WO2009102284A1

WO2009102284A1 - Electronic toll map

Info

Publication number: WO2009102284A1
Application number: PCT/SI2009/000006
Authority: WO
Inventors: Petar Vracar; Miroslav Madon; Simon Slatnar
Original assignee: Logina D.O.O.
Priority date: 2008-02-15
Filing date: 2009-02-13
Publication date: 2009-08-20
Also published as: SI22722A; EP2091022A1

Abstract

The invention discloses electronic toll map containing a multitude of virtual toll stations covering the entire toll area, where each one of the multitude of virtual toll stations contains one or several geographic areas, which are arbitrary polygons, where the toll map is being defined as a tree structure consisting of cells defined as rectangles with exact coordinates and sides parallel to meridians and parallels of latitude, where the data quantity in a cell is less than the OBU memory capacity, where each cell contains all toll stations and geographic areas which are at least partially within the area a cell covers, where the toll charge accounts for only those cells that represent leaves of the tree structure. The invention provides for minimum exchange of data between the MD and the OBU relieving the communication channel and consequently the costs and updating time.

Description

Electronic toll map

Field of invention

The invention relates to the electronic toll map used in electronic remote toll collection. The toll map is an arranged multitude of Λ irtual toll stations and covers the entire toll area which can be a country, region, continent or the entire world, and the toll objects include in addition to the entire road network (roads of all categories) also parking lots, tunnels, bridges, city centres and such.

More specifically, the invention deals with organisation of captured data within the toll map in the most efficient way possible.

Background of the invention and state of the art

Technically, electronic toll collection has been known for some time now. One of the most advanced remote toll collection systems is designed so that toll collection may take place in a smaller area (e.g. a part of a city) or a larger area (e.g. an entire country, continent or the world) divided into geographic areas.

The areas are defined as arbitrary polygons adapted to the form and layout of the roadway, and their nodes are given with GPS coordinates containing geographic latitude and longitude (excluding altitude).

One or several such geographic areas represent a virtual toll station.

In addition to nodes which define spatial placement, virtual toll stations include an identification mark, toll station type, identification mark of toll collector and specification of the map's layer in which the toll station is located, which is required if areas of virtual toll stations overlap.

The toll station type determines the method of toll collection, which may be by segment (motorway sections, tunnels, bridges, etc.), time the vehicle is located in the toll station (city centres, parking lots, etc.) or the length of road driven within a toll station (network of regional roads). Toll collection is performed by way of a communication unit located in each vehicle that communicates wirelessly (e.g. via the GPRS network) with the map distributor (MD). The established term is OBU (On Board Unit) which will be used hereinafter. The list of all virtual toll stations with coordinates represents a toll map of the area of toll collection. The toll stations map is located at and maintained by the map distributer (MD) who is also in charge for distribution of data on the map to OBU.

The OBU must know the toll station type so that it may prepare the appropriate data on the vehicle's movements and the transition from one geographic area to another. A "toll collection area" is defined as an additional toll station type representing a geographic boundary (e.g. national borders) within which the OBU charges toll in the default manner. When leaving the toll area, the OBU switches to a compatible mode of operation with regard to the toll collection category which it enters.

Technical problem

The described toll collection method results in vast quantity of captured data causing problems in their processing, updating of the vehicle's status and consequent delays or errors in toll charges.

As the OBU must know the geographic areas in which the vehicle moves or is located, it must contain data on those areas, which represents a practical problem, however, as the memory of OBU is limited and cannot contain the entire toll map.

Brief description of the invention

The invention solves the described technical problem by introducing a toll map defined as a tree structure consisting of cells defined as rectangles with specific coordinates and sides parallel to meridians and parallels of latitude.

Brief description of figures

The invention is presented below with the help of enclosed figures presenting: Figure 1: Tree structure of the toll map; Figure 2: Marking of new cells in cell division; Figure 3: Marking of pathways in the tree by arranging 2-bit blocks. Figure 4: Examples of identification markings of cells.

Detailed description of the invention

Organisation of the toll map should account for the following: β Spatial limit: o The OBU in a vehicle is limited with the size of its memory while the toll map of the toll collection area can have any size, and it is therefore impossible to transfer the entire map in OBU. • Minimum data exchange: o The basic precondition for correct charging of the length driven is consistent distribution of toll stations between OBU in a vehicle and the map distributor (MD). Any changes of the map (adding new virtual stations, changing the geographic location or abolishing existing stations) must be timely transferred to OBU so that the captured vehicle positions can be processed by using valid data. Communication between the device and the map distributor (MD) during data updating must be minimal due to restrictions of the communication channel and reduction of costs and/or updating time. o It should therefore be provided that during updating only changes on the map that the OBU actually needs at a given moment are transferred.

We should pay particular attention to the fact that processing of captured points is not always in real time. In the case of unstable GPRS communication, updating of the toll map would be disabled which may result in halting of processing of captured points while the OBU continues to record new positions of the vehicle. The processing of captured points will continue as soon as communication (and hence map updating) is re-established. If communication disturbance between the DM and the OBU occurs towards the end of the journey, it is highly likely that the driver will turn off the vehicle before the latest captured points are processed. If a vehicle is parked for a longer period (e.g. over the weekend or even several days), certain changes in the electronic map may have occurred in the meantime. When the driver restarts the vehicle, processing of captured points will continue where it has previously stopped. For the loll to be charged correctly, the toll area map applicable at the time of data capture must be transferred to the OBU and not the one applicable at the time of processing of those points.

The toll map is defined as a tree structure consisting of cells. Cells are defined as rectangles with exact coordinates. Sides of ceils are parallel to meridians and parallels of latitude.

Each cell contains all toll stations and geographic areas which are at least partially within the area a cell covers.

The tree structure is devised by applying the following principles:

β The entire toll collection area must be covered with the basic cell representing root of the tree structure. This cell is called the base cell.

• Maximum quantity of data contained in a cell is specified, otherwise it should be split into four equal pails by halving it in length and width. The new cells represent leaves of the divided cell. The division process is repeated until all leaves contain the permitted quantity of data per cell.

• Toll collection accounts only for the cells being leaves of the tree structure.

The described recursive procedure enables automatic preparation of the toll map. The final result is a hierarchic structure of cells that fully cover the entire toll collection area with cells not overlapping. Data quantity in individual cells has an upper limit (with system parameters) which is very useful in planning of the minimum memory capacity of the OBU and management of communication restrictions.

Figure 1 presents the tree structure of the toll map with the base cell 1 presented at the top, which is at the second level 2 divided into four cells, 2a, 2b. 2c and 2d, and one of the cells, here 2b, is divided at the next level (3) into four new cells 3a, 3b, 3c and 3d within which the division at additional two levels is presented. Cells after lhe last division are leaves of the tree structure. Cell division continues until all leaves contain the permitted data quantity.

Cells of the toll map have identification markings which in the binary form represent the path from root of the tree structure to the relevant cell. The procedure of cell division results in four new cells which use 2 bits for marking as presented schematically in Figure 1, which shows marking of new cells after division.

Setting a row of 2-bit blocks can mark the path in the tree down the hierarchy. Depth of a cell in the tree is further required for unique marking of a cell.

The number of bits for presentation of a cell's depth depends on the desired maximum depth of the tree structure, which represents the toll map (reduction of the maximum data quantity within a cell increases maximum depth of the map).

An example features the use of a 32-bit identification marking organised in the manner presented in Figure 3. Bits 31 to 28 determine the cell's depth and bits 27 to 0 (in two-bit blocks) represent the path from the tree's root to the cell. Such marking method enables setup of a loll map consisting of a maximum of 16384 cells.

Figure 4 presents an example of identification markings of the base cell and cells after division, where the cells to which the specified marking relates are shadowed.

By using the dimensions of the base cell (the root cell of the tree structure), the following can be determined uniquely for each observed cell on the basis of its identification marking:

• Spatial placement of the observed cell (geographic coordinates of the area it covers can be calculated);

• The relation of adjacent position (we can construct identification markings of all adjacent cells at the same depth of the tree structure or simply check if the given cells are adjacent);

• Relation of hierarchical position (we can construct identification markings of all cells in the sub-tree of the toll map with the root in the observed cell). Each OBU must know dimensions of the base cell. The minimum requirement for the toll collection procedure is presence of at least one cell in memory of OBU (the cell geographically corresponding to the captured point in processing). For toll charge, OBU must have a downloaded cell containing the driven station and representing a leave of the map's tree structure. On the basis of dimensions of the base cell, the division rules and its own position. OBU can calculate which cell it needs. An updated version of the cell may already be downloaded in its memory or is requested from the distributor (MD). If the requested cell is not a leave of the tree structure, the distributor will send a new- configuration and the procedure will be repeated until OBU requests a lea\e of the tree structure.

The downloaded cells are btored in the memory of OBU until it is full. When the memory of OBU is full, the cell that has been unused the longest will be deleted and replaced with a new one. This method ensures construction of a working multitude of the most needed cells given the driver's standard routes, which additionally relieves communications with the distributor (MD).

Claims

1. Electronic toll map. characterised in that, it contains a multitude of toll stations covering the entire toll area, where each one of the multitude of virtual toll stations contains one or several geographic areas, which are arbitrary polygons, is characteristic by being defined as a tree structure consisting of cells defined as rectangles with exact coordinates and sides parallel to meridians and parallels of latitude where the data quantity in a cell is less than the OBU memory capacity.

2. Electronic toll map according to claim 1 characterised in that, each cell contains all toll stations and geographic areas which are at least partially within the area a cell covers.

3. Electronic toll map according to claim 2 characterised in that, if data quantity in a cell is too large, the cell will be divided into four new cells where each new cell has data quantity less than the OBU memory capacity and with a unique identification markin Og.-

4. Electronic toll map according to claim 3 characterised in thai, the toll charge accounts for only those cells that represent leaves of the tree structure.

5. Electronic toll map according to claim 3 and 4 where data exchange between the MD and the OBU is made wirelessly characterised in that, OBU knows dimensions of the base cell and that the OBU updates only those cells which were changed and/or needed by the OBU at a time.

6. Electronic toll map under application 5 characterised in that, when the memory of the OBU is full, cells unused for the longest time are deleted and replaced with the cells needed bv the OBU.