JPH08220991A - Map preparing device - Google Patents

Abstract

PURPOSE: To provide a map preparing device effective for reducing a map data amount and improving a plotting speed and a scroll speed by surely thinning the surface data unnecessary for display at a specified display reduced scale. CONSTITUTION: An area calculation means 102 reads out the map data from a digital data storage means 101, and calculates an area occupied by the surface data in the map data to transfer it to a surface data elimination means 104. The surface data elimination means 104 eliminates the surface data from the map data when no value of the transferred area is satisfied with a threshold value from a threshold value setting means 103. A displaying map data forming means 105 forms the map data at every display reduced scale from the map data after the surface data are eliminated as stated above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly applied to in-vehicle navigation devices and the like, and thins plane data from digital map data which is an original database.
The present invention relates to a map creation device that automatically creates map data for each display scale.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing the structure of a conventional map creating apparatus. In FIG. 6, reference numeral 601 includes road network data, water system data such as oceans, lakes and rivers, railway data, facility data, etc., and stores digital map data segmented by a certain latitude and longitude. The digital map data storage means is a database, 602 is a perimeter calculation means for calculating the perimeter of the surface data in the digital map data read from the digital map data storage means 601, and 603 sets the threshold value for each display scale. Threshold setting means, 604 is perimeter calculation means 602
A surface data deleting unit 605 that compares the value of the perimeter with the threshold of the threshold setting unit 603 and deletes the corresponding surface data from the digital map data when the value of the perimeter is less than the threshold. Is a display map data creating means for creating map data for each display scale from the map data after the surface data is deleted.

Next, the operation of the conventional map making apparatus having the above structure will be described. First, the perimeter calculation means 602 calculates the perimeter of the surface data on the map data read from the digital map data storage means 601. The surface data includes interpolation point coordinate data, and the perimeter of the surface data is obtained by calculating the total distance between adjacent interpolation points.

The surface data deleting means 604 compares the calculated value of the perimeter with the threshold according to the display scale from the threshold setting means 603, and the value of the perimeter is less than the threshold. In this case, the corresponding surface data is deleted from the map data and the map data is thinned out. Next, the display map data creating means 6
Step 05 creates map data of the designated display scale based on the remaining map data. The map data of the designated display scale thus created is written in, for example, a CD-ROM for a vehicle-mounted navigation device.

As described above, in the conventional map creating apparatus, the data size is compressed by thinning out the surface data from the digital map data which is the original database with reference to the perimeter, and the display map data creating means 605 sets each display scale. Automatically create map data for. Compressing the data size of the map data for display is useful for improving the drawing speed and scrolling speed.

[0006]

However, in the above-described conventional map making apparatus, since it is determined whether or not to thin out the surface data by comparing the value of the perimeter of the surface data with the threshold value, In a small-scale map displaying a wide area, there is a problem that, for example, water system data such as long narrow rivers and lakes whose area is small for the perimeter is not thinned and remains.

In the case of water system data, the digital map data is, as shown in FIG. 7, an ID number 701, a water system type code 702 indicating whether it is line data or plane data, and a total number of interpolation points 70.
3, a plurality of interpolation point coordinates 704 including x and y coordinates. Thus, in the case of water system data,
Since there is only a distinction between line data and area data, rivers, lakes,
It was difficult to automatically perform thinning to distinguish the sea.

Since a small-scale map covers a wide area in particular, it is important to thin out and compress the data in order to reduce the map data amount and to improve the drawing speed and the scroll speed. . However, in the conventional example, since it is difficult to thin out the data as described above, there is a problem that it is difficult to reduce the map data amount and to improve the drawing speed and the scroll speed.

The present invention was devised in view of such circumstances, and it is possible to reliably perform thinning out of surface data that is not required to be displayed at a designated display scale, thereby reducing the map data amount and drawing speed. It is an object of the present invention to provide a map creation device useful for improving scroll speed and scroll speed.

[0010]

A first aspect of the present invention.
The map making device compares the calculated area value and a certain threshold value with the area calculation means for calculating the area occupied by the surface data of the digital map data, which is the original database. If the threshold value is not reached, the surface data is deleted from the digital map data and the map data for each display scale is created from the map data after the surface data has been deleted as described above. And means.

According to a second aspect of the map creating apparatus of the present invention, in the first aspect, when the target surface data is spread over a plurality of sections, the surface data deleting means has an area of the surface data for each section. It is characterized in that it is configured to compare the magnitude of the total sum of and a certain threshold value.

According to a third aspect of the present invention, in the map generating apparatus according to the second aspect, when the target surface data extends over a plurality of sections, the perimeter for calculating the perimeter of the surface data for each section. Comprising a calculating means, the surface data deleting means obtains the ratio of the area to the perimeter of the surface data for each section, and deletes the surface data of the section whose area ratio is lower than a predetermined value. It is characterized by.

According to a fourth aspect of the present invention, in the map generating apparatus according to the second aspect, when the target surface data extends over a plurality of sections, the perimeter for calculating the perimeter of the surface data for each section. The surface data deleting means is configured to calculate the ratio of the perimeter to the area of the surface data for each section, and delete the surface data in the section where the ratio of the perimeter is higher than a predetermined value. It is characterized by that.

[0014]

In the map making apparatus according to the first aspect of the present invention, the area of surface data is compared with the threshold value instead of comparing the perimeter of the surface data with the threshold value as in the conventional example. It becomes possible to thin out the water system data such as long narrow rivers and lakes whose area is small for the perimeter that was not thinned out.

In the map generating apparatus according to the second aspect, when the surface data spans a plurality of sections, the total area of the surface data spanning the plurality of sections is compared with the threshold value. The shape of the remaining surface data does not change by thinning out only a part of the collected surface data, and the entire data can be left as the surface data with the same shape.

In the map creation device according to the third aspect, when the surface data spans a plurality of sections, the area data of each section is not processed as a group of the surface data of the plurality of sections. Then, the perimeter is also calculated for each section, and when the ratio of the area to the perimeter is lower than a predetermined value, the surface data of that section is thinned out. You can aggressively remove the parts that don't make much sense.

The map making apparatus of claim 4 is directed to the determination of the ratio of the perimeter to the area instead of the ratio of the area to the perimeter, and is substantially the same as that of claim 3, It is possible to positively delete the part of the surface data that straddles the partition of, which has little meaning.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a map making apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the map creating apparatus of the first embodiment. In FIG. 1, reference numeral 101 is composed of road network data, water system data such as oceans, lakes and rivers, railway data, facility data, etc., and stores digital map data partitioned by a certain latitude and longitude. Digital map data storage means that is a database, 10
2 is an area calculating means for calculating the area occupied by the surface data in the digital map data read from the digital map data storing means 101, 103 is a threshold setting means for setting a threshold value for each display scale, and 104 is an area calculating means. The area data from 102 is compared with the threshold value of the threshold value setting means 103, and when the area value is less than the threshold value, the corresponding surface data is deleted from the digital map data. Is a display map data creating means for creating map data for each display scale from the map data after the surface data is deleted.

FIG. 2 illustrates the operation of the area calculating means 102. For example, the area occupied by the surface data 201 as shown in FIG. 2A is calculated as follows.
The surface data 201 is defined by a plurality of interpolation point coordinates (x coordinate, y coordinate) on the closed loop curve 202 that constitutes this surface data. The point indicated by the number 1 of the interpolation point coordinates is the start point 203, and the point indicated by the number N of the interpolation point coordinates is the end point 204. The area occupied by the surface data 201 is calculated as an approximate value by individually calculating the areas of the plurality of triangles 205, 206 and the like formed by the start point 203 and the other two interpolation point coordinate points, and summing the areas of all the triangles. It is calculated. 2B and 2C show the directionality of the triangle. In FIG. 2B, the direction from the front side interpolation point coordinate point 210 to the rear side interpolation point coordinate point 211 is clockwise around the start point 203. In this case, the sign of the triangle area is positive. Further, (c) shows the front side interpolation point coordinate point 21.
The direction from 0 to the rear interpolation point coordinate point 211 is the start point 20.
3 shows the case of counterclockwise rotation around the center, in which case the sign of the area of the triangle is minus. When the area of the surface data is calculated by such a method, the area of the surface data 220 having a complicated shape in which a convex portion and a concave portion coexist as shown in FIG. 2D can be easily obtained. The present invention is not limited to the method of calculating the area of the surface data as shown in FIG. 2, and any method may be adopted as long as the area of the surface data can be approximately calculated. .

Next, the operation of the map creating apparatus of the first embodiment having the above construction will be described. Digital map data storage means 10
The digital map data stored in 1 is generally partitioned by a certain latitude / longitude as described above. However, in order to explain the operation in principle,
The surface data that is not partitioned or the surface data that is partitioned but is included in only one partition will be described.

First, the area calculation means 102 calculates the area of the surface data on the map data read from the digital map data storage means 101. Surface data deleting means 10
4 compares the obtained area value with the threshold value according to the display scale from the threshold value setting means 103, and when the area value is less than the threshold value, the corresponding surface data is obtained from the map data. Delete and thin out map data. Next, the display map data creating means 105 creates map data of the designated display scale based on the remaining map data. The map data of the designated display scale thus created is written in, for example, a CD-ROM for a vehicle-mounted navigation device.

In this case, the peripheral length of the surface data is not compared with the threshold value as in the conventional example, but the area of the surface data is compared with the threshold value, so that the conventional example is not thinned out. It has become possible to thin out water system data such as long narrow rivers and lakes whose area is small for the perimeter. Therefore, when creating the map data for each display scale in the display map data creating means 105, the data size can be further compressed as compared with the conventional example, the map data amount in the CD-ROM or the like can be reduced, and the on-vehicle navigation device can be used. The drawing speed and scrolling speed in the map data display can be made faster than in the conventional example.

Next, the operation of the map making apparatus when the target surface data is spread over a plurality of sections will be described.
This is more realistic. FIG. 3 is a diagram showing surface data that extends over a plurality of sections. In FIG. 3, 30
Reference numeral 1 is map data read from the digital map data storage means 101, 302 is surface data of interest, 303 is a vertical division line, 304 is a horizontal division line, and 305 to 310 are individual divisions. Is surface data. The target surface data 302 corresponds to the grouped surface data 305 to 310 in each section.

Next, the operation will be described. Area calculation means 10
In the map data 301 read from the digital map data storage means 101, 2 sequentially calculates the area of the surface data for each section, and the value of the area is used as the surface data deleting means 1
Send to 04. The surface data deleting unit 104 sequentially adds the sent area values for each section to obtain the total area. That is, the area of the surface data 305 is first calculated and transferred to the surface data deleting unit 104. Next, when the area of the surface data 306 is calculated and transferred to the surface data deleting means 104, the surface data deleting means 104 adds the area of the subsequent surface data 306 to the area of the previous surface data 305,
Update the area value. Hereinafter, the same thing is executed for the surface data 310. As a result, the surface data deleting unit 104 obtains the total area of the grouped surface data 302. The surface data deleting means 104
The total area is compared with a predetermined threshold value from the threshold setting means 103, and if the total area is less than the threshold value, the entire surface data 302 grouped from the map data 301. Is deleted and the map data is thinned out. In the case of FIG. 3, the total area of the grouped surface data 302 is relatively large.
Is not thinned out. However, in the case of the grouped surface data 311 as shown in a small size in FIG. 3, the entire surface data 311 is thinned out.

For the case of relatively large surface data 302, if the surface data of each section is compared with each threshold value instead of comparing the total area with the threshold value, the area The small plane data 309 and 310 are thinned out, and the map data in a state where a part of the plane data 302 is missing is created. However, in the embodiment, since the total area is compared with the threshold value, the entire surface data 302 is left as it is.

Next, a map creating apparatus according to a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the map creating apparatus according to the second embodiment. In FIG. 4, reference numerals 101 to 105 are common to the configuration of FIG. 1, and in brief description, 101 is digital map data storage means, 102 is area calculation means, 103 is threshold value setting means, and 104 is Surface data deleting means 105 is a display map data creating means. In the second embodiment, when the target surface data spans a plurality of sections, the perimeter calculation means 1 for calculating the perimeter of the surface data for each section.
It is equipped with 06. Then, the surface data deleting means 104
Calculates the ratio of the area to the perimeter of the surface data for each section, and when the area ratio is lower than the threshold value from the threshold setting means 103, the surface data in the section is deleted. It is configured. Of course, the area calculation means 102 calculates the area of the surface data for each section,
The perimeter calculation means 106 is configured to calculate the perimeter of the surface data for each section. When calculating the perimeter of surface data for each section, include the length of the section line.

In the case of the method of FIG. 3 of the first embodiment, by grouping, it is based on the idea that when the surface data is left, the entire shape is not damaged and the shape is left as it is. There is. On the other hand, in the case of the second embodiment, when the surface data spans a plurality of sections, it is based on the idea of responding to the request to positively delete the portion that does not have much meaning. is there.

Next, the operation of the map creating apparatus of the second embodiment having the above construction will be described. Digital map data storage means 10
It is assumed that the surface data of the digital map data stored in 1 extends over a plurality of sections.

First, the area calculation means 102 obtains the area for the surface data of one section on the map data read from the digital map data storage means 101. In addition, the perimeter calculation unit 106 obtains the perimeter of the surface data of the same section on the map data read from the digital map data storage unit 101. This perimeter also includes the length of the section line. Surface data deleting means 104
Is the ratio of the area to the perimeter of the surface data of the target section, and compares the ratio of the area with the threshold value according to the display scale from the threshold value setting means 103. When the ratio is lower than the threshold value, the surface data of the section is deleted from the map data and the map data is thinned out. The above operation is repeated for each section.

Next, the display map data creating means 105
Creates map data of the designated display scale based on the map data remaining as a result of the above processing. The map data of the designated display scale thus created is written in, for example, a CD-ROM for a vehicle-mounted navigation device.

FIG. 5 shows a concrete processing example in the case of the second embodiment. Reference numeral 501 is map data read from the digital map data storage means 101. Surface data 5 showing the sea
02 has a high area-to-perimeter ratio and is left.
The surface data 503 indicating the sea and the river following the sea also remains because the ratio of the area to the perimeter is high. However, the surface data 504 indicating the sea has a low ratio of the area to the perimeter and is deleted. The plane data 505 and 506 indicating the upstream of the river are also deleted because the ratio of the area to the perimeter is low.

Since the surface data 505 and 506 are not very useful in the small scale map, there is no problem even if they are deleted, the data size can be reduced, and the drawing speed and the scroll speed can be improved.

The surface data 507 and 508 indicating the lake are left because the ratio of the area to the perimeter is high, but the surface data 509 and 510 are deleted because the ratio of the area to the perimeter is low and the shape of the lake as a whole. May change.

In the second embodiment, the ratio of the area to the perimeter is obtained and the surface data of the section whose area ratio is lower than the predetermined value is deleted. However, instead of this, the perimeter to the area is deleted. The same effect can be obtained even if the length ratio is obtained and the surface data of the section whose peripheral length ratio is higher than a predetermined value is deleted.

Although it is not possible to directly distinguish rivers, lakes, and seas from the water system data as they are, threshold values for rivers,
By appropriately adjusting for lakes, it is also possible to thin out the surface data while effectively distinguishing rivers, lakes, and seas.

In the above-mentioned embodiment, the water system data is particularly taken up as the surface data, but the present invention is not limited to this and can be applied to railway data, facility data and the like.

[0038]

According to the map creating apparatus of claim 1 of the present invention, the area of surface data is used as the threshold value instead of comparing the perimeter of the surface data with the threshold value as in the conventional example. Since it is compared, it becomes possible to thin out water system data such as long narrow rivers and lakes whose area is small for the perimeter that was not thinned in the conventional example, and in the map data creation means for display. When creating map data for each display scale, especially for small-scale maps, the data size can be further compressed to reduce the amount of map data compared to the conventional example, and the drawing speed and scroll speed in map data display can be reduced compared to the conventional example. You can also speed up.

According to the map generating apparatus of the second aspect of the present invention, when the surface data is spread over a plurality of sections, the total area of the surface data over the plurality of sections is compared with the threshold value. Therefore, the shape of the remaining surface data does not change by thinning out only a part of the surface data collected as a whole, and it is possible to leave it as the surface data of the shape as a whole.

According to the map making apparatus of claim 3 of the present invention, when the surface data spans a plurality of sections, the surface data of the plurality of sections are not collectively processed, but each section is processed. The area of the surface data is calculated, and the perimeter is also calculated for each section.When the ratio of the area to the perimeter is lower than a specified value, the surface data of that section is thinned out, so that it is spread over multiple sections. You can positively delete the part of the surface data that does not have much meaning, thus further reducing the data size,
The drawing speed and scrolling speed can be improved.

According to the map making apparatus of claim 4 of the present invention, the ratio of the perimeter to the area is used as the object of determination instead of the ratio of the area to the perimeter, and is substantially the same as that of claim 3. It is the same, and it is possible to aggressively delete the meaningless parts of the surface data that spans multiple partitions, thus reducing the data size more and improving the drawing speed and scrolling speed. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a map creating apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of an area calculation means.

FIG. 3 is a diagram of surface data showing a specific processing example in the case of the first embodiment.

FIG. 4 is a block diagram showing a configuration of a map creation device according to a second embodiment of the present invention.

FIG. 5 is a diagram of surface data showing a specific processing example in the case of the second embodiment.

FIG. 6 is a block diagram showing a configuration of a conventional map creation device.

FIG. 7 is a format of digital map data of water system data.

[Explanation of symbols]

 101 ... Digital map data storage means 102 ... Area calculation means 103 ... Threshold setting means 104 ... Surface data deletion means 105 ... Display map data creation means 106 ... Perimeter calculation means

Claims (4)

[Claims] 1. An area calculating means for calculating an area occupied by surface data of digital map data which is an original database,
Compare the calculated area value with a certain threshold value,
When the area value does not reach the threshold value, the surface data deleting means for deleting the surface data from the digital map data, and the map data for each display scale are created from the map data after the surface data is deleted by the above. A map creation device comprising: display map data creation means. 2. When the target surface data is spread over a plurality of sections, the surface data deleting means is configured to compare the sum of the area of the surface data for each section with a threshold value. The map making device according to claim 1, wherein 3. When the target surface data is spread over a plurality of sections, a peripheral length calculation means for calculating the perimeter of the surface data for each section is provided, and the surface data deletion means for the surface data for each section. 3. The map creation device according to claim 2, wherein the area ratio to the perimeter is obtained, and the surface data of a section whose area ratio is lower than a predetermined value is deleted. 4. When the target surface data is spread over a plurality of sections, a peripheral length calculating means for calculating the perimeter of the surface data for each section is provided, and the surface data deleting means stores the surface data for each section. 3. The map creation device according to claim 2, wherein the map generation device is configured to obtain the ratio of the perimeter to the area and delete the surface data of the section whose ratio of the perimeter is higher than a predetermined value.