Map display unit

Details Map display unit Map display unit

1999-09-24

2001-03-06

Cuchlinski, Jr., William A. (Department: 3661)

Data processing: vehicles, navigation, and relative location

Navigation

Employing position determining equipment

C701S212000, C340S990000, C340S995190

Reexamination Certificate

active

06199012

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a map display unit that utilizes, for example, global positioning system (GPS) satellites to measure its present position and displays a mark representing the present position along with map information, and more particularly to a map display unit suitable for carrying.
DESCRIPTION OF THE RELATED ART
As shown in
FIG. 16
, a navigation system mounted in a vehicle is constructed of a GPS antenna
1
, a GPS receiver
2
, a navigation control section
3
, a CD-ROM drive unit
4
, and a display unit
5
. Radio wave
7
from each of a plurality of GPS satellites
6
is received with the GPS antenna
1
. The received signal is modulated with the GPS receiver
2
in order to measure the present position of the system. Also, the navigation control section
3
synthesizes a mark representing the present position and the map information read out from the CD-ROM drive unit
4
. The synthesized information is sent to the display unit
5
to give the driver or the passenger visual route guidance. The vehicle navigational system, however, is bulky and unsuitable for carrying.
Hence, there is a portable GPS receiver can be carried. In a GPS receiver without a CD-ROM drive unit as an example, as illustrated in
FIG. 17
, after selecting a necessary range
8
a
from the map information displayed on a map server
8
, the map information included in the range
8
a
is downloaded from the map server
8
to a GPS receiver
9
. The map server
8
employs, for example, a personal computer. A map disk
11
is shoved into the CD-ROM drive unit
10
of the map server
8
. Then, the map server
8
executes a predetermined application program to transmit the map information included in the selected range to the GPS receiver
9
. The transmitted map information is stored in the semiconductor storage memory of the GPS receiver
9
. Thereafter, the stored map information is carried by the GPS receiver
9
and used for displaying a map.
Incidentally, the map disk
11
stores map information on various reduced scales from one which can overlook the entire territory to one which can overlook a partial region so that the shape of a building, etc. can be pinpointed, even when limited to Japanese territory, for example.
Therefore, the map information transmitted to the GPS receiver
9
includes map information in various scale levels of the selected range. For instance, when the “Kanto-Chubu” district is selected, the map information includes a wide-area map (first level- small scale far-off view) of the entire district, a sectional map (second level- medium scale) of each prefecture, etc., and a detailed map (third level-large scale) of each city, etc. Note that the number of levels is merely an example.
Carrying information about maps different in reduced scale is easy to use. The reason is that a small-scale map of a large area is easy to view in planning a route, while a large-scale map of a small area is easy to view at a place near an intermediate point or a destination.
However, a large-scale map (large-level map) is suitable for obtaining detailed information about geographical features or roads and for guiding routes, but display maps are frequently switched with movement of the present position. For this reason, there is a problem that the position of a mark (representing the present position) displayed on the screen of the GPS receiver
9
will frequently jump from one place to another every time a map is switched to another, causing a sense of incongruity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a map display unit that is capable of avoiding a great jump of a present-position mark according to map-switching to eliminate a sense of incongruity in the screen, by taking advantage of the overlapped portion between adjacent maps in map information.
To achieve the foregoing object and in accordance with one important aspect of the present invention, there is provided a map display unit, which comprises (1) position detection means for detecting its present position, (2) storage means for storing information about maps on various scales, (3) retrieval means for retrieving a group of maps corresponding to the present position detected by the position detection means from the storage means, (4) extraction means for extracting a map on the same scale as a map being displayed from the retrieved group of maps, and (5) display control means for performing a process of synthesizing the extracted map and a mark representing the present position and then displaying them on display means. Also, when there is an overlapped portion between the extracted map and the map being displayed, the display control means performs the synthesizing process with the overlapped portion held.
According to the present invention, a group of maps corresponding to the present position detected by the position detection means is retrieved from the storage means. Also, a map on the same scale as a map being displayed is extracted from the retrieved group of maps. If there is an overlapped portion between the extracted map and the map being displayed, the display control means performs the synthesizing process with the overlapped portion held. With this, both the map being displayed and the extracted map can be displayed as if they were continuous to each other, and the present-position mark can be displayed without being jumped considerably. Therefore, the display is nice to look at and a good sense of operability can be obtained.
In another important aspect of the present invention, there is provided a map display unit, which comprises (1) position detection means for detecting its present position, (2) storage means for storing information about maps on various scales, (3) retrieval means for retrieving a group of maps corresponding to the present position detected by the position detection means from the storage means, (4) extraction means for extracting a map on the same scale as a map being displayed from the retrieved group of maps; and (5) display control means for performing a process of synthesizing the extracted map and a mark representing the present position and then displaying them on display means. Also, when the present position moves out of a map being displayed and a new present position is not present in the stored maps, the display control means displays the new present position at a relative position with respect to the map being displayed, without a map.
According to the present invention, when the present position moves out of a map being displayed and a new present position is not present in the stored maps, the new present position is displayed at a relative position with respect to the map being displayed, without a map. With this, a map without an overlapped portion can be utilized without hindrance.
In a preferred form of the present invention, the map being displayed, a position at which the present position moves out of the map being displayed, and the new present position are displayed at the same time.
According to the preferred form of the present invention, the map being displayed, a position at which the present position moves out of the map being displayed, and the new present position can be displayed at the same time. Therefore, when the present position moves over an area having no map, route guidance can be performed with “the position at which the present position moves out of a map” as a reference.
In another preferred form of the present invention, when the map being displayed is moved out of the screen by movement of the new present position, the display control means displays the direction and distance of the present position with respect to a position at which the map being displayed is moved out, along with the new present position. Therefore, by making reference to the direction and distance of the present position, route guidance can be reliably performed in moving over an area having no map.
In still another preferred form of the present invention, there is provided a map display unit, which comprise

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