JPH0310278A - Map plotting method - Google Patents

Abstract

PURPOSE:To allow high-speed plotting and to obviate the deformation of a plotted map and to further obviate the erasing of the map by providing two VRAMs, a scroll means, a monitoring means and a storage means. CONSTITUTION:The images are so generated that a vehicle is positioned at a center. This images are stored in the 1st VRAM 12. The images are scroll- displayed by moving the image reading region in the 1st VRAM 12 according to the movement of the vehicle. Whether the map reading region arrives at a preset region or not is monitored. The images are so generated that the present position of the vehicle is brought to the center when the above- mentioned region arrives at the preset region. These images are stored in the VRAM 13. The window in the 2nd VRAM 12 is thereafter moved according to the movement of the vehicle to make scroll display. The generation and storage of the images and the scroll display according to the movement of the automobile are repeated at every arrival of the window at the region preset in the VRAMs. The high-speed plotting of the map is possible in this way and the scroll display is smoothly executed according to the movement of the automobile without the disappearance of the map. Further, the deformation of the plotted map is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industry> Second Field of Application The present invention relates to a map drawing method, and particularly relates to a map drawing method for automobile navigation.

<Prior art> CI) -ROM as a storage means for storing map data
There is an automotive navigation system that uses .

Such an automobile navigation system is a CD-R
In addition to storing a large amount of map data in the OM, a display device and a position measuring device to measure the current position of the vehicle are installed, and a mark (location cursor) indicating the current position of the vehicle is fixedly displayed at a fixed position on the display screen. At the same time, map data corresponding to the vehicle position is stored on a CD-ROM.
The map is read out from the map and drawn on the display screen, and the map is scrolled and displayed as the vehicle moves.

The map stored on the CD-ROM has a longitude width and a latitude width of an appropriate size depending on the scale level (for example, a longitude width of 7.5 mm).
Roads, rivers, railways, etc. are shown as a set of coordinates of vertices expressed in latitude and longitude, and these drawings are done by connecting each vertice with a straight line in order. This is done by

Figures 4 and 5 are explanatory diagrams of map data, and in Figure 4, the lower left 1 pb (xb, yb) is 139° east longitude.
7'30'', north latitude 35°O'O'', upper right position Pa (Xa
, Ya) is 139°15'0" east longitude, 35°5' north latitude
5 shows a map of the area of ``Road RD1 on the map
, 2, each expressed by the number of vertices and the latitude and latitude of each vertex. Note that the longitude and latitude of each point is actually expressed as normalized X, y coordinates where the longitude and latitude of the lower left @Pb is (0,0) and the latitude and longitude of the upper right position Pa is (1,1). There is.

Now, car navigation has a function that displays the route of your car along with a map. In such trajectory display, trajectory data, which is an actual distance, is obtained from the direction of the vehicle and the number of rotations of the tires, and the trajectory is superimposed and drawn on a map using the trajectory data. However, as mentioned above, maps are expressed in latitude and longitude, so in order to correctly draw the trajectory on top of the map, the map expressed in latitude and latitude must be converted so that distances are displayed correctly. There must be,.

That is, the latitude and longitude map must be converted into a planar map so that the length between any two points on the drawn map corresponds to the actual distance.

For this reason, the latitude and longitude map data is converted into planar map data so that the distance can be accurately expressed using the calculation formula shown below. In other words, the latitude and latitude data (Xmap, Ymap) are converted into position data (Xs, Ys) of a flat map with the car position at the center of the display screen (screen) using the following formulas: ing. In addition, in equations (1) and (2), (Xs, Ys)...coordinate values on the projected screen,
(Xc, Yc)...Longitude and latitude of the car position R...Radius of the earth - S...Scale (Xmap, Ymap)...Vertex on the latitude and latitude map (
point)'s longitude and latitude.

In the first conventional method, each time the car moves a predetermined distance, the latitude and latitude map data is converted into flat map data by calculating equations (1) and (2) so that the car position becomes the center of the screen. Then, a planar map image is generated and drawn based on the obtained planar map data.

In addition, in another conventional method, as shown in FIG.
The video RAM (VRAM) that stores map images is made considerably larger than the display screen SCR, and the vehicle position Pc is
Generates an image and stores it in VRAM so that
Thereafter, as the vehicle moves, the VRAM image reading area (
Window) WDk to move and scroll display.

<Problems to be Solved by the Invention> In the first conventional method, a map image must be regenerated every time the car moves a predetermined distance, which increases the load of drawing processing and requires high-speed drawing ability. Ru. However, since high-speed drawing is not possible with a microcomputer in an automobile navigation system, the predetermined distance must be made longer, and the automobile movement display becomes discontinuous and becomes very difficult to see.

Further, in the second conventional method, there is a problem that the larger the map stored in the VRAM, the more the length in the longitude direction on the pole side becomes narrower, and therefore, when the map is moved toward the pole, the displayed map is deformed and becomes difficult to see. In addition, drivers drive while considering the top direction of the screen to be north, but there is also the problem that the diagonally right or left direction is north on the displayed map. Furthermore, in the second conventional method, when the vehicle position exceeds the map range stored in the VRAM, a new map image must be generated and stored in the VRAM, and there is also the problem that the map display disappears during this time.

In light of the above, an object of the present invention is to provide a map drawing method that enables high-speed drawing and that does not cause the drawn map to be deformed or disappear.

<Means for Solving the Problems> In the present invention, the above problem is solved by using two VRAMs, a first and second VRAM each having a storage area larger than the display screen, and a map from a predetermined area of one VRAM according to the movement of the vehicle. means for reading and scrolling the image; means for monitoring whether the map image reading area has reached a preset area; and means for generating an image centered on the current position of the vehicle when the map image reading area has reached a predetermined area; This is accomplished by storing in RAM.

Effect> The first VR generates an image centered on the vehicle position.
AM, and moves and scrolls the image reading area (window) in the first VRAM according to the movement of the vehicle, and monitors whether the map reading area has reached a preset area. Sometimes, an image is generated centered on the vehicle's current position and the second VR
AM and then the second V as the vehicle moves.
Window 1-1 in the RAM is moved and displayed in a scroll manner, and thereafter, each time the window reaches an area preset in each VRAM, image generation, storage, and scrolling display as the vehicle moves are repeated.

<Embodiment> FIG. 1 is a block configuration diagram of an automobile navigation system that can realize the present invention.

In the figure, 1 is a CD-RO that serves as a map data storage means.
M, 2 is an operation unit equipped with various keys for searching a CD-ROM map, enlarging/reducing, etc., and 3 is an azimuth sensor for detecting absolute orientation, which includes a geomagnetic sensor and a steering sensor. Reference numeral 4 denotes a movement amount sensor, which includes a vehicle speed sensor that detects travel distance, a transmission sensor that detects forward and backward movement, and the like. 5
is the CPU for position calculation, and the direction sensor 3. Movement amount sensor 4
The current position (longitude, latitude) of your vehicle is calculated from each value input from the .

6 is a processing unit, a system controller (CPU) 7.
It has a map data buffer memory 8 and the like. The roller 7 to the system controller (1) instructs the display device which one of the two VRAs and VRAMs (described later) to read an image from and display it on a map, and (2) reads an image according to the vehicle position. Generates a read address (win1-address) and further (3) reads each VRAM.
It is monitored whether the window has reached the true drawing start position set in advance, and when the window has arrived, the latitude and longitude map data corresponding to the current vehicle position is read out from the CD-40M1 and stored in the buffer memory 8, and thereafter.

(4) The read map data expressed in latitude and longitude is converted into planar map data capable of displaying actual distances and output to a subsequent display device.

10 is a display device, and a CRT controller 1
1, first and second video RAM (VRAM) 12,1
．． 3. Readout control unit 14, cathode ray tube (CRT) 15
etc., to display a desired map and cursor on the CRT. As shown in Fig. 2, the storage areas of the first and second VRAMs 12 and 13 are considerably larger than one screen of the screen SCH, and back drawing start lines BDLI and BDL2 are located at positions slightly smaller than the storage areas. Each is set.

FIG. 3 is a flowchart of the map drawing process of the present invention, and the following description will be made according to this flowchart.

The system controller 7 reads the latitude and latitude map data corresponding to the vehicle's current position from the CD-40M2, and inputs the plane map data obtained by converting the latitude and latitude to the plane map into the display device 10, so that the vehicle position is at the center. An image is generated and stored in the first VRAM 12 (step 101).

Next, the system controller 7 specifies the VRAM (first VRAM) from which the image is to be read, and also positions the VRAM window WDI (see Figure 2) so that a cursor indicating the position is displayed in the center of the screen as the car moves. The control unit 1 determines the address and reads the address.
4 (step 102).

The read control unit 14 reads the specified VRAM (first VRAM
A map image is read out from a specified window of the RAM) in synchronization with raster scanning and displayed on the CRT]5. Thereafter, the map is scrolled by moving the position of the win +--WD in accordance with the movement of the vehicle (step 103).

In parallel with the scroll display process described in "2" above, it is monitored whether the window has reached the back drawing start line BDLI (Figure 2) (step 104), and if it has not reached it, the scroll display shown in "2" continues in response to the movement of the car. (Step 10)
4).

When the car moves a considerable distance and the window WDI reaches the back drawing start line BLDI (see Figure 2), the system controller 7 reads the latitude and latitude map data corresponding to the vehicle's current position from the CD-ROM 2, and also - Input the plane map data obtained by plane map conversion to the display device 10, generate an image centered on the vehicle position, and store it in the second VRAM 13 (step 1.5). Additionally, if the vehicle position moves during this time, the first VRAM
1. Read and display the image from 1.

Next, the system controller 7 determines the position of the window WD2 of the VRAM so that the cursor indicating the position of the car is displayed at the center of the screen, and inputs the address to the readout control unit 14 (step 106).

The read control unit 14 reads the specified VRAM (second VRAM).
A map image is read out from a designated window of the RAM) in synchronization with the raster scan and displayed on the CRT 15. Thereafter, the map is scrolled by moving the position of window WD2 according to the movement of the vehicle (step 107).

In parallel with the above scroll display processing, it is monitored whether the window has reached the back drawing start line BDT, 2 (step 108), and if it has not reached the back drawing start line BDT, 2, the above scroll display according to the movement of the car is continued. Further, when the car moves a considerable distance and reaches the back drawing start line BLD2, the processes from step 101 onward are repeated.

<Effects of the Invention> According to the present invention, an image is generated and stored in the first VRAM so that the vehicle position is the center, and the image is read in the first VRAM according to the movement of the vehicle. In addition to moving and scrolling the area (window), it also monitors whether the map reading area has reached a preset area, and when it reaches a preset area, generates an image centered on the current position of the vehicle and displays the first image. After that, the window in the second VRAM is moved and scrolled according to the movement of the vehicle, and thereafter, each time the window reaches an area preset in each VRAM, the image is stored in the second VRAM. Since the map is configured to repeat generation, memory, and scrolling display as the car moves, it is possible to draw the map at high speed, so the map does not disappear, and can be smoothly scrolled as the car moves. is not deformed.

[Brief explanation of drawings]

Figure 1 is a block diagram of a car navigation system that implements the method of the present invention; Figure 2 is an explanatory diagram of the map drawing process of the present invention; Figure 3 is a flowchart of the process of the present invention; Figures 4 and 5 are latitude and latitude; An explanatory diagram of map data, FIG. 6 is an explanatory diagram of the drawbacks of the conventional method. 1. CD-ROM, 5. CPU for position calculation, 7. System controller, 8. Map data buffer memory, 10. Display device,

Claims (1)

[Scope of Claims] A map drawing method for automobile navigation in which a mark indicating the current position of a vehicle is fixedly displayed at a fixed position on a display screen, and a map image is scrolled and displayed according to the movement of the vehicle, comprising: a memory larger than the display screen; The first and second areas have areas.
Two VRAMs are installed, and the first VR
AM, the map reading area in the first VRAM is moved and scrolled according to the movement of the vehicle, and the map reading area is monitored to see if it reaches a preset area. generate an image centered on the current position of and store it in the second VRAM;
Thereafter, the map reading area in the second VRAM is moved and scrolled according to the movement of the vehicle, and thereafter, each time the map reading area reaches a preset area in each VRAM, an image is generated, stored, A map drawing method characterized by repeating scroll display processing.