Positioning signal transmission apparatus

A reception high-frequency unit receives a GPS signal transmitted from a satellite configuring GPS. A signal generation unit generates a plurality of pseudo random noise codes that are used for the positioning operation by a positioning apparatus for implementing a positioning operation based on the GPS signal and that are in the same form as that of the GPS signal. A transmission high-frequency unit generates and transmits based on the pseudo random noise codes, a positioning signal in the same form as that of the GPS signal. A transmission control unit controls the transmission high-frequency unit in such a way that a time difference based on the GPS signal received by the reception high-frequency unit is assigned to each positioning signal and the thus-assigned positioning signal is transmitted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a technology of positioning a position using a radio signal. Especially, it is related to a technology of improving the convenience when the position of a mobile station is positioned using a global positioning system (GPS)

2. Description of the Related Art

Recently, an apparatus with a position-positioning function using GPS has become more and more widespread.

A GPS receiver (GPS positioning apparatus) for the position-positioning using a radio signal (hereinafter, referred to as “GPS signal”) that is transmitted from a satellite configuring the GPS has a system for the position-positioning at two or more dimensions with high accuracy using signals transmitted from, for example, three or more satellites from among the signals transmitted from about twenty-four satellites circulating around the earth. This GPS technology is also used in car navigation systems and PDAs (Personal Digital Assistant: portable type information communication devices for individual users). According to this technology, the position-positioning of a mobile station or a user is implemented.

Since the GPS receiver implements the position-positioning using a GPS signal, preferable position-positioning cannot be theoretically implemented in such an environment where the line-of-sight between a satellite and a mobile station (GPS receiver) is interfered. Accordingly, a mobile station cannot position its own position in a space which is not exposed to the sky, for example, indoors, in cars or the like and where a GPS signal cannot be directly received (hereinafter, referred to as a GPS signal non-receipt area) in a mobile station. Here, the sky indicates a range of about ±90 degrees to the zenith of a mobile station. Furthermore, the fact that a satellite exists in the sky indicates that the satellite exists (can be seen) in about ±90 degrees to the zenith of a mobile station if there is no obstacle in the way.

Regarding this technology, Japanese patent application laid-open publication No. 2000-111648 (hereinafter, referred to as [document 1]) discloses a technology such that a position ID oscillator for emitting infrared rays signal including position ID is provided indoors and a mobile station is configured to receive the radio wave from a satellite outdoors while it receives the infrared rays signal indoors, thereby enabling the position-positioning of a mobile station irrespective of whether the mobile station is indoors or outdoors.

In Japanese patent application laid-open publication No. 2003-57330 (hereinafter, referred to as [document 2]) discloses a technology of specifying the present position of a mobile station that is moving in a GPS signal non-receipt area by re-radiating a GPS signal to the GPS signal non-receipt area indoors, etc. and by radiating the pre-stored latitude and longitude data to this area using a position data transmission apparatus.

The following is the explanation of the outline of the positioning method using a GPS receiver.

A GPS receiver receives a GPS signal that is transmitted from a plurality of satellites with the same frequency. Each satellite generates a GPS signal based on a diffuse spectrum communication system using a pseudo random noise code having different code arrays. Therefore, the GPS receiver can receive and process with the same frequency the GPS signals that are transmitted from a plurality of satellites. Then, the GPS receiver calculates the attainment time of a signal from each satellite on the basis of the time when this pseudo random noise code is received. Meanwhile, the pseudo random noise code includes a C/A cord and a P cord (Y cord) that is kept confidential in order to restrict a user. The code that is generally disclosed is only C/A cord.

Furthermore, the GPS signal includes a navigation message in which the orbit information (ephemeris), the calendar (almanac), etc. of the satellite is shown together with the pseudo random noise code.

The almanac indicates orbit information about the outlines of all the satellites other than its own satellite that configure GPS, that is, the timetable of satellites. Accordingly, this information is used for determining a satellite that can be acquired by the GPS receiver. On the other hand, the ephemeris shows the exact position of its own satellite and it is this important information that is needed to calculate the position of a mobile station. The GPS receiver calculates the distance from each satellite using the attainment time of the signal from each satellite and then calculates the own position using those distances (at least three distances) and the orbit information about the satellites.

Furthermore, before receiving the GPS signal and starting the position-positioning, the GPS receiver selects the satellite that can be acquired during that period of time on the basis of the almanac received in the past. Subsequently, the GPS receiver implements a search operation for acquiring the signal from a satellite while subtly changing the clock frequency of the GPS receiver. This search operation usually requires several to several tens of seconds. However, in the case where the received almanac becomes old since the GPS receiver has not been used for a long time or in the case where the GPS receive is moved from the position where the positioning operation is previously implemented to the position that is far from the previous position, it takes a longer time since the GPS receiver automatically implements operations for acquiring all the satellites (it takes longer than twelve minutes and thirty seconds to receive all the almanacs).

Accordingly, in the case where the power of the GPS receiver is on and the almanac is kept old and not updated since the GPS receiver is positioned in a GPS signal non-receipt area for a long time, the initial positioning time requires a long time when the mobile station comes into a position where the GPS signal can be directly received.

Similarly, in the case where the power of the GPS receiver is on in the GPS signal non-receipt area and the ephemeris is kept old and not updated since the GPS receiver stays in the GPS signal non-receipt area for a long time, etc., the accuracy sometimes deteriorates at the time of the initial positioning.

Regarding this point, for example, Japanese patent application laid-open publication No. 7-280917 (hereinafter, referred to as [document 3]) discloses a technology of re-transmitting a GPS signal to a GPS signal non-receipt area so that the mobile station that moves in the GPS signal non-receipt area can be promptly positioned when the mobile station comes into a position where the GPS signal can be directly received. Additionally, this article discloses another technology of implementing maintenance, inspection, repair, etc. of the GPS receiver even indoors where the GPS signal cannot be received.

Meanwhile, the latest car navigation systems offer an apparatus for continuing the positioning of the own apparatus using a gyrocompass, a direction sensor, a distance sensor, etc. even in the position where such a GPS signal cannot be received.

The positioning method using a GPS receiver is described in detail, for example, in the following document. Jun Tsuchiya and Hiroshi Tsuji: “Foundation of new GPS measurement”, Japan Association of Surveyors, Sep. 30, 2002.

In the technology that is disclosed in the document 1, a reception unit for receiving the infrared rays signal including position ID is required so that the hard scale of a mobile station increases. Furthermore, position ID is required to be set up for each position ID oscillator and at the same time, a position coordinate should be stored in advance for each position ID of the mobile station. Since almanac and ephemeris are not updated while a mobile station stays indoors, the initial positioning time is delayed when the mobile station comes outdoors and can directly receive a GPS signal.

According to the above-mentioned technology disclosed in the document 2, it is necessary to store in advance the latitude and longitude data about the position of a transmission apparatus in this apparatus. Additionally, a receiver that can receive both the GPS signal and the latitude and longitude data in the mobile station is required. In the case where a GPS signal is received or the latitude and longitude data is received, the processing becomes complicated by adding a procedure for determining whether the position positioned by the GPS signal or the latitude and longitude data should be used. Furthermore, in the case where the position-positioning is implemented using the GPS signal that is re-transmitted, the GPS signal is not propagated through the original propagation path but through the re-transmission apparatus. Consequently, the accuracies of the positioning results sometimes become low since an error occurs on the attainment time of the GPS signal.

Even in the technology disclosed in either document 1 or 2, the latitude and longitude data that is stored in advance is transmitted to the mobile station in a GPS signal non-receipt area. Therefore, in the case where the GPS signal non-receipt area itself moves, for example, in the case where the GPS signal non-receipt area is an area in a car, a ship, an airplane, etc. and the terminal possessed by a person who is in the car, etc., is a mobile station, this technology cannot be used.

In the technology that is disclosed in the above-mentioned document 3, a mobile station can be promptly positioned when it comes into a position where the GPS signal can be directly received. However, in the case where the position-positioning is implemented using the GPS signal that is re-transmitted, the GPS signal is not propagated through the original propagation path but through the re-transmission apparatus. Consequently, the accuracies of the positioning results become low since an error occurs on the attainment time of the GPS signal.

In an apparatus for continuing a positioning operation for the own position in the GPS signal non-receipt area among the car navigation system, etc. using a gyrocompass, a direction sensor, a distance sensor, etc., the outputs of various kinds of sensors include errors so that the accuracies of the positioning results become low. Especially, in the case where the terminal possessed by a person is a mobile station, the output errors of such various kinds of sensors increase in accordance with the attitude and movement of the person so that the accuracies of the positioning results might further decrease.

SUMMARY OF THE INVENTION

The subject of the present invention is to implement the highly-accurate position-positioning using a GPS positioning apparatus in a GPS signal non-receipt area and also to direct the GPS positioning apparatus to be promptly positioned when this apparatus comes into a position where the GPS signal can be directly received, thereby increasing the positioning accuracy.

A positioning signal transmitting apparatus according to one of the preferred embodiments of the present invention comprises a reception unit for receiving a GPS signal transmitted from a satellite configuring a global positioning system (GPS); a signal generation unit for generating a plurality of positioning signals that are used for the positioning by a positioning apparatus for implementing the positioning based on the GPS signal and that are in a same form as that of the GPS signal; a transmission unit for transmitting the positioning signals; and a transmission control unit for controlling the transmission unit in such a way that this unit assigns a time difference based on the GPS signal received by the reception unit to each of the positioning signals and transmits the assigned positioning signals.

According to this configuration, since the positioning signal that is in the same form as that of a GPS signal is transmitted, the positioning apparatus need not be provided with a means for receiving the information other than a GPS signal so that the position-positioning can be implemented even in a GPS signal non-receipt area by receiving this positioning signal. Furthermore, a time difference based on the GPS signal that is received by the reception unit is assigned to each of the positioning signals to be transmitted. Therefore, the time difference of the transmission timing of positioning signals can be corrected with a high degree of accuracy by receiving the GPS signals from a plurality of satellites by the reception unit. Consequently, the positioning apparatus can implement the highly-accurate positioning based on this corrected positioning signal.

Meanwhile, in a positioning signal transmission apparatus according to the present invention, the signal generation unit can be configured to generate at least three kinds of positioning signals showing that transmission sources are different to each other.

In this way, the position-positioning at least at the two dimensions can be implemented by the positioning apparatus.

Furthermore, in the positioning apparatus according to the present invention, the signal generation unit can be configured to generate a positioning signal based on a navigation message shown in the GPS signal received by the reception unit.

Then, a positioning signal in a same form as that of the GPS signal that is not received by the reception unit can be generated.

Meanwhile, the transmission control unit can be configured to implement a control based on the navigation message shown in the GPS signal.

Thus, a positioning signal in a same form as that of the GPS signal that is not received by the reception unit can be controlled.

Furthermore, in the positioning signal transmission apparatus of the present invention, the signal generation unit can be configured to generate at least three kinds of positioning signals showing that the transmission sources are different to each other by configuring this unit to generate the positioning signal using pseudo random noise codes with different patterns.

Furthermore, in the positioning signal transmission apparatus of the present invention, the transmission unit can be configured to transmit the positioning signal including the navigation message shown in the GPS signal received by the reception unit.

In this way, when the reception unit comes into a position where the GPS signal can be directly received, this unit can be promptly positioned and the positioning accuracy is increased.

Furthermore, in the positioning signal transmission apparatus, the reception unit can be mounted in a position where the GPS signal is preferably received in comparison with the positioning apparatus.

Thus, the accuracy of the positioning apparatus is enhanced by receiving GPS signals from a plurality of satellites.

In the positioning signal transmission apparatus of the present invention, the transmission unit can be configured to direct a transmission direction of the positioning signal to have a directivity.

In this way, the interference of the positioning signals is suppressed in the case where the positioning signal transmission apparatuses are adjacently mounted, thereby decreasing the effect of the positioning signal that is transmitted from the adjacently mounted positioning signal transmission apparatus and is not used for the position-positioning, on the position-positioning performed at the positioning apparatus.

Furthermore, in the positioning signal transmission apparatus of the present invention, the signal generation unit can be configured to generate the positioning signal in a same form as that of the GPS signal transmitted by the satellite that is present in the sky when the positioning signal is generated, which is shown in the navigation message in the GPS signal received by the reception unit.

In this way, the positioning apparatus for implementing the search of a signal based on the navigation message can easily acquire the positioning signal transmitted from the positioning signal transmission apparatus.

Furthermore, in the positioning signal transmission apparatus of the present invention, the transmission control unit can be configured to implement the control so as to assign to each positioning signal a time difference according to a propagation time of the GPS signal from the satellite to the reception unit, thereby transmitting the assigned positioning signal.

Regarding the propagation time, the calculation accuracy can be enhanced by receiving GPS signals from a plurality of satellites so that the accuracy of the position-positioning by the positioning apparatus based on a positioning signal is also enhanced by implementing the above-mentioned operations.

At this time, the transmission control unit can be configured to calculate a propagation time of the GPS signal based on a position of the satellite shown in both a navigation message of the GPS signal and a position of the reception unit positioned based on the GPS signal.

In this way, positioning signals generated for the satellites of transmission sources of the GPS signals that are not fully received by the reception unit can be controlled.

At this time, the transmission control unit can be configured to calculate a propagation time of the GPS signal based on an altitude difference between a position of the reception unit and that of a positioning apparatus for receiving a positioning signal transmitted by the transmission unit.

In the case where the height of a mounting position of the reception unit and that of the positioning apparatus are too high to be ignored, the accuracy of the position-positioning performed by the positioning apparatus based on positioning signals can be enhanced.

Furthermore, in the positioning signal transmission apparatus, a detection unit for detecting the approach of a mobile station into a predetermined area is further provided and the transmission control unit can be configured to control the transmission unit in such a way that this unit transmits the positioning signal according to a detection of the approach.

According to this configuration, the electric power of the positioning signal transmission apparatus can be decreased and at the same time, in the case where the position signal transmission apparatuses are adjacently mounted, the interference between positioning signals can be prevented.

Furthermore, the positioning signal transmission apparatus is configured in such a way that the reception unit and the transmission unit are separately mounted and the transmission of a signal from the reception unit to the transmission unit is implemented through a signal cable.

In this way, it becomes easy to mount the reception unit in, for example, a position where the GPS signal preferably comes, separately from the transmission unit.

In the positioning signal transmission apparatus of the present invention, the reception unit and the transmission unit are separately mounted and the transmission of a signal from the reception unit to the transmission unit is implemented through a radio transmission path.

In this way, it becomes easy to mount the reception unit in, for example, a position where the GPS signal preferably comes, separately from the transmission unit.

Meanwhile, in the positioning signal transmission apparatus of the present invention, the signal transmission unit can be configured to generate the positioning signal in a same form as that of a GPS signal transmitted by the satellite that is present in the sky at a time of generating the positioning signal, which is shown in the navigation message but that cannot be used for the positioning in a position of the reception unit when generating the positioning signal.

Thus, it becomes possible to direct the positioning apparatus that receives the positioning signal to recognize that the positioning signal being received is not from the satellite but from the positioning signal transmission apparatus.

The positioning signal transmission apparatus of the present invention can be configured in such a way that the transmission unit includes a transmission antenna for transmitting the positioning signal, the reception unit includes a reception antenna for receiving the GPS signal, the transmission antenna and the reception antenna are separately mounted and the transmission control unit implements a control based on a difference between a position of the transmission antenna and that of the reception antenna.

In this way, the deterioration of an accuracy of the position-positioning by the positioning apparatus in which the transmission antenna and the reception antenna are separately mounted can be suppressed.

According to the method of transmitting a positioning signal of another preferred embodiment of the present invention comprises steps of generating a plurality of positioning signals that are used for a positioning operation by a positioning apparatus for implementing a positioning operation based on a GPS signal transmitted from a satellite configuring a global positioning system (GPS) and that are in a same form as a form of the GPS signal and assigning a time difference based on the received GPS signal to each positioning signal, thereby transmitting the assigned positioning signals.

By the above-mentioned method, the operation identical to that of the above-mentioned positioning signal transmission apparatus of the present invention can be also obtained.

A positioning apparatus of another preferred embodiment of the present invention is used in a positioning system including a positioning apparatus for implementing the positioning based on a GPS signal transmitted from the satellite configuring a global positioning system (GPS) and a positioning signal transmission apparatus for transmitting a positioning signal that is used for the positioning by the positioning apparatus and that is in a same form as that of the GPS signal. The positioning signal transmission apparatus comprises a reception unit for receiving the GPS signal; a signal generation unit for generating a plurality of positioning signals; a transmission unit for transmitting the generated positioning signal by the signal generation unit; a transmission control unit for controlling the transmission unit in such a way that this unit assigns a time difference based on a GPS signal received by the reception unit to each positioning signal and transmits the assigned positioning signal. The transmission unit transmits the positioning signal including a navigation message shown in the GPS signal received by the reception unit. The positioning apparatus comprises a signal reception unit for receiving a signal used for the positioning; a determination unit for determining, based on the navigation message included in the signal, whether or not a signal received by the signal reception unit is transmitted by the positioning signal transmission apparatus; and a notification unit for notifying the determination results.

By the above-mentioned positioning apparatus, the operation of the positioning apparatus of the present invention can be obtained. Furthermore, it can be recognized whether or not the positioning signal being received is from a satellite or the positioning signal transmission apparatus, thereby notifying the recognition results to a user of the positioning apparatus.

In the positioning apparatus of the present invention, the signal generation unit can be configured to generate the positioning signal in a same form as that of a signal transmitted by the satellite that is not present in the sky, which is shown in the navigation message. The determination unit can be also configured to determine that the positioning signal is transmitted by the positioning signal transmission apparatus in the case where the signal reception unit receives the positioning signal in a same form as that of a signal transmitted by the satellite that is not present in the sky, which is shown in the navigation message.

In this way, it can be determined by the determination unit based on the navigation message whether or not the signal received using the signal reception unit is transmitted by the positioning signal transmission apparatus.

Consequently, the present invention can realize the precise position-positioning using a GPS positioning apparatus in a GPS signal non-receipt area.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is the explanation of the preferred embodiments of the present invention in reference to the drawings.

FIG. 1shows the first mounting example of a positioning signal transmission apparatus for implementing the present invention and especially it shows an example of mounting a positioning signal transmission apparatus2in a vehicle5.

InFIG. 1, a mobile station provided with a positioning apparatus3that can implement the positioning on the basis of a GPS signal is a person4. The positioning apparatus3is attached to the person4or the person4carries the positioning apparatus3.

A reception antenna7of the positioning signal transmission apparatus2is mounted outside etc. a vehicle5where a radio wave (that is, a GPS signal10) from a satellite1configuring GPS comes more preferably than at the present position of the positioning apparatus3, which is apparent.

A transmission antenna8is mounted for enabling a positioning signal11that is the output of the positioning signal transmission apparatus2to reach to the positioning apparatus3in the vehicle5. In the present embodiment, the transmission apparatus2outputs at least three kinds of the positioning signals11so that at least three transmission antennas8are mounted. Furthermore, the positioning result of the positioning apparatus3shows the position of the reception antenna7. Therefore, an antenna that has the directivity, for example, an array antenna, etc. is used as the transmission antenna8so that an attainment range9of the positioning signal11is restricted as occasion demands.

The positioning signal transmission apparatus2receives the GPS signal10from the satellite1and positions its own position. Then, the apparatus generates at least three pseudo random noise codes based on this positioned position and the navigation message that is shown in the received GPS signal10and assigns a time difference to each pseudo random noise code by delaying the code, thereby transmitting these codes as the positioning signals11from the transmission antenna8. Furthermore, the form (carrier wave frequency, radio wave form, modulation method, information storage form, etc.) of the positioning signal11is the same as that of the GPS signal10. That is, the form of the positioning signal11is such that the positioning apparatus3that receives the positioning signal11can easily implement the position-positioning based on the positioning signal11.

The time difference that is assigned to the positioning signal11at this time is controlled in such a way that the positioned position becomes the same as that of the positioning signal transmission apparatus2in the case where the positioning apparatus3for receiving the positioning signal11implements the position-positioning. According to this control, the positioned position of the positioning apparatus3is the same as that of the positioning signal transmission apparatus2as long as the positioning apparatus3receives the positioning signal11. Accordingly, the positioning apparatus3can continue the positioning without directly receiving the GPS signal10.

Furthermore, the navigation message that is shown in the received GPS signal10is included in the positioning signal11in accordance with the signal form of the GPS signal10. In this way, the positioning apparatus3can sequentially update the navigation message without directly receiving the GPS signal10since it receives the positioning signal11. Consequently, the apparatus3can be promptly conditioned when it comes out of the vehicle5where the GPS signal10can be directly received.

The following is the explanation ofFIG. 2.FIG. 2shows the second mounting example of the positioning signal transmission apparatus for realizing the present invention and especially shows an example of mounting the positioning signal transmission apparatus2on a building6that is built on the ground.

InFIG. 2, a mobile station provided with the positioning apparatus3for implementing the positioning on the basis of the GPS signal is the person4. The positioning apparatus3is attached to the person4or the person4carries the positioning apparatus3.

The reception antenna7of the positioning signal transmission apparatus2is mounted on the roof, etc. outside the building6where a radio wave (that is, the GPS signal10) from the satellite1configuring GPS comes more preferably than in the present position of the positioning apparatus3, which is apparent.

The transmission antenna8is mounted for enabling the positioning signal11that is the output of the positioning signal transmission apparatus2to reach to the positioning apparatus3inside the building6. In the present preferred embodiment, the positioning signal transmission apparatus2outputs at least three kinds of the positioning signals11so that at least three transmission antennas8are mounted for each positioning signal transmission apparatus2. The positioning result of the positioning apparatus3shows the position of the reception antenna7so that an antenna having the directivity, for example, an array antenna, etc. is used as the transmission antenna8. As occasion demands, the attainment range9of the positioning signal11is restricted.

InFIG. 2, three positioning signal transmission apparatuses2are mounted on the building6but the number of these apparatuses mounted on the building6can be changed according to the accuracy that is required for the positioning in the building6using the positioning apparatus3or the width of the building6.

Furthermore, in the case where a plurality of the positioning signal transmission apparatuses2is mounted on the building6, the attainment range9of the positioning signal11is narrowly restricted by sharpening the directivity of the transmission antenna8of the positioning signal transmission apparatus2. Accordingly, the influence (interference etc. of the positioning signal11) of adjacently mounted positioning signal transmission apparatus2on the positioning of the positioning apparatus3can be prevented. Here, if the number of the positioning signal transmission apparatuses2mounted on the building6increases and the attainment range9for each positioning signal transmission apparatus2is narrowed, the relative position relation between the positioning apparatus3for implementing the positioning based on the positioning signal11and the signal transmission apparatus2for outputting the positioning signal11become closer by the narrowed amount. Consequently, the accuracy of the positioning using the positioning apparatus3improves.

Furthermore, also in the mounting example shown inFIG. 2like that shown inFIG. 1, the navigation message that is shown in the received GPS signal10is included in the positioning signal11in accordance with the signal form of the GPS signal10. In this way, the positioning apparatus3can sequentially update the navigation message without directly receiving the GPS signal10since it receives the positioning signal11. Consequently, the apparatus3can be promptly conditioned when it comes out of the building6where the GPS signal10can be directly received.

The following is the explanation ofFIG. 3.FIG. 3is a block diagram showing the configuration of the positioning signal transmission apparatus2for realizing the present invention. InFIG. 3, the reception antenna7, a reception high-frequency unit21, a reception signal processing unit22and a positioning computation unit26function in the same way as those of the units mounted on the well-known GPS receiver.

The reception antenna7receives a radio wave from the satellite1configuring GPS, that is, the GPS signal10. The reception antenna7is mounted in the position where the radio wave from the satellite1comes preferably. For example, the reception antenna7is mounted sufficiently far from the transmission antenna8. Otherwise, an electromagnetic wave shield should be mounted between the reception antenna7and the transmission antenna8or the like to prevent the reception antenna7from receiving the positioning signal11that is transmitted from the transmission antenna8.

The reception high-frequency unit21amplifies the GPS signal10that is received by the reception antenna7up to a predetermined signal level and at the same time it analogue-digital converts the amplified signal.

The reception signal processing unit22calculates a pseudo range23from each satellite1on the basis of the GPS signal10that is converted into digital data and at the same time it takes out a navigation message24from the GPS signal10to be supplied to the positioning computation unit26. Furthermore, in order to offer the high positioning accuracy, it is possible to obtain a carrier wave phase25and supply the obtained phase to the positioning computation unit26.

The following is the explanation of the pseudo range23.

The pseudo range23is a pseudo range between the satellite1and the positioning signal transmission apparatus2(reception antenna7) and this range can be calculated by an equation such as (pseudo propagation delay time)×(light velocity). Here, this pseudo propagation delay time includes a difference between the time indicated by a clock possessed by the satellite1and the time indicted by a clock possessed by the signal processing unit22. Accordingly, the pseudo range23is an algebraic sum of the real distance from the satellite1to the positioning signal transmission apparatus2and the distance error based on the clock error.

In the case of the two-dimensional positioning for positioning only a position on the surface of earth without positioning a position in a height direction, the real distance is obtained from a total of three unknowns of this clock error and two-dimensional coordinate so that at least three pseudo ranges23from satellites1are required.

Thus, at least three pseudo rages are required in the case of two-dimensional positioning and accordingly at least three reception signal processing units22are also required. Furthermore, in a usual GPS receiver, eight or eighteen reception signal processing units22are sometimes mounted by reason of enabling the three-dimensional positioning for positioning the position in a height direction, by reason of enhancing the positioning accuracy by obtaining the unknowns using a least-square method on the basis of the pseudo ranges23from many satellites1, or the like.

The positioning computation unit26calculates a positioned position27etc. of the positioning signal transmission apparatus2(reception antenna7) on the basis of at least three pseudo ranges23, the navigation message24and the carrier wave phase25that are supplied from the reception signal processing unit22. Then, the unit26supplies the calculated positioned position27etc. to a transmission control unit30and at the same time it supplies the navigation message24to a signal generation unit28and the transmission control unit30.

The signal generation unit28selects the satellite1that exists in the sky at that point in reference to the navigation message24and generates the pseudo random noise code29(C/A cord: Clear and Acquisition Code or Coarse and Access Code) regarding the selected satellite1, thereby transmitting the generated code to the transmission control unit30. In order to enable the two-dimensional positioning using the positioning apparatus3, the signal generation unit28selects at least three satellites that exist in the sky at that point and generates the pseudo random noise code29for each of the selected satellites1. Consequently, at least three kinds of pseudo random noise codes29are generated.

The pseudo random noise code29is a cord that is individually assigned to each of the satellites1configuring GPS and this code is used for the GPS receiver to specify from which satellite the received signal is transmitted. Namely, the signal generation unit28generates the pseudo random noise code29that is the same as the code of the GPS signal10transmitted from the satellite1.

The transmission control unit30calculates the distance to each satellite1that is selected by the signal generation unit28according to the positioned position27and the orbit information about the satellite that is shown in the navigation message24. Furthermore, the unit30calculates a time (propagation time) required when a radio wave propagates each calculated distance. Then, the unit calculates the difference among the calculated propagation times with regard to the respective satellites1and assigns the propagation time differences to the codes by individually delaying the respective pseudo random noise codes29, thereby supplying the assigned codes to a transmission high-frequency unit31. In order to delay the pseudo random noise code29, the generated pseudo random noise code29is stored once in a semiconductor memory and the generated pseudo random noise code29is read out from the memory at a timing based on the above-mentioned time difference.

Furthermore, the signal generation unit30includes the navigation message24that is obtained from the satellite1in the pseudo random noise code29that is generated to belong to the satellite1. Then, the thus-processed pseudo random noise code29is supplied to the transmission control unit30. As a method of including the navigation message24in the pseudo random noise code29, a method that is publicly-known in the field of the GPS can be used as it is.

The transmission high-frequency unit31PSK-modulates (Phase Shift Keying) using the pseudo random noise code29the carrier wave having a frequency same as that used in a GPS satellite in accordance with the publicly-known diffuse spectrum communication system that is used in a GPS satellite. Then, the unit31amplifies the obtained modulation signal up to a specified signal level so as to obtain the positioning signal11. Then, the obtained positioning signal11is supplied to the transmission antenna8to be transmitted. In this way, the positioning signal11is identical to the GPS signal10in the form of a signal such as a carrier wave frequency, a radio wave form, a modulation form, an information storage form, etc. Therefore, if the positioning apparatus3can implement the positioning on the basis of the GPS signal10, this apparatus can also implement the positioning based on the positioning signal11.

Furthermore, at least three kinds of the pseudo random noise codes29are generated as mentioned above. Therefore, at least three transmission high-frequency units31are mounted to correspond one-to-one with the codes. Then, the generated three kinds of pseudo random noise codes29are supplied to the respective transmission high-frequency units31for each kind and the positioning signal11is transmitted in accordance with the time difference that is assigned to the pseudo random noise code29using the transmission control unit30.

Furthermore, it is assumed inFIG. 3that the signal generation unit28generates three kinds of the pseudo random noise codes29and consequently three kinds of the transmission high-frequency units31are also mounted. Here, in the case where the three-dimensional positioning is implemented by the positioning apparatus3, the signal generation unit28generates four kinds of the pseudo random noise codes29and four kinds of the transmission high-frequency units31are also mounted.

For the transmission antenna8, an antenna that has the directivity, for example, an array antenna, etc. is used and the attainment range9of the positioning signal11is restricted as occasion demands. Furthermore, the above-mentioned action is taken to prevent the positioning signal11that is transmitted from the transmission antenna8from being received by the reception antenna7.

The following is further explanation of a delay processing of the pseudo random noise code29by the signal generation unit30.

FIG. 4shows one example of the relation between the arrangement of satellites in the sky and the reception situation of GPS signals.

In the example ofFIG. 4, it is assumed that the positioning signal transmission apparatus2mounted outside the vehicle5recognizes that eight satellites from SV1to SV8exist in the sky at present based on the contents of the navigation message included in the previously-received GPS signal10. It is further assumed that the GPS signals10from the respective satellites from SV2to SV6each having the comparatively high angle of elevation among the satellites can be actually received at a sufficient signal level. On the other hand, the respective signal levels regarding the GPS signals10from the respective satellites such as SV1, SV7and SV8each having the comparatively low angle of elevation are not sufficient so that these signals cannot be used for the position-positioning. Furthermore, it is assumed that the positioning signal transmission apparatus2has at least five reception signal processing units22.

Here,FIG. 5is explained.FIG. 5shows the acquisition timings of the pseudo random noise codes that are obtained from the GPS signals10of the respective satellites, which are received using the positioning signal transmission apparatus2inFIG. 4.

In the following explanation, for the simplification of the explanation, it is assumed that the correction rate of a clock possessed by each satellite included in a navigation message is already reflected and the times of clocks of the respective satellites are in synchronization with a standard time. In addition, the pseudo random noise codes are repeatedly received in cycles of 1 ms but hereFIG. 5shows the reception timings of the pseudo random noise code that assigns the realistic positioning solution in the neighborhood of the surface of earth.

InFIG. 4, it is assumed that the time of the clock possessed by the positioning signal transmission apparatus2is delayed by only Te regarding the standard time of a satellite. Accordingly, the propagation delay time of the pseudo random noise code transmitted from, for example, the satellite SV2is observed by the positioning signal transmission apparatus2as the total time (Te+T2) that is obtained by adding a delay time Te from the standard time and a real propagation delay time T2of the GPS signal from the satellite SV2. This total time becomes the above-mentioned pseudo delay time regarding the satellite SV2. Same applies to the propagation delay time of the GPS signal with regard to each of other satellite SV3to SV6.

As mentioned before, in the case of the two-dimensional positioning of only a position on the surface of earth, a total of three unknowns such as an error Te and a two-dimensional coordinate of this clock (for example, the coordinate (X, Y)) should be obtained. In order to obtain the unknowns, the simultaneous equation including three equations using the coordinate of at least three satellites and the attainment time of the GPS signals10from these satellites should be solved. Here, the positioning computation unit26calculates the pseudo range23of each of a total of five satellites from SV2to SV6that receive GPS signals at the reception signal level greater than the standard value. Then, the unit solves five equations obtained using the thus-obtained pseudo ranges23and the coordinate value that shows the position of each satellite and is obtained from the navigation message, according to a least-square method. Consequently, the unit26enhances the accuracy of the calculation results of the unknowns.

Then,FIG. 6is explained.FIG. 6shows the transmission timings of the pseudo random noise codes transmitted by the positioning signal transmission apparatus2inFIG. 4.

First of all, from among the satellites that transmit the received GPS signals10, the signal generation unit28selects three satellites each having a preferable geometrical arrangement relation between the unit and the positioning signal transmission apparatus2, for example, satellites having significantly different directions from the positioning signal transmission apparatus2on the basis of the navigation message24. Then, the unit28generates the pseudo random noise codes29with regard to the selected satellites and supplies the generated codes to the transmission control unit30.

The transmission control unit30calculates the distance to each satellite that is selected using the signal generation unit28according to the positioned position27and the orbit information about the satellite that is shown in the navigation message24. Furthermore, the unit calculates a time (propagation time) required when a radio wave propagates each calculated distance. Then, the unit30calculates a difference among the calculated propagation times with regard to the respective satellites and assigns the time difference to each of the codes by delaying the respective pseudo random noise codes29that are supplied from the signal generation unit28. Then, the unit30supplies the assigned code to the transmission high-frequency unit31. Lastly, the unit31transmits the code as the positioning signal11.

InFIG. 4, it is assumed that the signal generation unit28selects the satellites SV2, SV3and SV6at this time. The transmission timing (supply timing from the signal generation unit28to the transmission high-frequency unit31) of the pseudo random noise code29with regard to the satellite SV2in this case is explained in reference toFIG. 6.

The transmission timing of the pseudo random noise code29with regard to the satellite SV2in this case is the algebraic sum of the above-mentioned propagation delay time Te+T2with regard to the satellite SV2that is observed by the positioning signal transmission apparatus2, a correction value AT2for improving the accuracy of T2that is obtained by the calculation by the positioning computation unit26using a least-square method and a correction value ATh2reflecting the difference between the positioning signal transmission apparatus2and the positioning apparatus3regarding the position in a height direction. Here, ΔTh2is set according to the altitude difference between the altitude of a place where the reception antenna7of the positioning position transmission apparatus2is mounted and that of the positioning apparatus3. In the case where this difference is small enough to be ignored, this correction value need not be set.

The time difference assigned to the pseudo random noise code29that is generated by the signal generation unit28is corrected using the correction value such as ΔT2or ΔTh2. Therefore, the position-positioning with a high accuracy becomes possible using the positioning apparatus3in comparison with a relay apparatus (for example, the apparatus that is disclosed in the above-mentioned document 3) for simply re-transmitting the received GPS signal10to a GPS signal non-receipt area.

The transmission timing of the pseudo random noise codes29of other satellites SV3and SV6are set like the timing of the satellite SV2. Then, the transmission control unit30assigns the time differences to the codes by delaying the respective pseudo random noise codes29so as to reflect these transmission timing. Then, the unit30supplies the assigned codes to the high-frequency unit31. Consequently, the unit30directs the unit31to transmit the assigned codes as the positioning signals11.

In this way, the positioning apparatus3can implement the position-positioning with high accuracy even if it is located in the vehicle5that is the non-receipt area of the GPS signal10inFIG. 4.

The following is the variant example of the present invention.

First of all,FIG. 7is explained.FIG. 7shows the transmission timings of the pseudo random noise code that is transmitted by the positioning signal transmission apparatus2in the case ofFIG. 4likeFIG. 6.

In this variant example, the signal generation unit28further selects a satellite from which the GPS signal10is not actually received although the navigation message24shows a fact such that the satellite exists in the sky at that point, and the unit28further generates the pseudo random noise code29with regard to the selected satellite.

The ones matching with the above-mentioned condition in the case ofFIG. 4are satellites SV1, SV7and SV8each having the low angle of elevation which is seen from the positioning signal transmission apparatus2. The signal generation unit28further selects these satellites and generates the pseudo random noise codes29that are the same as those used by the selected satellites.

The transmission control unit30calculates the distance to the positioning signal transmission apparatus2from each of the satellites SV1, SV7and SV8based on the positioned position27and the present position of each of the satellites SV1, SV7and SV8, which is obtained from the navigation message24. Then, the unit30divides the calculated distance by the velocity of light, thereby calculating the propagation time required in the case where the GPS signal10propagates the distance from each of the satellites SV1, SV7and SV8to the positioning signal transmission apparatus2. After this, the unit30sets the transmission timing (supply timing from the signal generation unit28to the transmission high-frequency unit31) of the pseudo random noise code29of each of the satellites SV1, SV7and SV8on the basis of this calculation result.

For example, inFIG. 7, the transmission timing T1′ of the pseudo random noise code29with regard to the satellite SV1is the algebraic sum of a propagation time T1required in the case where the GPS signal10propagates the distance from the satellite SV1to the positioning signal transmission apparatus2, the above-mentioned difference Te from the standard time calculated using the positioning computation unit26and the correction value ΔTh1reflecting the position difference in height between the positioning signal transmission apparatus2and the positioning apparatus3. Here, ΔTh1need not be set in the case where the altitude difference between the place of mounting the reception antenna7of the positioning signal transmission apparatus2and that of the positioning apparatus3is small enough to be ignored.

Furthermore, the transmission timing T7′ and T8′ of the respective pseudo random noise codes29of other satellites SV7and SV8are also set in the same way as in the satellite SV1. Then, the transmission control unit30assigns the timing difference to the code in such a way that a difference time between the transmission timing can be reflected by individually delaying each pseudo random noise code29.

Then, the unit30supplies this assigned code to the transmission high-frequency unit31to be transmitted as the positioning signal11.

In this way, the positioning signal transmission apparatus2also transmits the pseudo random noise code29with regard to the satellite that cannot receive the GPS signal10. Meanwhile, by being configured as shown inFIG. 8, the positioning apparatus3can specify whether a signal that is the foundation of the position-positioning is received directly from a satellite or received from the positioning signal transmission apparatus2.

In the configuration example of the positioning apparatus3shown inFIG. 8, the reception antenna7, the reception high-frequency unit21, the reception signal processing unit22and the positioning computation unit26function in the same way as those provided in the positioning signal transmission apparatus2, that is, those provided in the publicly-known GPS receiver. The reception signal processing unit22supplies the information (reception satellite information41) that shows to which satellite the pseudo range23supplied to the positioning computation unit26belong, is supplied to a determination processing unit42.

The positioning apparatus3searches for the signal that can be received on the basis of the navigation message24so that the apparatus can easily acquire the positioning signal11with regard to the satellite that exists in the sky at the point, which is shown in the navigation message24.

When the determination processing unit42receives the positioned position27and the navigation message24that are supplied from the positioning computation unit26, the unit42determines whether or not there is a satellite that calculates the pseudo range23and obtains the reception level greater than a predetermined level although it is shown in the navigation message24that the satellite originally exists in the present position of the positioning apparatus3where the signal level becomes low, from among satellites shown in reception satellite information41that is supplied from the reception high-frequency unit21and include both the number of the satellite that receives signals and the levels of the signals. Here, if such a satellite exists, it is assumed that the positioning apparatus3receives the signal set as the foundation of the position-positioning not from the satellite but from the positioning signal transmission apparatus2(in other words, the position-positioning is implemented on the basis of the positioning signal11). On the other hand, in the case where such a satellite does not exist, the positioning apparatus3receives the signal set as the foundation of the position-positioning directly from the satellite (in other words, the position-positioning is implemented on the basis of GPS signal10).

A determination report unit43receives the determination result using a determination processing unit42and outputs this result in a form of character display and diagram display, by sound, etc., thereby notifying this report to the person4that carries the positioning apparatus3. Furthermore, this unit notifies the result as data to another apparatus. In a center notified a fact by radio transmission, for example, a fact that the data include the positioning result from the positioning apparatus3and the signal received from the positioning signal transmission apparatus2, it is understood that the positioning result measured by the positioning apparatus3is positioned using the positioning signal transmitted by the positioning signal transmission apparatus2using the positioning signal transmitted when displaying the position of the positioning apparatus3on the map of a screen used by an operator of the center.

As mentioned above, the positioning signal transmission apparatus2is configured to transmit the pseudo random noise code29with regard to the satellite that cannot receive the GPS signal10and the positioning apparatus3is configured like the one shown inFIG. 8. Consequently, the person4can recognize whether the signal set as the foundation of the position-positioning is received directly from a satellite or from the positioning signal transmission apparatus2.

The following is the explanation of another variant example of the poisoning signal transmission apparatus2shown inFIG. 3.

As shown inFIG. 9, a mobile body approach detection unit51is added to the positioning signal transmission apparatus2and the detection output is supplied to the transmission control unit30.

The mobile body approach detection unit51is configured using a sensor, for example, an infrared rays sensor, a photoelectric sensor, etc. This unit51detects a fact that a mobile body moves in the attainment range9of the positioning signal11that is transmitted from the transmission antenna8and then it supplies the detection result to the transmission control unit30. The transmission control unit30controls the transmission high-frequency unit31based on this detection result in such a way that the unit31transmits the positioning signal11from the transmission antenna8only while the mobile body is moving in the attainment range9of the positioning signal11or only in a predetermined time period since the approach of the mobile body in the attainment range9is detected.

In this way, by providing the mobile body approach detection unit51with the positioning signal transmission apparatus2, the transmission of the positioning signal11does not constantly continue so that the low consumption electric power of the positioning signal transmission apparatus2can be realized. At the same time, the interference among the positioning signals11can be prevented in the case where a plurality of positioning signal transmission apparatuses2are adjacently mounted in the building6as shown inFIG. 2.

The following is the explanation of a mounting example of separately mounting the constituent elements of the positioning signal transmission apparatus2shown inFIG. 3.

In the mounting example shown in10, among the constituent elements of the positioning signal transmission apparatus2shown inFIG. 3, the reception antenna7, the reception high-frequency unit21, the reception signal processing unit22and the positioning computation unit26are set as a reception positioning block61to be packed in one case and then this case is mounted on the roof of the building6or the like. On the other hand, the signal generation unit28, the transmission control unit30, the transmission high-frequency unit31and the transmission antenna8are set as a transmission block62to be packed in one case. This case is separately mounted on the ceiling, etc. inside the building6that is far from the reception positioning block61. Then, the reception positioning block61and the transmission block62are connected via a signal cable63and a signal that shows the positioned position27and the navigation message24is supplied from the reception positioning block61to the transmission block62. Here, since the position of the reception antenna7becomes identical to the positioned position of the positioning apparatus3at the two-dimensional positioning, the transmission block62is mounted directly below the reception positioning block61by elongating the signal cable63and then the directivity of the transmission antenna8is turned in the direction right under the transmission block62. According to this configuration, an opening for penetrating the positioning signal transmission apparatus2need not be made in the ceiling of the building6.

Instead of using the signal cable63for supplying a signal that shows the positioned position27and the navigation message24, from the reception positioning block61to the transmission block62that are separately mounted, a radio transmission path can be used.

Namely, a radio transmission apparatus64is connected to the reception positioning block61and at the same time, a radio reception apparatus65is connected to the transmission block62, as shown inFIG. 11. Then, the navigation message24that is outputted from the reception positioning block61and a signal that shows the positioned position27are inputted into the radio transmission apparatus64and the electromagnetic wave that is modulated by the signal is transmitted. This electromagnetic wave that is transmitted via a radio transmission path is received using the radio reception apparatus65and this wave is demodulated into the original signal. Then, a signal that shows the demodulated positioned position27and the navigation message24are supplied to the transmission block62. Thus, an opening for penetrating the positioning signal transmission apparatus2need not be made in the ceiling of the building6.

Meanwhile, it is preferable that the frequency of the electromagnetic wave that is transmitted from the radio transmission apparatus64and that is received at the radio reception apparatus65is significantly different from those of the GPS signal10and positioning signal11. In this way, the influence of this electromagnetic wave on the position-positioning performed by the positioning apparatus3can be reduced. In addition, the attenuation of an electromagnetic wave can be reduce by the electromagnetic wave shield that is mounted to prevent the positioning signal11that is transmitted from the transmission antenna8from being received by the reception antenna7.

When the reception antenna7is mounted far from the transmission antenna8like the above-mentioned example, it is preferable to adjust the transmission timing of the pseudo range code29in consideration of this position difference. In this way, the deterioration of the accuracy of the position-positioning using the positioning apparatus3, which is caused by separately mounting the reception antenna7and the transmission antenna8can be reduced.

The present invention is not limited to the above-mentioned preferred embodiments and the various improvements/changes may be made without departing from the scope of the main purpose of the present invention.

For example, according to the configuration of the positioning signal transmission apparatus2as shown inFIG. 3, the transmission control unit30assigns a specified time difference to each of pseudo random noise codes29supplied from the signal generation unit28. Then, the unit30supplies the assigned codes to the separate transmission high-frequency units31to be transmitted from the separate transmission antennas8. Instead, the pseudo random noise codes29each of which is assigned a specified time difference are combined into one signal using the transmission control unit30. After this, the combined signal is supplied to the transmission high-frequency unit31to be transmitted from the transmission antenna8. In this way, the number of the transmission high-frequency units31and the transmission antennas8that are mounted on the positioning signal transmission apparatus2can be reduced.