Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-08-22
2001-12-25
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S212000, C340S990000
Reexamination Certificate
active
06334090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a GPS terminal and position measuring system which measure the current position of an object by using a GPS (Global Positioning System) and display a map centered on the measured position, and a map display method using them and, more particularly, to a GPS terminal and position measuring system which can automatically change the sale of a map to be displayed, and a map display method using them.
2. Description of the Prior Art
As a system for measuring the current position of a moving object such as a vehicle, a position measuring system called a GPS is widely used, in which a moving object receives radio signals from a plurality of (three or more in general) artificial satellites and measures the current position of the moving object by using the received radio signals.
In a position measuring system using a GPS, map data is stored in a GPS-equipped GPS terminal in advance, and a map centered on the measured position is displayed on the screen of the GPS terminal, thereby allowing the user recognize the current position of the GPS terminal.
Of position measuring systems using GPSs, a network-dependent position measuring system in which each GPS terminal is equipped with a network-dependent GPS to measure the current position of the GPS terminal by using network communication has become popular, as compared with a conventional position measuring system in which each GPS terminal is used singly.
In comparison with a general GPS terminal using a GPS singly, a GPS terminal equipped with a network-dependent GPS exhibits high reception sensitivity with respect to radio signals from artificial satellites and a short communication establishment time for artificial satellites because of accurate calculation of position information on the network side.
According to such a GPS terminal equipped with a network-dependent GPS, when the reception sensitivity level with respect to radio signals from artificial satellites is high, the position of the GPS terminal can be recognized with a precision of several m. When, however, the reception sensitivity level is low, e.g., the GPS terminal is influenced by a multi-path effect between buildings, in a room, or the like, or the network is disconnected, the recognition precision of the position of the GPS terminal deteriorates to several hundred m.
In a general GPS terminal using a GPS singly, while the reception sensitivity level is low, the terminal cannot establish communication with any artificial satellite before deterioration in position recognition precision., and hence the position cannot be quickly recognized.
If, therefore, the reception sensitivity level with respect to radio signals from artificial satellites drops and the position recognition precision deteriorates while a map is displayed on the screen at a small reduction ratio, an accurate map may not be displayed on the screen. Then, the user of the GPS terminal may erroneously recognize the current position more often.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above problems in the prior art, and has as its object to provide a GPS terminal and position measuring system which can reduce the possibility that the user of the GPS terminal may erroneously recognize the current position when the reception sensitivity in the GPS terminal deteriorates and position recognition precision deteriorates, and a map display method using them.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a GPS terminal comprising reception means, equipped with a GPS, for receiving radio signals transmitted from a plurality of artificial satellites, control means for recognizing latitude/longitude data of a current position on the basis of the radio signals received by the reception means, and display means for displaying a map centered on the latitude/longitude data recognized by the control means,
wherein the reception means measures reception sensitivity with respect to the radio signals transmitted form the plurality of artificial satellites, and
the control means automatically changes a scale of the map displayed by the display means on the basis of the measurement result on the reception sensitivity in the reception means with respect to the radio signals.
According to the second aspect of the present invention, there is provided a GPS terminal comprising reception means, equipped with a GPS capable of network communication, for receiving radio signals transmitted from a plurality of artificial satellites, communication means for receiving latitude/longitude data of a current position by network communication with a base station, control means for recognizing the latitude/longitude data of the current position on the basis of the radio signals received by the reception means and the latitude/longitude data received by the communication means, and display means for displaying a map centered on the latitude/longitude data recognized by the control means,
wherein the reception means measures reception sensitivity with respect to the radio signals transmitted from the plurality of artificial satellites, and
the control means automatically changes a scale of the map displayed by the display means on the basis of the measurement result on the reception sensitivity in the reception means with respect to the radio signals.
According to the third aspect of the present invention, in the GPS terminal according to one of the first and second aspects, the reception means measures reception sensitivity with respect to radio signals transmitted from the plurality of artificial satellites upon reception of a request to scale down the map displayed by the display means, and
the control means automatically changes the scale of the map displayed by the display means on the basis of the measurement result on the reception sensitivity in the reception means with respect to the radio signals.
According to the fourth aspect of the present invention, in the GPS terminal according to any one of the first to third aspects,
the terminal further comprises storage means for storing a wide-area map in advance, and
the control means displays the wide-area map stored in the storage means upon changing a scale of the wide-area map on the basis of the measurement result in the reception means with respect to the radio signals.
According to the fifth aspect of the present invention, in the second or third aspect, the control means accesses the Internet through the communication means and the base station, downloads a map whose scale is changed from a map server on the Internet on the basis of the measurement result on the reception sensitivity in the reception means with respect to the radio signals, and displays the map on the display means.
According to the sixth aspect of the present invention, there is provided a position measuring system comprising a base station which is equipped with a GPS capable of network communication and receives radio signals transmitted from a plurality of artificial satellites, and a GPS terminal which is equipped with a GPS capable of network communication, receives radio signals transmitted from the plurality of artificial satellites, recognizes latitude/longitude data of a current position by performing network communication with the base station, and displays a map centered on the latitude/longitude data,
wherein the GPS terminal measures reception sensitivity with respect to the radio signals transmitted from the plurality of artificial satellites, and automatically changes a scale of the displayed map on the basis of the measurement result.
According to the seventh aspect of the present invention, in the position measuring system according to the sixth aspect,
the GPS terminal comprises:
reception means for receiving radio signals transmitted from a plurality of artificial satellites and measuring reception sensitivity with respect to the radio signals transmitted from the plurality of artificial satellites;
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Cuchlinski Jr. William A.
Hernandez Olga
NEC Corporation
Sughrue & Mion, PLLC
LandOfFree
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