Providing digital map data

Abstract

The invention relates to a method for providing digital map data for a calculated route (401). The method comprises the following steps: specifying a plurality of basic shapes (301 to 326) for tile sub-areas of a tile (200) of a map database, determining an initial tile (402) of the map database that has the highest level among all tiles of the map database that completely cover the route (401), determining the tile sub-areas that, in sum, completely cover the calculated route (401) in the initial tile (402) with a minimal area, and assigning the digital map data of the map database associated with the determined tile sub-areas to the calculated route (401).

Description

[0001] The invention relates to a method for providing digital map data for a calculated route.

[0002] Map data is collected in map databases. A standardized and common format for map databases in navigation systems is the NDS (Navigation Data Standard). A digital map is divided into so-called tiles, which cover the map when placed adjacent to one another, each representing a geographical area. Each tile is assigned map data that provides information about the area represented by the tile. The map data represents geographical objects and associated information, such as streets, paths, intersections, squares, railway lines, waterways, buildings, bridges, terrain features, national borders, parking facilities, rest areas, towns, traffic regulations, and speed limits. The size of a tile depends on a zoom level.From one level to the next, the edge lengths of the tiles are halved, thus reducing the size of the area represented by each tile by a quarter. At the same time, the information provided by the map increases with increasing levels.

[0003] To provide digital map data for a route, the tiles through which the route passes are determined, and the map data from these tiles is assigned to the route. This map data can comprise a significant amount of data, particularly if the route is long and therefore passes through many tiles. Downloading this map data can therefore require significant storage space and be time-consuming. Furthermore, downloading may incur costs if a user of the map data has to pay for the data volume to be downloaded, for example, because they are abroad.

[0004] CN 1 05 758 407 B discloses a method and apparatus for data generation, in which basic map elements in electronic map data are stored in an exchange format, for example, in a corresponding NDS category of a preset intermediate data table. The data format of the basic map elements in the intermediate data table is converted into, for example, an NDS data format and stored, for example, in a corresponding NDS category of a preset hierarchical data table. The electronic map is tiled to obtain a plurality of tiles constituting the electronic map, and the tiles to which the basic map elements each belong in the hierarchical data table are determined.For each category in the hierarchical data table, the basic map elements with the same tiles belonging to the corresponding category are subclassed, and the attributes of the basic map elements in the hierarchical data table are converted after subclassing to obtain electronic map data in the desired format. This converts the map data in the exchange format into map data in the desired format.

[0005] The invention is based on the object of specifying a method for providing digital map data for a calculated route, which in particular reduces the amount of data for the map data that is assigned to the route.

[0006] The object is achieved according to the invention by a method having the features of claim 1.

[0007] Advantageous embodiments of the invention are the subject of the subclaims.

[0008] A method according to the invention for providing digital map data for a calculated route comprises the steps: - Specifying a variety of basic shapes for tile sub-areas of a tile in a map database, - Determining an initial tile of a map database that has the highest level among all tiles of the map database that completely cover the route, - Determining the tile sub-areas that in total completely cover the calculated route in the initial tile with minimal area, and - Assigning the digital map data from the map database belonging to the specific tile sub-areas to the calculated route.

[0009] The statement that a tile has a certain level is to be understood as meaning that the tile belongs to this level or is a tile in the map database with this level.

[0010] According to the invention, tile sub-areas are determined for a route which completely cover the route with a minimal area, and the map data from the map database belonging to the tile sub-areas are assigned to the route. In other words, the route is not assigned map data from tiles which completely cover the route, but rather map data from tile sub-areas which completely cover the route with a minimal area and which are not themselves tiles in the map database but sub-areas of tiles. The individual tile sub-areas available for this purpose are specified by a set of basic shapes for tile sub-areas. With suitably specified basic shapes, the area covered by tile sub-areas over the route can be considerably reduced compared to the area covered by tiles over the route. By reducing the area of ​​coverage, the amount of data assigned to the route is also reduced.This reduces the storage space required to store the map data associated with the route, the time required to download the map data and, where applicable, the cost of downloading the map data.

[0011] In one embodiment of the method according to the invention, the tile sub-areas are determined such that they cover the route without overlap.

[0012] This avoids assigning map data from two (or more) tile sub-areas to a route section, which could lead to problems in describing the route section and its surroundings.

[0013] In a further embodiment of the method according to the invention, 64 basic shapes for tile partial surfaces are specified.

[0014] 64 basic shapes allow for sufficient diversity of tile sub-areas to cover different routes. Furthermore, this number of basic shapes is manageable with acceptable computational effort, even for longer routes, and the basic shapes can be indexed with one byte.

[0015] In a further embodiment of the method according to the invention, each tile sub-area is a polygon which is defined by the arrangement of its vertices relative to the starting tile.

[0016] This embodiment of the method according to the invention enables a simple characterization of the shape and arrangement of tile sub-areas in the initial tile by specifying the position of the vertices of each tile sub-area in the initial tile, for example using a coordinate system related to the initial tile.

[0017] In a further embodiment of the method according to the invention, each tile partial surface has at least two sides, each of which is parallel to a side of the starting tile.

[0018] This allows the tile sub-areas to be easily aligned to the original tile and combined to cover the route.

[0019] In a further embodiment of the method according to the invention, the tile partial surface of at least one basic shape is a rectangle, a triangle, a trapezoid or a hexagon.

[0020] Rectangles, triangles, trapezoids, and hexagons are suitable tile sub-areas because they are suitable for covering different route sections of a route that runs through a tile or sub-tile (see below). Rectangles are suitable, for example, for covering route sections that run essentially parallel to one side of the tile or sub-tile. Triangles are suitable, for example, for covering route sections that run through a corner area of ​​a tile or sub-tile. Trapezoids and hexagons are suitable, for example, for covering route sections that run diagonally through a tile or sub-tile. See also the Fig. 3 and Fig. 4 examples shown.

[0021] In a further embodiment of the method according to the invention, subtiles are determined in the starting tile that have a higher level than the starting tile and completely cover the route with minimal area, and each tile sub-area is a sub-area of ​​a subtile. For example, each subtile is divided into a number of equal-sized squares, for example, nine squares, and each vertex of each tile sub-area is a vertex of one of these squares.

[0022] The route is therefore initially completely covered by sub-tiles of a specific (predefined) level. Such a coverage is known from the prior art and is used there to assign the map data of the sub-tiles of this coverage to the route. In the method according to the invention, however, for each of these sub-tiles, tile sub-areas are determined that cover the route section running through the sub-tile. For this purpose, each sub-tile is divided into equal-sized squares, for example, into nine equal-sized squares. The corner points of these squares form a grid in the sub-tile for the tile sub-areas, the grid points of which provide the possible points for the corner points of the tile sub-areas in the sub-tile.The route section running through a sub-tile is then not assigned all of the map data of the sub-tile as in the prior art, but only the map data of the tile sub-areas of the sub-tile that cover the route section running through the sub-tile.

[0023] Embodiments of the invention are explained in more detail below with reference to the drawings. Fig. 1 a flowchart of an embodiment of the method according to the invention, Fig. 2 a tile of a digital map, Fig. 3 a basic shape set of basic shapes for tile faces, Fig. 4 a route coverage of a route by tile subareas.

[0024] Corresponding parts are provided with the same reference numerals in the figures.

[0025] Fig. 1 ( Fig. 1) shows a flowchart 100 of an embodiment of the method according to the invention with method steps 101 to 105 for providing digital map data for a calculated route.

[0026] In a first method step 101, a plurality of basic shapes for tile sub-areas of a tile in a map database are specified. In the embodiment of the method described here, 64 basic shapes for tile sub-areas are specified.

[0027] The Fig. 2 and Fig. Figure 3 illustrates the definition of the basic shapes. The basic shapes are defined for any tile, i.e., independent of the tile size and level.

[0028] Fig. 2 ( Fig. 2) shows a tile 200. To define the basic shapes, the tile 200 is divided into equal-sized squares 201. In the embodiment shown here, the tile 200 is divided into nine equal-sized squares 201. To describe the basic shapes, Fig. 2 also shows a coordinate system with x and y coordinates relative to the tile 200. The vertices of the squares 201 each have coordinates (x,y) with x,y ∈ {0,1,2,3} in this coordinate system.

[0029] Fig. 3 ( Fig. 3) shows basic shapes 301 to 326 of a basic shape set 300. Each basic shape 301 to 326 specifies a geometric shape and a position of a tile face in the tile 200. The tile face of each basic shape 301 to 326 is a polygon whose vertices coincide with the vertices of a square 201. Therefore, the vertices of the tile faces in the Fig. 2, each coordinate system has coordinates (x,y) with x,y ∈ {0,1,2,3}. Furthermore, at least two vertices of each tile sub-area lie on an edge of the tile 200, and each tile sub-area has at least one side that lies on an edge of the tile 200.

[0030] A first partial figure of the Fig. Figure 3 shows the tile surfaces of three basic shapes 301 to 303. These tile surfaces are each rectangles that cover three squares 201. The corner points of the tile surface of basic shape 301 have the coordinates (0,0), (0,3), (1,3), and (1,0). The corner points of the tile surface of basic shape 302 have the coordinates (1,0), (1,3), (2,3), and (2,0). The corner points of the tile surface of basic shape 303 have the coordinates (2,0), (2,3), (3,3), and (3,0). By rotating the first sub-figure by 90 degrees, the tile surfaces of three further basic shapes are obtained.

[0031] A second part of the Fig. Figure 3 shows the tile surfaces of three basic shapes 304 to 306. These tile surfaces are each rectangles that cover two squares 201. The corner points of the tile surface of basic shape 304 have the coordinates (0,0), (0,2), (1,2), and (1,0). The corner points of the tile surface of basic shape 305 have the coordinates (1,0), (1,2), (2,2), and (2,0). The corner points of the tile surface of basic shape 306 have the coordinates (2,0), (2,2), (3,2), and (3,0). By rotating the second subfigure by 90 degrees, 180 degrees, and 270 degrees, the tile surfaces of nine further basic shapes are obtained.

[0032] A third part of the Fig. Figure 3 shows the tile faces of four basic shapes 307 to 310. The tile faces of basic shapes 307 and 310 are triangles, and the tile faces of basic shapes 308 and 309 are parallelograms. The vertices of the tile face of basic shape 307 have the coordinates (0,0), (0,3), and (1,0). The vertices of the tile face of basic shape 308 have the coordinates (1,0), (0,3), (1,3), and (2,0). The vertices of the tile face of basic shape 309 have the coordinates (2,0), (1,3), (2,3), and (3,0). The vertices of the tile face of basic shape 310 have the coordinates (3,0), (2,3), and (3,3). By rotating the third part of the figure by 90 degrees, reflecting the third part of the figure about a horizontal line and reflecting the third part of the figure about a horizontal line and then rotating it by 90 degrees, you get the tile surfaces of twelve further basic shapes.

[0033] A fourth part of the Fig. Figure 3 shows the tile faces of five basic shapes 311 to 315. The tile faces of basic shapes 311 and 315 are triangles, the tile faces of basic shapes 312 and 314 are trapezoids, and the tile face of basic shape 313 is a hexagon. The vertices of the tile face of basic shape 311 have the coordinates (0,0), (0,1), and (1,0). The vertices of the tile face of basic shape 312 have the coordinates (1,0), (0,1), (0,2), and (2,0). The vertices of the tile face of basic shape 313 have the coordinates (2,0), (0,2), (0,3), (1,3), (3,1), and (3,0). The corner points of the tile face of basic shape 314 have the coordinates (3,1), (1,3), (2,3), and (3,2). The corner points of the tile face of basic shape 315 have the coordinates (3,2), (2,3), and (3,3). Rotating the fourth sub-figure by 90 degrees yields the tile faces of five additional basic shapes.

[0034] A fifth part of the Fig. Figure 3 shows the tile surface of a basic shape 316. This tile surface is a square that covers four squares 201. The corner points of the tile surface of basic shape 316 have the coordinates (0,1), (0,3), (2,3), and (2,1). Rotating the third sub-figure by 90 degrees, 180 degrees, and 270 degrees yields the tile surfaces of three additional basic shapes.

[0035] A sixth part of the Fig. 3 shows the tile faces of eight basic shapes 317 to 324. Each of these tile faces is a square that covers exactly one square 201, whereby only the central square 201 is not covered by any of these tile faces.

[0036] A seventh part of the Fig. Figure 3 shows the tile faces of two basic shapes, 325 and 326. These tile faces are trapezoids, each covering one half of tile 200. The corner points of the tile face of basic shape 325 have the coordinates (0,0), (0,3), (1,3), and (2,0). The corner points of the tile face of basic shape 326 have the coordinates (2,0), (1,3), (3,3), and (3,0). By rotating the seventh sub-figure by 90 degrees, reflecting the seventh sub-figure about a horizontal line, and reflecting the seventh sub-figure about a horizontal line, followed by a 90-degree rotation, the tile faces of six further basic shapes are obtained.

[0037] For example, each basic form is assigned a unique identification number. The identification number is a number between 1 and 64 (or between 0 and 63).

[0038] Fig. 4 ( Fig. 4) illustrates the further procedural steps. Fig. 4 shows a route coverage 400 of a route 401 by tile sub-areas of the basic shapes 301 to 326, which in Fig. 3, as well as the other basic forms that result from the rotations and / or reflections of partial figures of the Fig. 3 emerge.

[0039] In a second method step 102, a starting tile 402 of the map database is determined that has the highest level among all map database tiles that completely cover route 401. This can also be described as the starting tile 402 being the map database tile that represents the smallest geographical area among all map database tiles that completely cover route 401.

[0040] The second method step 102 is executed, for example, by a server. The server can also calculate the route 401. In this case, a user of the map data sends the server a route request, for example, with a starting position and a destination position of the route 401.

[0041] In a third method step 103, subtiles 403 are determined in the source tile 402. These subtiles have a higher level than the source tile 402 and completely cover the route 401 with a minimal area. The level of the subtiles 403 is specified according to a desired or required level of detail of the map data.

[0042] In Fig. 4, each sub-tile 403 has a level two units higher than the starting tile 402 and accordingly represents only 1 / 16 of the geographical area represented by the starting tile 402.

[0043] To determine the subtiles 403 that completely cover the route 401 with minimal area, the starting tile 402 is first divided into subtiles 403 of the required level. Fig. 4, the initial tile 402 is divided into 16 subtiles 403. Then, those of these subtiles 403 through which the route 401 runs are determined. If a subtile 403 is merely touched by the route 401, this subtile 403 is also counted among the subtiles 403 through which the route 401 runs, since this subtile 403 can provide information relevant to the route 401, and in order to assign map data to this route section in the (unlikely but possible) case that a route section of the route 401 runs entirely along the boundary line between two subtiles 403.

[0044] In Fig. 4, route 401 runs through all subtiles 403 of the source tile 402, with the exception of subtile 403 at the bottom left and subtile 403 to the right of it. In this example, the complete coverage of route 401 by subtiles 403 with minimal area therefore encompasses all subtiles 403 of the source tile 402, with the exception of subtile 403 at the bottom left and subtile 403 to the right of it, and thus almost the entire area of ​​the source tile 402, more precisely 14 / 16 of this area.

[0045] The third method step 103 is also executed, for example, by a server. The server determines the subtiles 403 of the initial tile 402 that have the required level and completely cover the route 401 with a minimal area. According to the prior art, the server would now assign the map data of these subtiles 403 to the route 401 and make them available to the user of the map data. The method according to the invention, however, continues with a fourth method step 104. For this purpose, the server loads, for example, the subtiles 403 determined in the third method step 103 into a working memory or a clipboard in order to use them in the fourth method step 104.

[0046] In a fourth method step 104, partial tile areas are determined which, in total, completely cover the route 401 in the output tile 402 without overlap and with a minimal area.

[0047] The tile sub-areas are as shown in the Fig. 2 and Fig. 3, wherein the subdivision of a tile 200 into squares 201 underlying the definition now refers to each sub-tile 403 determined in the third method step 103. In other words, each tile sub-area is a tile sub-area of ​​a sub-tile 403 of one of the Fig. 3 shown basic forms 301 to 326 or one of the further basic forms resulting from the rotations and / or reflections of partial figures of the Fig. 3 emerge.

[0048] The requirement that the tile sub-areas completely cover route 401 without overlap and with a minimum area means that no other complete, non-overlapping coverage of route 401 by the available tile sub-areas exists that has a smaller area. It should be noted that a non-overlapping complete coverage of a route 401 by tile sub-areas with a minimum area is generally not unique, because for a route 401, there can be several non-overlapping complete coverages of route 401 by tile sub-areas with the same minimum area. In fact, this is also the case in the Fig. This is the case in the example shown in Figure 4. However, this is irrelevant to the invention. It is sufficient to determine such an overlap.

[0049] Fig. Figure 4 shows such complete coverage of route 401 by the available tile sub-areas. It is evident that this coverage has a significantly smaller area than the complete minimal coverage of route 401 by sub-tiles 403. While the complete minimal coverage of route 401 by sub-tiles 403 encompasses almost the entire area of ​​the source tile 402, the complete minimal coverage of route 401 by tile sub-areas only encompasses a partial area of ​​the source tile 402 surrounding route 401 in a "tube-like" manner.

[0050] An overlap-free, complete coverage of route 401 by tile sub-areas with minimal area is uniquely described, for example, by uniquely characterizing the sub-tiles 403 determined in the third method step 103 and, for each of these sub-tiles 403, the tile sub-areas that are included in the coverage (including the case where a sub-tile 403 has only one tile sub-area included in the coverage). The sub-tiles 403 are each described, for example, by the coordinates of one of their vertices relative to the starting tile 402 (for example, by the coordinates of the lower left vertex), whereby they are uniquely characterized by the starting tile 402. Each tile sub-area of ​​a sub-tile 403 that is included in the coverage is uniquely characterized, for example, by an identification number, see above.Each tile sub-area included in the coverage can thus be uniquely characterized by a number tuple that includes the coordinates of the sub-tile 403 in which it is located and its own identification number.

[0051] The fourth method step 104 is also carried out, for example, by a server. The server calls the above-mentioned Fig. 2 and Fig. 3 and executes a computer program designed to determine a non-overlapping, complete coverage of Route 401 by tile sub-areas with minimal area.

[0052] In a fifth method step 105, the map data associated with the tile sub-areas determined in the fourth method step 104 are assigned to route 401. Since the complete minimum coverage of route 401 by tile sub-areas has a significantly smaller area than the complete minimum coverage of route 401 by sub-tiles 403, significantly less map data is assigned to route 401 than with a complete minimum coverage of route 401 by sub-tiles 403 according to the prior art. It is estimated that less than 40% of the data volume is generated that would be generated with a complete coverage of route 401 by sub-tiles 403.This also has the advantage of significantly reducing the storage space required to store the map data associated with Route 401, the time required to download the map data and, where applicable, the costs of downloading the map data.

[0053] The fifth method step 105 is also executed, for example, by a server. The server assigns the corresponding map data from the map database to each tile sub-area determined in the fourth method step 104 and makes this map data available so that the user can retrieve it, or sends it directly to the user. The user can then use the map data, for example, for offline navigation. List of reference symbols 100 Flowchart 101 to 105 process step 200 tiles 201 square 300 basic form quantity 301 to 326 basic form 400 route coverage 401 Route 402 Exit tile 403 sub-tile x, y coordinate

Claims

[1] Method for providing digital map data for a calculated route (401) comprising the steps: - specifying a plurality of basic shapes (301 to 326) for tile sub-areas of a tile (200) of a map database, - Determining an output tile (402) of the map database which has the highest level among all tiles of the map database which completely cover the route (401), - Determining the tile sub-areas which in sum completely cover the calculated route (401) in the initial tile (402) with minimal area, and - Assigning the digital map data of the map database belonging to the specific tile sub-areas to the calculated route (401). [2] Method according to claim 1, wherein the tile sub-areas are determined such that they cover the route (401) without overlap. [3] Method according to claim 1 or 2, wherein 64 basic shapes (301 to 326) are specified for tile sub-areas. [4] Method according to one of the preceding claims, wherein each tile patch is a polygon defined by the arrangement of its vertices relative to the starting tile (402). [5] A method according to any one of the preceding claims, wherein each tile patch has at least two sides, each of which is parallel to a side of the starting tile (402). [6] Method according to one of the preceding claims, wherein the tile partial area of ​​at least one basic shape (301 to 326) is a rectangle. [7] Method according to one of the preceding claims, wherein the tile partial surface of at least one basic shape (301 to 326) is a triangle, a trapezoid or a hexagon. [8] Method according to one of the preceding claims, wherein sub-tiles (403) are determined in the starting tile (402) which have a higher level than the starting tile (402) and completely cover the route (401) with a minimum area, and each tile sub-area is a sub-area of ​​a sub-tile (403). [9] Method according to claim 8, wherein each sub-tile (403) is divided into a number of equal-sized squares (201) and each vertex of each tile sub-area is a vertex of one of these squares (201). [10] The method of claim 9, wherein each sub-tile (403) is divided into nine equal-sized squares (201).

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