JP2003294457A - Navigation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speedily and three dimensionally display a map even with few memory in a navigation system. <P>SOLUTION: An image for high resolution texture mapping and an image for low resolution texture mapping are prepared. The image for the high resolution is stored by a unit of a small area together and the image for the low resolution is stored by a unit of a large area. A GPS receiving part 4 displays a present position acquired on a map of the navigation system 1. A control means 2 judges a range of a passing route based on route setting and a road class when traveling. The range of the passing route is preferentially three dimensionally displayed with the high resolution. High real display is normally provided, but the image for low resolution texture mapping is provided when memory to be allocated to a memory 6 for a texture image or a read time from a map data base 7 is insufficient. Map display in response to restriction can be performed even when the memory 6 for the texture image is few or when traveling at a high speed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a navigation device, and more particularly to a navigation device that stereoscopically displays a route guidance map of a moving body such as an automobile.

[0002]

2. Description of the Related Art A navigation device mounted on a moving body such as an automobile is a GPS from a GPS satellite which is an example of a positioning satellite.
The signal is received to detect the current position, and the current position of the vehicle and the direction to the destination are displayed on a map to facilitate traveling. Digital map data stored in a storage medium such as a CD-ROM or a DVD is read out, and a map on which buildings, roads, etc. are drawn is displayed on the screen. If necessary, it is possible to display more detailed information such as the shapes and positions of buildings and the like in the city map and the number of floors. At that time, in order to more easily display the vicinity of the own vehicle, the destination, the intersection to be passed, etc., a building as a landmark on the route may be three-dimensionally displayed on the planar map. When the city map is displayed in a bird's-eye view, buildings and the like are displayed three-dimensionally so that the current position on the map can be easily grasped. It is also possible to display a three-dimensional map using an image that is texture-mapped to the exterior of the building. The following is an example of a conventional technique for stereoscopically displaying a map.

[3] Japanese Patent Laid-Open No. 11-120374 discloses "3
"Method and apparatus for creating three-dimensional cityscape information" is a method for creating a three-dimensional cityscape information that can easily and quickly create a multimedia database that integrates the three-dimensional information of the buildings contained therein based on the plan map information. A method and an apparatus for making. The reading unit reads and digitalizes city planning maps, color aerial photographs, individual building photographs, etc. A two-dimensional digital map is created by the map information creation unit based on the read city planning map and color aerial photograph data. The three-dimensional data of the individual building included in the map information is created by the three-dimensional data creation unit of the building based on the read data of the individual building photo. 3D data of the created individual building,
The two-dimensional digital map created by the map information creation unit is placed at the corresponding building position by the on-map placement processing unit of the individual building.

[0004]

However, the conventional navigation device has a problem that a large amount of memory is required for displaying with high realism. Further, if the displayed map is updated at high speed during high-speed traveling, there is a problem in that the reading from the map database will not be in time, and the map display will be delayed or missing.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above conventional problems and to realize a navigation device capable of displaying a stereoscopic map having a high degree of realism at high speed even with a small memory capacity.

[0006]

In order to solve the above-mentioned problems, in the present invention, a position detecting means for detecting a current position by using a positioning signal transmitted from a positioning satellite and an appearance of a building are expressed. In the navigation device, a map data storage unit for storing map data including a texture mapping image for storing the data is divided into regions, and a reading unit for reading the map data around the current position from the map data storage unit. Route determining means for determining the expected traveling road based on the road shape data of the selected route, and the priority display range is determined so as to sequentially increase the priority of regions near the current position along the expected traveling road and display them three-dimensionally. The priority display range determining means and the read control means for preferentially reading the texture mapping image corresponding to the priority display range are provided. With such a configuration, it is possible to display a map that stereoscopically expresses roads and buildings around the current location with a small memory capacity and at high speed.

Further, the map data storage unit is provided with a storage area for holding a plurality of texture mapping images of different resolutions for the same building, and the read control means can use the resolution of the texture mapping images and the speed. A selection means for selecting according to at least one of the memory amounts is provided. With this configuration, it is possible to select and display the texture mapping image having the resolution according to the limitation of the operation state of the navigation device.

Further, the map data storage section is provided with a storage area for collectively storing texture mapping images of a plurality of buildings within a predetermined range. With this configuration, the process of reading the texture mapping image of the building can be simplified.

Further, the map data storage unit stores a storage area for collectively storing high-resolution texture mapping images of a plurality of buildings in a small area and a storage area for a plurality of buildings in a large area including a plurality of small areas. A storage area for collectively storing the resolution texture mapping images is provided, and the reading control means reads the low resolution texture mapping images from the map data storage portion, and the map data according to the traveling speed and the available memory amount. A means for reading the high resolution texture mapping image from the storage unit is provided. With this configuration, the texture mapping image for representing the building can be efficiently read, and the memory usage of the navigation device can be reduced.

Further, the navigation device for three-dimensionally displaying the building on the map image is provided with control means for controlling the display so that the resolution of the appearance of the building is made different between the front direction of the map image and the depth direction of the map image. It was configured. With this configuration, the information about the position closer to the driver's point of view is displayed closer to the actual scene, while the information about the position far from the driver's point of view is reduced in resolution and the amount of memory used. It is possible to save a lot of space, and to display a map of a nearby building in a stereoscopically realistic manner with a small amount of memory and at high speed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. The embodiment of the present invention uses a map database that stores high-resolution and low-resolution texture mapping images and map data, and a texture mapping image of a priority display range near a predicted road according to a memory amount and a read time limit. The navigation device is provided with a control means for preferentially reading out and a display control unit for stereoscopically displaying the map image by referring to the texture image memory.

FIG. 1 is a functional block diagram of a navigation device according to an embodiment of the present invention. In FIG. 1, a navigation device 1 is a device that is mounted on a vehicle, displays a current position and the like on a map, and provides route guidance. The control unit 2 is a calculation unit that performs route setting, reading of map data, display control, and the like. GPS antenna section 3
Is an antenna that receives GPS signals from GPS satellites.
The GPS receiving unit 4 is a means for obtaining the current position based on the GPS signal. The display control unit 5 is means for controlling the display device to display the map information. The texture image memory 6 is a means for temporarily storing the texture mapping image for display. The map database 7 is a means for storing map data including shape data of buildings and roads and texture mapping images used for the appearance of buildings.

Texture mapping is a process of pasting an image on the surface of an object. By this processing, it is possible to give a sense of reality to an object drawn by computer graphics (CG). The texture mapping image used for texture mapping is
A real texture image obtained by cutting out a two-dimensional real image of a natural object or an artificial texture image created by CG is used. In the navigation device according to the embodiment of the present invention, it is possible to use either an actual texture image or an artificial texture image as the texture image.

FIG. 2 is a diagram showing a method of storing map data used in the navigation device according to the embodiment of the present invention. FIG. 3 is a map data structure diagram showing the contents included in one unit of map data. FIG. 4 is a diagram showing a method of mapping and displaying a texture mapping image on a building. FIG. 4A is a diagram illustrating that a high-resolution texture mapping image is used for a nearby building and a low-resolution texture mapping image is used for a distant building. FIG. 4B shows an image in which a high-resolution texture mapping image is used for a building in the foreground, a medium-resolution texture mapping image is used for a building in the middle, and a low-resolution texture mapping image is used for a building in the distant view. It is a display example. FIG. 5 is a diagram showing a state in which road shape data is displayed. FIG. 6 is a flow chart showing a procedure for reading an exterior image of a building. FIG. 7 is a flowchart showing the procedure for drawing a building.

The operation of the navigation device according to the first embodiment of the present invention configured as described above will be described. First, the general functions of the navigation device will be described with reference to FIG. The map database 7 stores shape data of buildings and roads and texture mapping images used for the appearance of buildings. The texture mapping image includes a high resolution texture mapping image and a low resolution texture mapping image. If necessary, a medium resolution texture mapping image may be prepared, but here, a case where two types of a high resolution texture mapping image and a low resolution texture mapping image are mainly used will be described.
The high-resolution texture mapping images are grouped in small area units (small areas), and the low-resolution texture mapping images are grouped in large area units (large areas). The area unit will be described later.

The GPS antenna unit 3 receives GPS signals from GPS satellites. The GPS receiving unit 4 obtains the present location and the traveling direction based on the GPS signal. The control unit 2 determines a range that may pass in the future based on the route setting and the type of road on which the vehicle is running. If the route is likely to pass, the high-resolution texture mapping image is read out and stored in the texture image memory 6. If the route is unlikely to pass, the low-resolution texture mapping image is read out and stored in the texture image memory 6.
When the memory capacity that can be used as the texture image memory 6 is small and when the reading time is limited, the low resolution texture mapping image is used. Display control unit 5
Then, read the data in the texture image memory 6,
Display map information on the display. Even if the memory capacity that can be used for temporary storage of the texture mapping image is small, the map display will not be delayed, and the display can be displayed with the highest degree of realism.

A method of storing map data used in the navigation device of the present embodiment will be described with reference to FIG. The texture mapping image includes a low resolution texture mapping image and a high resolution texture mapping image. The data of the low-resolution texture mapping image is data that is collected as one object for the building included in the entire area of one unit (large area unit (large area) shown on the left of FIG. 2) divided in a grid pattern. is there. The data of the high-resolution texture mapping image is data that is collected as one target for buildings in a range (small area unit (small area) shown on the right in FIG. 2) in which one area is subdivided into rectangular shapes. .

The low-resolution texture mapping image and the high-resolution texture mapping image have resolutions inversely proportional to the areas so that the combined texture mapping images have the same data size. When the map data is read from the map database 7, the appearance images of the buildings in the large area unit or the small area unit are collectively read. By doing so, the process of determining the texture mapping image to be read can be simplified. Since the area of the range in which the texture mapping images are collectively stored is made inversely proportional to the resolution, it is possible to set the speed threshold value for reading the texture mapping images and using them for drawing step by step.

A method of setting the speed threshold will be described. By changing the area of the range where the texture mapping images are put together, the time taken for the vehicle to pass through the range is changed. In other words, if the vehicle passes through the range at the same time, the speed will be different depending on whether the range is wide or narrow. Since the resolution of the texture mapping image is inversely proportional to the area of the combined area, the amount of data read at one time is almost constant. That is, the reading time is also constant. Therefore, if the area of the area where the texture mapping images are collected is divided into large and small areas, the speed at which the vehicle passes through the area also becomes stepwise according to the area.

As a high resolution texture mapping image, the size of data collected in a narrow range is A. Let B be the size of data collected in a wide range as a low-resolution texture mapping image. Since the area and the resolution are inversely proportional, A≈B. There are cases where A≈B does not hold due to the density of the building. The reading time of the texture mapping image from the recording medium to the memory is almost the same regardless of the resolution. Let this time be T. If the time taken for the vehicle to pass through the combined range is shorter than the reading time T, the vehicle will pass through the range even before the texture mapping image is read.

Since the range for gathering the high resolution texture mapping images is narrow and the range for gathering the low resolution texture mapping images is wide, the speed at which the vehicle passes through each region at time T is S.
If a and Sb, then the magnitude relationship is Sa <Sb. If the moving speed S of the vehicle is S <Sa, the image is drawn using the high resolution texture mapping image. The moving speed S is S
If a <S <Sb, the high resolution texture mapping image cannot be read in time, so only the low resolution texture mapping image is drawn. The moving speed S is Sb <S
If so, the image for low resolution texture mapping cannot be read, so only the frame of the building is drawn. That is, the resolution of the texture mapping image to be read can be controlled by the moving speed of the vehicle. Sa is the low speed threshold and Sb is the high speed threshold. In this way, it is possible to set the speed threshold value for reading the texture mapping image and using it for drawing step by step.

Referring to FIG. 3, the map database 7
The data structure of the map data stored in will be described. 1
The map data of the unit area includes building shape data, other data such as road shapes, one low-resolution texture mapping image, and four high-resolution texture mapping images. In the example of FIG. 3, the high-resolution texture mapping image has four times the data amount of the low-resolution texture mapping image, but since the map area of the target area is 1/4, The low-resolution texture mapping image has the same amount of data as one group. When the image for medium resolution texture mapping is prepared in the middle, the amount of data may be doubled and the map area of the target area may be set to 1/2 of the image for low resolution texture mapping.

A method of stereoscopically displaying one building will be described with reference to FIG. To express the appearance of the building,
As an image of the appearance of a building, one or more texture mapping images with different resolutions are prepared for each building. As shown in FIG. 4A, the texture mapping image for each building includes a high resolution texture mapping image 9 and a low resolution texture mapping image 10, and an intermediate resolution texture mapping image (FIG. 4 (a) (not shown). Depending on the distance from the viewpoint to the building, the high resolution texture mapping image 9 and the low resolution texture mapping image 10 are switched and used. When the distance to the building is close from the viewpoint,
Since the area to be drawn is large, the high resolution texture mapping image 9 is used. As shown in the left diagram of FIG. 4A, the high resolution texture mapping image 9 is pasted on the wall surface of the outer frame image 8 of the building, and the wall surface image 11 of the building is drawn. The texture mapping image with high resolution is
The data size of one sheet is large. When the distance to the building is far from the viewpoint, the area to be drawn is small, so the low-resolution texture mapping image 10 is used. The image data for texture mapping having a low resolution has a small data size.

As shown in FIG. 4 (b), the visible size changes depending on the distance from the current location to the building.
The resolution of the texture mapping image used is changed according to the distance. When displaying a distant building, use a low-resolution image for texture mapping to display it in a small size. If a medium-resolution texture mapping image for the middle ground is prepared, the image can be displayed in three stages, and a more realistic map can be presented to the person viewing the image.

A method of displaying the road shape will be described with reference to FIG. Road shape data around the current location is read from the map database 7. The road shape data is composed of a link that continuously connects a plurality of points and a road branch that connects three or more links to the same point.
In order to find the road on which the vehicle is expected to travel, a link ahead of the current position is searched based on the route information. The high-resolution texture mapping images are read into the texture image memory 6 as much as possible in the order from the current position of the automobile along the route expected to travel. For other ranges, the low resolution texture mapping image is read. In this way, it is possible to mechanically determine which part of the map is important by using a simple method in which the route on which the vehicle is expected to travel is used as the criterion. High-resolution texture mapping images are used to display highly realistic maps for important map parts along the travel route. Other than that, it draws using a low resolution texture mapping image. Whether or not the vehicle is traveling along the travel route may be determined by whether or not the travel route is included in the large area described above, or by whether or not the travel route is included in the small area. Good.

The procedure for reading the texture mapping image for drawing the appearance of the building will be described with reference to the flowchart of FIG. When the map display range is determined, the shape data of the building corresponding to the range and the texture mapping image are read. As the vehicle moves, it is determined whether or not the current position has crossed the boundary of one unit of large area (step
100). If it does not exceed the boundary of the large area of the map data, the process moves to the process of reading out the map data of the range of the new small area from the map database 7. When the boundary of the large area of the map data is crossed, the map data in the range of the large area that has passed is no longer necessary and is deleted from the texture image memory 6 (step 101). Of the map data for displaying the front map, the minimum map data necessary for displaying, that is, the texture mapping required for displaying without map of the map data shown in FIG. The data other than the image for use (step
102).

It is determined whether the moving speed of the vehicle is above or below the high speed threshold (step 103). The high speed threshold is the higher speed threshold and is the speed at which texture mapping becomes impossible. If the moving speed is higher than the high speed threshold, it is too fast to read the low resolution texture mapping image, so in order to prioritize display, the low resolution texture mapping image is not read and a new small area is displayed. The process moves to the process of reading the map data in the range of from the map database 7. When the moving speed of the vehicle is lower than the high speed threshold, the low resolution texture mapping image is read (step 104).

The storage range of the high resolution texture mapping image is narrower than the large area which is the division unit of the map data, and is set to a small area of 1/4 of the large area. Storage range (small area)
It is determined whether or not the boundary of is exceeded (step 105). If it does not exceed the boundary of the small area, the processing ends. If it exceeds the boundary of the small area, the high-resolution texture mapping image for the passage is deleted from the texture image memory 6 (step 106).

It is determined whether the moving speed of the vehicle is above or below the low speed threshold (step 107). The low speed threshold is a lower speed threshold and is a threshold for determining whether to display the high resolution texture mapping image or the low resolution texture mapping image. Since the high-resolution texture mapping image has a narrow target range, the moving speed threshold for determining whether to read the high-resolution texture mapping image is the moving speed for determining whether the low-resolution texture mapping image can be read. Is smaller than the threshold value of. If the movement speed is higher than the low speed threshold, it is too fast to read the high resolution texture mapping image, so the processing is terminated without reading the high resolution texture mapping image in order to prioritize displaying. . If the moving speed of the vehicle is lower than the low speed threshold, a high resolution texture mapping image in the range of a new small area in front is read from the map database 7 (step 108).

In step 108, when the high-resolution texture mapping image is read from the map database 7, if the texture image memory 6 does not have sufficient capacity, it is not read. In step 104, when the low-resolution texture mapping image is read from the map database 7, if the texture image memory 6 does not have sufficient capacity, it is not read. That is, in the case where the other high-priority function of the navigation device 1 requires a large amount of memory capacity, the reading area of the high-resolution texture mapping image is provided. If it is still insufficient, it also provides a reading area for low-resolution texture mapping images. In this way, whether to read the texture mapping image is controlled according to the allocation status of the texture image memory 6.

When the moving speed is fast and the data reading time is limited, or when the capacity of the texture image memory 6 for temporarily storing the texture mapping image is insufficient, the reading thinning is performed. The thinning is performed in order from the high resolution texture mapping image. If there is no limit, for example, when the memory capacity of the entire device is sufficiently large, or when the moving speed of the vehicle is sufficiently slow,
The image is displayed in the highest resolution possible, and when there is a limitation, the low-resolution texture mapping image is drawn in order from the region with the lowest priority. If there are more restrictions, the entire image is drawn in low resolution. When drawing at a low resolution is impossible, for example, when the capacity of the texture image memory 6 is extremely short, or when the moving speed of the vehicle is extremely high,
Display only the outer frame of the building or display it in a plane. By doing so, it is possible to maintain drawing quality with high realism while avoiding lack of map display.

A processing procedure for drawing a building with the read texture mapping image will be described with reference to the flowchart of FIG. The drawing process is performed in parallel with the reading process of the texture mapping image. Draw for each building. It is checked whether or not a high resolution texture mapping image is read into the texture image memory 6 as an image of the appearance of the building (step 200). If it is read, the appearance of the building is drawn using the high resolution texture mapping image (step 202). If not, it is checked whether or not a low-resolution texture mapping image has been read as an image of the appearance of the building (step 201). If the low resolution texture mapping image has been read, the appearance of the building is drawn using the low resolution texture mapping image (step 203). If the low-resolution texture mapping image has not been read, only the outer frame of the building is drawn (step 204).

As described above, at the stage of drawing a building, the texture mapping image to be used is determined only by whether or not the texture mapping image has been read into the texture image memory. In parallel with this, you can draw buildings efficiently with a simple method.

As described above, in the embodiment of the present invention,
The navigation device, map data of high-resolution texture mapping images summarized in small area units, and map data of low-resolution texture mapping images summarized in large area units, the amount of memory for texture mapping images, According to the read-out time limit according to the moving speed of the vehicle and the possibility of passing the route (whether or not the route is expected to be passed by the vehicle), the high-resolution map image is displayed in 3D as much as possible. , A 3D map can be displayed according to the memory capacity and the speed limit of the vehicle.

【The invention's effect】

As is clear from the above description, according to the present invention, the resolution of the texture mapping image for representing the building displayed on the map of the navigation device is set to the memory capacity corresponding to the limitation of the operating state of the navigation device. By selecting according to the speed of the vehicle, it is possible to obtain an effect that a map in which the roads and buildings around the current location are three-dimensionally represented can be displayed efficiently and at high speed by simple processing.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a navigation device according to an embodiment of the present invention,

FIG. 2 is a diagram showing a method of storing map data used in the navigation device according to the embodiment of the present invention;

FIG. 3 is a diagram for explaining contents included in map data used in the navigation device according to the embodiment of the present invention;

FIG. 4 is a diagram showing a method of displaying a building by the navigation device according to the embodiment of the present invention;

FIG. 5 is a diagram showing a state in which road shape data is displayed on the navigation device according to the embodiment of the present invention;

FIG. 6 is a flowchart showing a procedure of reading an exterior image of a building by the navigation device according to the embodiment of the present invention;

FIG. 7 is a flowchart showing a procedure for drawing a building by the navigation device according to the embodiment of the present invention.

[Explanation of symbols]

1 Navigation device 2 control means 3 GPS antenna section 4 GPS receiver 5 Display controller 6 Texture image memory 7 map database Outer frame image of 8 buildings 9 High resolution texture mapping image 10 Low resolution texture mapping image 11 Building wall image

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09B 29/10 G09B 29/10 AF term (reference) 2C032 HB03 HB05 HB22 HC08 HC23 HD03 2F029 AA02 AB07 AC02 AC14 AC19 5B050 AA07 BA10 BA17 CA07 CA08 DA02 DA04 EA07 EA19 FA02 FA06 FA13 FA19 GA08 5B080 FA02 FA08 GA22 5H180 AA01 CC12 FF05 FF22 FF27 FF38

Claims (5)

[Claims] 1. Map data including a position detection means for detecting a current position by using a positioning signal transmitted from a positioning satellite and a map data including a texture mapping image for expressing the appearance of a building is divided into regions. In a navigation device that includes a map data storage unit that stores the map data and a reading unit that reads out map data around the current position from the map data storage unit, a predicted travel road is determined based on road shape data of a set route. Corresponding to the route determining means, the priority display range determining means for determining the priority display range so that areas closer to the current position along the predicted traveling road are displayed in order of increasing priority. A navigation device, comprising: a read control unit that preferentially reads out the texture mapping image. 2. The map data storage unit is provided with a storage area for holding a plurality of texture mapping images of different resolutions for the same building, and the read control means sets the resolution of the texture mapping images to a traveling speed. 2. The navigation device according to claim 1, further comprising a selection unit that selects according to at least one of the available memory amount and the available memory amount. 3. The navigation device according to claim 1, wherein the map data storage unit is provided with a storage area for collectively storing texture mapping images of a plurality of buildings within a predetermined range. 4. A storage area for collectively storing high-resolution texture mapping images of a plurality of buildings in a small area in the map data storage section, and a plurality of buildings in a large area including a plurality of the small areas. And a storage area for collectively storing the low-resolution texture mapping images, and the reading control unit includes means for reading the low-resolution texture mapping images from the map data storage unit, running speed, and available memory amount. The navigation device according to claim 1, further comprising means for reading out a high-resolution texture mapping image from the map data storage unit. 5. A navigation device for three-dimensionally displaying a building on a map image, wherein display resolution is controlled so that the exterior resolution of the building is different between the front direction of the map image and the depth direction of the map image. A navigation device comprising a control means.