Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-12-22
2001-06-12
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S214000
Reexamination Certificate
active
06246959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a positioning apparatus and a positioning information receiving method/apparatus used in the GPS system. More specifically, the present invention is directed to such portable type positioning apparatus and positioning information receiving method/apparatus, capable of minimizing a shift between reception timing and transmission timing of GPS positioning information when GPS positioning operation is restarted.
2. Description of the Related Art
Conventionally, in positioning apparatuses used to measure present positions of the own positioning apparatuses in the GPS (global positioning system) system, the present own positions can be measured by receiving the navigation signals (namely, positioning information) known as ephemeris and almanac signals transmitted from a plurality of GPS satellites. It should be noted that the ephemeris signal corresponds to data related to orbit information of the own satellite as a GPS signal transmitting source and timepiece correction information, whereas the almanac signal corresponds to data related to brief orbit information about all of the GPS satellite. To receive data transmitted from the respective positioning satellites, reception timing of this data is required to be synchronized with transmission timing of the data transmitted from the respective GPS satellites during reception operation. In other words, these positioning apparatuses must capture the GPS satellites. However, since the GPS satellites and these positioning apparatuses are always moved, this transmission timing is continuously changed. In connection with such a positional change, for instance, since a present position of a car navigation apparatus with employment of the GPS system is updated every second, this car navigation apparatus may synchronize the reception timing to the transmission timing to some allowable extent. That is, such a GPS type car navigation apparatus continuously may establish the synchronization between the reception timing and the transmission timing up to a maximum car speed, e.g., several hundreds Km/h. Namely, while the reception timing is once synchronized with the transmission timing, the maximum shift between the transmission timing and the reception timing, which is caused by movement of both the car navigation apparatus and the relevant GPS satellites, is corrected during the next position measuring process operation. In other words, the present position measuring operation is once commenced, and then this present position measuring operation is continuously carried out in such a car navigation apparatus.
However, for example, when a wrist watch type portable positioning apparatus is realized, this portable positioning apparatus may be readily adversely influenced by geographical features and disturbance objects, so that such positioning information can be hardly received, as compared with such a car navigation apparatus capable of updating the present position every second, namely capable of capturing the GPS satellites every second. Furthermore, since the most portable type positioning apparatuses employ cells as power sources thereof, operators are required to frequently turn OFF these power sources. As a result, in such a portable positioning apparatus, every time the present position is measured, the reception timing must be synchronized with the transmission timing of the navigation signal so as to receive the navigation signal, or to capture this GPS satellites. Therefore, there is a problem that lengthy time is necessarily required so as to measure the present position of the own portable positioning apparatus. Also, since relatively high electric power is required in order to measure the present own position, there is another problem that the lifetime of the battery mounted on the portable positioning apparatus is shortened.
SUMMARY OF THE INVENTION
The present invent ion has been made to solve the above-explained problems, and therefore, has an object to provide a positioning apparatus and a positioning information receiving method, capable of minimizing a shift between reception timing of GPS data and transmission timing thereof, while reducing electric power consumption of GPS positioning operation.
To achieve the above-described object, a positioning apparatus, according to an aspect of the present invention, is featured by comprising:
a receiving unit for receiving positioning information transmitted from a plurality of positioning satellites;
a measuring unit for measuring a present position of the own positioning apparatus based upon a plurality of positioning information received from the receiving unit;
a timing holding counter for counting a time instant and for establishing a synchronization between the time count timing thereof and reception timing of the positioning information when the reception operation of the receiving unit is accomplished; and
a control unit for causing the reception timing of the positioning information in the case that the reception operation of the receiving unit is commenced within a preselected time period after such a time instant when the own present position has been measured by the measuring unit during the preceding measuring operation to be synchronized with the time count timing of the timing holding counter.
In accordance with this positioning apparatus, once the present position of the own positioning apparatus is measured by the measuring unit, when the present own position is remeasured within a preselected time period after the first position measuring process operation is ended, positioning information transmitted from a plurality of GPS satellites is received while using as a starting point, the reception timing saved in the timing holding counter during the preceding position measuring process operation. As a result, since there is a small shift between the transmission timing of the positioning information received at the time instant when the position remeasuring process operation is commenced, and the reception timing of this positioning information, the capturing operation of the positioning satellites can be done within a short time period during the position remeasuring process operation.
As a consequence, the above-described positioning apparatus of the present invention can properly perform the desirable positioning operation even under such difficult conditions that this positioning apparatus can hardly receive the present position measurement information (namely, positioning information) due to adverse influences caused by geographical aspects and electromagnetic-wave disturbing objects.
Also, to achieve the object, a positioning information receiving method, according to another aspect of the present invention, is featured by such a method for receiving positioning information transmitted from a plurality of positioning satellites used in a positioning apparatus capable of measuring a present position of the own positioning apparatus, comprising:
a step for saving reception timing of the positioning information at a time instant when a first reception operation of the positioning information is accomplished; and
a step for performing a reception operation of positioning information by employing the saved reception timing when a second reception operation subsequent to the first reception operation is carried out, the second reception operation being located within a predetermined time period after the reception timing saving time instant.
In accordance with this positioning information receiving method, at such a time instant when the position remeasuring process operation is commenced within a preselected time period after the present position measuring process operation has been once carried out, since there is a small shift between the transmission timing of the positioning information received at the time instant when the position remeasuring process operation is commenced, and the reception timing of this positioning information, the capturing operation of the posi
Camby Richard M.
Casio Computer Co. Ltd.
Frishauf, Holtz Goodman, Langer & Chick, P.C.
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