JP5731425B2 - Processing unit designating apparatus and method, computer program for designating processing unit, and recording medium storing computer program - Google Patents

Description

  The present invention relates to an apparatus and a method for specifying a processing unit when vector map data is simplified using a Douglas-Peucker algorithm.

In recent years, along with the widespread use of mobile terminal devices such as smartphones, applications applied to such devices have been widely developed.
One such application is vector map data. However, unlike the stand-alone type, using conventional vector map data as it is in communication-type navigation that acquires data by communication has a high load due to its large data size, and it is necessary to reduce the data size as much as possible. It had been.
On the other hand, the Douglas-Peucker algorithm is known as a method for reducing the data size of map data by thinning out some points in a diagram formed by connecting multiple points in map data for representing a map. ing.
See also Patent Documents 1 and 2, which disclose the prior art related to the present invention.

JP 2006-113457 A JP 2007-086462 A

  As described above, if the Douglas-Peucker algorithm (hereinafter also referred to as DP processing) is used, the data size of the vector map data can be reduced. However, the present inventor uses the algorithm to simplify some points of the vector map data by thinning out. As a result, the shape of the road formed from the map data reflects the actual rough shape of the road. I noticed that there was a case that I couldn't do.

The case where the actual shape of the road is not reflected as a result of simplifying the data by the above-described method will be described below with reference to FIG.
FIG. 1A shows vector map data that connects points to form a loop road. When this is the target of the DP process, first, points X ₂ , X ₃ , X ₈ , and X ₉ are deleted as points that can be thinned out based on the point X ₁ as the start point and the point X ₁₀ as the end point. . That is, a straight line Y ₁ connecting the point X ₁ and the point X ₁₀ is drawn, and points X ₂ , X ₃ , X ₈ , X ₉ included in a range formed based on the straight line Y ₁ and a predetermined threshold value t are obtained. delete. Next, determine the X ₅ that the length of the orthogonal line perpendicular to the straight line Y ₁ is the longest. Then, as shown in (b), a straight line Y ₂ connecting the point X ₅ and the point X ₁ and a straight line Y ₃ connecting the point X ₅ and the point X ₁₀ are drawn, and the above processing is repeated. That is, the points X ₄ , X ₆ , and X ₇ included in the range formed based on the straight line Y ₂ and the threshold value t and the range formed based on the straight line Y ₃ and the threshold value t are deleted. (C) shows vector map data after DP processing.
In such a case, by performing the DP process, the actual road shape that has been in a loop shape is represented as a square shape, and the actual road shape is not reflected.

  Therefore, the present inventor has intensively studied to simplify the vector map data so that the outline shape of the actual road can be reflected while reducing the data size of the vector map data. As a result, it has been conceived that, by appropriately designating a processing unit when performing DP processing, vector map data after DP processing can generate map data reflecting the approximate shape of the actual road.

The present invention has been made in view of the above-mentioned problems, and the first aspect is defined as follows. That is,
A processing unit designating device for designating a processing unit when simplifying vector map data using the Douglas-Peucker algorithm,
A base point specifying unit for specifying a point that is a base point of the processing unit from the vector map data;
A separation distance calculation unit that calculates a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the value obtained by subtracting the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point turns inflection. An inflection point identification part for identifying a point;
A processing unit designating unit for designating from the base point to the identified inflection point as the processing unit;
A processing unit designating device comprising:

According to the processing unit designating apparatus of the first aspect defined as described above, a point that is a base point of the processing unit is specified from the vector map data, and the specified base point and a target point connected to the base point are determined. A separation distance is calculated, and an inflection point of the separation distance is specified. Then, the processing unit is designated from the base point to the target point corresponding to the specified inflection point. If the DP processing is performed using the processing unit specified in this way, the actual road shape can be reflected while reducing the data size of the vector map data.
Here, the “base point” refers to a point that is a starting point of a processing unit.
The “target point connected to the base point” means a point constituting the road L formed including the specified base point.
The “inflection point of the separation distance” refers to the target point at which the amount of change between the separation distance between the target point and the base point and the separation distance between the target point next to the target point and the base point turns negative.
The next target point after the target point may be an adjacent point along the line constituting the road, or may be a point adjacent at an interval based on a predetermined rule.

The second aspect of the present invention is defined as follows. That is,
A processing unit designation method for designating a processing unit when simplifying vector map data using the Douglas-Peucker algorithm,
A base point specifying unit for specifying a point that is a base point of the processing unit from the vector map data;
A separation distance calculating unit calculates a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the inflection point specifying unit negatively subtracts the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point. An inflection point identifying step of identifying the target point to turn as an inflection point;
A processing unit designating step in which a processing unit designating unit designates from the base point to the identified inflection point as the processing unit;
A processing unit designation method comprising:
According to the invention of the second aspect defined as described above, the same effect as that of the first aspect can be obtained.

Furthermore, the third aspect of the present invention is defined as follows. That is,
A computer program for designating a processing unit when simplifying vector map data using the Douglas-Peucker algorithm,
Base point specifying means for specifying a point serving as a base point of the processing unit from the vector map data;
A separation distance calculating means for calculating a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the value obtained by subtracting the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point turns inflection. An inflection point identifying means for identifying a point;
Processing unit designating means for designating from the base point to the specified inflection point as the processing unit;
A computer program that functions as a computer program.
According to the invention of the third aspect defined in this way, the same effect as the first aspect is achieved.

  A recording medium for recording the computer program defined in the third aspect is defined as the fourth aspect.

It is a schematic diagram which shows the process of the process at the time of performing DP process without considering a process unit. It is a block diagram which shows the structure of the processing unit designation | designated apparatus 1 of embodiment of this invention. It is a schematic diagram explaining the designation | designated method of the processing unit designation | designated apparatus 1 of this invention. It is a flowchart which shows operation | movement of the process unit designation | designated apparatus 1 of embodiment of this invention. The computer program which comprises the processing unit designation | designated apparatus 1 of embodiment of this invention is shown. It is a schematic diagram explaining the processing method at the time of performing DP process for every process unit designated with the apparatus 1 of this invention. It is a schematic diagram which shows the case where the vector map data of another shape is DP processed as before, and the case where DP processing is performed for each processing unit in the present invention. It is a schematic diagram which shows the case where the vector map data of another shape is DP-processed for every process unit in this invention.

A processing unit designating apparatus according to an embodiment of the present invention will be described.
FIG. 2 shows a schematic configuration of the processing unit designating apparatus 1. This will be described below with reference to the schematic diagram shown in FIG.
As shown in FIG. 2, the processing unit specifying device 1 includes a vector map data storage unit 3, a base point specifying unit 5, a separation distance calculating unit 6, an inflection point specifying unit 7, a processing unit specifying unit 8, and a processing unit storing unit. 9 is provided.

  Vector map data storage unit 3 stores vector map data. The vector map data is data composed of any one of a point, a line, and a surface, and is composed of information on a coordinate position and direction from a certain reference point and a continuous length. For example, a line (also referred to as a line) having length information and direction and connecting a plurality of points displays roads, railways, rivers, and the like on the map. It is preferable that attribute data is set in the vector map data. Examples of the attribute data include information such as “This line is a road” as information set for the line. Other examples include information that the point is a signal, information that the surface is a playground, and the like.

  The base point specifying unit 5 refers to the vector map data storage unit 3 and specifies the point P that is the base point of the DP processing unit from the vector map data (see FIG. 3A). The method for specifying the base point is not particularly limited. For example, an arbitrary point located within a predetermined region can be automatically specified. As another method, it is possible to design the base point manually by the operator. In this case, a desired point on the map displayed on the display based on vector map data in an arbitrary range may be specified by touch input via an input unit (not shown). Here, the base point is a starting point of the processing unit, and when attribute data indicating a road is set in the vector map data, the starting point of the section in which the road attribute is set is used as a base point. It can be specified. In addition, if a branch point on a branch road such as a three-way road is thinned out, the continuity of the road at the branch point may be impaired. Therefore, in view of the fact that the base point is not a target to be thinned out in the DP process, the branch point may be specified as the base point.

Distance calculating section 6, respectively calculate the distance D ₁ to D _n of the target point A ₁ to A _n which leads to the base point P and the origin specified in the base point specification unit 5. As the calculation method of the separation distance, for example, the separation distance can be calculated based on the coordinate position of the identified base point and the coordinate position of the target point. Here, the “target point connected to the base point” may be a point constituting the road L formed including the specified base point, and is connected directly to the base point in addition to the point directly connected to the base point. Includes points. When attribute data indicating that the road is a road is associated with the vector map data, a point on the line L including the identified base point can be set as a target point. When calculating the separation distance, the separation distance calculation unit 6 may set all points on the line as target points, or may set points at predetermined intervals on the line as target points. The predetermined interval on the line can be a predetermined point interval or a predetermined distance interval. Further, the separation distance calculation unit 6 may calculate the separation distance with respect to a target point located within a predetermined range. As the fixed range, for example, the range up to a branch point on the line including the identified base point can be set as the range. As in the case of the base point described above, by setting the end point to be processed as a branch point, it is possible to avoid thinning out of the branch point in the DP process, and it is possible to maintain road continuity at the branch point. Because.

Based on the separation distances D _{1 to} D _n calculated in association with the base point P in the separation distance calculation unit 6, the inflection point specifying unit 7 calculates the amount of change between D ₁ and D _2, and D ₂ and D ₃ . The amount of change,... Is calculated in order to identify the inflection point Q of the separation distance (see FIG. 3B). That is, the inflection point specifying unit 7 specifies a target point having a characteristic that the amount of change in the separation distance turns to a negative value as the inflection point.
The processing unit designating unit 8 designates the processing unit U ₁ from the base point P to the target point Q (= target point A ₄ ) as the inflection point in response to the identification result of the inflection point identifying unit 7 ( (See FIG. 3C). The designated processing unit is stored in the processing unit storage unit 9.

An example of the operation of the processing unit designating apparatus 1 shown in FIG. 1 will be described with reference to FIG.
First, in Step 1, the base point specifying unit 5 specifies an arbitrary point in the data to which the attribute of being a line is given in the vector map data as the base point P of the DP processing unit.
In step 3, the distance calculation unit 6 identifies a target point A _n the following points of the identified base point P in Step 1. That is, a point that constitutes the same line L together with the base point P, and a particular target point A _n a point adjacent to the base point P.
In step 5, the distance calculation unit 6 calculates a distance D _n between the identified target point A _n in the base point P and step 3. That is, the distance D _n, based on the coordinate position of the coordinate position and the target point A _n of the base point P, and calculates the linear distance between the two points.
In step 7, the distance calculating section 6, has been the target point A _n the following points identified in step 3 is specified as A _{n + 1.} That is, a point that constitutes the same line L with the base point P and the target point A _n, specifying the target point A _{n + 1} points adjacent to the object point A _n.

In step 9, as in step 5, the separation distance calculation unit 6 calculates a separation distance D _{n + 1} between the base point P and the target point A _{n + 1} identified in step 3.
In step 11, the separation distance D _n calculated in step 5 is compared with the separation distance D _{n + 1} calculated in step 9. As a result of the comparison, a value obtained by subtracting D _n from D _{n + 1} becomes a negative value. (step 13: Yes), (in FIG. 3 (a) _a 4 = Q) the target point _{a n} of the inflection point Q and identify (step 15).
On the other hand, when No in step 13, the target point _{A n + 1} of the next target point _{A n} executes step 5-13 (step 17, 19).
In step 21, the range from the base point P identified in step 1 to the inflection point Q identified in step 15 is designated as the DP processing unit _Un and stored.
After the processing unit U _{1 is} designated, the processing units U ₂ and U ₃ can be designated by repeating Step 1 to Step 21 with the target point Q (= A ₄ ) in Step 15 as the base point P (FIG. 3 (C )reference).

FIG. 5 is a block diagram showing a hardware configuration of the processing unit designating apparatus 1.
The hardware configuration of the apparatus 1 is such that various elements are coupled to the central controller 221 via the system bus 222 in the same manner as a general computer system.
The central controller 221 includes a general-purpose CPU, a memory controller, a bus controller, an interrupt controller, and a DMA (direct memory access) device. The system bus 222 also includes a data line, an address line, and a control line. A memory circuit including a RAM (Random Access Memory) 223 and a nonvolatile memory (ROM 224, CMOS-RAM 225, etc.) is connected to the system bus 222. Data stored in the RAM 223 is read or rewritten by the central controller 221 or other hardware elements. The data in the non-volatile memory is read-only, and the data is not lost when the device is turned off. The system program for controlling the hardware is stored in the hard disk device 227 and also stored in the RAM 223, and is read and used by the central control device 221 as appropriate via the disk drive control device 226. The hard disk device 227 has an area for storing a computer program for operating a general-purpose computer system as the processing unit designating device 1.

A predetermined area of the hard disk device 227 is allocated to a storage unit that stores information specified, calculated, or specified by the base point specifying unit 5, the separation distance calculating unit 6, the inflection point specifying unit 7, and the processing unit specifying unit 8. It is done.
Another area of the hard disk device 227 is allocated for the vector map data storage unit 3.
Connected to the system bus 222 are a flexible drive control device 231 that reads and writes data from and to the flexible disk 232, and a CD / DVD control device 233 that reads data from the compact disk 234. In this example, a printer 238 is connected to the printer interface 237.
A keyboard / mouse control device 241 is connected to the system bus 222 to enable data input from the keyboard 242 and the mouse 243. A monitor 245 is connected to the system bus 222 via the monitor control device 244. The monitor 245 can be a CRT type, a liquid crystal type, a plasma display type, or the like.
An empty slot 251 is prepared in order to allow the addition of various elements (such as a modem).

  Programs (OS program and application program (including those of the present invention)) necessary for operating the processing unit designating apparatus 1 comprising this computer system are installed in the system via various recording media. For example, it is possible to install in the form of a non-write recording medium (CD-ROM, ROM card, etc.), a writable recording medium (FD, DVD, etc.), or a communication medium using the network N. Of course, these programs can be written in advance in the nonvolatile memories 224 and 225 and the hard disk device 227.

FIG. 6 is a schematic diagram when the DP processing is performed for each of the processing units U _{1 to} U ₃ designated by the processing unit designating apparatus 1 on the line L shown in FIG.
FIG. 6A shows vector map data in which processing units U _{1 to} U ₃ are designated for the line L by the apparatus 1. FIG. 6B shows a case where the processing is divided for each processing unit so that the DP processing can be easily described. FIG. 6C shows vector map data after DP processing of each processing unit, and FIG. 6D shows a result of connecting the processing units after DP processing.
When DP processing is performed without considering the processing unit as in the past, it is difficult to maintain the loop shape that is the actual road shape as shown in FIG. When DP processing is performed based on the processing unit specified by the processing unit specifying apparatus 1 of the invention, the approximate shape of the actual loop shape is maintained even in the simplified vector map data shown in FIG. Thus, map data can be generated.

FIG. 7 shows an example of a case where a processing unit is designated for vector map data showing another shape and DP processing is performed.
When a line-shaped vector map data having a curve as shown in FIG. 7A is subjected to DP processing without considering the processing unit, it is difficult to maintain the actual road shape as shown in FIG. 7B. . On the other hand, the vector map data shown in FIG. 7A is DP-processed for each processing unit designated based on the processing unit designating device 1 of the present invention, so that the schematic shape of the actual road shown in FIG. It is possible to generate map data while maintaining (see FIGS. 7C and 7D).
As a further example, FIG. 8 shows an example in which DP processing is performed by designating a processing unit for vector map data representing a circularly overlapping road.
As shown in FIG. 8, even if the road shape is relatively complicated, if the DP process is performed for each processing unit designated by the apparatus 1 of the present invention, the data size can be reduced and an outline of the actual road shape can be obtained. It is possible to generate map data by reflecting.

  As mentioned above, although embodiment of this invention has been described, you may implement combining 2 or more embodiment among these. Alternatively, one of these embodiments may be partially implemented. Furthermore, among these, two or more embodiments may be partially combined.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

DESCRIPTION OF SYMBOLS 1 Processing unit designation | designated apparatus 3 Vector map data preservation | save part 5 Base point specific | specification part 6 Separation distance calculation part 7 Inflection point specific | specification part 8 Processing unit designation | designated part

Claims (4)

A processing unit designating device for designating a processing unit when simplifying vector map data using the Douglas-Peucker algorithm,
A base point specifying unit for specifying a point that is a base point of the processing unit from the vector map data;
A separation distance calculation unit that calculates a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the value obtained by subtracting the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point turns inflection. An inflection point identification part for identifying a point;
A processing unit designating unit for designating from the base point to the identified inflection point as the processing unit;
A processing unit designating device comprising: It is a processing unit specification method that specifies the processing unit when simplifying vector map data using the Douglas-Peucker algorithm, and is a processing unit specification method that is realized as a computer function,
A base point specifying unit for specifying a point that is a base point of the processing unit from the vector map data;
A separation distance calculating unit calculates a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the inflection point specifying unit negatively subtracts the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point. An inflection point identifying step of identifying the target point to turn as an inflection point;
A processing unit designating step in which a processing unit designating unit designates from the base point to the identified inflection point as the processing unit;
A processing unit designation method comprising: A computer program for designating a processing unit when simplifying vector map data using the Douglas-Peucker algorithm,
Base point specifying means for specifying a point serving as a base point of the processing unit from the vector map data;
A separation distance calculating means for calculating a separation distance between the identified base point and a target point connected to the base point;
Based on the calculated separation distance, the value obtained by subtracting the separation distance between the target point and the base point from the separation distance between the target point next to the target point and the base point turns inflection. An inflection point identifying means for identifying a point;
Processing unit designating means for designating from the base point to the specified inflection point as the processing unit;
A computer program that functions as a computer program.   A recording medium for recording the computer program according to claim 3.

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