The present invention relates to a map drawing device which draws roads, background faces, and various icons each showing a facility, which are map objects, on a map.
A conventional map drawing device assigns priorities to each road type, to each background face type, and to each icon type, respectively, and performs control to either display or not display each map object according to the priority assigned to this map object. Therefore, assuming that a road A having the lowest priority passes through a hill displayed on an upper left side of a map shown in
A further problem is that because an icon B showing a shop, which is the only one existing along the road A, cannot be discriminated from any other icons B of the same type showing shops existing in a very crowded area, as shown in
Further, patent reference 1 proposes a technique of reducing the drawing load at the time of scrolling a map by switching from scale map data currently being displayed to scale map data having a smaller scale to display this map when the drawing load increases, as shown in
A problem with the technique disclosed by this patent reference 1 is, however, that because the scale map data currently being displayed is suddenly switched to scale map data having a smaller scale, this sudden change of the displayed information of the map confuses the user.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a map drawing device which can calculate the degrees of importance of each road, each background face, and each of various icons showing a facility, which are map objects, according to both the amounts of visual information which the map objects have, and a current traveling state, and which can draw appropriate map objects depending upon the current conditions on a map according to those degrees of importance.
In accordance with the present invention, there is provided a map drawing device including: a drawing data converting unit for converting map data acquired from a map database into map data having a data format which can be drawn to calculate a degree of importance of a road which is a map object, a degree of importance of a background face which is a map object, and a degree of importance of an icon which is a map object, a drawing data sorting unit for rearranging the drawing data according to the degrees of importance, and a drawing data management unit for managing the drawing data processed by the drawing data sorting unit, in which the map drawing device includes a drawing data cache unit for enabling control to either display or not display the road, the background face, and the icon which are the map objects according to whether or not each of the calculated degrees of importance is equal to or higher than a threshold.
Because the map drawing device in accordance with the present invention calculates the degree of importance of a road which is a map object, the degree of importance of a background face which is a map object, and the degree of importance of each of various icons showing a facility which is a map object, and enables control to either display or not display the road, the background face, and each of the icons according to these degrees of importance, the map drawing device can display map objects assumed to be important for the user independently of their types. As a result, for example, the map drawing device in accordance with the present invention can discriminate between a minor street which is the only one existing in a certain area and minor streets existing in a heavily built-up area, such as a residential area, even if they are the same minor streets, and can display only the minor street which is the only one existing in the certain area.
Hereafter, in order to explain this invention in greater detail, the preferred embodiments of the present invention will be described with reference to the accompanying drawings.
The positioning unit 1 determines the position of a vehicle according to information, the vehicle speed, etc. from a GPS (Global Positioning System) receiving unit 6 and sensors 7 including a gyro. The user operation input unit 2 accepts information about a user's scroll operation from the touch panel, a remote control, etc. The position determining unit 3 determines a point for which the user desires the map drawing device to display a map according to the user information from the user operation input unit 2. The map drawing unit 4 draws a map centered at the position specified by the positioning unit 1 and the position determining unit 3. The map database 5 stores map data.
The map drawing unit 4 is provided with a map drawing control unit 4-1, a drawing unit 4-2, a drawing data cache unit 4-3, and a map data acquiring unit 4-4. The drawing data cache unit 4-3 includes a drawing data converting unit 4-3a for converting map data acquired by the map data acquiring unit 4-4 into map data in a data format which can be drawn by the drawing unit 4-2, a drawing data sorting unit 4-3b for rearranging drawing data according to degrees of importance, and a drawing data management unit 4-3c for managing the drawing data processed by the drawing data sorting unit 4-3b.
Next, the operation of the map drawing device in accordance with the present invention will be explained with reference to
On the other hand, as shown in the flow chart of
Next, the operation of the map drawing unit 4 will be explained in detail with reference to a flow chart of
The drawing data cache unit 4-3 determines whether it has already cached the map data about the range for drawing (step ST3-2), and, when the result of the determination is NO, acquires the map data from the map database 5 via the map data acquiring unit 4-4 (step ST3-3). Next, the drawing data converting unit 4-3a converts the map data acquired by the drawing data cache unit into data for drawing (step ST3-4). This transforming process is, for example, a process of converting the coordinates in the map data into those in a coordinate system which is used at the time of drawing.
At this time, the drawing data cache unit 4-3 divides drawing data about each region which the drawing data cache unit can acquire from the map database 5 into a plurality of data about smaller blocks (in the illustrated example, sixteen data about 16 blocks), as shown in
The drawing data converting unit 4-3a stores data about each map object for a block corresponding to the coordinates of the map object, the block being one of blocks into which a region is divided. More specifically, the drawing data converting unit specifies the block for which the drawing data converting unit stores the data about each map object, and carries out calculation of the degree of importance of each map object (step ST3-5). The stored data is managed for each type of map object, for each type, and for each block ID, as shown in
Next, the map drawing device calculates the degree of importance of each of roads, the degree of importance of each of background faces, and the degree of importance of each of various icons showing a facility, the roads, the background faces and the icons being map objects, according to the following equations.
The degree of importance of a road is given by the following equations.
VE
R
=bw
R
·p·l·w
R
·dw
R
bw
R=1/nR
where
VER: the degree of importance of the road,
bwR: the degree of importance of the road in each block,
p: the occurrence probability in blocks,
l: the length of the road,
wR: the weight set for each road type, and
dwR: the weight set for the road which varies dependently upon the traveling state.
The degree of importance of a background face is given by the following equations.
VE
B
=bw
B
·p·s·w
B
·dw
B
bw
B=1/nB
where
VEB: The degree of importance of the background face,
bwB: The degree of importance of the background face in each block,
p: the occurrence probability in blocks,
s: the area of the background face,
wB: the weight set for each background face type, and
dwB: the weight set for the background face which varies dependently upon the traveling state.
The degree of importance of an icon is given by the following equations.
VE
B
=bw
B
·p·s·w
B
·dw
B
bw
B=1/nB
where
VEI: the degree of importance of the icon,
bwI: the degree of importance of the icon in each block,
IwI: the weight according to the position of the icon,
wI: the weight set for each icon type, and
dwI: the weight set for the icon which varies dependently upon the traveling state.
In this case, the degree of importance of a road in each block, the degree of importance of a background face in each block, and the degree of importance of an icon in each block are acquired by carrying out normalization by using the total number of roads in each block shown in above-mentioned
The occurrence probability in blocks shows to how many blocks included in all the blocks which are the target for calculation of the degree of importance the road or the background face belongs.
Further, the weights set for types of roads, types of background faces, and types of icons which are map objects, are managed by using a table as shown in
Next, the weight set for an icon and depending on its position is determined according to, for example, the distance to an intersection, as shown in
The weight which varies dependently upon the traveling state is defined as follows. For example, in the case of a road, the weight which varies dependently upon the traveling state is set according to whether or not the road is a route line 1, whether or not the road is a one 1-1 connected to the route line 1, and whether or not the road is a one 1-2 which is further connected to a road 1-1 connected to the route line 1, as shown in
The drawing data sorting unit 4-3b sorts the map objects in each block according to the degrees of importance calculated as above (step ST3-6), and the map drawing device caches the data processed by the drawing data management unit 4-3c in a memory (step ST3-7).
For the drawing data about the range for drawing, the drawing unit 4-2 selects the map objects each of which has a degree of importance equal to or higher than the set threshold from the drawing data cached above, and draws the map objects (step ST3-8). More specifically, a road A or icons B having a higher degree of importance are displayed as shown in
As mentioned above, as compared with a conventional case in which a display or non-display process is performed only according to types, such as road types, background face types, or icon types, as shown in
Although the map drawing device in accordance with Embodiment 1, in step ST3-8, filters the drawing data by using the fixed threshold, the map drawing device can alternatively change the threshold according to a scroll speed.
For example, as shown in
As mentioned above, the map drawing device in accordance with Embodiment 2 can display a map which gradually changes to a rough one as the scroll speed increases. Further, unlike conventional map drawing devices, the map drawing device in accordance with this embodiment can scroll the map while keeping as many map objects important for the user as possible displayed.
Although the map drawing device in accordance with Embodiment 2 changes the threshold according to the scroll speed to draw the map, the map drawing device can alternatively change the threshold according to the drawing load imposed on the system.
For example, as shown in
As mentioned above, the map drawing device in accordance with Embodiment 3 can stabilize the drawing update cycle by displaying a rough map when the drawing load is high. Further, unlike conventional map drawing devices, the map drawing device in accordance with this embodiment can draw the map while keeping as many map objects important for the user as possible displayed. Instead of the CPU load, the load imposed on the H/W for drawing can be defined as the drawing load.
Although the distance from the vehicle position is not taken into consideration for the calculation of the degree of importance of each map object in Embodiment 1, the degree of importance of each map object can be changed according to the distance from the vehicle position.
What is necessary is to multiply the equation 1, the equation 2, and the equation 3 by weights distR, distR and distI depending on the distance from the vehicle position, respectively, to calculate the degree of importance.
The degree of importance of a road is given by the following equation.
VE
R
=bw
R
·p·l·w
R
·dw
R
The degree of importance of a background face is given by the following equation.
VE
B
=bw
B
·p·s·w
B
·dw
B
The degree of importance of an icon is given by the following equation.
VE
I
=bw
I
·Iw·w
I·distI·dwI
As mentioned above, because the map drawing device according to this Embodiment 4 changes the degree of importance according to the distance from the vehicle position, the map drawing device can draw map objects assumed to be important for the user independently of their types.
Although the weight which varies dependently upon the traveling state in the case of a road is set according to whether or not the road is a one 1 on the route line, a one 1-1 connected to the route line, a road 1-2 connected to a road connected to the route line, or another road other than those roads, as shown in
As mentioned above, because when the vehicle is travelling along a highway, for example, the map drawing device according to this Embodiment 5 can change the weight which is set for a road and which varies dependently upon the traveling state according to whether or not the road is connected to an interchange of the highway, the map drawing device in accordance with this embodiment can display map objects on the map while keeping as many map objects important for the user as possible displayed independently of their types.
Although the map drawing device in accordance with Embodiment 1 changes the weight which varies dependently upon the traveling state in the case of an icon according to the distance from the route line 1, the map drawing device can alternatively change the weight according to whether the icon is on either a driving lane or an opposite lane, for example.
Next, a traveling direction vector (xa, ya) corresponding to the traveling direction of the vehicle is determined from the determined line segment. An icon direction vector (xb, yb) which consists of both the coordinates of the center of each of the icons and the start point of the traveling direction vector is also determined. Next, the outer product (=xayb−xbya) of these two vectors is calculated to determine whether or not this outer product is equal to or larger than zero. When the outer product is negative, it can be seen that the icon is placed on the right-hand side of the road, and this icon faces the opposite lane.
As mentioned above, the map drawing device in accordance with Embodiment 6 adjusts the weight for an icon placed on an opposite lane, i.e. an icon showing something which it is difficult for the user to reach in light of the present circumstances to change the icon placed on the opposite lane unnecessary for the user to a non-display state.
Although the map drawing device in accordance with Embodiment 1 carries out table management of the weight for each type, as shown in
As mentioned above, because the map drawing device in accordance with embodiment 7 changes the weight for each road type according to road information or traffic information, the map drawing device can display roads on the map while keeping as many roads important for the user as possible displayed, and can change roads unnecessary for the user to a non-display state.
Although the map drawing device in accordance with Embodiment 1 carries out table management of the weight for each type, as shown in
As mentioned above, because the map drawing device in accordance with Embodiment 8 changes weight for each icon type according to facility attribution information, the map drawing device can display icons on the map while keeping as many icons important for the user as possible displayed, and can change roads unnecessary for the user to a non-display state.
Although the map drawing device in accordance with Embodiment 1 carries out table management of the weight for each type, as shown in
As mentioned above, because the map drawing device in accordance with Embodiment 9 changes the weight for each icon type according to the degree of complexity of arrival to each icon, the map drawing device can display icons on the map while keeping as many icons important for the user as possible displayed, and can change icons unnecessary for the user to a non-display state.
Although the map drawing device in accordance with Embodiment 1 carries out table management of the weight for each type, as shown in
As mentioned above, because the map drawing device in accordance with Embodiment 9 changes the weight for each icon type according to the time required for the vehicle to reach a position shown by an icon, the map drawing device can display icons on the map while keeping as many icons important for the user as possible displayed, and can change icons unnecessary for the user to a non-display state.
This map drawing device is suitable for use as a map drawing device which displays roads, background faces, and various icons each showing a facility which are map objects and which are necessary for the user on the map while changing map objects unnecessary for the user to a non-display state.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2009/005664 | 10/27/2009 | WO | 00 | 3/14/2012 |