JP7752913B2 - Detection method and device for detecting satellites whose direction of arrival of received signals does not match the satellite orientation, and GNSS receiver - Google Patents

Description

The present invention relates to a technique for detecting a case where a satellite in a GNSS (Global Navigation Satellite System) has a mismatch between the direction of arrival of a received signal and the satellite orientation.

One known method for estimating the direction of arrival of a received signal is a device that determines whether a signal received from a GPS (Global Positioning System, short for Global Positioning Satellite) satellite has been affected by multipath interference (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2010-256301

The device in Patent Document 1 determines whether the received signal from each GPS satellite has been affected by multipath based on the phase difference between the received signals from each GPS satellite. However, the device in Patent Document 1 needs to have multiple receiving antennas in order to estimate the direction of arrival based on information from each GPS satellite.

Therefore, an object of the present invention is to provide a detection method and detection device that can detect with good accuracy, and with at least one receiving antenna, cases where the direction of arrival of a received signal does not match the satellite position in the satellite orbit information (specifically, the orientation in which the satellite is located as seen from the receiving antenna), as well as a GNSS receiver equipped with such a detection device.

In order to solve the above problem, the detection method of the present invention is characterized in that it detects a case where a satellite whose satellite orientation does not match the direction of arrival of a received signal for the positioning satellite, i.e., a case where the satellite positioning signal is present behind the receiver in the direction of travel and the positioning satellite is located in front of the receiver, or a case where the satellite positioning signal is present in front of the receiver in the direction of travel and the positioning satellite is located behind the receiver in the direction of travel, based on whether or not an observation code, which is the code of the amount of change over time of the Doppler shift with respect to the positioning satellite and is calculated based on a satellite positioning signal transmitted from the positioning satellite, matches an inference code, which is the code of the amount of change over time of the Doppler shift with respect to the positioning satellite and is the code that is the same over a predetermined length of time , and a

The detection method according to the present invention may take into consideration the magnitude of a Doppler residual calculated as the difference between the actual measured Doppler shift amount with respect to the positioning satellite observed based on the satellite positioning signal and the sum of the Doppler shift amount associated with the movement of the positioning satellite, the Doppler shift amount associated with the movement of the receiver, and the clock drift of the receiver.

Furthermore, the detection device according to the present invention is characterized in that it detects a case where a satellite whose satellite orientation does not match the direction of arrival of the received signal for the positioning satellite, i.e., a case where the satellite positioning signal is present behind the receiver in the direction of travel and the positioning satellite is located in front of the receiver, or a case where the satellite positioning signal is present in front of the receiver in the direction of travel and the positioning satellite is located behind the receiver in the direction of travel, based on whether or not an observation code, which is the code of the amount of change over time of the Doppler shift with respect to the positioning satellite and is calculated based on a satellite positioning signal transmitted from the positioning satellite, matches an inference code, which is the code of the amount of change over time of the Doppler shift with respect to the positioning satellite and is the code that is the same over a predetermined length of time , and a

The detection device according to the present invention may take into consideration the magnitude of a Doppler residual calculated as the difference between the actual measured Doppler shift amount with respect to the positioning satellite observed based on the satellite positioning signal and the sum of the Doppler shift amount associated with the movement of the positioning satellite, the Doppler shift amount associated with the movement of the receiver, and the clock drift of the receiver.

A GNSS receiver according to the present invention is characterized by including the above- described detection device.

According to the detection method , detection device, and GNSS receiver of the present invention, a satellite whose satellite orientation does not match the direction of arrival of a received signal from a positioning satellite is detected based on whether an observation code of the amount of change in Doppler shift with respect to the positioning satellite matches an inference code, making it possible to detect with high accuracy, and with at least one receiving antenna, a satellite whose satellite orientation does not match the direction of arrival of a received signal in the GNSS. By detecting a satellite whose satellite orientation does not match the direction of arrival of a received signal, the receiver can, for example , improve its positioning accuracy.

According to the detection method , detection device, and GNSS receiver of the present invention, if consideration is given to whether the observation code is the same over a predetermined length of time, it becomes possible to more accurately detect satellites whose arrival direction of the received signal in the GNSS does not match the satellite orientation.

According to the detection method , detection device, and GNSS receiver of the present invention, when the magnitude of the Doppler residual is taken into consideration, it becomes possible to more accurately detect satellites whose arrival direction of the received signal in the GNSS does not match the satellite orientation.

1 is a functional block diagram showing a schematic configuration of a GNSS receiver including a detection device according to an embodiment of the present invention; 2 is a flowchart showing the processing procedure in the detection device of FIG. 1 and the processing procedure of the detection method according to the embodiment of the present invention. FIG. 10 is a functional block diagram showing a schematic configuration of a GNSS receiver including a detection device according to another embodiment of the present invention.

The present invention will be described below based on the illustrated embodiment.

Fig. 1 is a functional block diagram showing a schematic configuration of a GNSS receiver 1 including a detection device 4 according to an embodiment of the present invention. Fig. 2 is a flowchart showing the processing procedure in the detection device 4 and the processing procedure of the detection method according to the embodiment of the present invention.

The GNSS receiver 1 according to the embodiment has the function of receiving satellite positioning signals transmitted from each of the multiple positioning satellites that make up the GNSS (Global Navigation Satellite System) to perform satellite positioning of its own position, and the function of detecting satellites whose arrival direction of the received GNSS signal does not match the satellite orientation (i.e., the orientation in which the positioning satellite is located as viewed from the GNSS receiver 1), and mainly has a GNSS receiving unit 2, a GNSS positioning unit 3 , and a detection device 4.

The GNSS receiver 1 is configured as a mechanism equipped with a central processing unit (CPU: abbreviation for Central Processing Unit) that performs calculations related to, for example, satellite positioning of its own position and detection of satellites whose satellite orientation does not match the direction of arrival of received GNSS signals, a ROM (abbreviation for Read Only Memory) that is a readable storage device, and a RAM (abbreviation for Random Access Memory) that is a readable and writable storage device. Specifically, the GNSS receiver 1 may be configured, for example, by using a computer to execute a program, or may be configured as hardware using one or more ICs (abbreviation for Integrated Circuits).

In this embodiment , a program for controlling the operation of a computer to function as a GNSS receiver 1 equipped with a detection device 4 is stored in ROM, and a central processing unit (CPU) executes the program to realize the GNSS receiving unit 2, GNSS positioning unit 3, and detection device 4 that constitute the GNSS receiver 1 as functional blocks. In addition, the RAM is used as a working area as necessary.

The GNSS receiver 2 receives via an antenna satellite positioning signals transmitted from each of the multiple positioning satellites Si (where i is a satellite number used to distinguish and identify each of the multiple positioning satellites) that make up the GNSS, and converts them into electrical signals (particularly digital signals). An example of a GNSS is the Global Positioning System (GPS, an abbreviation for Global Positioning Satellite).

The satellite positioning signal is superimposed on a carrier wave and transmitted sequentially from the positioning satellite Si as radio waves (called "GNSS radio waves"). The GNSS receiver 2 receives the GNSS radio waves and demodulates them to extract the satellite positioning signal.

The GNSS receiver 2 generates observation data for each positioning satellite Si from the extracted satellite positioning signals, including the pseudorange ρi, Doppler shift amount Di, Doppler shift time change amount ΔDi, satellite position, satellite status, and navigation data.

The pseudorange is the distance determined from the difference between the time when a satellite positioning signal (in other words, a GNSS radio wave) is transmitted from a positioning satellite Si and the time when it is received via the antenna at the GNSS receiver 2. The difference between the transmission time and the reception time can be calculated based on the phase shift of the C/A code. The C/A code is a unique code for each positioning satellite, and functions as information indicating the sender.

The pseudorange ρi of each positioning satellite Si is calculated by multiplying the difference between the time when the positioning satellite Si transmits a satellite positioning signal (GNSS radio waves) and the time when the GNSS receiver 2 receives the satellite positioning signal (GNSS radio waves) (i.e., the radio wave propagation time) by the speed of light.

The Doppler shift amount is a parameter that represents the difference between the carrier frequency of GNSS radio waves and the reception frequency at the GNSS receiver 2, which is caused by the Doppler effect.

The Doppler shift amount Di of each positioning satellite Si is calculated as the frequency difference between the carrier frequency of the GNSS radio waves transmitted by the positioning satellite Si and the carrier frequency of the GNSS radio waves received by the GNSS receiver 2. The carrier frequency of the GNSS radio waves transmitted by the positioning satellite Si is predetermined and stored in advance in a specified storage device provided in the GNSS receiver 1 (i.e., it is known). In other words, the Doppler shift amount Di of each positioning satellite Si is an observed and measured value.

The time change ΔDi of the Doppler shift of each positioning satellite Si is a parameter that represents the time change of the Doppler shift Di of each positioning satellite Si (i.e., the magnitude of change per unit time).

The satellite position is information indicating the current position of the positioning satellite Si on its satellite orbit, and specifically, its coordinates in a Cartesian three-dimensional coordinate system.

The satellite position (Xsi, Ysi, Zsi) of each positioning satellite Si is calculated based on the satellite orbit information of the positioning satellite Si (specifically, the almanac and ephemeris) and the time at which the positioning satellite Si transmitted the satellite positioning signal (GNSS radio waves).

Navigation data includes, for example, the satellite number, satellite orbit information (specifically, almanac and ephemeris) for the positioning satellite Si, and the time when the satellite positioning signal (GNSS radio waves) was transmitted.

The GNSS receiver 2 outputs the above observation data as satellite information for each positioning satellite Si at regular intervals (for example, each time a satellite positioning signal is received), along with the signal strength of the received satellite positioning signal and the time the satellite positioning signal (GNSS radio waves) was received. Instead of signal strength, the GNSS receiver 2 may also output the S/N (Signal-to-Noise ratio) or C/N (Carrier-to-Noise ratio).

The period at which the GNSS receiver 2 outputs satellite information is not limited to a specific time length, but may be set to a time length within a range of, for example, 50 to 200 milliseconds.

In addition, there are multiple positioning satellites, and the GNSS receiver 2 generates satellite information along with observation data from all satellite positioning signals that can be demodulated from GNSS radio waves, and outputs all of the generated satellite information. Positioning satellites that can be used for GNSS satellite positioning (in other words, positioning satellites that can capture GNSS radio waves and demodulate satellite positioning signals from the GNSS radio waves) are called "visible satellites," and the number of visible satellites is called the "number of visible satellites."

In other words, the GNSS receiver 2 outputs satellite information for each visible satellite Si at a regular interval, for the number of visible satellites.

The GNSS positioning unit 3 receives satellite information for each visible satellite Si output at regular intervals from the GNSS receiving unit 2, and uses this satellite information to perform calculations for satellite positioning of its own position.

The satellite positioning method used by the GNSS positioning unit 3 is a well-known technology and various methods exist (e.g., Patent No. 6546730). This invention is not limited to any particular method, so a detailed explanation will be omitted here.

The GNSS positioning unit 3 outputs at least information indicating the current position of the GNSS receiver 1 (specifically, coordinates in a Cartesian three-dimensional coordinate system) as a result of satellite positioning.

The detection device 4 is a mechanism for detecting satellites whose arrival direction of a received signal in the GNSS does not match the satellite orientation, and includes an acceleration vector calculation unit 41, a satellite selection unit 42, a Doppler residual calculation unit 43, a Doppler residual verification unit 44, a sign inference unit 45 for the time change amount of DS, and a sign verification unit 46 for the time change amount of DS (note that DS is an abbreviation for Doppler Shift).

The detection device 4 receives satellite information for each visible satellite Si output at regular intervals from the GNSS receiving unit 2; in other words, acquires satellite information for each visible satellite Si (step S1), and performs calculations based on the satellite information to detect satellites whose arrival direction of the received signal in the GNSS does not match the satellite orientation.

The detection device 4 and detection method according to the embodiment detect satellites whose satellite orientation does not match the direction of arrival of the received signal for a visible satellite Si, based on whether or not an observation code, which is the sign of the amount of change ΔDi in Doppler shift with respect to visible satellite Si calculated based on the satellite positioning signal transmitted from the visible satellite Si, matches an inference code, which is the sign of the amount of change ΔDi in Doppler shift with respect to visible satellite Si over time inferred from the direction of travel of the GNSS receiver 1 and the orientation in which the visible satellite Si is located as seen from the GNSS receiver 1 based on the satellite orbit information included in the satellite positioning signal.

The detection device 4 executes the processes from step S2 onwards every time it receives satellite information for each visible satellite Si output at a constant period from the GNSS receiving unit 2 (step S1), executes the processes from step S3 onwards for each visible satellite Si, and executes the processes from step S4 onwards for each visible satellite Si selected in the process of step S3. Then , for each visible satellite Si, the detection device 4 determines whether or not there is a satellite whose arrival direction of the received signal for that visible satellite Si does not match the satellite orientation.

The detection device 4 uses the Doppler residual to detect, from among multiple satellite positioning signals, satellites whose arrival direction of the received signal does not match the satellite orientation. By using the Doppler residual, if a satellite positioning signal arrives at the GNSS receiver 1 from a direction different from the actual position of a visible satellite due to the effects of multipath, for example, an error will be introduced into the satellite line of sight direction vector of the actual visible satellite Si, improving the detection accuracy of satellite positioning signals affected by multipath and reducing erroneous detection.

The detection device 4 also detects, from among the multiple satellite positioning signals, satellite positioning signals of satellites whose arrival direction of the received signal does not match the satellite orientation, based on the direction of change in the time change amount ΔDi of the Doppler shift for each visible satellite Si, which is inferred from the direction of travel of the GNSS receiver 1 and the relative positional relationship between the GNSS receiver 1 and each visible satellite Si.

If there is no satellite whose direction of arrival of the received GNSS signal does not match the satellite orientation, and the positioning satellite is located directly in front of the GNSS receiver 1 in the direction of travel, the GNSS receiver 1 and the positioning satellite will move relatively closer due to the acceleration of the GNSS receiver 1, and the sign of the time change in Doppler shift will be positive.

On the other hand, if there is no satellite whose direction of arrival of the received signal in the GNSS does not match the satellite orientation, and the positioning satellite is located behind the GNSS receiver 1 in the direction of travel, the GNSS receiver 1 and the positioning satellite will move relatively farther apart due to the acceleration of the GNSS receiver 1, and the sign of the time change in Doppler shift will be negative.

In contrast, if there is a satellite in the GNSS where the direction of arrival of the received signal does not match the satellite orientation, and the positioning satellite is located directly in front of the GNSS receiver 1 in the direction of travel, and the signal from the satellite where the direction of arrival of the received signal does not match the satellite orientation is located behind the GNSS receiver 1 in the direction of travel, the GNSS receiver 1 will move with acceleration, and the sign of the time change in Doppler shift will be negative, contrary to the expectation that the sign would be positive if the signal were from the original positioning satellite. Furthermore, in this case, the Doppler residual will be large.

Furthermore, if there is a satellite in the GNSS where the direction of arrival of the received signal does not match the satellite orientation, and a positioning satellite is located behind the GNSS receiver 1 in the direction of travel, and the signal of the satellite where the direction of arrival of the received signal does not match the satellite orientation is located in front of the GNSS receiver 1 in the direction of travel, the GNSS receiver 1 will move with acceleration, and the sign of the time change in Doppler shift will be positive, contrary to the expectation that the sign would be negative if the signal were from the original positioning satellite. Also, in this case, the Doppler residual will be large.

For this reason, if the Doppler residual is large and the sign of the observed value of the time change in Doppler shift ΔDi with respect to visible satellite Si does not match the sign of the time change in Doppler shift with respect to visible satellite Si inferred from the orientation of visible satellite Si as viewed from GNSS receiver 1 and the direction of travel of GNSS receiver 1, it is considered (highly likely) that there is a satellite for which the direction of arrival of the received signal for that visible satellite Si does not match the satellite orientation.

Based on the above concept, the detection device 4 performs the following processing in each unit to detect satellites for which the arrival direction of the received signal in the GNSS does not match the satellite orientation, on a visible satellite Si basis.

The acceleration vector calculation unit 41 calculates the acceleration vector of the GNSS receiver 1 (step S2).

The method for calculating the acceleration vector of the GNSS receiver 1 is well-known technology and there are various methods available. This invention is not limited to any particular method, so a detailed explanation will be omitted here.

The acceleration vector calculation unit 41 calculates the relative acceleration of the GNSS receiver 1 with respect to each visible satellite Si based on, for example, the time change in Doppler shift ΔDi contained in the satellite information for each visible satellite Si, and calculates the acceleration vector of each visible satellite Si based on the satellite orbit information (specifically, almanac and ephemeris) contained in the satellite information for each visible satellite Si and the time at which the positioning satellite Si transmitted a satellite positioning signal (GNSS radio waves).

The acceleration vector calculation unit 41 also calculates the direction of each visible satellite Si as seen from the GNSS receiver 1 (specifically, the azimuth in which each visible satellite Si is located as seen from the GNSS receiver 1) based on information indicating the current position of the GNSS receiver 1 (specifically, coordinates in a Cartesian three-dimensional coordinate system) output from the GNSS positioning unit 3 and the satellite position (Xsi, Ysi, Zsi) included in the satellite information for each visible satellite Si.

The acceleration vector calculation unit 41 further calculates the acceleration of the GNSS receiver 1 for each direction of each visible satellite Si based on the relative acceleration of the GNSS receiver 1 with respect to each visible satellite Si calculated above, the acceleration vector of each visible satellite Si, and the direction of each visible satellite Si as seen from the GNSS receiver 1, and calculates the acceleration vector of the GNSS receiver 1 based on the acceleration of the GNSS receiver 1 for each direction of each visible satellite Si.

Alternatively, the acceleration vector calculation unit 41 may calculate the acceleration vector of the GNSS receiver 1 based on the information output from the acceleration sensor 5 and the information output from the gyro sensor 6 (or yaw rate sensor) (see Figure 3).

The acceleration sensor 5 detects and outputs the acceleration of the GNSS receiver 1, in other words, the acceleration of the moving body (e.g., vehicle, ship, aircraft, etc.) on which the GNSS receiver 1 is mounted.

The gyro sensor 6 (or yaw rate sensor) detects and outputs the yaw rate of the GNSS receiver 1, in other words, the yaw rate of the moving body (e.g., vehicle, ship, aircraft, etc.) on which the GNSS receiver 1 is mounted.

In this case, the acceleration vector calculation unit 41 receives input of the acceleration detection value output from the acceleration sensor 5, and input of the yaw rate detection value output from the gyro sensor 6. Based on the yaw rate detection value, it integrates the yaw rate to determine the amount of change in yaw angle (in other words, azimuth angle) to calculate the traveling direction of the GNSS receiver 1, and also calculates the acceleration vector of the GNSS receiver 1 based on the traveling direction and the acceleration detection value. Note that the actual traveling direction (in other words, azimuth) is determined and set as a reference/initial value at least once.

The satellite selection unit 42 selects visible satellites Si to be subjected to the process of detecting satellites whose arrival direction of the received signal does not match the satellite orientation (step S3).

The satellite selection unit 42 first generates a set of Doppler shift time changes ΔDi for each visible satellite Si using the Doppler shift time changes ΔDi contained in the satellite information acquired in the most recent N (where N is a natural number) chronologically successive steps of step S1 processing (including the most recent step S1 processing).

The number N (referred to as the "continuation count N") above is not limited to a specific value (in other words, a length of time), but is set to an appropriate value, taking into consideration, for example, whether the positioning signals are transmitted/emitted from the same direction, given that the GNSS receiver 1 is moving with acceleration. The continuation count N may be set to a value in the range of approximately 3 to 5 (i.e., approximately 300 to 500 milliseconds), for example, when satellite information is output from the GNSS receiver 2 every 100 milliseconds and the GNSS positioning unit 3 performs satellite positioning calculations of its own position.

The satellite selection unit 42 then determines whether the signs of the Doppler shift time change amounts ΔDi included in the set of Doppler shift time change amounts ΔDi (i.e., for N consecutive occurrences) are all the same.

If the signs of the Doppler shift time change ΔDi for the N consecutive times are different (step S3: No), the satellite selection unit 42 determines that there is no satellite for the visible satellite Si whose direction of arrival of the received signal does not match the satellite orientation (step S8).

On the other hand, if the signs of the Doppler shift time change amounts ΔDi for the N consecutive times are all the same (step S3: Yes), the satellite selection unit 42 proceeds to step S4 to detect a satellite whose satellite orientation does not match the direction of arrival of the received signal for the visible satellite Si.

When the sign of the Doppler shift time change ΔDi for N consecutive times is the same, the GNSS receiver 1 and the signal source (including satellite signal sources where the direction of arrival of the received signal does not match the satellite orientation) are continuously moving closer to or farther away from each other with acceleration for a specified period of time.

The Doppler residual calculation unit 43 calculates the Doppler residual (step S4).

Specifically, the Doppler residual calculation unit 43 calculates the Doppler residual Ri of a visible satellite Si according to the following equation 1. The Doppler residual Ri of a visible satellite Si is the difference between the amount of Doppler shift Di from the visible satellite Si and the sum of the amount of Doppler shift Dsi associated with the movement of the visible satellite Si, the amount of Doppler shift Dr associated with the movement of the GNSS receiver 1, and the clock drift Δfrc of the GNSS receiver 1.
(Math. 1) Ri = Di-(Dsi+Dr+Δfrc)
where Ri: Doppler residual of visible satellite Si
Di: Doppler shift amount with visible satellite Si
Dsi: Doppler shift amount due to movement of visible satellite Si
Dr: Doppler shift amount associated with movement of the GNSS receiver 1
Δfrc: Clock drift of GNSS receiver 1

Specifically, Dsi is the amount of Doppler shift in the satellite line of sight to visible satellite Si due to changes in relative distance caused by movement of visible satellite Si, and is calculated as a quantity in the satellite line of sight to visible satellite Si based on the velocity vector of visible satellite Si and the current position of GNSS receiver 1 (specifically, coordinates in a Cartesian three-dimensional coordinate system).

Specifically, Dr is the amount of Doppler shift in the satellite line of sight to visible satellite Si due to changes in relative distance caused by movement of GNSS receiver 1, and is calculated as a quantity in the satellite line of sight to visible satellite Si based on the velocity vector of GNSS receiver 1 and the satellite position (Xsi, Ysi, Zsi) of visible satellite Si.

Δfrc is the clock drift of the GNSS receiver 1, and is estimated sequentially by the GNSS receiver 1 itself by calculating the receiver's velocity using the least squares method, a Kalman filter, etc.

The Doppler residual verification unit 44 determines whether the absolute value of the Doppler residual Ri of the visible satellite Si is greater than or equal to the Doppler residual threshold Rthr (step S5).

The Doppler residual threshold value Rthr is not limited to a specific value, but is set appropriately, taking into consideration, for example, whether it can properly detect deviations from the level normally expected for the Doppler residual Ri when receiving satellite positioning signals from the original positioning satellites that make up the GNSS. The Doppler residual threshold value Rthr may be set to, for example, any value within the range of approximately 0.6/λ to 2.0/λ [Hz]. However, this uses the fact that, where λ is the wavelength [m] of the carrier wave and the relative movement speed is v [m/s], the Doppler shift amount d [Hz] can be expressed as d = v/λ.

If |Ri|<Rthr (step S5: No), the Doppler residual verification unit 44 determines that the Doppler residual Ri of the visible satellite Si is small, and therefore that there is no satellite for which the direction of arrival of the received signal does not match the satellite orientation for that visible satellite Si (step S8).

On the other hand, if |Ri|≧Rthr (step S5: Yes), the Doppler residual verification unit 44 proceeds to step S6 to detect satellites whose arrival direction of the received signal for the visible satellite Si does not match the satellite orientation.

The DS time change sign inference unit 45 infers whether the sign of the time change ΔDi of the Doppler shift with respect to the visible satellite Si is expected to be positive or negative (step S6).

Specifically, the DS time change amount sign inference unit 45 infers whether the sign of the time change amount ΔDi of the Doppler shift with respect to visible satellite Si should be positive or negative, based on the relative relationship between the direction of travel of the GNSS receiver 1, which is based on the acceleration vector of the GNSS receiver 1 calculated in the processing of step S2, and the orientation of the visible satellite Si as seen from the GNSS receiver 1, which is based on the ephemeris included in the satellite information.

In other words, based on the direction of travel of GNSS receiver 1 and the orientation in which visible satellite Si is located, if GNSS receiver 1 and visible satellite Si are approaching each other due to acceleration, the time change in Doppler shift ΔDi with visible satellite Si should be positive; conversely, if GNSS receiver 1 and visible satellite Si are moving away due to acceleration, the time change in Doppler shift ΔDi with visible satellite Si should be negative.

The DS time change sign verification unit 46 determines whether the sign of the time change in Doppler shift ΔDi (referred to as the "observation sign") included in the satellite information for each visible satellite Si matches the sign of the time change in Doppler shift for the visible satellite Si inferred in the processing of step S6 (referred to as the "inference sign") (step S7).

If the observed code and inferred code for the amount of change in Doppler shift over time match (step S7: Yes), the DS time change code verification unit 46 determines that the signs of the observed values of the amount of change in Doppler shift over time ΔDi are consistent, and therefore that there is no satellite for the visible satellite Si in question whose direction of arrival of the received signal does not match the satellite orientation (step S8).

On the other hand, if the observed code and inferred code of the time change in Doppler shift do not match (step S7: No), the DS time change code verification unit 46 determines that the signs of the observed values of the time change in Doppler shift ΔDi are inconsistent, and that a satellite has emerged for which the direction of arrival of the received signal does not match the satellite orientation for the visible satellite Si (step S9).

When the detection device 4 detects a visible satellite Si whose satellite orientation does not match the direction of arrival of the received signal, it may exclude the satellite information about the visible satellite Si from the information used in the satellite positioning calculation process, and may also notify the user that a satellite whose satellite orientation does not match the direction of arrival of the received signal has occurred (or is highly likely to exist), for example, by displaying a message on a display (not shown) or emitting a sound from a speaker (not shown).

According to the detection method , detection device 4, and GNSS receiver 1 of the embodiment, a satellite whose direction of arrival of a received signal for a visible satellite Si does not match the satellite orientation is detected based on whether the observation code and inference code of the time change amount ΔDi of the Doppler shift with respect to the visible satellite Si match. Therefore, it is possible to detect with good accuracy, and with at least one receiving antenna, a satellite whose direction of arrival of a received signal in the GNSS does not match the satellite orientation.

The detection method , detection device 4, and GNSS receiver 1 according to the embodiment also take into consideration whether the sign (i.e., observation code) of the time change amount ΔDi of the Doppler shift with respect to a visible satellite Si remains the same for N consecutive times (in other words, a predetermined length of time), making it possible to more accurately detect satellites whose arrival direction of a received signal in the GNSS does not match the satellite orientation.

The detection method , detection device 4, and GNSS receiver 1 according to the embodiment also take into account the magnitude of the Doppler residual, making it possible to more accurately detect satellites whose arrival direction of the received signal in the GNSS does not match the satellite orientation.

The above describes an embodiment of the present invention, but the specific configuration is not limited to the above embodiment, and design changes that do not deviate from the gist of the present invention are also included in the present invention.

For example, in the above embodiment, the detection device 4 according to the present invention is incorporated into the GNSS receiver 1 whose schematic configuration is shown in Fig. 1, but the equipment/devices in which the detection device 4 according to the present invention can be incorporated or linked are not limited to the GNSS receiver 1 whose schematic configuration is shown in Fig. 1. The detection device according to the present invention may be incorporated into or linked to a GNSS receiver having another configuration. Furthermore, the detection device according to the present invention may be incorporated into or linked to other types of equipment or devices that use GNSS. Furthermore, the detection device according to the present invention may be used alone. Furthermore, the GNSS receiving unit 2 may be configured to output only the observation data/satellite information necessary for the detection device 4 to perform a calculation process to detect satellites whose satellite orientation does not match the direction of arrival of the received GNSS signal.

In addition to the configuration of the above embodiment, for example, if a certain number of positioning satellites or more are detected as positioning satellites whose incoming direction of the received signal and satellite orientation do not match, it may be determined that there is a risk of a decrease in positioning accuracy, and satellite positioning may be suspended. In that case, if a gyro sensor or acceleration sensor is available, it may be possible to switch to inertial navigation.

As an example of how the above embodiment can be used, for example, when a transmission signal containing positioning information and orbital information from multiple positioning satellites is transmitted from a single transmitting antenna and received by a receiver, applying this invention makes it possible to detect satellites whose direction of arrival of the received signal does not match the satellite orientation. The above situation can also be said to be one in which signals appear to be transmitted from multiple positioning satellites. In this regard, "signals transmitted from multiple positioning satellites" in this invention includes signals transmitted from a single transmitting antenna while appearing to be transmitted from multiple positioning satellites.

REFERENCE SIGNS LIST 1 GNSS receiver 2 GNSS receiving unit 3 GNSS positioning unit 4 Detection device 41 Acceleration vector calculation unit 42 Satellite selection unit 43 Doppler residual calculation unit 44 Doppler residual verification unit 45 Sign inference unit for DS time change amount 46 Sign verification unit for DS time change amount 5 Acceleration sensor 6 Gyro sensor

Claims (5)

Among observation codes which are codes of the time change amount of Doppler shift with respect to the positioning satellite calculated based on the satellite positioning signal transmitted from the positioning satellite, the observation codes which remain the same over a predetermined time length ;
an inference code that is a code of a time change amount of Doppler shift with respect to the positioning satellite, which is inferred from the traveling direction of a receiver that receives the satellite positioning signal while moving with acceleration and the orientation of the positioning satellite as seen from the receiver based on satellite orbit information included in the satellite positioning signal;
and detects whether or not there is a satellite whose arrival direction of the received signal for the positioning satellite does not match the satellite orientation , i.e., whether or not the satellite positioning signal is present behind the receiver in the traveling direction and the positioning satellite is located in front of the receiver in the traveling direction, or whether or not the satellite positioning signal is present in front of the receiver in the traveling direction and the positioning satellite is located behind the receiver in the traveling direction .
A detection method characterized by: taking into consideration the magnitude of a Doppler residual calculated as the difference between the actual measured Doppler shift amount with respect to the positioning satellite observed based on the satellite positioning signal and the sum of the Doppler shift amount associated with the movement of the positioning satellite, the Doppler shift amount associated with the movement of the receiver, and the clock drift of the receiver;
2. The detection method according to claim 1 . Among observation codes which are codes of the time change amount of Doppler shift with respect to the positioning satellite calculated based on the satellite positioning signal transmitted from the positioning satellite, the observation codes which remain the same over a predetermined time length ;
an inference code that is a code of a time change amount of Doppler shift with respect to the positioning satellite, which is inferred from the traveling direction of a receiver that receives the satellite positioning signal while moving with acceleration and the orientation of the positioning satellite as seen from the receiver based on satellite orbit information included in the satellite positioning signal;
and detects whether or not there is a satellite whose arrival direction of the received signal for the positioning satellite does not match the satellite orientation , i.e., whether or not the satellite positioning signal is present behind the receiver in the traveling direction and the positioning satellite is located in front of the receiver in the traveling direction, or whether or not the satellite positioning signal is present in front of the receiver in the traveling direction and the positioning satellite is located behind the receiver in the traveling direction .
A detection device characterized by: taking into consideration the magnitude of a Doppler residual calculated as the difference between the actual measured Doppler shift amount with respect to the positioning satellite observed based on the satellite positioning signal and the sum of the Doppler shift amount associated with the movement of the positioning satellite, the Doppler shift amount associated with the movement of the receiver, and the clock drift of the receiver;
4. The detection device according to claim 3 . A detection device according to claim 3 or 4 ,
GNSS receiver characterized by: