JP3768115B2 - Navigation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a navigation device that receives map information.
[0002]
[Prior art]
In order to reduce the size and weight, a navigation device with a small storage medium such as a smart media, a compact flash, a memory stick, or an SD card without a disk drive device such as a CD-ROM or DVD-ROM is considered. It was.
[0003]
Such a small navigation device cannot store many maps because the storage capacity of the storage medium is small. Therefore, in order to make up for a small storage capacity, it has been considered to receive a map or surrounding information that is insufficient using radio such as a mobile phone (see Japanese Patent No. 2910544).
[0004]
[Problems to be solved by the invention]
However, when moving outside the unreceivable area, the radio wave intensity gradually weakens, and eventually the map and surrounding information cannot be received.
[0005]
[Means for Solving the Problems]
The navigation device of the present invention has been made in view of the above points, and receives a map information received from a station that wirelessly distributes map information having different area sizes based on the reception strength of the communication circuit. Control means for selecting the area of the map information area.
[0006]
This makes it possible to display a map that can be used for a long time when the map becomes out of service and the map cannot be received.
[0007]
In addition, a communication circuit that receives map information from a station that wirelessly distributes map information of a plurality of scales, and a control unit that selects a scale of map information to be received based on the reception strength of the communication circuit.
[0008]
Thereby, when it becomes out of range and a map cannot be received, a wide range map can be displayed.
[0009]
A communication circuit that receives map information from a station that wirelessly distributes the map information divided into a plurality of sections; and a control unit that determines the number of map information sections to be received based on the reception strength of the communication circuit; Is provided.
[0010]
Thereby, when it becomes out of range and a map cannot be received, a wide range map can be displayed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to the drawings. The navigation device of this embodiment is a device that reads map information and peripheral information from a storage medium having a small storage capacity.
[0012]
FIG. 1 is a block diagram showing the configuration of the main part of the first embodiment. (1) is a control circuit which controls each part based on the program written in ROM (2). (3) is a RAM which stores information necessary for the operation of the control circuit (1). (4) is a GPS (Global Positioning System) positioning means that receives radio waves from GPS satellites, measures the current position, and outputs the measurement data to the control circuit (1). (5) is a compact flash composed of a non-volatile memory having a storage capacity of 32 MB, in which map information is written. Since the compact flash (5) has a smaller storage capacity than a CD or DVD, it stores a nationwide map with a small scale. A local map having a large scale of the current position is received by communication and stored in the RAM (3). (6) is a liquid crystal display unit that displays map information and the current position based on the control of the control circuit (1). (7) is an input unit operated by the user.
[0013]
Next, the operation of the first embodiment will be described. FIG. 2 is a flowchart showing the operation of the control circuit (1) of the navigation apparatus, and FIG. 3 is a table showing the operation of the control circuit (1).
[0014]
Here, as shown in FIG. 3, the control circuit (1) determines the strength of the reception strength received by the communication circuit (8) as “strong” when −50 dB or more, “medium” when −85 dB or more and less than −50 dB. 100 dB or more, less than −85 dB is determined as “weak”, and less than −100 dB is determined as “weak”. Then, the base station transmits a plurality of maps divided by sections of the size of the screen of the display unit 1 of the navigation device, respectively, on four scales. Each map information includes latitude and longitude information and scale information of the area, and the navigation apparatus can selectively receive a map of a desired scale including the current position. As shown in FIG. 4 to FIG. 7, the four types of scales are 1/2500, 1/10000, 1/50000, 1/200000 in descending order, and the larger the scale, the more detailed the map information.
[0015]
In FIG. 2, every time the control circuit (1) travels a predetermined distance (S1, S2), the communication circuit (8) receives a map including the current position (S3-S13). The control circuit (1), as shown in FIG. 2 and FIG. 3, receives a scale 1/2500 map if the received intensity is “strong” or “medium” (Y in S3) and less than 70 km / h. It is stored in the RAM (3) (Y in S4, S5), and if it is 70 km / h or more, a scale of 1/10000 is received and stored in the RAM (3) (N in S4, S6). If the reception strength is "weak" (Y in S7), if the speed is less than 70 km / h, a scale of 1/10000 is received and stored in the RAM (3) (Y in S9, S9). For example, a scale 1/50000 map is received and stored in the RAM (3) (N in S9, S10). When the reception strength is “weak” (N in S7), if the speed is less than 70 km / h, a scale 1/50000 map is received and stored in the RAM (3) (Y in S11, S12). For example, a map having a scale of 1/200000 is received and stored in the RAM (3) (N in S11, S13).
[0016]
As described above, when the scale of the map to be received can be selected, the navigation apparatus of the present invention selects and receives a map with a small scale and stores a wide range map when the reception strength becomes weak. Thereby, when it becomes out of service area and a map cannot be made, a wide range map can be displayed. At this time, when the moving speed is high, a map that can be used for a long time can be displayed by giving priority to a wide range over the degree of detail by receiving a smaller scale map.
[0017]
In the first embodiment, a map with a small scale is received when the moving speed is fast, but a map with a small scale may be received when the road is an expressway or a toll road. This is the second embodiment and the operation is shown in the table of FIG.
[0018]
Next, a third embodiment will be described. As shown in FIG. 10, the size of the unit section in the third embodiment is obtained by dividing the display unit of the navigation device into three parts in the vertical direction and three parts in the horizontal direction. The base station transmits the map divided by this section on one scale. The map information of each section includes the latitude and longitude information of the area, and the navigation apparatus can selectively receive a plurality of maps of a desired section.
[0019]
FIG. 9 is a flowchart showing the operation of the control circuit (1) of the navigation device of the third embodiment. The control circuit (1) has a shortage so that when the current position section becomes the end section of the map stored in the RAM (3) (S21), the current position plan becomes the central section. The map of the section is received by the communication circuit (8) and stored in the RAM (3) (S22 to S24). The area to be received varies depending on the electric field strength, and the control circuit (1) receives the map area of 9 sections (see FIG. 10) if it is less than 100 dB (Y in S22, S23), and if it is 100 dB or more, 49 sections. A map area (see FIG. 11) is received (N in S22, S24).
[0020]
For example, in the case of FIG. 10 with 9 sections, if the current position moves from L1 in the center section to L2 in the upper right end section, it is stored in RAM (3) among the 9 sections centered on the section where L2 is located. There are no five sections (shaded lines in FIG. 10). In this case, the minimum reception necessary for screen display is always performed, and communication costs and storage capacity are reduced. In the case of FIG. 11 with 49 sections, when the current position moves from L1 of the center section to L2 of the upper right end section, the section 40 where the section where L2 is located is not stored in the RAM (3) 40. A section (shaded line in FIG. 10) is received. When a map of 49 sections is stored, it is not necessary to receive a new map until the current position reaches the end of the 24 sections. In this case, it is possible to prepare for a case where a map of an area larger than the screen display is received and the map cannot be received.
[0021]
【The invention's effect】
As described above, according to the present invention, when a map is received during traveling, a wide range map is received when the reception strength becomes weak. This makes it possible to receive a wide range of maps in advance so that a map that can be used for a long time can be displayed when the map becomes out of service and cannot be received.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the first embodiment.
FIG. 3 is a table showing the operation of the first embodiment.
FIG. 4 is a diagram showing a map of scale 1/2500.
FIG. 5 is a diagram showing a map with a scale of 1/10000.
FIG. 6 is a diagram showing a map of scale 1/50000.
FIG. 7 is a diagram showing a map with a scale of 1/200000.
FIG. 8 is a table showing the operation of the second embodiment.
FIG. 9 is a flowchart showing the operation of the third embodiment.
FIG. 10 is a diagram showing a narrow map area received in the third embodiment.
FIG. 11 is a diagram showing a wide map area received in the third embodiment.
[Explanation of symbols]
1 Control circuit 3 RAM
4 GPS positioning means 5 Compact flash 6 Display means 8 Communication circuit

Claims (3)

A communication circuit that receives map information from a station that wirelessly distributes map information having different area sizes, and a control unit that selects the area size of the map information to be received based on the reception intensity of the communication circuit. A navigation device characterized by that. A communication circuit that receives map information from a station that wirelessly distributes map information of a plurality of scales, and a control unit that selects a scale of map information to be received based on the reception strength of the communication circuit. Navigation device. A communication circuit that receives map information from a station that wirelessly distributes map information divided into a plurality of sections, and a control unit that determines the number of map information sections to be received based on the reception strength of the communication circuit. A navigation device characterized by that.

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