JP2003035763A - Position calculation device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a position calculation device including a GPS receiving unit and a communication unit that communicates with a center station capable of acquiring GPS ephemeris, the power consumption of the GPS calculating unit is reduced by shortening the energizing time of the GPS receiving unit. Reduce power. SOLUTION: A GPS receiving unit 1 for receiving a radio wave from a GPS satellite 11 to calculate a position, a storage unit 3 for holding ephemeris and the like, a clock unit 4, a backup battery 5,
A power supply unit 6, a power switch unit 7 for turning on / off the power supply to the GPS receiving unit 1, a communication unit 8 for communicating with the center station 10, and a display / operation for performing operations such as position display and power on / off. And a control unit 2 for performing on / off control of the power switch unit 7 and control of the entire apparatus. After the communication unit 8 finishes receiving ephemeris from the center station 10, the control unit 2 controls the GPS reception unit 1 by the power switch unit 7.
Turn on the power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position calculating device for receiving a radio wave from a navigation satellite and detailed orbit information of a satellite from a center station to measure its own position, and more particularly to a position calculating device which consumes power by controlling power on / off. The present invention relates to a position calculation device that saves electric power.

[0002]

2. Description of the Related Art Conventionally, as a position calculation device, Japanese Patent Laid-Open No.
One disclosed in Japanese Patent Publication No. 130144 is cited as an example. The configuration diagram is shown in FIG.

As shown in FIG. 10, this position calculating device includes a GPS receiver 21 that receives radio waves from GPS satellites 31 to calculate a position, and a storage unit that holds ephemeris and the like.
23, clock section 24, backup battery 25, power supply section 26
, A communication unit 28 for communicating with a center station (ground station of DGPS) 30, a display / operation unit 29 for displaying a position and turning on / off the power, and a control unit 32 for controlling the entire apparatus.
It has and. Here, since power is supplied from the backup battery 25 to the storage unit 23 and the clock unit 24, the clock unit 24 operates even when the power supply unit 26 is off, and the data stored in the storage unit 23 is retained. It

Next, the operation will be described with reference to FIG. When the display / operation unit 29 is turned on, the power supply unit 26 supplies electric power to the entire device. The control unit 32 has, in the storage unit 23, ephemeris within the valid period (ephemeris has valid period information indicating a period with a small error because the error increases as time elapses). It is confirmed whether or not (Yes) is held, and if the held ephemeris is within the valid period, the ephemeris in the storage unit 23 is sent to the GPS receiver 21. On the other hand, if the held ephemeris is outside the valid period, the center station 30 is requested to request the ephemeris through the communication unit 28, and the center station 30
The ephemeris received from 30 is stored in the storage unit 23 and sent to the GPS receiver 21. Further, the control unit 32 is a clock unit.
The time of 24 is sent to the GPS receiver 21. The GPS receiver 21 selects a receivable GPS satellite 31 based on the ephemeris and time received from the control unit 32 and performs a capture process. If the signal can be captured from the GPS satellite 31, the PRN included in the signal
Measure the phase of the code and measure GPS satellite 31 and GPS receiver 21
And the position of the GPS satellite 31 is calculated using the ephemeris. If the distance between the GPS satellite 31 and the GPS receiver 21 and the position of the GPS satellite 31 can be calculated for three or more GPS satellites 31, the GPS
The position of the receiver 21 can be calculated.

Since the data transmitted from the GPS satellite 31 has the structure shown in FIG. 11 and the ephemeris is included in the data, the ephemeris cannot be acquired without receiving the ephemeris from the center station 30. Possible, but
Transfer rate of data transmitted from GPS satellite 31 is 50b
Since it is ps and the ephemeris is sent every 30 seconds for 12 seconds, it takes at least 12 seconds to acquire the ephemeris from the GPS satellite 31, and it takes 20 seconds or more on average.

Generally, it is possible to synchronize with the signal of the GPS satellite 31 and capture the signal in a few seconds. Therefore, if the ephemeris is held, the position can be calculated in a few seconds.
If the ephemeris needs to be acquired from the GPS satellite 31, it will take several tens of seconds to calculate the position.

Therefore, when the effective ephemeris is not held, by receiving the ephemeris from the center station 30 at a high speed, even the above-mentioned conventional position calculating device has the communication time + the signal acquisition time of the GPS satellite 31 (from several seconds to ten seconds). The position can be calculated in a few seconds.

[0008]

However, in the above-mentioned conventional position calculating device, the GPS receiver 21 is supplied with power while the control unit 23 confirms the effectiveness of the ephemeris and receives the ephemeris from the center station 30. Therefore, there is a problem that useless power is consumed. General GP
Since the power consumption of the S receiver is about 500 mW, the influence is particularly great when the position calculation device is powered by a battery.

The present invention has been made to solve such a problem, and wastes electric power by shortening the energization time of the position calculation unit that receives radio waves from a navigation satellite and calculates the position. It is intended to provide a position calculation device capable of suppressing the consumption of

[0010]

A position calculating device of the present invention communicates with a position calculating unit which receives a radio wave from a navigation satellite and calculates a position, and a center station which provides orbit information of the navigation satellite. A communication unit, a storage unit that holds the orbit information, and a power supply control unit that controls on / off of power supply to the position calculation unit, and the power supply control unit receives orbit information of the navigation satellite from the center station. The power supply to the position calculation unit is turned on after the reception. With this configuration, the time from turning on the power supply to the position calculation unit to performing the positioning calculation can be shortened.

Further, the position calculating device of the present invention is characterized in that when the orbit information is requested to the center station, the orbit information stored in the storage section is transmitted. With this configuration, the number of orbit information sent from the center station to the position calculation device can be reduced.

Further, the position calculating device of the present invention further comprises a deciding means for deciding whether or not to request the orbit information to the center station, the deciding means being the orbit held in the storage section. It is characterized in that whether or not to request the orbit information to the center station is determined according to the validity of the information. With this configuration, it is possible to realize efficient position calculation processing such as reduction of communication frequency with the center station, reduction of position calculation time, reduction of processing load, and speeding up of ephemeris request after long-distance movement.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. There are various navigation satellite systems that receive radio waves from navigation satellites and perform positioning, such as GPS operated by the United States and GLONASS operated by Russia. Although the present invention is applicable to all satellite navigation systems, GPS will be described as an example here.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3 is a block diagram showing a configuration of a position calculation device of the embodiment.

The position calculation device 20 receives a radio wave from a GPS satellite 11 to calculate a position, a storage unit 3 for holding ephemeris, a clock unit 4, a backup battery 5, and a power supply. Unit 6, a power switch unit 7 for turning on and off the power supply from the power supply unit 6 to the GPS receiving unit 1,
A communication unit 8 that communicates with the center station 10, a display / operation unit 9 that performs operations such as position display and power on / off, and a control unit 2 that controls on / off of the power switch unit 7 and the entire device. Is equipped with. Here, the storage unit 3 and the clock unit 4
Since power is supplied from the backup battery 5 to the power source, the clock unit 4 operates even when the power supply unit 6 is off, and the data stored in the storage unit 3 is retained.

FIG. 2 is a flow chart of processing in the position calculating apparatus according to the first embodiment of the present invention. Next, FIG. 1 and FIG.
The operation will be described using.

When the power of the display / operation unit 9 is turned on, the power supply unit 6 supplies power to the entire apparatus (step 10).
1). The control unit 2 requests the ephemeris from the center station 10 through the communication unit 8 (step 102) and stores the ephemeris received from the center station 10 in the storage unit 3 (step 103). Next, the control unit 2 turns on the power switch unit 7 to activate the GPS receiving unit 1 (step 104), and sets the ephemeris, the previous positioning position, and the time of the clock unit 4 stored in the storage unit 3 to the GPS position. Send to receiver 1 (step
105).

The GPS receiving unit 1 uses the ephemeris, the previous positioning position, and the time received from the control unit 2 for all GPs.
The elevation angles of the S satellites 11 are calculated, and, for example, 10 satellites are selected as the satellites to be captured in descending order of elevation angle (step 106). Then, the acquisition processing is performed for the selected satellite (step 107), and if the three or more GPS satellites 11 can be acquired (YES in step 108), the phase of the PRN code is measured and the GPS satellite 11 and the GPS receiver 1 are connected. In addition to calculating the distance between them, the position of the GPS satellite 11 is calculated using the ephemeris, the position of the GPS receiving unit 1 is calculated, and the position is displayed on the display / operation unit 9 (step 10).
9).

Finally, the measured position is stored in the storage unit 3, and the accurate time obtained at the same time is set in the clock unit 4 (step 110).

It should be noted that here, the power switch section 7 is used for GPS.
Although the power of the receiving unit 1 is turned on and off, instead of turning on and off the GPS receiving unit 1 as a whole, the GPS receiving unit 1 is divided into a plurality of parts, for example, a receiving part and an arithmetic processing part, and each part is independently powered. It may be possible to turn it on and off.

As described above, since the position calculating apparatus according to the first embodiment of the present invention turns on the power of the GPS receiving unit 1 after receiving the ephemeris from the center station 10, It is possible to shorten the time from turning on the power to performing positioning calculation. This allows
The energization time of the GPS receiver 1 can be shortened, and wasteful power consumption can be suppressed.

(Second Embodiment) The position calculating apparatus according to the second embodiment of the present invention considers the possibility that there is a satellite whose effective ephemeris is already stored in the storage unit.
When requesting the ephemeris from the center station, the satellite number of the ephemeris and IODE (Is
sue of Data Ephemeris: the Ephemeris issue number) and the center station sends the ephemeris for a satellite that is a visible satellite and is not stored in the memory, or a satellite whose IODE is updated to a new one. The number of ephemeris sent from the center station to the position calculation device can be reduced.

FIG. 3 is a part of a flow chart of processing in the position calculating apparatus according to the second embodiment of the present invention. The configuration of the position calculation device according to the present embodiment is the same as that of the first embodiment, and only a part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 3.

When the power supply unit 6 is turned on (step 20
1), the control unit 2 reads the satellite number and IODE of ephemeris held in the storage unit 3 (step 20).
2) The satellite number and IODE of the ephemeris held in the center station 10 are transmitted through the communication unit 8 to request the ephemeris (step 203). The center station 10 determines from the sent Ephemeris satellite number and IODE,
Ephemeris is transmitted for a satellite which is a visible satellite and is not held in the storage unit 3, or a satellite whose IODE is updated. The position calculation device receives the ephemeris sent from the center station 10 and stores it in the storage unit 3 (step 204). After that, the control unit 2 turns on the power switch unit 7 to activate the GPS receiving unit 1 (step 205). Subsequent processing is the same as the processing from step 105 onward in the first embodiment, and will be omitted.

As described above, the position calculating apparatus according to the second embodiment of the present invention transmits the satellite number and IODE of the ephemeris held in the storage unit 3 to the center station 10, and the center station 10 Since the ephemeris of visible satellites that are not stored in the storage unit 3 or satellites whose IODEs have been updated are transmitted, the number of ephemeris sent from the center station 10 to the position calculation device can be reduced. .

(Third Embodiment) A position calculating apparatus according to a third embodiment of the present invention requests an ephemeris to a center station only when the number of valid ephemeris held is equal to or less than a certain value. By doing so, the frequency of communication with the center station can be reduced, and the position can be calculated more quickly.

FIG. 4 is a part of a flow chart of processing in the position calculating device according to the third embodiment of the present invention. The configuration of the position calculation device according to the present embodiment is the same as that of the first embodiment, and only part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 4.

When the power supply unit 6 is turned on (step 30
1), the control unit 2 reads the expiration date of the ephemeris and the time of the clock unit 4 stored in the storage unit 3 and calculates the number of effective ephemeris (step 302). Then, only when the number of effective ephemeris is N (for example, 5) or less (YES in step 303), the satellite number and IODE of the ephemeris held in the storage unit 3 are transmitted to the center station 10 through the communication unit 8. Request ephemeris (step 304).

The center station 10 transmits the ephemeris from the sent satellite number and IODE of the ephemeris with respect to a satellite which is not a visible satellite and is not held, or a satellite whose IODE is updated to a new one.

The position calculation device receives the ephemeris sent from the center station 10 and stores it in the storage unit 3 (step 305). After that, the control unit 2 turns on the power switch unit 7 to activate the GPS receiving unit 1 (step 30).
6). Subsequent processing is the same as the processing from step 105 onward in the first embodiment, and will be omitted.

As described above, the position calculating device according to the third embodiment of the present invention requests the ephemeris to the center station 10 only when the number of effective ephemeris held in the storage unit 3 is small. The communication frequency with 10 can be reduced. Therefore, the position can be calculated more quickly.

(Fourth Embodiment) In the position calculating apparatus according to the fourth embodiment of the present invention, among the ephemeris held in the storage unit, the remaining time until the expiration date is a certain time or more. By requesting the ephemeris to the center station only when the value is a certain value or less, the frequency of communication with the center station is reduced and the position can be calculated more quickly.

FIG. 5 is a part of a flow chart of processing in the position calculating apparatus according to the fourth embodiment of the present invention. The configuration of the position calculation device according to the present embodiment is the same as that of the first embodiment, and only a part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 5.

When the power supply unit 6 is turned on (step 40
1), the control unit 2 reads the expiration date of the ephemeris and the time of the clock unit 4 held in the storage unit 3, and only the remaining time until the expiration date is a certain time (for example, 1 hour) or more is valid ephemeris. , Calculate the number of effective ephemeris (step 402). Since the subsequent processing is the same as the processing from step 303 onward in the third embodiment, description thereof will be omitted.

As described above, in the position calculating apparatus according to the fourth embodiment of the present invention, among the ephemeris held in the storage unit 3, the ephemeris having a short remaining time until the expiration date is not counted as the effective ephemeris. After processing, when the number of effective ephemeris held is small (for example, 3
By requesting the ephemeris to the center station only (less than or equal to the number), the frequency of communication with the center station 10 can be reduced. Therefore, the position can be calculated more quickly.

(Fifth Embodiment) A position calculating apparatus according to a fifth embodiment of the present invention uses almanac (rough orbit information of all satellites in orbit), current time, and position measured last time. Then, the elevation angles of all GPS satellites are calculated, and if there are a certain number or more of visible satellites or satellites with an elevation angle of a certain value or more in addition to the satellites that hold effective ephemeris,
By requesting the ephemeris from the center station, the frequency of communication with the center station can be reduced and the position can be calculated more quickly.

FIG. 6 is a part of a flow chart of processing in the position calculating apparatus according to the fifth embodiment of the present invention. The configuration of the position calculation device according to the present embodiment is the same as that of the first embodiment, and only a part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 6.

When the power supply unit 6 is turned on (step 50
1), the control unit 2 reads the almanac and the previous positioning position stored in the storage unit 3, and the time of the clock unit 4, and calculates the elevation angles of all GPS satellites 11. If no almanac is stored in the storage unit 3, the center unit 10 is requested to request the almanac, and the received almanac is stored in the storage unit 3.
(Step 502). Next, the control unit 2 reads out the ephemeris stored in the storage unit 3, and
The elevation angles of all the GPS satellites obtained in 502 are equal to or greater than a certain value (for example, 10 degrees or more) and the ephemeris is not held, and the corresponding satellite number is calculated (step 503).

The number of applicable satellites is N (for example, 3).
Only when this is the case (YES in step 504), the satellite number and IODE of the ephemeris held in the storage unit 3 are transmitted to the center station 10 through the communication unit 8 to request the ephemeris (step 505). Subsequent processing is the third
Since it is the same as the processing after step 305 in the above embodiment, the description thereof will be omitted.

As described above, the position calculating apparatus according to the fifth embodiment of the present invention sends to the center station only when there are a large number of receivable satellites (elevation angle is a certain value or more) other than the held ephemeris. Since the ephemeris is requested, the frequency of communication with the center station can be reduced. Therefore, the position can be calculated more quickly.

(Sixth Embodiment) In order to simplify the processing, the position calculating apparatus according to the sixth embodiment of the present invention uses the center when the time elapsed since the last reception of the ephemeris is equal to or more than a certain value. It is a request for ephemeris from the station.

FIG. 7 is a part of a flow chart of processing in the position calculating apparatus according to the sixth embodiment of the present invention. The configuration of the position calculation device of the present embodiment is the same as that of the first embodiment, and only part of the processing is different. Therefore, the different points will be mainly described with reference to FIGS. 1 and 7.

When the power supply unit 6 is turned on (step 60
1), the control unit 2 reads out the time when the last ephemeris was received and the time stored in the clock unit 4, which is held in the storage unit 3, and calculates the elapsed time since the last reception of the ephemeris (step 602). Then, only when the elapsed time is T (for example, 2 hours) or more (YES in step 603), the satellite number and IO of the ephemeris stored in the storage unit 3 are stored.
DE is transmitted to the center station 10 through the communication unit 8 to request ephemeris (step 604).

The center station 10 transmits the ephemeris from the transmitted satellite number and IODE of the ephemeris with respect to a satellite which is a visible satellite and is not held, or a satellite whose IODE is updated.

The position calculation device receives the ephemeris sent from the center station 10 and stores it in the storage unit 3, and further stores the time when the ephemeris was received in the storage unit 3 (step 605). Thereafter, the control unit 2 turns on the power switch unit 7 to activate the GPS receiving unit 1 (step 60).
6). Subsequent processing is the same as the processing from step 105 onward in the first embodiment, and will be omitted.

As described above, the position calculating apparatus according to the sixth embodiment of the present invention determines whether or not to request the ephemeris from the center station 10 based on the elapsed time after receiving the ephemeris from the center station 10. Therefore, the processing load can be reduced.

(Seventh Embodiment) The position calculating apparatus according to the seventh embodiment of the present invention receives the previous ephemeris when the approximate position of the position calculating apparatus can be calculated from the position of the center station. By requesting the ephemeris from the center station when the distance traveled from is a certain amount or more, it is possible to quickly request the ephemeris after moving a long distance.

FIG. 8 is a part of a flow chart of processing in the position calculating device according to the seventh embodiment of the present invention. The configuration of the position calculation device according to the present embodiment is the same as that of the first embodiment, and only a part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 8.

When the power supply unit 6 is turned on (step 70
1), the control unit 2 acquires the position of the center station 10 from the center station 10 through the communication unit 8 (step 702) and assumes that it is the approximate position of the position calculation device.

Next, the control unit 2 reads out the position of the center station 10 when the last ephemeris is received, which is stored in the storage unit 3, and calculates the approximate movement distance after the last ephemeris is received (step). 703).

Then, the moving distance is L (for example, 100 k
m) or more (YES in step 704), the ephemeris satellite number and IODE held in the storage unit 3
Is transmitted to the center station 10 through the communication unit 8 to request the ephemeris (step 705), the ephemeris sent from the center station 10 is received and stored in the storage unit 3, and the center station 10 that has received the ephemeris is received. The position of is stored in the storage unit 3 (step 706).

Thereafter, the control unit 2 turns on the power switch unit 7 to activate the GPS receiving unit 1 (step 70).
7). Subsequent processing is the same as the processing from step 105 onward in the first embodiment, and will be omitted. When the movement distance is less than L (NO in step 704),
The processing after step 302 in FIG. 4 is executed.

As described above, the position calculating device of the seventh embodiment of the present invention uses the moving distance to determine whether or not to request the ephemeris, so that the ephemeris is requested quickly after the long distance movement. can do.

(Eighth Embodiment) A position calculating device according to an eighth embodiment of the present invention uses an approximate position of the position calculating device obtained from a position of a center station, an almanac, and a current time, By calculating the elevation angles of all GPS satellites and requesting the ephemeris from the center station when there are a certain number or more of visible satellites or satellites whose elevation angle is above a certain value, the frequency of communication with the center station is reduced and position calculation is performed. It's designed to be faster.

FIG. 9 is a part of a flow chart of processing in the position calculating apparatus according to the eighth embodiment of the present invention. The configuration of the position calculation device of the present embodiment is the same as that of the first embodiment, and only a part of the processing is different. Therefore, different points will be mainly described with reference to FIGS. 1 and 9.

When the power supply section 6 is turned on (step 80)
1), the control unit 2 acquires the position of the center station 10 from the center station 10 through the communication unit 8 (step 802), reads the almanac held in the storage unit 3 and the time of the clock unit 4, and reads all Calculate the elevation angle of GPS satellite 11. If the almanac is not held, the center station 10 is requested for the almanac, and the received almanac is stored in the storage unit 3 (step 803). The subsequent processing is the same as the processing from step 503 onward in the fifth embodiment, and will be omitted.

As described above, the position calculating apparatus according to the eighth embodiment of the present invention sends to the center station only when there are a large number of receivable satellites (elevation angle is a certain value or more) other than the held ephemeris. By requesting the ephemeris, it is possible to reduce the frequency of communication with the center station. Therefore, the position can be calculated more quickly.

[0058]

As described above, according to the present invention, the energization time of the position calculation unit is shortened by turning on the power supply to the position calculation unit after receiving the navigation satellite orbit information from the center station. Thus, it is possible to provide a position calculation device having an excellent effect of suppressing unnecessary power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a position calculation device according to a first embodiment of the present invention,

FIG. 2 is a flowchart of processing in the position calculation device according to the first embodiment of the present invention,

FIG. 3 is a flowchart of processing in the position calculation device according to the second embodiment of the present invention,

FIG. 4 is a flow chart of processing in a position calculation device according to a third embodiment of the present invention,

FIG. 5 is a flow chart of processing in a position calculation device according to a fourth embodiment of the present invention,

FIG. 6 is a flow chart of processing in a position calculation device according to a fifth embodiment of the present invention,

FIG. 7 is a flowchart of processing in the position calculation device according to the sixth embodiment of the present invention;

FIG. 8 is a flow chart of processing in a position calculation device according to a seventh embodiment of the present invention,

FIG. 9 is a flow chart of processing in the position calculation device according to the eighth embodiment of the present invention;

FIG. 10 is a block diagram showing a configuration of a conventional position calculation device,

FIG. 11 is a configuration diagram of data transmitted from a GPS satellite.

[Explanation of symbols]

1 GPS receiver 2 control unit 3 storage 4 clock section 5 backup battery 6 power supply 7 Power switch section 8 Communications department 9 Display and operation unit 10 Center station 11 GPS satellites

Claims (13)

[Claims] 1. A position calculation unit that receives a radio wave from a navigation satellite and calculates a position, a communication unit that communicates with a center station that provides orbit information of the navigation satellite, and a storage unit that holds the orbit information. And a power supply control unit that controls on / off of power supply to the position calculation unit, and the power supply control unit supplies power to the position calculation unit after receiving orbit information of the navigation satellite from the center station. A position calculation device which is turned on. 2. The position calculation device according to claim 1, wherein when the orbit information is requested to the center station, the orbit information stored in the storage unit is transmitted. 3. The position calculation device according to claim 1, wherein the power supply control unit supplies the power when at least the orbit information is received from the center station. 4. A determination means for determining whether or not to request the orbit information to the center station is further provided, and the determination means is adapted to determine the validity of the orbit information stored in the storage unit. The position calculation device according to claim 1, wherein the position calculation device determines whether or not to request orbit information from the center station. 5. The determining means determines whether or not to request orbit information from the center station according to the number of valid orbit information stored in the storage unit. The position calculation device described in 1. 6. The determination means requests the orbit information to the center station according to the number of valid orbit information stored in the storage unit, which has a remaining time until a valid period is equal to or more than a certain time. The position calculation device according to claim 4, wherein whether or not the position is calculated. 7. The center station determines the determining means according to whether or not there are a certain number or more of visible satellites or satellites having an elevation angle of a certain value or more other than the satellites in which the effective orbit information is held in the storage unit. The position calculation device according to claim 4, wherein it is determined whether or not to request orbit information. 8. The determining means determines whether to request orbit information to the center station according to whether or not the time elapsed since the last time the orbit information was received is equal to or more than a certain time. The position calculation device according to claim 4. 9. The determining means includes means for acquiring a rough position of the self and calculating a moving distance based on the rough position, and whether or not the moving distance after receiving the trajectory information is a certain value or more. The position calculation device according to claim 4, wherein it is determined whether or not to request the orbit information to the center station according to the above. 10. The determining means uses the general position, general satellite orbit information of all navigation satellites, and current time,
It is characterized in that the elevation angle of all navigation satellites is calculated, and whether or not to request orbit information to the center station is determined depending on whether there are a certain number or more of visible satellites or satellites whose elevation angle is a certain value or more. The position calculation device according to claim 9. 11. A center station for providing orbit information to a position calculation device using a navigation satellite, wherein the position calculation is performed when the orbit information held by the position calculation device is received from the position calculation device. A center station, which transmits orbit information not held by the device to the position calculation device. 12. The center station according to claim 11, wherein the orbit information not held by the position calculation device is orbit information of visible satellites. 13. The center station according to claim 11, wherein the orbit information which is not held by the position calculation device is orbit information of the satellite whose orbit information is updated.