or portions of sections, taking into account the standard times of section travel, to which affects the following penalties: -if d <ni, no impact on the length of the section;

if ni <= d <n2, the length of the section is increased by p1; -if d> = n2, the length of the section is increased by p2.

11. A method for evaluating the time of travel of a route according to claim 10, wherein ni is 3.

12. A method of evaluating the journey time of a route according to one of claims 10 or 11, wherein n2 is 5.

13. A method for evaluating the journey time of a route according to one of claims 10 to -12, wherein p1 is 10%.

14. A method for evaluating the journey time of a route according to one of claims 10 to 13, wherein p2 is 20%.

15. A method for evaluating the journey time of a route according to one of claims 10 to 14, wherein obtaining the data relating to the route further comprises the following sub-steps:

-a) we explore the sections adjacent to the node (or point) of departure or the selected node so as to determine the cost of each node to which these sections lead;

-b) among these nodes, we select the one whose cost is the most favorable according to the established criteria;

(c) taking up step "a" and continuing said exploration until the node whose cost is the most favorable corresponds to the arrival point.

16. A method for evaluating the travel time of a route according to claim 15, wherein the exploration of the nodes is carried out using the Dijkstra algorithm.

A method of evaluating the travel time of a route according to claim 15, wherein the exploration of the nodes is performed using the FORD algorithm.

18. Software comprising code elements programmed for the implementation of the method according to one of claims 10 to 17, when said software is loaded into a computer system and executed by said computer system.

19. Software in the form of a product recorded on a computer-readable medium, comprising programmed code elements according to claim 18.