Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1998-08-14
2001-03-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S200000, C340S990000, C340S995190
Reexamination Certificate
active
06202025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a vehicle-use map data processing device and method in which map data is externally acquired via a communication means, and in particular, to a device and method which can clear redundant map data at an appropriate timing.
2. Description of the Related Art
The use of on-vehicle map data processing devices is spreading, with the most common of these devices being a navigation device. A conventional navigation device comprises a memory medium, such as CD-ROM, for storing map data, and utilizes originally installed map data for navigation.
A new technology has been proposed and developed, in which a vehicle is connected to an information center via a communication means, and receives various useful information from the center via data communication. With this development as a background, offering map data to a vehicle via data communication is also proposed.
As shown in
FIG. 1
, an information center holds detailed map data for a wide area divided into a number of sectional maps. A vehicle acquires map data needed at that time from the information center. For example, a vehicle can acquire the map data of a sectional map covering the area around the present point, around the destination, or for any point designated by a user. Acquired map data (i.e., map data of maps A, B, C in
FIG. 1
) is held in the memory device (medium) on a vehicle side for use in navigation.
The advantage of this system lies in the fact that a vehicle need not hold large quantities of map data, and can nevertheless have access to a detailed map of a desired area. As an example, a vehicle need not store map data which the vehicle does not normally use, such as for maps around a sightseeing attraction because the vehicle can acquire map data concerning the attraction from an information center when it is actually needed.
Such a device is disclosed in, for example, Japanese Patent Laid-open No. Hei 7-262493. According to this publication, map data which a vehicle always carries is limited to that for basic maps showing main roads, and the like. The vehicle externally acquires map data of other detailed maps via communication with an external source.
Acquired map data via communication is stored in a memory device of a map data processing device. In other words, the memory device is accumulatively loaded with acquired map data. However, as the memory capacity of the memory device is limited, the quantity of map data which can be stored therein is naturally limited. Therefore, if map data kept in the memory device is not sometimes cleared to enlarge the vacancy, the stored map data overflows the memory capacity.
The easiest way of enlarging vacancy in the memory device is to delete some of the stored map data. However, deleted map data might be required later, and, in such a case, it might be necessary to externally acquire the same data again. Even more problematic, needed map data is not available for immediate use when needed because data transmission and subsequent processing must first be carried out. Moreover, extra communication costs may incur for reacquisition of map data. In light of this, reacquisition of map data is preferably avoided. However, no available conventional technology can meet this demand.
Also, with the device disclosed by the JP Laid-open No. Hei 7-262493, a user is required to designate map data to be deleted (delete object) and to then execute a clearance operation. In order to do this, the user must detect by himself which map data is stored in a memory device and which one of them is unnecessary. Such judgement may be hardly made by a user. Even if it is made, map data clearance is troublesome for a user to conduct. Also, unlike a PC user, a vehicle operator can not be expected to be familiar with file clearance operations, and it may be quite troublesome for such a user to perform a clearance operation by using a device such as is provided in a vehicle with a limited inside space, which is generally small. In this view, there is great desire for a device that can automatically and appropriately perform a data clearance operation on behalf of a user.
SUMMARY OF THE INVENTION
The present invention aims to provide a map data processing device and method for automatically and reliably clearing map data on behalf of a user. In particular, the present invention aims to provide a device which can avoid as much as possible a situation in which the same map data as that which was once cleared, needs to be acquired again so that map data is always kept available for immediate use, and communication costs are reduced.
In order to achieve the above object, a vehicle-use map data processing device of this invention predicts a possibility of reusing map data and performs map data compression for the purpose of avoiding reacquisition of map data.
(1) According to one aspect of the present invention, there is provided a vehicle-use map data processing device which utilizes map data acquired externally through a communication means, comprising: map data storing means for storing the map data acquired; selection means for judging a possibility of reusing map data stored in the map data storing means to automatically select map data with a lower possibility of being reused as a delete object; and deleting means for deleting the delete object prior to deleting other map data from the map data storing means.
A possibility of reusing map data is the possibility that respective map data may be used again later. The map data storing means stores various map data, including that which has been used only once and is quite unlikely to be used again in the future, and that which has been used often and is therefore more likely to be used again in the future. The first type of map data has a low possibility of being reused, while the latter map data has a higher possibility of being reused.
Preferably, judgement of the possibility of reusing map data factors in at least one of an acquisition date or a last used date of the map data, with map data with a recent acquisition or last used date being more likely to be used again in the future.
Also, preferably, a possibility of reusing map data is judged based on positional relationship between a predetermined judgement standard point and an area corresponding to the map data. A judgement standard point may be the user's home or another point set by a user. Preferably, map data concerning areas around the judgement standard point is excluded from delete objects as it has a higher possibility of being reused. Map data concerning areas far from the standard point may be initially selected as a delete object. In particular, if a judgement standard point is determined for every user, the map data processing device is able to make appropriate judgement so as to meet the needs of each user.
Also preferably, a possibility of reusing map data is judged based on the frequency at which map data has been used. Map data which has often been used may have a higher possibility of being reused in the future.
According to the present invention, map data with a low possibility of being reused of all map data stored in the map data storing means is selected as a delete object and deleted prior to other data, while those with a high possibility are kept in the storing means. As a result, a wasteful process, i.e., reacquisition of map data which was once acquired and deleted, is performed less often. Therefore, map data can be appropriately cleared on behalf of a user.
(2) Preferably, the vehicle-use map data processing device of the present invention further may comprise a compression means for compressing delete objects to thereby enlarge free space in the map data storing means. The deleting means deletes a delete object when the available memory for map data remains insufficient after compression of the delete object.
Specifically, as shown in
FIG. 2
, a delete object with a low possibility of being reused is compressed. Compressed map data cannot be used intact, but can be u
Cuchlinski Jr. William A.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hernandez Olga
Toyota Jidosha & Kabushiki Kaisha
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