JPWO2016129042A1 - Map drawing apparatus and map drawing program - Google Patents

Abstract

When the extended display request is accepted, the drawing data generation unit (130) generates extended drawing data (182) using the map data (191). When the extension area includes an area outside the preparation area, the map drawing unit (140) uses the preparation drawing data (181) to generate a map of an intermediate area that is an area obtained by extending the display area within the preparation area. Draw on the screen without reducing it to the scale of the map in the extended area. Then, the map drawing unit waits until extended drawing data is generated, and draws a map of the extended area on the screen using the extended drawing data.

Description

  The present invention relates to a reduced display of a map.

The map drawing device holds a plurality of map data with different scales, and uses map data differently according to the scale of the map to be drawn. A car navigation system is an example of a map drawing device.
When switching map data, map data is loaded and drawing data is generated from the map data. Therefore, it takes time to draw a map as compared with the case where the map data is not switched. In preparation for operations such as scrolling, drawing data in a preparation area, which is an area wider than the screen range, is prepared.

When a scale change is requested, it takes time to switch the map data and draw the map after the scale change.
Patent Document 1 discloses a transition method for allowing a user to visually recognize that the scale is being changed. This transition method is a zoom animation that displays an intermediate scale map obtained by enlarging or reducing the map using drawing data of the map being displayed.
In addition, since the map data after switching is loaded during the zoom animation, the waiting time from drawing the zoom animation to drawing the map after the scale change is shortened.
However, in zoom-out in which the scale is changed from the detailed scale to the wide scale, the map after the scale change may include an area outside the preparation area. In that case, the area outside the preparation area is masked.

Japanese Patent No. 3577607

  An object of the present invention is to prevent a map including a masked area from being displayed on a screen when a map is displayed in a reduced size.

The map drawing apparatus of the present invention
A drawing data generation unit that generates preparation drawing data representing a map of a preparation area that is an area included in the area, using map data of the area;
A map drawing unit for drawing a map of a display area on the screen, which is an area included in the preparation area, using the preparation drawing data;
A request reception unit that receives an extended display request for requesting display of a map of an extended area that is an area obtained by extending the display area;
When the extended display request is accepted, the drawing data generation unit generates extended drawing data representing a map of the extended area using the map data,
The map drawing unit, when the extension area includes an area outside the preparation area, uses the preparation drawing data to display a map of an intermediate area that is an area obtained by extending the display area within the preparation area. The extended area map is drawn on the screen without being reduced to a scale that fits on the screen, and waits until the extended drawing data is generated. The extended drawing data is used to display the extended area map on the screen. To draw.

  According to the present invention, when the map is displayed in a reduced size, it is masked in order to wait without reducing the map of the intermediate area in the preparation area to the scale of the map of the extended area until the extended drawing data is generated. The map including the area can be prevented from being displayed on the screen.

1 is a functional configuration diagram of a map drawing device 100 according to Embodiment 1. FIG. 1 is a hardware configuration diagram of a map drawing device 100 according to Embodiment 1. FIG. 3 is a flowchart of a map drawing method in the first embodiment. 3 is a flowchart of a map drawing method in the first embodiment. 3 is a flowchart of a map drawing method in the first embodiment. 2 is a conceptual diagram of a preparation area 102 and a display area 103 in Embodiment 1. FIG. FIG. 3 is a conceptual diagram of an extended area 105 in the first embodiment. The conceptual diagram of the map corresponding | compatible data 194 in Embodiment 1. FIG. FIG. 3 is a conceptual diagram of a limit area 106 in the first embodiment. FIG. 3 is a conceptual diagram of an intermediate area 107 in the first embodiment. FIG. 3 is a conceptual diagram of an intermediate extension area in the first embodiment.

Embodiment 1 FIG.
A map drawing apparatus 100 that displays a reduced map will be described with reference to FIGS.

*** Explanation of configuration ***
Based on FIG. 1, the functional configuration of the map drawing apparatus 100 will be described.
The map drawing apparatus 100 includes a request accepting unit 110, an area determining unit 120, a drawing data generating unit 130, a map drawing unit 140, and a change width determining unit 150.
Further, the map drawing apparatus 100 includes a map data storage unit 190, a drawing data storage unit 180, and a drawing parameter storage unit 170.

  The drawing data generation unit 130 generates the preparation drawing data 181 using the area map data 191. The preparation drawing data 181 is drawing data representing a map of a preparation area that is an area included in the region.

  The map drawing unit 140 draws a map of the display area on the screen using the preparation drawing data 181. The display area is an area included in the preparation area.

The request reception unit 110 receives an extended display request.
The extended display request requests display of a map of an extended area that is an area obtained by expanding the display area.

  When the extended display request is accepted, the drawing data generation unit 130 generates the extended drawing data 182 using the map data 191. The extended drawing data 182 is drawing data representing a map of the extended area.

For example, the drawing data generation unit 130 generates the extended drawing data 182 as follows.
The drawing data generation unit 130 selects map information for the extended area from the map data 191.
The drawing data generation unit 130 selects, as priority information, map information of a priority type from the map information of the extended area.
Then, the drawing data generation unit 130 generates the extended drawing data 182 using the priority information without using the map information other than the priority information.

When the extended display request is received, the area determination unit 120 determines whether or not the extended area includes an area outside the preparation area as follows.
The area determination unit 120 calculates a limit area. The limit area is the maximum area when the display area is expanded within the range of the preparation area without changing the ratio of the length from the reference point in the display area to each point of the edge of the display area.
The area determination unit 120 calculates a limit scale. The limit scale is a scale at which a map of the limit area fits on the screen.
When the extended scale is smaller than the limit scale, the area determination unit 120 determines that the extended area includes an area outside the preparation area. The extended scale is a scale at which the map of the extended area fits on the screen.

  When the extended area includes an area outside the preparation area, the map drawing unit 140 uses the preparation drawing data 181 to reduce the map of the intermediate area, which is an area obtained by extending the display area within the range of the preparation area, to the expansion scale. Draw on the screen without Thereafter, the map drawing unit 140 stands by until the extended drawing data 182 is generated, and draws a map of the extended area on the screen using the extended drawing data 182.

The map drawing unit 140 draws a map of the intermediate area as follows.
The map drawing unit 140 draws each of the maps whose scales have changed from the display area map to the limit area map as the intermediate area map in descending order of scale. The change width is determined by the change width determination unit 150.

The change width determination unit 150 determines the change width of the scale per time until the map drawn on the screen changes from the display area map to the limit area map as follows.
The change width determination unit 150 determines the number of maps in the intermediate area based on the change time and the drawing time. The change time is the time until the map drawn on the screen changes from the display area map to the limit area map. The drawing time is the time required for drawing a map in one intermediate area.
The change width determination unit 150 determines the change width based on the scale width and the number of maps in the intermediate area. The scale width is the scale width from the display scale to the limit scale. The display scale is a scale at which a map of the display area fits on the screen.

For example, the change width determination unit 150 calculates the change time as follows.
Based on the amount of map information in the extended area of the map information included in the map data 191, the change width determining unit 150 calculates a time having the same length as the time required to generate the extended drawing data 182 as the change time. .

The map data storage unit 190 stores map data 191 and map correspondence data 194.
The map data 191 includes first map data 192 and second map data 193 having a smaller scale than the first map data 192.
The first map data 192 and the second map data 193 include regional map information.
Map information is information on objects in the area. Targets include roads, stores, and land. The target information includes type information and position information. The type information indicates the type of the target, and the position information indicates the position or range of the target.
The map correspondence data 194 associates map data with a map scale.

In the first embodiment, the first map data 192 is data representing a detailed map of 100 m scale, and the second map data 193 is data representing a wide area map of 200 m scale. The 100 m scale is a scale in which 100 m is reduced to a unit distance, and the 200 m scale is a scale in which 200 m is reduced to a unit distance. m represents a meter. When the unit distance is 1 cm, the detailed map of 100 m scale is a 1/10000 map, and the wide area map of 200 m scale is a 1/20000 map. cm represents centimeters.
The detailed map shows detailed map information. On the other hand, a wide area map shows main map information, and detailed map information is thinned out or collected. Detailed map information includes narrow streets and store names, and main map information includes arterial roads and prefecture names.

  The drawing data storage unit 180 stores preparation drawing data 181 and extended drawing data 182.

The drawing parameter storage unit 170 stores drawing parameters 171.
The drawing parameter 171 includes various sizes necessary for drawing the map, such as the screen size, the preparation area, the display area and the expansion area, display scale, expansion scale, limit scale, change time, drawing time, and reference point. It is a parameter.

  The scale is the ratio of the display size to the actual size. The actual size is the size in the world coordinate system. The smaller the scale, the smaller the value.

A hardware configuration example of the map drawing apparatus 100 will be described based on FIG.
The map drawing apparatus 100 is a computer including hardware such as a processor 901, an auxiliary storage device 902, a memory 903, a communication device 904, an input interface 905, and a display interface 906.
The processor 901 is connected to other hardware via a signal line 910. The input interface 905 is connected to the input device 907 via a cable 911. Display interface 906 is connected to display 908 via cable 912.

The processor 901 is an IC that performs processing, and controls other hardware. For example, the processor 901 is a CPU, DSP, or GPU. IC is an abbreviation for Integrated Circuit. CPU is an abbreviation for Central Processing Unit, DSP is an abbreviation for Digital Signal Processor, and GPU is an abbreviation for Graphics Processing Unit.
The auxiliary storage device 902 is, for example, a ROM, a flash memory, or an HDD. ROM is an abbreviation for Read Only Memory, and HDD is an abbreviation for Hard Disk Drive.
The memory 903 is, for example, a RAM. RAM is an abbreviation for Random Access Memory.
The communication device 904 includes a receiver 9041 that receives data and a transmitter 9042 that transmits data. For example, the communication device 904 is a communication chip or a NIC. NIC is an abbreviation for Network Interface Card.
The input interface 905 is a port to which a cable 911 is connected, and an example of the port is a USB terminal. USB is an abbreviation for Universal Serial Bus.
The display interface 906 is a port to which the cable 912 is connected, and the USB terminal and the HDMI terminal are examples of ports. HDMI (registered trademark) is an abbreviation for High Definition Multimedia Interface.
The input device 907 is, for example, a mouse, a keyboard, or a touch panel.
The display 908 is, for example, an LCD. LCD is an abbreviation for Liquid Crystal Display.

The auxiliary storage device 902 stores an OS. OS is an abbreviation for Operating System.
Further, the auxiliary storage device 902 stores a program that realizes the function of “unit” provided in the map drawing device 100. However, the “storage unit” is excluded.
At least a part of the OS is loaded into the memory 903, and the processor 901 executes a program that realizes the function of “unit” while executing the OS. A program that realizes the function of “unit” is loaded into the memory 903, read into the processor 901, and executed by the processor 901.
The map drawing apparatus 100 may include a plurality of processors 901, and the plurality of processors 901 may execute a program that realizes the function of “unit” in cooperation with each other.

  Data, information, signal values, variable values, and the like indicating the processing result of “part” are stored in the memory 903, the auxiliary storage device 902, a register in the processor 901, or a cache memory in the processor 901.

The “part” may be implemented as “circuitry”. “Part” may be read as “circuit”, “process”, “procedure”, or “processing”.
“Circuit” and “circuitry” are concepts including a processing circuit such as the processor 901, logic IC, GA, ASIC, and FPGA. GA is an abbreviation for Gate Array, ASIC is an abbreviation for Application Specific Integrated Circuit, and FPGA is an abbreviation for Field-Programmable Gate Array.

*** Explanation of operation ***
The operation of the map drawing apparatus 100 corresponds to a map drawing method. The map drawing method corresponds to the processing procedure of the map drawing program.
A map drawing method when an extended display request is accepted will be described with reference to FIGS. In the figure, Rs means a display scale, Rf means an extended scale, and Rw means a limit scale.

S111 is an extended display request acceptance process.
Prior to S111, the preparatory drawing data generation processing and the display area drawing processing have been executed. That is, the drawing data generation unit 130 has already generated the preparation drawing data 181 using the first map data 192. Further, the map drawing unit 140 has drawn the map of the display area 103 on the screen of the display 908 using the preparation drawing data 181.
In Embodiment 1, the display scale (Rs) which is the scale of the map of the display area 103 displayed on the screen is 100 m scale.
As shown in FIG. 6, the preparation area 102 is a rectangular area included in the area 101, and the display area 103 is a rectangular area included in the preparation area 102.

In S <b> 111, when the user wants to zoom out the map of the display area 103 and display the map of the extended area 105 on the screen, the map drawing apparatus 100 issues an extended display request specifying the extended scale (Rf) and the reference point 104. To enter. In the first embodiment, the expansion scale, which is the scale of the map of the expansion area 105 displayed on the screen, is 200 m.
The reference point 104 is a point in the display area 103. However, the reference point 104 may not be in the display area 103 as long as the extended scale and the limit scale can be obtained. The reference point 104 may not be a point designated by the user but may be a predetermined point. For example, the reference point 104 is the center point of the display area 103.

  As shown in FIG. 7, the extended area 105 is an area obtained by extending the display area 103 without changing the ratio of the length from the reference point 104 in the display area 103 to each point on the edge of the display area 103.

  Then, the request receiving unit 110 receives an extended display request input to the map drawing device 100.

S112 is an extended drawing data generation process.
In S112, the drawing data generation unit 130 calculates an expansion rate obtained by dividing the display scale by the expansion scale. When the display scale is 100 m scale and the expansion scale is 200 m scale, the expansion ratio is double.
The drawing data generation unit 130 calculates the range of the extended area 105 using the range of the display area 103, the reference point 104, and the expansion rate. The extended area 105 can also be obtained from the reference point 104 and the drawing parameter 171.

The drawing data generation unit 130 selects map data associated with the expanded scale in the map correspondence data 194 from the first map data 192 and the second map data 193.
In the map correspondence data 194 in FIG. 8, when the expansion scale is 200 m, the drawing data generation unit 130 selects the second map data 193 associated with the 200 m scale.

  Then, the drawing data generation unit 130 starts generating the extended drawing data 182 using the selected map data.

For example, the drawing data generation unit 130 generates the extended drawing data 182 as follows.
The drawing data generation unit 130 selects target map information in the extended area 105 from the map data.
The drawing data generation unit 130 selects target map information of a priority type among the selected map information as priority information. The priority type is a predetermined type. For example, the priority type is road.
Then, the drawing data generation unit 130 generates the extended drawing data 182 using the priority information without using the map information other than the priority information.

S113 is a limit area calculation process. The limit area calculation process is a part of the area determination process.
In S <b> 113, the region determination unit 120 calculates the limit region 106.
As shown in FIG. 9, the limit area 106 has a display area 103 within the range of the preparation area 102 without changing the ratio of the length from the reference point 104 in the display area 103 to each point on the edge of the display area 103. This is the maximum area when expanding.

S114 is a limit scale calculation process. The limit scale calculation process is a part of the area determination process.
In S <b> 114, the area determination unit 120 calculates a limit scale (Rw) that is a map scale of the limit area 106 displayed on the screen.

S115 is a scale comparison process. The scale comparison process is a part of the area determination process.
In S115, the area determination unit 120 compares the expansion scale (Rf) and the limit scale (Rw), and determines whether or not the limit area 106 includes an area outside the preparation area 102 based on the comparison result.
If the expanded scale is smaller than the limit scale, the limit area 106 includes an area outside the preparation area 102.
When the limit area 106 includes an area outside the preparation area 102 (YES), the process proceeds to S121 (see FIG. 4).
When the limit area 106 does not include an area outside the preparation area 102 (NO), the process proceeds to S131 (see FIG. 5).

S121 (see FIG. 4) is a change width determination process. In the figure, CW means a change width.
In S121, the change width determination unit 150 determines the number of maps in the intermediate area based on the change time and the drawing time. The change time is the time until the map drawn on the screen changes from the map in the display area 103 to the map in the limit area 106. The drawing time is the time required for drawing a map in one intermediate area. When it is assumed that the drawing time of one map in the intermediate area is constant, the number of maps in the intermediate area is a value obtained by dividing the change time by the drawing time. When the drawing time of one map in the intermediate area is not considered to be constant, the number of maps in the intermediate area can be determined according to the total drawing time and the change time. In addition, the number of maps in the intermediate area may be a predetermined parameter.
The change width determination unit 150 determines the change width based on the scale width and the number of maps in the intermediate area. The scale width is the scale width from the display scale to the limit scale. When it is assumed that the drawing time of one map in the intermediate area is constant, the change width is a value obtained by dividing the scale width by the number of maps in the intermediate area. If the drawing time of one map in the intermediate area is not considered to be constant, the conversion width is the scale width, the drawing time when generating one map of the intermediate area, and the elapsed time from the start of the scale change. It can be decided according to.
However, the change width may be a predetermined parameter.

For example, the change width determination unit 150 calculates the change time as follows.
Based on the amount of map information in the extended area of the map information included in the map data 191, the change width determining unit 150 calculates a time having the same length as the time required to generate the extended drawing data 182 as the change time. . Here, the map data 191 is map data used for generating the extended drawing data 182 among the first map data 192 and the second map data 193.
However, the change time may be a predetermined parameter.

S122 and S123 are intermediate area drawing processing or limit area drawing processing. In the figure, VR means a scale variable.
S122 and S123 are repeated while the value of the scale variable (VR) is smaller than the limit scale (Rw). The initial value of the scale variable is the display scale (Rs).

  In S122, the map drawing unit 140 adds a change width to the value of the scale variable.

In S123, the map drawing unit 140 calculates the range of the intermediate region 107 using the range of the current region, the reference point 104, and the change width. The maximum range of the intermediate area 107 is the limit area 106. The current area is an area represented by a map displayed on the screen.
The map drawing unit 140 draws the map of the intermediate area 107 on the screen at the scale indicated by the value of the scale variable, using the preparation drawing data 181.
As shown in FIG. 10, the intermediate area 107 is displayed within the range of the preparation area 102 without changing the ratio of the length from the reference point 104 in the display area 103 to each point on the edge of the display area 103. This is an area obtained by expanding the area 103.

  When the loop of S122 and S123 is completed, a map of the limit area 106 is displayed on the screen.

S124 is a standby process.
In S124, the map drawing unit 140 waits until generation of the extended drawing data 182 is completed.

S125 and S126 are intermediate extended area drawing processing or extended area drawing processing.
S125 and S126 are repeated while the value of the scale variable (VR) is smaller than the expansion scale (Rf). The initial value of the scale variable is the limit scale (Rw).

  In S125, the map drawing unit 140 adds a change width to the value of the scale variable. However, a change width different from the change width determined in S121 may be used in S125.

In S <b> 126, the map drawing unit 140 calculates the range of the intermediate extended area 108 using the current area range, the reference point 104, and the change width. The maximum range of the intermediate extension area 108 is the extension area 105.
The map drawing unit 140 uses the extended drawing data 182 to draw the map of the intermediate extended area 108 on the screen at a scale indicated by the value of the scale variable.
As shown in FIG. 11, the intermediate extension area 108 extends the limit area 106 within the extension area 105 without changing the ratio of the length from the reference point 104 to each point of the edge of the limit area 106. It is an area.

  When the loop of S125 and S126 is completed, a map of the extended area 105 is displayed on the screen as a new map of the display area 103.

S127 is a preparation drawing data generation process.
In S <b> 127, the drawing data generation unit 130 generates new preparation drawing data 181 using the map data 191. Here, the map data 191 is map data used for generating the extended drawing data 182 among the first map data 192 and the second map data 193.

S131 (see FIG. 5) is a change width determination process.
In S131, the change width determination unit 150 determines the change width (CW). The method for determining the change width is the same as in S121. However, the intermediate area 107 in S121 is replaced with the intermediate extension area 108 in S131.

S132 and S133 are intermediate extended area drawing processing or extended area drawing processing.
S132 and S133 are repeated while the value of the scale variable (VR) is smaller than the expansion scale (Rf). The initial value of the scale variable is the display scale (Rs).
S132 is the same process as S122, and S133 is the same process as S123. However, in S133, the maximum range of the intermediate extension area 108 is the extension area 105.
When the loop of S132 and S133 is completed, a map of the extended area 105 is displayed on the screen.

S134 is a standby process.
In S134, the map drawing unit 140 waits until generation of the extended drawing data 182 is completed.

S135 is an extended area drawing process.
In S <b> 135, the map drawing unit 140 draws the map of the extended area 105 on the screen as a map of the new display area 103 using the extended drawing data 182.

S136 is a preparation drawing data generation process.
In S <b> 136, the drawing data generation unit 130 generates new preparation drawing data 181 using the map data 191. Here, the map data 191 is map data used for generating the extended drawing data 182 among the first map data 192 and the second map data 193.

*** Supplementary explanation ***
The map drawing apparatus 100 can cope with a continuous scale change. The continuous scale change is a scale change when the scale change button is continuously pressed a plurality of times. When there are three scales of 100 m scale, 200 m scale, and 300 scale, and when a scale change button is pressed twice in succession when a map of 100 m scale is drawn, the map drawing device 100 displays the map of 200 m scale. The map may be drawn in the order of the map of 300 m scale, or the map of 300 m scale may be drawn without drawing the map of 200 m scale. The scale may be determined according to an operation such as scrolling.
The map drawing apparatus 100 can handle zoom-in that increases the scale of the map. In the case of zooming in, since the reduced area after zooming in does not include the area outside the preparation area 102, the map of the reduction area is drawn using the preparation drawing data 181.
When the generation of the extended drawing data 182 is completed while the map of the intermediate area 107 is being extended to the map of the limit area 106, the map drawing unit 140 finishes extending the map of the intermediate area 107 to the map of the limit area 106. Before, the extended area 105 may be drawn using the extended drawing data 182. Further, when the extended area 105 does not include an area outside the preparation area 102, the same applies to the case where the post-change scale preparation area 102 is completed during the expansion from the limit area 106 to the expansion area 105.

*** Explanation of effects ***
Since the extended drawing data 182 is generated while the map of the intermediate area 107 is being drawn using the preparation drawing data 181, the time until the map of the extended area 105 is displayed can be shortened.
Until the extended drawing data 182 is generated, the map of the intermediate area 107 is waited without being reduced to the extended scale, so that the map including the masked area is not displayed on the screen.
By carefully selecting the map information and generating the extended drawing data 182, the time required to generate the extended drawing data 182 can be shortened.

The embodiments are exemplifications of preferred forms and are not intended to limit the technical scope of the present invention. The embodiment may be partially implemented.
The processing procedure described using the flowchart and the like is an example of the processing procedure of the map drawing device 100, the map drawing method, and the map drawing program.

  100 map drawing device, 101 area, 102 preparation area, 103 display area, 104 reference point, 105 extended area, 106 limit area, 107 intermediate area, 108 intermediate extended area, 110 request reception section, 120 area determination section, 130 drawing data Generation unit, 140 Map drawing unit, 150 Change width determination unit, 170 Drawing parameter storage unit, 171 Drawing parameter, 180 Drawing data storage unit, 181 Preparation drawing data, 182 Extended drawing data, 190 Map data storage unit, 191 Map data, 192 1st map data, 193 2nd map data, 194 map compatible data, 901 processor, 902 auxiliary storage, 903 memory, 904 communication device, 9041 receiver, 9042 transmitter, 905 input interface, 906 display Ray interface, 907 input device, 908 display, 910 signal line, 911 cable, 912 cable.

Claims (7)

A drawing data generation unit that generates preparation drawing data representing a map of a preparation area that is an area included in the area, using map data of the area;
A map drawing unit for drawing a map of a display area on the screen, which is an area included in the preparation area, using the preparation drawing data;
A request reception unit that receives an extended display request for requesting display of a map of an extended area that is an area obtained by extending the display area;
When the extended display request is accepted, the drawing data generation unit generates extended drawing data representing a map of the extended area using the map data,
The map drawing unit, when the extension area includes an area outside the preparation area, uses the preparation drawing data to display a map of an intermediate area that is an area obtained by extending the display area within the preparation area. The extended area map is drawn on the screen without being reduced to a scale that fits on the screen, and waits until the extended drawing data is generated. The extended drawing data is used to display the extended area map on the screen. Map drawing device to draw on. A limit area which is the maximum area when the display area is expanded within the range of the preparation area without changing the ratio of the length from the reference point in the display area to each point of the edge of the display area. Calculate
Calculating a limit scale that is a scale at which the map of the limit area fits on the screen;
The area determination unit according to claim 1, further comprising: an area determination unit that determines that the expansion area includes an area outside the preparation area when an expansion scale, which is a scale that fits the map of the expansion area, is smaller than the limit scale. Map drawing device. The map drawing device
A change width determining unit that determines a change width of a scale per time until a map drawn on the screen changes from a map of the display area to a map of the limit area;
The map drawing unit
The map drawing device according to claim 2, wherein each map whose scale has changed from the map of the display area to the map of the limit area is drawn on the screen as a map of the intermediate area in descending order of the scale. . The change width determining unit includes:
Based on the change time until the map drawn on the screen changes from the display area map to the limit area map and the drawing time required to draw one intermediate area map, the intermediate area map Determine the number of
The map drawing apparatus according to claim 3, wherein the change width is determined based on a scale width from a display scale that is a scale in which a map of the display area fits on a screen to the limit scale and a number of maps in the intermediate area. . The change width determining unit includes:
The time of the same length as the time required for the generation of the extended drawing data is calculated as the change time based on the amount of map information of the extended area in the map information included in the map data. Map drawing device. The map data includes map information of the area,
The drawing data generation unit selects map information of the extension area from the map data, selects map information of a priority type among the map information of the extension area as priority information, and maps information other than the priority information. The map drawing apparatus according to claim 1, wherein the extended drawing data is generated using the priority information without being used. A preparation drawing data generation process for generating preparation drawing data representing a map of a preparation area that is an area included in the area, using map data of the area;
Display area drawing processing for drawing a map of a display area, which is an area included in the preparation area, on the screen using the preparation drawing data;
An extended display request receiving process for receiving an extended display request for requesting display of a map of an extended area that is an area obtained by extending the display area;
When the extended display request is received, using the map data, extended drawing data generation processing for generating extended drawing data representing a map of the extended area;
When the extension area includes an area outside the preparation area, a map of the intermediate area, which is an area obtained by extending the display area within the range of the preparation area, is obtained using the preparation drawing data. Draws on the screen without reducing to a scale that fits on the screen, waits until the extended drawing data is generated, and draws a map of the extended region on the screen using the extended drawing data A map drawing program that causes a computer to execute processing.

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