Data processing: vehicles – navigation – and relative location – Navigation – Determination of travel data based on the start point and...
Reexamination Certificate
2001-11-19
2004-11-16
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Navigation
Determination of travel data based on the start point and...
C701S211000, C340S990000, C707S793000, C707S793000
Reexamination Certificate
active
06820001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a navigation system for vehicle in which a current position of a vehicle is detected, map data of a specific area including the current position is read out from a recording medium, and a route from the current position to a received destination is determined according to the map data to guide the vehicle to take the route to the destination along the route by using picture and voice.
2. Description of Related Art
In a conventional navigation device for vehicle, a current position of a vehicle is detected by using a global positioning system (GPS), road map data and information relating to a road map are read out from a recording medium (for example, a compact disk) mounted on a disk unit, a route from the current position to a destination input by a user is determined according to a Dijkstra method, and the vehicle is guided to take the determined route to the destination by using picture and voice.
In this case, the road map data and the information relating to a road map are in advance read out from the recording medium to a memory of a data buffer. Therefore, the user can gain access to the road map data and the information stored in the data buffer memory at high speed.
The road map data and the information are successively read out while performing the navigation operation during the movement of the vehicle. Therefore, the road map data and the information can be read out without delay. However, the user sometimes requires that the navigation device for vehicle has a function other than the navigation function. In this case, it is required that the disk unit of the navigation device can be used to read out not only the road map data recording in a map recording medium but also another type of data recorded in another recording medium. Therefore, in recent years, as is described in Published Unexamined Japanese Patent Application No. H9-96532 of 1997, a pre-reading process is performed prior to the performance of the navigation to set the disk unit to a standby condition after the pre-reading process. Therefore, even though the navigation function is performed by the conventional navigation device for vehicle after the pre-reading process, a function other than the navigation function can be performed by using the disk unit during the navigation.
FIG. 6
schematically shows a plurality of map units of a map area to explain a pre-reading process in which map data of map units placed around a route is in advance read out prior to the navigation in the conventional navigation device for vehicle.
As shown in
FIG. 6
, a map area indicated by map data is partitioned into a plurality of map units. Each map unit has a squared area which is 1 km by 1 km. Also, each of all roads (not shown) of the map area indicated by the map data is divided into a plurality of links, and a route from a current position to a destination is placed on a road or a plurality of roads. Therefore, the route is composed of a plurality of links (hereinafter, called route links) corresponding to a plurality of parts of the route.
Each map unit including at least one route link is indicated by a densely hatched squared area and is called a route link map unit. Each map unit adjacent to one route link map unit is indicated by a sparsely hatched squared area and is called an adjacent map unit. Also, the other map units are respectively indicated by a non-hatched squared area. A pre-reading process is performed for the route link map units and the adjacent map units. That is, when a route from a current position to a destination is determined by a route determining unit according to map data, map data corresponding to both route link map units and adjacent map units is read out as map data relating to the route from a recording medium and is stored in a memory of a data buffer. Therefore, the user can gain access to the map data relating to the route stored in the memory of the data buffer at high speed. In contrast, no data of map units other than the route link map units and the adjacent map units is stored in the memory of the data buffer.
The route links of the route are identified by a plurality of identification names (that is, L
1
, L
2
, L
3
, - - - ) expressed by consecutive numbers. Because map data indicates two-dimensional area, each map unit is identified by an identification number M(i,j). Each route link is included in one route link map unit, and no route link is included in a plurality of map units. Therefore, only one route link map unit M(i,j) including an arbitrary route link Lk exists. Also, one route link map unit can include a plurality of route links. Therefore, one route link map unit can include all the route.
For example, three route links L
1
, L
2
and L
3
are included in the route link map unit placed on the most left side of the route.
FIG. 7
is a flow chart showing the procedure of the pre-reading process performed for the map data prior to the navigation performed in the conventional navigation device for vehicle. The procedure of the pre-reading process will be described below with reference to FIG.
6
and FIG.
7
.
In a step ST
11
, to initially perform the pre-reading process for the route link L0, k=0 is set. In a step ST
12
, map data of a route link map unit M(i,j) including a route link Lk and map data of eight adjacent link map units M(i−1,j−1), M(i,j−1), M(i−1,j), M(i−1,j+1), M(i+1,j), M(i,j+1), M(i+1,j−1) and M(i+1,j+1) adjacent to the route link map unit M(i,j) are read out from a recording medium and are stored in a memory of a data buffer.
In a step ST
13
, it is checked whether or not the route link Lk is a final part of the route. In other words, it is checked whether or not the pre-reading process for the route from the current position to the destination is completed. In cases where the route link Lk is a final part of the route, the procedure proceeds to a step ST
14
, and the pre-reading process is completed.
In contrast, in cases where the route link Lk is not a final part of the route, the number k is incremented. That is, k=k+1 is set. Thereafter, the steps ST
12
and ST
13
are again performed.
As is described above, to make preparations for the use of a function other than the navigation function in the conventional navigation device for vehicle, it is required that the disk unit is set to a standby condition. Therefore, the disk unit is in advance used for the pre-reading process to transfer map data of the route link map units and map data of the adjacent map units from a recording medium to a memory of a data buffer, and the user can gain access to the map data of the route link map units and the map data of the adjacent map units stored in the memory of the data buffer at high speed.
However, in cases where a length of a route from a current position of a vehicle to a destination is extremely long, because a storage capacity of the data buffer is limited, it is impossible to write road map data of all route link map units and all adjacent map units relating to the extremely long route in the data buffer. Therefore, only a part of the road map data is written in the data buffer, but the other parts of the road map data cannot be written in the data buffer. In this case, each time the part of the road map data written in the data buffer is used for the navigation function, it is required that another part of the road map data is written in the data buffer. In this case, to write another part of the road map data in the data buffer, it is required that a recording medium of the road map data is again mounted on the disk unit. Also, it is sometimes required that another recording medium used for a function other than the navigation function is demounted from the disk unit to mount the recording medium of the road map data on the disk unit.
Also, because it is required that the recording medium of road map data and the recording medium used for a function other than the navigation
Birch & Stewart Kolasch & Birch, LLP
Black Thomas G.
Mancho Ronnie
Mitsubishi Denki & Kabushiki Kaisha
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