JP2008298715A - Gps receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce deterioration in the accuracy of position positioning due to altitude errors and multi-passes. <P>SOLUTION: A GPS receiver includes a holding means for holding the history of a position-positioning result; a position-positioning means for positioning three-dimensional positional information by using received GPS signals; an altitude range setting means for setting a prescribed altitude range, based on altitude information acquired, by acquiring the altitude information of nearby history held in the holding means; a determining means for determining whether the altitude information included in the three-dimensional position information is within the altitude range; and an output means for outputting the three-dimensional position information as the position positioning information, only when it is determined that it lies within a prescribed altitude range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a GPS receiver that performs positioning by receiving a GPS signal from a GPS (Global Positioning System) satellite.

  GPS is a positioning system for acquiring position information and the like using GPS signals transmitted from GPS satellites orbiting the earth. For example, mobile terminals such as passenger cars and mobile terminals such as mobile phones are equipped with GPS receivers that perform positioning and the like using GPS, and are widely used in daily life.

  GPS receiver positioning methods include two-dimensional positioning and three-dimensional positioning. In 3D positioning, for example, by using GPS signals from captured and tracked GPS satellites, by solving the four unknowns of "latitude", "longitude", "altitude", and "error of GPS receiver built-in clock", Three-dimensional position information can be obtained. In the two-dimensional positioning, for example, two-dimensional position information can be obtained by solving the other three unknowns with “altitude” as a fixed value.

For example, the following Patent Document 1 discloses a vehicle position detection device that performs two-dimensional positioning. The vehicle position detection device of Patent Document 1 below reads altitudes corresponding to the previously detected latitude and longitude from the table, and executes two-dimensional positioning using the read altitudes.
Japanese Patent No. 2783924

  However, the following inconvenience can occur in the above-mentioned Patent Document 1. For example, in an undulating place such as a mountain road, an error may occur between the altitude read from the table and the actual altitude. When an error is included in the altitude used in the two-dimensional positioning, positioning is performed using the erroneous altitude, so the two-dimensional positioning position (latitude and longitude) also has a value including an error. Further, when the altitude is read from the table using the latitude and longitude including the error in this way, the altitude also includes the error. As a result, the altitude obtained again reduces the accuracy of the two-dimensional positioning position as before. The vicious circle in which the latitude and longitude errors lower the altitude accuracy and the altitude error lowers the latitude and longitude accuracy continues until it moves to a place with less undulations. In some cases, errors may accumulate during that time, and the two-dimensional positioning position may deviate greatly from the actual position.

  The same applies when the GPS signal is affected by multipath in Patent Document 1. In this case as well, an error occurs in the altitude, and positioning is performed using the erroneous altitude. Therefore, the same inconvenience as before may occur. In addition, in the case of multipal, there is a problem that an error due to the influence occurs suddenly and is large.

  As described above, in the conventional positioning, there is a disadvantage that the altitude error causes a decrease in accuracy of latitude and longitude, and improvement thereof is desired. Further, in order to prevent a large error from occurring suddenly, it is also desired to satisfactorily remove the influence of multipath.

  In view of the above circumstances, an object of the present invention is to provide a GPS receiver capable of reducing a decrease in accuracy of position measurement due to altitude error and multipath.

  The GPS receiver according to one aspect of the present invention that solves the above-described problem is to receive a GPS signal from a GPS satellite and perform positioning. The GPS receiver obtains altitude information of the latest history held in the holding means for holding the history of the positioning results, the positioning means for positioning the three-dimensional position information using the received GPS signal, and the holding means. Altitude range setting means for setting a predetermined altitude range based on the acquired altitude information; and determining means for determining whether altitude information included in the three-dimensional position information is within the predetermined altitude range; Only when it is determined to be within the predetermined altitude range, an output means for outputting the three-dimensional position information as a position positioning result is provided.

  According to the GPS receiver configured in this way, only when the altitude included in the three-dimensional positioning result is within the predetermined altitude range, the three-dimensional positioning result is output as an official position positioning result. The Accordingly, a position measurement result in which accuracy degradation due to altitude error and multipath is suppressed (that is, high altitude accuracy and high accuracy of latitude and longitude accordingly) is output to the output destination.

  Moreover, the GPS receiver which concerns on another aspect of this invention which solves said subject receives a GPS signal from a GPS satellite, and performs a position measurement. The GPS receiver includes a holding unit that holds a history of position measurement results, a storage unit that stores latitude and longitude information and altitude information corresponding to the latitude and longitude information, and a three-dimensional position using the received GPS signal. Position measuring means for positioning information, altitude information extracting means for extracting corresponding altitude information from the storage means using the latitude and longitude information of the latest history held in the holding means as keys, and the extracted altitude information An altitude range setting means for setting a predetermined altitude range based on the information, a determination means for determining whether altitude information included in the three-dimensional position information is within the predetermined altitude range, and within the predetermined altitude range The output means for outputting the three-dimensional position information as a position positioning result only when it is determined that the position information is determined.

  According to the GPS receiver configured in this way, only when the altitude included in the three-dimensional positioning result is within the predetermined altitude range, the three-dimensional positioning result is output as an official position positioning result. The Accordingly, a position measurement result in which accuracy degradation due to altitude error and multipath is suppressed (that is, high altitude accuracy and high accuracy of latitude and longitude accordingly) is output to the output destination.

  Further, for example, when it is determined by the determination means that it is outside the predetermined altitude range, the position positioning means measures the two-dimensional position information by using the altitude information of the latest history held in the holding means, and the output means May be configured to output the measured two-dimensional position information.

  In addition, for example, when it is determined by the determining means that the position is outside the predetermined altitude range, the position measuring means determines that the altitude range when the altitude information included in the three-dimensional position information exceeds the upper limit of the predetermined altitude range. If the altitude information included in the 3D position information is below the lower limit of the predetermined altitude range, the lower limit value of the altitude range is used as the altitude. The configuration may be such that the two-dimensional position information is measured, and the output means outputs the measured two-dimensional position information.

  Further, for example, when the PDOP (Position Dilution Of Precision) of a GPS satellite used for positioning exceeds a predetermined threshold value, the position positioning means uses the altitude information of the latest history held in the holding means to support two-dimensional position information. The output unit may be configured to output the measured two-dimensional position information.

  Moreover, the GPS receiver which concerns on another aspect of this invention which solves said subject receives a GPS signal from a GPS satellite, and performs a position measurement. The GPS receiver includes a positioning unit that measures the three-dimensional position information using the received GPS signal, a determination unit that determines whether the altitude information included in the three-dimensional position information satisfies a predetermined condition, Only when it is determined that a predetermined condition is satisfied, an output means for outputting the three-dimensional position information as a position positioning result is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the GPS receiver which can output the positioning result by which the altitude error and the precision fall by multipath were suppressed is provided.

  The configuration and operation of the GPS receiver according to the embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a GPS receiver 100 according to an embodiment of the present invention. The GPS receiver 100 can be employed in various devices such as a so-called car navigation mounted on a vehicle, a PND (Personal Navigation Device) that is a simple navigation device, and a mobile terminal such as a mobile phone.

  The GPS receiver 100 is roughly divided into a down converter unit 1, a received signal processing unit 2, and a positioning calculation control unit 3. The down-converter unit 1 receives the GPS signal, down-converts it, and passes it to the received signal processing unit 2. When the reception signal processing unit 2 receives a signal from the down-converter unit 1, the reception signal processing unit 2 operates in cooperation with the positioning calculation control unit 3 to execute GPS signal acquisition, tracking, and positioning processes. The positioning calculation control unit 3 outputs a GPS positioning result obtained as a result of operating in cooperation with the received signal processing unit 2 to a control chip of the device. The “device control chip” here is a chip provided in a device on which the GPS receiver 100 is mounted, and executes predetermined processing using the GPS positioning result received from the GPS receiver 100. For example, when the device is a car navigation system, this control chip controls each component inside the car navigation system, and performs final positioning result determination and map matching based on the GPS positioning result and autonomous navigation result. Thus, a function for providing navigation information to the user is realized.

  First, the down converter unit 1 will be described. The down converter unit 1 includes a GPS antenna 10, an RF (radio frequency) input unit 11, a BPF (Band Pass Filter) 12 and 14, an LNA (Low Noise Amplifier) 13, a down converter 15, an AGC (Auto Gain Control) 16, a TCXO. (Temperature Compensated Crystal Oscillator) 17, frequency synthesizer 18, and A / D converter 19.

  When the GPS antenna 10 receives a GPS signal transmitted from a GPS satellite, the received signal is input to the BPF 12 via the RF input unit 11. The received signal passes through the BPF 12 and is limited to a predetermined band. Noise outside the GPS band is attenuated through the LNA 13 and the BPF 14 which are low noise amplifiers, and is input to the down converter 15.

  The TCXO 17 is a local oscillator that oscillates at a frequency lower than the frequency of the reception signal input to the down converter 15. The frequency synthesizer 18 generates a local oscillator signal based on the output from the TCXO 17 and outputs it to the down converter 15. The down converter 15 uses the local oscillator signal from the frequency synthesizer 18 to convert the received signal into an intermediate frequency, that is, an IF (Intermediate Frequency) signal under which the stable operation and selection characteristics are improved under the control of the AGC 16.

  The A / D converter 19 samples the IF signal, performs quadrature demodulation, and converts it into an I (In-phase) signal and a Q (Quadra-phase) signal. The I signal is an in-phase component in quadrature demodulation. The Q signal is a component that is orthogonal to the I signal. Hereinafter, for convenience of explanation, the I signal and the Q signal are collectively abbreviated as “IQ signal”. The A / D converter 19 outputs the IQ signal obtained by the conversion process to the received signal processor 2.

  The received signal processing unit 2 includes a plurality of channels 21 and an NCO (Number Controlled Oscillator) 22. IQ signals from the A / D converter 19 are input to a plurality of channels 21. Each of the channels 21 has a configuration for capturing and tracking one GPS satellite. IQ signals corresponding to each GPS signal are input to separate channels 21 for processing. By executing the processing in parallel on each channel 21, the GPS receiver 100 can simultaneously capture and track a plurality of GPS satellites.

  The NCO 22 is an oscillator that oscillates a numerically controlled frequency. A reference clock is input from the frequency synthesizer 18 to the NCO 22. Based on the reference clock, the NCO 22 performs NCO control on the carrier, reference code generation of a PRN (Pseudo Random Noise) code, and NCO control on the code. Each channel 21 performs Doppler removal, code correlation detection by at least one correlator, and integration processing on the input IQ signal based on the output of the NCO 22. Next, the signal subjected to these processes is output to the positioning calculation control unit 3.

  The positioning calculation control unit 3 includes a CPU 31, an RTC (Real-Time Clock) 32, a ROM 33, a RAM 34, and an interface 35. The CPU 31 operates based on the clock output from the frequency synthesizer 18 and performs overall control of the positioning calculation control unit 3. The RTC 32 is a timepiece IC (Integrated Circuit) operated by a crystal oscillator (not shown), and functions as, for example, a time measuring means. The ROM 33 stores programs and data for performing positioning calculations, for example. The CPU 31 expands the program in the ROM 33 to the RAM 34 and performs positioning calculation processing. For example, when the CPU 31 receives a signal from each channel 21, the CPU 31 calculates a measurement value related to the signal.

  Here, a process for obtaining a desired measurement value based on a signal input to each channel 21 will be described. The range of the search frequency necessary for capturing the GPS signal is mainly due to deviations in the received frequency due to the Doppler effect and deviations such as variations (individual differences and aging) and variations (temperature characteristics and power supply variations) of the TCXO17. It is determined. First, the CPU 31 estimates the Doppler frequency and code phase search range of the signal based on the navigation message that is the satellite orbit information, the previous positioning position, and the current time, generates those set values, and outputs them to the NCO 22 To do. Then, the search process executed in each channel 21 is controlled.

  Further, the CPU 31 designates the PRN code searched for in each channel 21 for each channel 21. Thereby, in each channel 21, Doppler removal based on the set Doppler frequency is performed, and a correlation peak between the reference code of the PRN code specified in the set phase search range and the input signal is detected. Next, integration processing is executed, and when the level of the input signal exceeds a predetermined threshold, the input signal is captured as a GPS signal. Note that the longer the integration time is set, the higher the capture sensitivity. This accumulated time is also set by the CPU 31.

  In each channel 21, the tracking error in the GPS signal carrier and code captured via the tracking loop filter included in the CPU 31 and the NCO 22 is corrected, and tracking of the GPS signal is continued. When acquisition of the GPS signal fails, the CPU 31 normally resets a wider search frequency range, code phase range, and higher sensitivity, and outputs the result to the NCO 22. Then, the above processing is retried in the channel 21 under the control of the NCO 22.

  CPU31 acquires the navigation message contained in the several GPS signal required for positioning, code phase (pseudorange), carrier frequency (pseudorange rate), carrier phase (delta pseudo range), SN ratio, in GPS receiver 100 Calculate GPS time lag. And based on the measured value and data from these GPS signals, a position, speed, direction, and time are calculated (that is, positioning calculation). The calculated GPS positioning result is output to the control chip of the device via the interface 35.

  Next, the position positioning process executed by the GPS receiver 100 will be described with reference to the flowchart of FIG. In the following description of the position positioning process, it is assumed that the moving body on which the GPS receiver 100 is mounted moves to some extent and the position positioning result is acquired a plurality of times.

  The position measurement process of FIG. 2 is executed at predetermined timings while the GPS receiver is activated. As shown in FIG. 2, first, it is determined whether or not there are four or more positioning usable satellites (step 1, step is abbreviated as “S” in the following specification and drawings). “Positioning usable satellite” means a GPS satellite that satisfies conditions such as being able to capture and track GPS signals and receive ephemeris information, and not satisfying the conditions of an elevation mask (for example, the elevation angle is greater than 10 degrees). Means. If there are four or more positioning usable satellites (S1: YES), the process proceeds to S2, and if there are three or less satellites (S1: NO), the process proceeds to S11. The processes after S11 will be described in detail later, and here, the processes after S2 will be described first.

  In the process of S2, PDOP (Position Dilution Of Precision) for the positioning usable satellite is calculated. Next, in step S3, it is determined whether the PDOP calculated in step S2 is equal to or less than a predetermined threshold. When PDOP is equal to or smaller than the threshold (S3: YES), it is determined that the geometrical arrangement of positioning usable satellites is suitable for three-dimensional positioning and that there are few error factors, and the process proceeds to S4. If the PDOP exceeds the threshold (S3: NO), it is determined that the geometrical arrangement of the positioning usable satellites is a large error factor, and the process proceeds to S12.

  In the process of S4, a three-dimensional positioning calculation is executed using a GPS signal from a positioning-usable satellite, and the obtained three-dimensional positioning position is temporarily held in, for example, the RAM 34 as a temporary three-dimensional positioning position. . When there are five or more positioning usable satellites, PDOPs of various combinations including at least four positioning usable satellites are calculated in the process of S2, and after executing the process of S3, the PDOP is determined in the process of S4. Three-dimensional positioning may be executed using a positioning-enabled satellite with a minimum combination. In this case, the three-dimensional positioning position obtained by the process of S4 becomes a more accurate value.

  In the next processing of S5 and S6, it is determined whether or not the altitude obtained at the provisional three-dimensional positioning position (hereinafter referred to as “temporary altitude β”) falls within a predetermined altitude range. For example, the RAM 34 holds a history of positioning results. At this time, in the process of S5, for example, a range of ± 100 m centered on the altitude of the history referred to in the RAM 34 (for example, the altitude included in the previous positioning result, hereinafter referred to as “reference altitude α”) is a predetermined altitude. The range is set and used in the determination process of S6. That is, in the process of S6, it is determined whether or not | α−β | ≦ 100 is satisfied.

  Various other forms of setting the predetermined altitude range are possible. For example, the ROM 33 stores an altitude database in which a plurality of records in which latitude and longitude are associated with altitudes corresponding to latitude and longitude are registered. The altitude step is relatively rough, for example, 100 m step. In the case of 100 m steps, an altitude of 50 m or more and less than 150 m is actually treated as an altitude of 100 m, and an altitude of 150 m or more and less than 250 m is treated as an altitude of 200 m. In this case, in the process of S5, the altitude database is searched using the latitude and longitude included in the previous positioning result as a key, and the reference altitude α corresponding to the key is obtained as a search result (in other words, a rough position of the current position). Altitude). Then, a range of ± 100 m centering on the obtained reference altitude α is set as a predetermined altitude range and used in the determination process of S6. Note that the 100 m step is a relatively large step and has an advantage of reducing the capacity of the advanced database. This is extremely advantageous in a resource-limited device such as a GPS receiver.

  When the temporary altitude β is a value that falls within a predetermined altitude range in the process of S6 (S6: YES), it is determined that the accuracy of the temporary altitude β is high and the accuracy of the latitude and longitude is accordingly high. Furthermore, since the temporary altitude β is within a predetermined altitude range, it is determined that it is not affected by an excessive error that occurs unexpectedly, that is, by multipath. Therefore, since the three-dimensional positioning position assumed in the process of S4 has high accuracy and is not affected by the multipath, it is output to the control chip as a formal positioning result in the process of S7. The positioning process returns. Further, the positioning result output to the control chip is stored in the RAM 34 as a history.

  If the temporary altitude β is a value that does not fall within the predetermined altitude range in the process of S6 (S6: NO), it is determined that the temporary altitude β is highly likely to have been affected by multipath. The Furthermore, it is determined that the accuracy of latitude and longitude is low as the accuracy of the temporary altitude β decreases due to the influence of multipath. Therefore, since the three-dimensional positioning position assumed in the process of S4 has a low accuracy due to the influence of multipath or the like and cannot be adopted as a positioning result, the process proceeds to S12.

  Next, the process of S11 will be described. In the process of S11, it is determined whether there are three positioning usable satellites. If there are three positioning usable satellites (S11: YES), the process proceeds to S12. If two or less satellites are available (S11: NO), the process proceeds to S21. When the number of positioning usable satellites is two or less, the positioning calculation is not executed (S21), and the positioning processing of FIG. 2 returns.

  In the process of S12, HDOP (horizontal dilution of precision) is calculated. Next, in the process of S13, it is determined whether or not the HDOP calculated in the process of S2 is equal to or less than a predetermined threshold value. If HDOP is less than or equal to the threshold value (S13: YES), it is determined that the geometrical arrangement of positioning usable satellites is suitable for two-dimensional positioning and that there are few error factors, and the process proceeds to S14. If HDOP exceeds the threshold value (S13: NO), it is determined that the geometrical arrangement of the positioning usable satellites is a large error factor, the process proceeds to S21, and the positioning calculation is not performed. The positioning process returns.

  In the process of S14, the altitude of the previous positioning position is acquired with reference to the RAM 34, for example. Next, the GPS signal from the positioning-enabled satellite is used, and the obtained altitude is used to execute a two-dimensional positioning calculation, and the obtained two-dimensional positioning position is output to the control chip. Further, the positioning result output to the control chip is stored in the RAM 34 as a history.

  According to the processing of S6 in FIG. 2, the altitude used at the time of two-dimensional positioning in this embodiment is not affected by multipath. In addition, according to the processing of S3 and S13 in FIG. 2, the GPS satellites are obtained by using a combination of GPS satellites having a low PDOP or HDOP. Therefore, the altitude used during two-dimensional positioning is guaranteed for accuracy. When two-dimensional positioning is performed using such a highly accurate altitude, it is possible to suitably remove the decrease in accuracy of latitude and longitude caused by altitude error, and as a result, the latitude and longitude obtained by two-dimensional positioning is highly accurate. Become.

  In the process of S14, for example, when the temporary altitude β exceeds the upper limit value of the predetermined altitude range, the upper limit value (that is, the reference altitude α + 100 m), and the temporary altitude β is less than the lower limit value of the predetermined altitude range. The lower limit (that is, the reference altitude α-100 m) may be used as an altitude that is used in two-dimensional positioning. In this case, since the altitude error can be suppressed within a certain range, as a result, the latitude and longitude obtained by two-dimensional positioning are also suppressed in error.

  That is, according to the GPS receiver 100 of the present embodiment, by setting a predetermined altitude range based on the altitude database and the altitude of the history, the altitude having a large error outside the range is not used for the positioning calculation. . Therefore, a large error due to, for example, the occurrence of multipath can be removed satisfactorily. In addition, if the altitude is within the predetermined altitude range, the 3D positioning result is adopted as it is, and if it is outside the predetermined altitude range, the 2D positioning is executed using the altitude with the error suppressed, so that errors are difficult to accumulate. And the effect of reducing the error of latitude and longitude during two-dimensional positioning is expected.

  The above is the embodiment of the present invention. The present invention is not limited to these embodiments and can be modified in various ranges. For example, since the altitude steps in the altitude database are relatively rough, the process of S5 in FIG. 2 does not need to be executed every time during the position positioning process in FIG. 2 and can be omitted. For example, the position positioning process may be performed once every time the position measurement process is performed a plurality of times.

  Further, when the device on which the GPS receiver 100 is mounted is, for example, a car navigation system, the altitude database may be added to an HDD, a DVD, or the like that stores map data. Further, when the device is, for example, a mobile device, the altitude database may be stored in a memory card. The advanced database may be placed on a database management server on the Web. In this case, the GPS receiver 100 has a communication function and acquires altitude data by performing data communication with the database management server. By placing the altitude database in the external storage device in this way, it is possible to construct an altitude database rich in information. As an example, it is possible to make a high-level step finer.

  Further, the altitude step may be changed for each region in the altitude database. For example, the altitude step may be increased in a region with a high undulation such as a mountainous area, and the altitude step may be decreased in a flat region.

  Further, continuous latitude and longitude having the same altitude in the altitude database may be expressed by a region (for example, vector data). In this case, since the number of records in the advanced database can be reduced, an effect of resource saving can be expected.

It is a block diagram which shows the structure of the GPS receiver of embodiment of this invention. It is a flowchart which shows the position positioning process performed in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Down converter part 2 Received signal processing part 3 Positioning calculation control part 100 GPS receiver

Claims (6)

In a GPS receiver that receives a GPS signal from a GPS (Global Positioning System) satellite and performs positioning,
Holding means for holding a history of positioning results;
Position positioning means for positioning three-dimensional position information using the received GPS signal;
Altitude range setting means for acquiring altitude information of the latest history held in the holding means and setting a predetermined altitude range based on the acquired altitude information;
Determining means for determining whether the altitude information contained in the three-dimensional position information is within the predetermined altitude range;
A GPS receiver comprising: output means for outputting the three-dimensional position information as a position positioning result only when it is determined to be within the predetermined altitude range. In a GPS receiver that receives a GPS signal from a GPS satellite and performs positioning,
Holding means for holding a history of positioning results;
Storage means for storing latitude and longitude information and altitude information corresponding to the latitude and longitude information in association with each other;
Position positioning means for positioning three-dimensional position information using the received GPS signal;
Altitude information extraction means for extracting corresponding altitude information from the storage means using the latitude and longitude information of the latest history held in the holding means as a key;
Altitude range setting means for setting a predetermined altitude range based on the extracted altitude information;
Determining means for determining whether the altitude information contained in the three-dimensional position information is within the predetermined altitude range;
A GPS receiver comprising: output means for outputting the three-dimensional position information as a position positioning result only when it is determined to be within the predetermined altitude range. When it is determined that the determination means is outside the predetermined altitude range,
The positioning means measures the two-dimensional position information with the aid of altitude information of the latest history held in the holding means,
The GPS receiver according to claim 1, wherein the output unit outputs the measured two-dimensional position information. When it is determined that the determination means is outside the predetermined altitude range,
If the altitude information included in the three-dimensional position information exceeds the upper limit of the predetermined altitude range, the position positioning means uses the upper limit value of the altitude range as the altitude to measure the two-dimensional position information, and When the altitude information included in the original position information is below the lower limit of the predetermined altitude range, the lower limit value of the altitude range is used as the altitude to measure the two-dimensional position information,
The GPS receiver according to claim 1, wherein the output unit outputs the measured two-dimensional position information. When the PDOP (Position Dilution Of. Precision) of the GPS satellite used for positioning exceeds a predetermined threshold,
The positioning means measures the two-dimensional position information with the aid of altitude information of the latest history held in the holding means,
The GPS receiver according to claim 1, wherein the output unit outputs the measured two-dimensional position information. In a GPS receiver that receives a GPS signal from a GPS satellite and performs positioning,
Position positioning means for positioning three-dimensional position information using the received GPS signal;
Determination means for determining whether altitude information included in the three-dimensional position information satisfies a predetermined condition;
A GPS receiver comprising: output means for outputting the three-dimensional position information as a position measurement result only when it is determined that the predetermined condition is satisfied.

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