JP2015087227A - Positioning method and positioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the positioning error by multipath in positioning calculation using a Kalman filter.SOLUTION: Kalman filter processing is performed using a position and speed of a GPS receiver 10 as state vectors PosX and VelX, and using a received code phase of capture satellite signal as an observed value Z. The position R value as an error of the observed value Z (code phase) is set using (1) the distance difference ΔL between a pseudo distance L1 of the capture satellite signal and a geometric distance L2 based on the geometric positional relationship between a GPS satellite S and the GPS receiver 10, and (2) the signal intensity of the capture satellite signal.

Description

  The present invention relates to a positioning method and the like.

  A GPS (Global Positioning System) is widely known as a positioning system using positioning signals. In GPS, position calculation using information such as the positions of a plurality of GPS satellites and pseudo distances to the respective GPS satellites is performed to obtain the position and clock bias of the GPS receiver. As a position calculation method using such positioning signals, a method using a Kalman filter is widely known. For example, Patent Document 1 discloses a position calculation method using a Kalman filter whose observation values are the reception frequency and code phase of a received GPS satellite signal.

JP 2009-92540 A

  Incidentally, multipath is one of the major causes of GPS positioning errors. Multipath is a phenomenon in which a GPS satellite signal is received as an indirect wave signal due to reflection or diffraction on a building or the ground.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce a positioning error due to multipath in a positioning calculation using a Kalman filter.

  A first form for solving the above-described problem is that, for each captured satellite, a geometric distance obtained from a geometric positional relationship between the positioning device and the captured satellite, and the positioning device from the captured satellite. Calculating the difference from the pseudorange obtained using the signal propagation time until, and, for each captured satellite, the intensity of the captured satellite signal of the captured satellite by the positioning device and the difference related to the captured satellite Calculating an index value indicating an error of the captured satellite signal, and using the captured satellite signal of each captured satellite and positioning using the index value, and calculating the index value If the difference is longer than the geometric distance and the pseudorange is greater and the intensity satisfies a predetermined weak signal condition, the index value indicates that the error of the captured satellite signal is large. A value of 1 and the above When the pseudorange is shorter than the geometric distance and the intensity satisfies a predetermined strong signal condition, the index value is a second value indicating that the error of the captured satellite signal is small. Positioning method.

  As another invention, for each captured satellite, the geometric distance obtained from the geometric positional relationship between the positioning device and the captured satellite, and the signal propagation time from the captured satellite to the positioning device are calculated. A difference calculating unit that calculates a difference from the pseudo distance obtained by using the captured satellite signal intensity of the captured satellite by the positioning device and the difference related to the captured satellite for each captured satellite, An error index value calculation unit for calculating an index value indicating an error of a captured satellite signal, wherein the difference is longer than the geometric distance and the intensity is a predetermined weak signal condition. The index value is a first value indicating that the error of the captured satellite signal is large, the difference is shorter than the geometric distance, the pseudo distance is shorter, and the intensity is a predetermined strong signal condition. If it does, An error index value calculation unit that sets a second value indicating that the error of the captured satellite signal is small, and a positioning device that performs positioning using the captured satellite signal of each captured satellite and the index value It may be configured.

  According to the first aspect and the like, the difference between the geometric distance obtained from the geometric positional relationship between the positioning device and the acquisition satellite and the pseudo distance obtained using the signal propagation time, and the acquisition An index value indicating an error of the captured satellite signal is calculated using the intensity of the satellite signal, and positioning using the index value is performed. When multipath occurs, the difference between the geometric distance and the pseudo distance becomes large, and the index value is a value indicating that the error is large. Thereby, the positioning error can be reduced and the positioning accuracy can be improved.

  In addition, when the pseudo distance is longer than the geometric distance and the signal strength is weak, it can be estimated that the multipath environment exists. In such a case, the index value can be a first value indicating that the error of the received captured satellite signal is large.

  In addition, it is possible to reduce positioning errors due to positioning position errors. That is, when the pseudo distance is shorter than the geometric distance and the signal strength is strong, it can be considered that the positioning position of the positioning device is incorrect. In such a case, the index value can be a second value indicating that the error of the captured satellite signal is small.

  Further, as a second form, the index value is the first value when the difference is longer than the geometric distance so that the pseudo distance satisfies a predetermined length condition, and the strength is If a predetermined weak signal condition is satisfied, a positioning method may be configured in which the index value is set to the first value.

  According to the third embodiment, as a further condition, the index value is set to the first value when the pseudo distance is longer than the geometric distance so as to satisfy a predetermined length condition. Even if the pseudo distance is longer than the geometric distance, if the difference is a slight difference, it cannot be regarded as a multipath effect. Therefore, when the pseudo distance is sufficiently “long” with respect to the geometric distance, the index value is set as the first index value indicating that the error of the captured satellite signal is large.

  In addition, as a third aspect, setting the index value to the second value means that the difference is shorter than the geometric distance so that the pseudo distance satisfies a predetermined short condition, and the intensity is the predetermined value. When the strong signal condition is satisfied, a positioning method may be configured in which the index value is set to the second value.

  According to the third embodiment, as a further condition, the index value is set to the second value when the pseudo distance is shorter than the geometric distance so as to satisfy a predetermined short and short condition. Even if the pseudo distance is shorter than the geometric distance, if the difference is a slight difference, the positioning position cannot always be regarded as incorrect. Therefore, when the pseudo distance is sufficiently “short” with respect to the geometric distance, the index value is set as the second index value indicating that the error of the captured satellite signal is small.

  Further, as a fourth mode, the positioning may be performed by executing a Kalman filter process using the position of the positioning device as a state vector component, the pseudorange as an observed value, and the index value as a measurement error. A positioning method may be configured.

  According to the fourth embodiment, in the positioning using the Kalman filter, the position of the positioning device is a state vector component, the pseudorange is an observation value, and the index value indicating the error of the captured satellite signal is the measurement error. Thus, the positioning accuracy can be improved.

Explanatory drawing of distance calculation between a GPS satellite and a GPS receiver. Example of occurrence of positioning error. 1 is a configuration diagram of a portable electronic device. The block diagram of a baseband process circuit part. An example data structure of measurement data. The data structural example of signal strength data. The data structural example of positioning history data. 6 is a data configuration example of a reference position R value setting table. The flowchart of a KF positioning process. The flowchart of a speed correction process. The flowchart of a position correction process. The flowchart of a position R value setting process.

[principle]
(A) Outline of GPS A GPS receiver that is a positioning device receives a GPS satellite signal that is a positioning signal transmitted from a GPS satellite that is a positioning satellite, and is superimposed on the received GPS satellite signal and conveyed. Based on the navigation message such as the orbit information (ephemeris and almanac) of the GPS satellites, the satellite information such as the position and moving direction of the GPS satellites and the speed information is calculated.

  Next, based on the difference between the reception time of the GPS satellite signal measured by the built-in quartz clock and the transmission time of the received GPS satellite signal from the GPS satellite, the distance from the GPS satellite to its own device (pseudo Distance). This is a calculation of a distance (pseudo distance) based on the signal propagation time. Then, the values of the four parameters, the three-dimensional coordinate value indicating the position of the aircraft and the clock error, are used as the orbit information of a plurality of GPS satellites, the distance from each GPS satellite to the aircraft (pseudo distance), etc. By performing a positioning calculation calculated based on the current position, the current position of the own device is determined.

  In addition, four GPS satellites are arranged on each of the six orbital planes, and in principle, four or more GPS satellites are operated from anywhere on the earth.

  By the way, in positioning using GPS satellite signals, positioning error due to multipath becomes a problem. In the present embodiment, an index value indicating an error of the received GPS satellite signal (pseudo distance error of the received signal) is calculated, and this index value is used for positioning calculation, thereby improving the positioning error. The index value is set based on the distance between the GPS satellite and the GPS receiver, and the reception strength (signal strength) of the GPS satellite signal in the GPS receiver, so to speak, it indicates the reliability of the received GPS satellite signal. It can be said that there is.

  Specifically, as shown in FIG. 1, the pseudo distance L1 and the geometric distance L2 are calculated as the distance between the GPS satellite S and the GPS receiver 10. The position PS (xS, yS, zS) of the GPS satellite S is acquired based on the navigation message. Further, the position P2 (x2, y2, z2) of the GPS receiver 10 is assumed to be a predicted position calculated from the positioning position calculated by the previous positioning calculation, the moving speed, or the like. The position calculated by performing the positioning calculation is the positioning position. The position P1 (x1, y1, z1) is the position of the GPS receiver 10 calculated from the pseudo distance L1. 1 and 2, the straight line of the signal indicates the pseudo distance L1, and the broken line indicates the geometric distance L2. In FIGS. 2A and 2B, the position described as “true value” is a correct position (or a position close to the correct position).

The pseudo distance L1 is calculated from the propagation time of the received GPS satellite signal. Further, the geometric distance L2 is calculated from the geometric positional relationship as in the following formula (1).

  A difference between the pseudo distance L1 and the geometric distance L2 is a distance difference ΔL (= pseudo distance L1−geometric distance L2). Based on the distance difference ΔL and the signal strength of the GPS satellite signal, an index value of the GPS satellite signal is calculated. As shown in FIG. 1, in a normal state in which no positioning error has occurred, the pseudo distance L1 and the geometric distance L2 match or substantially match, and the distance difference ΔL becomes “0” or a minute value.

  On the other hand, FIG. 2 shows an example in the case where some error has occurred. FIG. 2A shows a case of a so-called multipath environment where the predicted position P2 is a true value and multipath occurs. The pseudo distance L1 is longer than the geometric distance L2 due to the influence of the multipath, and the distance difference ΔL becomes a “positive value”. Further, since the GPS satellite signal is an indirect wave, the signal strength is “weak” (normally satisfies the weak signal condition) as compared with the normal time. In such a case, the received GPS satellite signal is regarded as having a large error (low reliability), and the index value is set to a “large value”, for example, compared with the normal value.

  FIG. 2B shows a case where the position P1 is a true value and the predicted position P2 of the GPS receiver 10 is incorrect. For example, when a so-called position jump occurs in the previous positioning, or the calculated speed (speed or direction) is greatly incorrect. If there is no influence of multipath, in this case, the pseudo distance L1 is the position PS (xS, yS, zS) of the GPS satellite S and the true position P1 (x1, y1, z1) of the GPS receiver 10. The distance between. For this reason, the geometric distance L2 is longer than the pseudo distance L1, and the distance difference ΔL is a “negative value”. Further, since the GPS satellite signal is a direct wave signal, the signal strength is “strong” (strong signal condition is satisfied). In such a case, the error of the received GPS satellite signal is considered to be small (high reliability), and the index value is set to a “small value” as compared with, for example, normal.

(B) Positioning calculation In this embodiment, a positioning process (KF positioning process) using a Kalman filter (KF: Kalman Filter) is performed to determine the current position. The Kalman filter is an estimation method based on probability theory that estimates an amount of state that changes from moment to moment by using observation values including errors. In the present embodiment, prediction calculation and correction processing are performed using the state (position, velocity, etc.) of the GPS receiver 10 as the state vector X, and the position of the GPS receiver 10 that is a state estimated value is calculated.

  The Kalman filter is based on the premise that an error is included in the observed value, and the error included in the observed value is reflected in the correction process as an observation error (R value). In this embodiment, since the measurement having two components of the code phase of the GPS satellite signal and the reception frequency is used as an observation value, an error included in each of these two components is set. Specifically, a speed R value that is an observation error of the reception frequency and a position R value that is an observation error of the code phase are set.

  Specifically, the index value indicating the error of the received GPS satellite signal described with reference to FIGS. 1 and 2 is reflected in the position R value. That is, the position R value is changed based on the sign of the distance difference ΔL and the reception strength (signal strength) of the GPS satellite signal. Specifically, when the distance difference ΔL is “positive value” and the signal intensity is “weak” (corresponding to FIG. 2A), the position R value is changed to increase, and the distance difference When ΔL is a “negative value” and the signal strength is “strong” (corresponding to FIG. 2B), the position R value is changed to decrease.

[Constitution]
FIG. 3 is a configuration diagram of the portable electronic device 1 in the present embodiment. The portable electronic device 1 is a small electronic device that is worn on the body or carried and used. The portable electronic device 1 is realized by, for example, a wristwatch type wearable computer called a so-called runners watch. According to FIG. 3, the portable electronic device 1 includes a GPS receiver 10, a main processing unit 30, an operation unit 32, a display unit 34, a sound output unit 36, a clock unit 38, and a communication unit 40. The main storage unit 42 is provided.

  The GPS receiver 10 includes a GPS antenna 12, an RF receiving circuit unit 14, and a baseband processing circuit unit 16, and receives a GPS satellite signal transmitted from a GPS satellite to receive the portable electronic device 1 Measure the position of.

  The GPS antenna 12 is an antenna that receives an RF (radio frequency) signal including a GPS satellite signal transmitted from a GPS satellite.

  The RF receiving circuit unit 14 down-converts an RF signal received by the GPS antenna 12 into an intermediate frequency signal (IF (Intermediate Frequency) signal), amplifies the signal, converts the signal into a digital signal, and outputs the digital signal.

  The baseband processing circuit unit 16 captures and tracks a GPS satellite signal using the received signal data input from the RF receiving circuit unit 14, and uses time information, satellite orbit information, and the like extracted from the captured GPS satellite signal. Thus, the position of the portable electronic device 1, the clock error, etc. are calculated.

  FIG. 4 is a configuration diagram of the baseband processing circuit unit 16. According to FIG. 4, the baseband processing circuit unit 16 includes a BB processing unit 100 and a BB storage unit 200.

  The BB processing unit 100 is realized by a processor such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), and controls each part of the baseband processing circuit unit 16 according to a baseband program 210 stored in the BB storage unit 200. To control. The BB processing unit 100 includes a measurement acquisition unit 110 and a KF positioning calculation unit 120.

  The measurement acquisition unit 110 captures GPS satellites (signals) by performing digital signal processing such as carrier removal and correlation calculation on the received signal data input from the RF receiving circuit unit 14. Then, a measurement (measured value) including the reception frequency and code phase of the captured GPS satellite signal is acquired. In addition, the signal strength of the captured GPS satellite signal is measured. The measurement acquired by the measurement acquisition unit 110 is stored as measurement data 230, and the measured signal strength is stored as signal strength data 240.

  FIG. 5 is a data configuration example of the measurement data 230. According to FIG. 5, the measurement data 230 stores the measurement actual measurement value 232 in association with each captured satellite 231. The actual measurement value 232 includes the reception frequency F of the GPS satellite signal and the code phase CP.

  FIG. 6 is a data configuration example of the signal strength data 240. According to FIG. 6, the signal strength data 240 stores the signal strength 242 in association with each captured satellite 241.

  Returning to FIG. 4, the KF positioning calculation unit 120 includes a position R value setting unit 122 and performs KF positioning processing (see FIG. 9) according to the KF positioning program 212. In the KF positioning process, the position and speed of the portable electronic device 1 are calculated by performing a positioning calculation using a Kalman filter based on the measurement of the captured satellite acquired by the measurement acquisition unit 110. Various parameters (state vectors VelX, PosX, error covariance matrices VelP, PosP, etc.) of the Kalman filter used for the positioning calculation are stored as KF parameter data 250.

  Further, the calculated position and speed are accumulated and stored as positioning history data 260. FIG. 7 is a data configuration example of the positioning history data 260. According to FIG. 7, the positioning history data 260 stores the positioning time 261, the position 262, and the speed 263 in association with each other.

  The position R value setting unit 122 sets a position R value used in the KF position correction process (see FIG. 12). Specifically, the reference position R value is set according to the reference position R value setting table 220 based on the reception intensity (signal intensity) of the GPS satellite signal received from the GPS satellite.

  FIG. 8 is a data configuration example of the reference position R value setting table 220. According to FIG. 8, the reference position R value setting table 220 stores the signal intensity 221 and the reference position R value 222 in association with each other. In the example of FIG. 8, it is determined that the reference position R value increases as the signal strength decreases.

  The position R value setting unit 122 changes the reference position R value. Specifically, the reference position R value is updated by adding a value corresponding to the observed value Z, which is the code phase of the GPS satellite signal. Further, when the portable electronic device 1 is stopped, a predetermined value is added to change the reference position R value.

  Further, the reference position R value is changed based on the distance between the GPS satellite and the portable electronic device 1 and the reception strength (signal strength) of the GPS satellite signal in the portable electronic device 1. Specifically, the pseudo distance L1 is calculated from the time difference between the transmission time and the reception time of the received GPS satellite signal. Further, the geometric distance L2 is calculated from the geometric position relationship between the position P1 of the GPS satellite and the predicted position P2 of the portable electronic device 1 according to the equation (1). Then, a distance difference ΔL that is a difference between the pseudo distance L1 and the geometric distance L2 is calculated and set as a determination value Y.

そして、この候補値Ｒｔ、及び、基準位置Ｒ値のうち、大きい方の値を、基準位置Ｒ値として設定する。 Next, the reference position R value is changed according to the determination value Y and the reception intensity (signal intensity) of the GPS satellite signal. That is, when the determination value Y is a “positive value”, the determination value Y is larger than a predetermined first threshold value (long condition is satisfied), and the signal strength of the GPS satellite signal is smaller than the average signal strength (predetermined weakness). If the signal condition is satisfied, the candidate value Rt (first value) is calculated according to the following equation (2).

Then, the larger one of the candidate value Rt and the reference position R value is set as the reference position R value.

そして、この候補値Ｒｔ、及び、基準位置Ｒ値のうち、小さい方の値を、基準位置Ｒ値として設定する。 On the other hand, when the distance difference ΔL is a “negative value”, the determination value Y is smaller than a predetermined second threshold value (satisfaction condition is satisfied), and the GPS satellite signal reception strength is greater than the average signal strength (predetermined strength). If the signal condition is satisfied, a candidate value Rt (second value) is calculated according to the following equation (3).

The smaller value of the candidate value Rt and the reference position R value is set as the reference position R value.

  Here, the average signal strength is an average value of the signal strength of each captured satellite. The first threshold is a statistical value of pseudorange error in the case of a strong signal in a non-multipath environment, and is 10 m, for example. The second threshold is a statistical value of the pseudorange error in the case of a strong / medium signal, and is 20 m, for example.

  The pseudorange error is the difference between the geometric distance between the GPS satellite S and the GPS receiver 10 obtained using the coordinates at a position where the coordinates are known and the pseudorange at the position (pseudorange-geometric Distance). That is, in the position R value setting process (FIG. 12) described later, when it is determined that there is a high possibility of multipath in the determination up to step D19, a pseudo distance error that may occur when the reception state is good, The distance difference ΔL is compared. Further, when it is determined that the possibility of multipath is low, the pseudo-range error under the condition including multipath and the distance difference ΔL are compared. This is to more accurately estimate the presence or absence of multipath effects.

  Returning to FIG. 4, the BB storage unit 200 is a storage device including a ROM, a RAM, and the like, and a system program for the BB processing unit 100 to control each unit of the baseband processing circuit unit 16 and a base A program and data for realizing various functions of the band processing circuit unit 16 are stored, used as a work area of the BB processing unit 100, and temporarily stores calculation results of the BB processing unit 100. In the present embodiment, the BB storage unit 200 includes a baseband program 210 including a KF positioning program 212, a reference position R value setting table 220, measurement data 230, signal strength data 240, KF parameter data 250, The positioning history data 260 is stored.

  Returning to FIG. 3, the main processing unit 30 comprehensively controls each unit of the portable electronic device 1 according to various programs such as a system program stored in the main storage unit 42.

  The operation unit 32 is an input device configured with a touch panel, a button switch, and the like, and outputs an operation signal corresponding to a user operation to the main processing unit 30.

  The display unit 34 is a display device configured with an LCD (Liquid Crystal Display) or the like, and performs various displays based on display signals from the main processing unit 30.

  The sound output unit 36 is a sound output device including a speaker or the like, and performs various sound outputs based on the sound signal from the main processing unit 30.

  The clock unit 38 is an internal clock and is configured by an oscillation circuit having a crystal oscillator or the like, and measures the current time, the elapsed time from the designated timing, and the like.

  The communication unit 40 is configured with a wireless communication device such as a wireless local area network (LAN) or Bluetooth (registered trademark), and performs communication with an external device.

  The main storage unit 42 is a storage device configured by a ROM, a RAM, and the like. The main processing unit 30 performs system control for overall control of each unit of the portable electronic device 1 and various types of the portable electronic device 1. A program and data for realizing the functions are stored and used as a work area of the main processing unit 30 to temporarily store calculation results of the main processing unit 30, operation data from the operation unit 32, and the like.

[Process flow]
FIG. 9 is a flowchart showing the flow of the KF positioning process. This process is a process executed by the KF positioning calculation unit 120 at predetermined positioning intervals (for example, 1 second) in accordance with the KF positioning program 212.

式（４）において、「ｕ，ｖ，ｗ」は、携帯型電子機器１の三次元の速度ベクトル、「ｄ」は、クロックドリフトであり、式（５）において、「ｘ，ｙ，ｚ」は、携帯型電子機器１の三次元の位置ベクトル、「ｂ」は、クロックバイアス、である。 According to FIG. 9, first, initial setting is performed (step A1). Specifically, as shown in the following equations (4) and (5), a position state vector PosX having the position of the portable electronic device 1 as a component and a speed state vector VelX having a speed as a component are defined.

In Expression (4), “u, v, w” is a three-dimensional velocity vector of the portable electronic device 1, “d” is a clock drift, and in Expression (5), “x, y, z” Is a three-dimensional position vector of the portable electronic device 1 and “b” is a clock bias.

Further, the error covariance matrix (state noise) PosP of the position state vector PosX and the error covariance matrix (state noise) VelP of the velocity state vector VelX are defined as shown in the following equations (6) and (7). . The subscript “k” in the expression represents time.

Next, a speed prediction process for predicting the speed of the portable electronic device 1 is performed (step A3). Specifically, the following equation (8), according to (9), the predicted value of the velocity state vector velx velx ^-, and the prediction value of the error covariance matrix Velp Velp ^- is calculated.

式（１０）において、「Ａ」は、位置、及び、速度用のプロセスノイズ係数、「Ｄｆ」は、クロックドリフト用のプロセスノイズ係数である。 In Equation (9), “VelQ” is process noise and is defined as shown in Equation (10).

In Expression (10), “A” is a process noise coefficient for position and speed, and “Df” is a process noise coefficient for clock drift.

  Subsequently, a speed correction process for correcting the predicted speed is performed (step A5). FIG. 10 is a flowchart showing the flow of speed correction processing. In the speed correction process, the loop A process for each captured satellite is repeatedly executed.

In the loop A, first, based on the position of the target capturing satellite (captured satellite to be processed) and the position of the portable electronic device 1 obtained from the predicted value VelX ⁻ of the speed state vector calculated in the speed prediction process. Then, an observation matrix H indicating the line-of-sight direction from the portable electronic device 1 to the target capturing satellite is calculated (step B1). Further, an actual measurement value (measurement actual measurement value) of the reception frequency of the GPS satellite signal from the target capturing satellite is set as an observation value Z (step B3). Further, an error estimation matrix R in which a predetermined value is set as an error (speed R value) of the reception frequency as the observation value Z is set as a matrix indicating the measurement error of the observation value Z as an input value of the Kalman filter (step B5). ).

Next, the Kalman gain K is calculated according to the following equation (11) using the predicted value VelP ⁻ of the error covariance matrix calculated in the speed prediction process, the observation matrix H, and the error estimation matrix R (step B7). ).

Subsequently, the predicted value of the velocity state vector velx ^- and, by using the Kalman gain K, the observed value Z, an observation matrix H, in accordance with the following equation (12) calculates a correction value velx speed status vector (step B9).

このように、全ての捕捉衛星を対象としたループＡの処理を終了すると、速度補正処理を終了する。 Further, the correction value VelP of the error covariance matrix VelP is calculated according to the following equation (13) using the Kalman gain K, the observation matrix H, and the error covariance matrix predicted value VelP ⁻ (step B11).

As described above, when the processing of the loop A for all captured satellites is finished, the speed correction processing is finished.

When the speed correction process is completed, a position prediction process for predicting the position (predicted position) of the portable electronic device 1 is subsequently performed (step A7). Specifically, the following equation (14), according to (15), the predicted value PosX position state vector PosX ^-, and the predicted value of the error covariance matrix POSP POSP ^- is calculated.

式（１６）において、「Ａ」は、位置、速度用のプロセスノイズ係数、「Ｂｆ」は、クロックバイアス用のプロセスノイズ係数である。 In Expressions (14) and (15), “φ” is a state transition matrix, and is defined as a matrix that includes an elapsed time “Δt” from the previous KF positioning process as a component. “PosQ” is process noise and is defined as shown in Expression (16).

In Expression (16), “A” is a process noise coefficient for position and velocity, and “Bf” is a process noise coefficient for clock bias.

  Subsequently, position correction processing for correcting the predicted position is performed (step A9). FIG. 11 is a flowchart showing the flow of position correction processing. In the position correction process, the loop B process for each captured satellite is repeatedly executed.

  In the loop B, first, an observation matrix H indicating the line-of-sight direction from the portable electronic device 1 to the target capturing satellite is calculated (step C1). Further, an actual measurement value (measurement actual measurement value) of the code phase of the GPS satellite signal from the countermeasure capturing satellite is set as an observation value Z (step C3). Next, the position R value setting unit 122 performs position R value setting processing to set the position R value. (Step C5). The position R value setting process corresponds to calculating an index value.

  FIG. 12 is a flowchart showing the flow of the position R value setting process. According to FIG. 12, first, the reference position R value is set based on the signal strength of the GPS satellite signal of the target capturing satellite (step D1). Next, the reference position R value is changed based on the observation value Z which is the code phase of the captured satellite (step D3). That is, the reference position R value set based on the signal intensity is adjusted based on the observed value Z of the code phase. Subsequently, it is determined whether or not the portable electronic device 1 is stopped. If the portable electronic device 1 is stopped (step D5: stop), a predetermined value is added to change the reference position R value (step D7). If the portable electronic device 1 is not stopped (step D5: movement), the next step D7 is skipped. Further, an average value of the signal strengths of all captured satellites is calculated (step D9),

Further, the distance between the target capturing satellite and the portable electronic device 1 is simulated based on a time difference between the transmission time of the GPS satellite signal from the target capturing satellite and the reception time of the GPS satellite signal in the portable electronic device 1. The distance L1 is calculated (step D11). Moreover, the position P1 of the captured satellite, predicted value VelX speed status vector calculated by the velocity prediction processing ^- based on the predicted position of the portable electronic device 1 obtained from P2, the geometric positional relationship geometric An academic distance L2 is calculated (step D13). Then, a distance difference ΔL between the pseudo distance L1 and the geometric distance L2 is calculated and set as a determination value Y (step D15).

  Thereafter, whether the determination value Y is positive or negative is determined, and if it is “positive value” (step D17: positive (Y> 0)), the signal intensity of the target capturing satellite is compared with the average signal intensity (step D19). If the signal intensity of the target capturing satellite is smaller than the average signal intensity (step D19: YES), the determination value Y is further compared with the first threshold value (step D21). If the determination value Y is larger than the first threshold (step D21: YES), a value “Y × Y” is calculated as the candidate value Rt based on the determination value Y (step D23). Then, the calculated candidate value Rt is compared with the reference position R value, and if the reference position R value is smaller than the candidate value Rt (step D25: YES), the candidate value Rt is set as the reference position R value (step D27). ).

  Further, when the signal strength of the target captured satellite is equal to or higher than the average signal strength (step D19: NO), when the determination value Y is equal to or lower than the first threshold value (step D21: NO), and when the reference position R value is equal to or higher than the candidate value Rt In any case (step D25: NO), the subsequent processing is skipped.

  On the other hand, if the determination value Y is “negative value” (step D17: negative (Y ≦ 0)), the signal intensity of the target captured satellite is compared with the average signal intensity (step D29). If the signal strength is larger than the average signal strength (step D29: YES), the determination value Y is further compared with the second threshold value (step D31). If the determination value Y is smaller than the second threshold (step D31: YES), the value “(0.2 × Y) × (0.2 × Y)” is set as the candidate value Rt based on the determination value Y. Calculate (step D33). Then, the calculated candidate value Rt is compared with the reference position R value, and if the reference position R value is larger than the candidate value Rt (step D35: YES), the candidate value Rt is set as the reference position R value (step D37). ).

  Further, when the signal strength of the target captured satellite is equal to or lower than the average signal strength (step D29: NO), when the determination value Y is equal to or larger than the second threshold value (step D31: NO), and when the reference position R value is equal to or smaller than the candidate value Rt. In any case of (Step D35: NO), the subsequent processing is skipped. When the above process is performed, the position R value setting process is terminated.

  When the position R value setting process ends, an error estimation matrix R in which the position R value set in the position R value setting process is set is set as a matrix indicating the measurement error of the observed value Z that is the input value of the Kalman filter (step C7).

Subsequently, the Kalman gain K is calculated according to the following equation (17) using the predicted value PosP ⁻ of the error covariance matrix calculated in the position prediction process, the observation matrix H, and the error estimation matrix R (step) C9).

Subsequently, the position state vector correction value PosX is calculated according to the following equation (18) using the predicted value PosX ⁻ of the position state vector, the Kalman gain K, the observed value Z, and the observed matrix H (step) C11).

このように、全ての捕捉衛星を対象としたループＢの処理を終了すると、位置補正処理を終了する。 Further, the correction value PosP of the error covariance matrix is calculated according to the following equation (19) using the Kalman gain K, the observation matrix H, and the predicted value PosP ⁻ of the error covariance matrix (step C13).

As described above, when the process of loop B for all the captured satellites is completed, the position correction process is terminated.

  Thereafter, the position of the portable electronic device 1 calculated in the position calculation process is output (step A11), and the KF positioning process is terminated.

[Function and effect]
Thus, according to the present embodiment, it is possible to improve accuracy in positioning using the Kalman filter. That is, the position and velocity of the GPS receiver is set to the state vectors PosX and VelX, and the Kalman filter processing is performed with the code phase of the received captured satellite signal as the observation value Z. The R value is determined by (1) the distance difference ΔL between the pseudorange L1 of the captured satellite signal and the geometric distance L2 based on the geometric positional relationship between the GPS satellite and the GPS receiver, and (2) the captured satellite signal Set using signal strength.

  It should be noted that embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can of course be changed as appropriate without departing from the spirit of the present invention.

  For example, the GPS has been described as an example of the satellite positioning system, but other satellite positioning systems such as WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), and GALILEO. May be.

DESCRIPTION OF SYMBOLS 1 Portable electronic device, 10 GPS receiver, 12 GPS antenna, 14 RF receiving circuit part, 16 Baseband processing circuit part, 100 BB processing part, 110 Measurement acquisition part, 120 KF positioning calculation part, 122 Position R value setting part , 200 BB storage unit, 210 baseband program, 212 KF positioning program, 220 reference position R value setting table, 230 measurement data, 240 signal strength data, 250 KF parameter data, 260 positioning history data, 30 main processing unit, 32 operation Unit, 34 display unit, 36 sound output unit, 38 clock unit, 40 communication unit, 42 main storage unit

Claims (5)

For each captured satellite, the geometric distance obtained from the geometric positional relationship between the positioning device and the captured satellite, and the pseudo-range obtained using the signal propagation time from the captured satellite to the positioning device, Calculating the difference between
For each captured satellite, calculating an index value indicating an error of the captured satellite signal using the captured satellite signal intensity of the captured satellite by the positioning device and the difference regarding the captured satellite;
Positioning using the captured satellite signal of each captured satellite and the index value;
Including
To calculate the index value,
If the difference is longer than the geometric distance and the pseudorange is greater and the intensity satisfies a predetermined weak signal condition, the index value is a first value indicating that the error of the captured satellite signal is large. Value and
When the difference is shorter than the geometric distance and the pseudorange is shorter and the intensity satisfies a predetermined strong signal condition, the index value is a second value indicating that the error of the captured satellite signal is small. Value and
Positioning method including. The index value is set to the first value when the difference is longer than the geometric distance so that the pseudo distance satisfies a predetermined long condition and the intensity satisfies the predetermined weak signal condition. In addition, the index value is the first value.
The positioning method according to claim 1. The index value is set to the second value when the difference is shorter than the geometric distance so that the pseudo distance satisfies a predetermined short condition and the intensity satisfies the predetermined strong signal condition. The index value is the second value.
The positioning method according to claim 1 or 2. The positioning is to perform positioning by executing a Kalman filter process with the position of the positioning device as a state vector component, the pseudo distance as an observation value, and the index value as a measurement error.
The positioning method as described in any one of Claims 1-3. For each captured satellite, the geometric distance obtained from the geometric positional relationship between the positioning device and the captured satellite, and the pseudo-range obtained using the signal propagation time from the captured satellite to the positioning device, A difference calculation unit for calculating the difference between
For each captured satellite, an error index value calculation unit that calculates an index value indicating an error of the captured satellite signal using the intensity of the captured satellite signal of the captured satellite by the positioning device and the difference related to the captured satellite. When the pseudo distance is longer than the geometric distance and the intensity satisfies a predetermined weak signal condition, the difference between the index value and the captured satellite signal is large. When the pseudo-distance is shorter than the geometric distance and the intensity satisfies a predetermined strong signal condition, the index value is set as an error of the captured satellite signal. An error index value calculation unit serving as a second value indicating a small value;
A positioning device that performs positioning using a captured satellite signal of each captured satellite and the index value.

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