Patent Description:
In an independent positioning scheme in which a positioning device independently determines a position by using code information of a GNSS signal from a satellite positioning system (GNSS: Global Navigation System) such as a GPS (Global Positioning System ), an error included in the GNSS signal results in positioning accuracy on the order of meters.

Compared to the independent positioning scheme, a positioning scheme using reinforcement information realizes high accuracy positioning on the order of centimeters.

This positioning scheme uses observed data at an electronic reference point or the like, the accurate coordinates of which are known, to estimate an error arising from a positioning satellite and an error arising from an atmospheric state for each positioning satellite and provide an amount of error correction as the reinforcement information to a positioning device.

The reinforcement information is transmitted from a quasi-zenith satellite or a wireless LAN (Local Area Network) network, for example, to be provided to the positioning device.

The positioning device performs error correction on a result of independent positioning by using the amount of error correction in the reinforcement information to thus be able to realize high accuracy positioning on the order of centimeters.

A technique disclosed in Patent Literature <NUM> relates to the high accuracy positioning using the reinforcement information, for example.

Patent Literature <NUM>: <CIT>
<CIT> aims at disclosing a special dilution of precision (DOP) GPS optimization utilizing DOP minimization measures to select a constellation of four (and fewer, with constraints) GPS satellites to form a navigation solution with optimized accuracy in the desired orthogonal component(s) of position and velocity, and the desired component of time. OA9803 aims at disclosing a GPS receiver for use with NAVSTAR, comprising means to process a signal using an open loop estimator of signal parameters. <CIT> aims at disclosing a method for determining a normal performance of the navigation augmentation system and determining a predicted performance of the navigation augmentation system based on determining the normal performance. Journal article "<NPL> relates to a Japanese centimeter-class augmentation system utilizing the Quasi-Zenith Satellite System (QZSS) estimating individual GPS error components using the undifferenced observables by a State Space Model and generating a State Space Representation that is a functional and stochastic description of a state.

It is desired to use reinforcement information on the order of centimeters in order to realize satellite positioning with high accuracy.

On the other hand, a communication bandwidth of as much as <NUM> kbps (wherein bps is bits per second) is required to transmit the reinforcement information on the order of centimeters.

The quasi-zenith satellite or the wireless LAN network transmits information used in various services in addition to the reinforcement information, where there is a problem that transmission of the reinforcement information constrains a communication bandwidth used for another information.

It is one of the main objects of the present invention to solve the aforementioned problem, and it is the main object to achieve high accuracy positioning without constraining the communication bandwidth.

In order to solve the problem, a positioning device is provided according to claims <NUM>-<NUM>. The invention is defined by the device claim <NUM>. Further details are defined by dependent claims <NUM>-<NUM>.

In a further development of the invention, cf. dependent claim <NUM>, there is provided a process noise adjustment unit which is adapted to select process noise smaller in an altitude direction than a default value when the moving body is any of a vehicle, a train and a ship.

According to the present invention, the communication bandwidth can be used effectively by reducing an amount of information in reinforcement information.

Moreover, according to the present invention, the reinforcement information is manipulated to realize high accuracy positioning so that relatively high positioning accuracy can be maintained.

The first and second embodiments do not pertain to the claimed invention, which is instead based on the third and fourth embodiments.

<FIG> is a diagram illustrating a configuration example of a positioning system according to the present embodiment.

An information processing device <NUM> in <FIG> generates reinforcement information on the order of centimeters and degrades the generated reinforcement information on the order of centimeters to generate reinforcement information on the order of decimeters.

The information processing device <NUM> then provides the reinforcement information on the order of decimeters to a quasi-zenith satellite <NUM> or a wireless LAN network <NUM> to be described.

Note that the reinforcement information on the order of centimeters is a piece of information used to correct a positioning error that occurs in independent positioning using a positioning signal from a GPS satellite, and is a piece of reinforcement information by which positioning accuracy on the order of centimeters is achieved as positioning accuracy after the correction.

The positioning accuracy on the order of centimeters means that the positioning error falls within the order of two to three centimeters with a probability of <NUM> % or higher.

On the other hand, the reinforcement information on the order of decimeters is a piece of information used to correct the positioning error that occurs in independent positioning using the positioning signal from the GPS satellite, and is a piece of reinforcement information by which positioning accuracy on the order of decimeters is achieved as the positioning accuracy after the correction.

The positioning accuracy on the order of decimeters means that the positioning error falls within the order of <NUM> to <NUM> centimeters with a probability of <NUM> % or higher.

The quasi-zenith satellite <NUM> receives reinforcement information on the order of decimeters <NUM> obtained by the information processing device <NUM> from a transmitter <NUM>, and transmits the reinforcement information on the order of decimeters being received to the earth.

The quasi-zenith satellite <NUM> transmits the reinforcement information on the order of decimeters <NUM> with any one of frequencies L1, L2, and L5, for example.

Note that while the present embodiment describes an example of transmitting the reinforcement information on the order of decimeters <NUM> from the quasi-zenith satellite <NUM>, the reinforcement information on the order of decimeters <NUM> may instead be transmitted from a satellite other than the quasi-zenith satellite <NUM>. Alternatively, the reinforcement information on the order of decimeters <NUM> may be transmitted from the wireless LAN network <NUM> providing a wireless LAN environment.

A GPS satellite <NUM> being a positioning satellite transmits a positioning signal <NUM>.

A GNSS satellite such as GLONASS, Galileo, or BeiDou may be used instead of the GPS satellite <NUM>.

Moreover, the GPS satellite <NUM> may be adapted to transmit the reinforcement information on the order of decimeters <NUM>.

The positioning signal <NUM> includes observed data <NUM> and a broadcast ephemeris <NUM>.

A pseudorange between a positioning point and the GPS satellite <NUM> as well as a carrier phase can be derived from the observed data <NUM>.

Each of the pseudorange and the carrier phase derived from the observed data <NUM> includes an error.

A positioning device <NUM> uses the reinforcement information on the order of decimeters <NUM> to eliminate the error included in each of the pseudorange and the carrier phase.

The broadcast ephemeris <NUM> is a piece of data notifying of an accurate satellite orbit of the GPS satellite <NUM> from which the broadcast ephemeris <NUM> is transmitted, and is also called an ephemeris.

The positioning device <NUM> can be a smart phone, a mobile phone, a tablet terminal, or a car navigation system, for example.

The positioning device <NUM> receives the positioning signal <NUM> transmitted from the GPS satellite <NUM>.

The positioning device <NUM> also receives the reinforcement information on the order of decimeters <NUM> transmitted from the quasi-zenith satellite <NUM> or the wireless LAN network <NUM>.

When receiving the reinforcement information on the order of decimeters <NUM> from the quasi-zenith satellite <NUM>, the positioning device <NUM> needs to support any one of the frequencies L1, L2, and L5.

The positioning device <NUM> applies the reinforcement information on the order of decimeters <NUM> to the positioning signal <NUM> (including a positioning error on the order of meters) to be able to obtain a positioning result with positioning accuracy on the order of decimeters.

The transmitter <NUM> transmits the reinforcement information on the order of decimeters <NUM> generated by the information processing device <NUM> to the quasi-zenith satellite <NUM>.

Now, there will be described an error value included in the reinforcement information on the order of centimeters.

The reinforcement information on the order of centimeters includes a value of a satellite clock error (hereinafter simply referred to as a satellite clock error), a value of a satellite orbit error (hereinafter simply referred to as a satellite orbit error), an inter-frequency bias, a value of an ionospheric delay error (hereinafter simply referred to as an ionospheric delay error), and a value of a tropospheric delay error (hereinafter simply referred to as a tropospheric delay error).

The satellite clock error, the satellite orbit error, and the inter-frequency bias are errors independent of a region.

The ionospheric delay error and the tropospheric delay error are errors dependent on a region and are calculated for each grid point.

The grid point is a virtual measurement point arranged at approximately <NUM>-km intervals in each of a latitude direction and a longitude direction as illustrated in <FIG>.

The ionospheric delay error and the tropospheric delay error correspond to a geographic interval error value to be described later.

Note that the reinforcement information on the order of centimeters is updated in a predetermined update cycle (specifically, the satellite clock error is updated in a cycle of five seconds, while the other errors being the satellite orbit error, the inter-frequency bias, the ionospheric delay error and the tropospheric delay error are updated in a cycle of <NUM> seconds).

<FIG> is a diagram illustrating a configuration example of the information processing device <NUM> according to the present embodiment.

A reinforcement information generation unit <NUM> in <FIG> generates the reinforcement information on the order of centimeters.

The reinforcement information generation unit <NUM> may generate the reinforcement information on the order of centimeters by an arbitrary method.

A reinforcement information adjustment unit <NUM> reduces the amount of information in the reinforcement information on the order of centimeters generated by the reinforcement information generation unit <NUM> to generate the reinforcement information on the order of decimeters.

More specifically, the reinforcement information adjustment unit <NUM> reduces the amount of information in the reinforcement information on the order of centimeters by combining update cycle adjustment processing <NUM>, geographic interval error value adjustment processing <NUM>, and bit count adjustment processing <NUM>.

The update cycle adjustment processing <NUM> is processing that sets the update cycle of the reinforcement information on the order of centimeters to be an integer multiple of the predetermined update cycle.

In the present embodiment, as an example of the update cycle adjustment processing <NUM>, there will be described processing that sets the update cycle of the reinforcement information on the order of centimeters to a cycle of <NUM> seconds being twice the original cycle of <NUM> seconds. Note that in the update cycle adjustment processing <NUM>, the update cycle of the reinforcement information on the order of centimeters may be adjusted to an integer multiple being twice or larger of the original update cycle, not necessarily twice.

The geographic interval error value adjustment processing <NUM> is processing that reduces the number of geographic interval error values by selecting the geographic interval error value every geographic interval being an integer multiple of a predetermined geographic interval from among a plurality of geographic interval error values that is an error in the every predetermined geographic interval.

In the present embodiment, as an example of the geographic interval error value adjustment processing <NUM>, there will be described processing that reduces the number of each of the ionospheric delay errors and the tropospheric delay errors by extracting the ionospheric delay error and the tropospheric delay error every <NUM> being three times as long as <NUM> that is the grid point interval in each of the latitude direction and the longitude direction. Note that in the geographic interval error value adjustment processing <NUM>, the ionospheric delay error and the tropospheric delay error may be extracted every geographic interval being an integer multiple being twice or larger of the original grid point interval, not necessarily three times.

The bit count adjustment processing <NUM> is processing that reduces a bit count of the error value for each error value.

In the present embodiment, as an example of the bit count adjustment processing <NUM>, there will be described processing that reduces the bit count, for each error value relevant to the carrier wave, starting from the least significant bit, such that the bit count after reduction is equal to any bit count between <NUM> % and <NUM> % of the bit count before the reduction. Note that in the bit count adjustment processing <NUM>, the bit count may be reduced starting from the least significant bit such that the bit count after the reduction is smaller than the bit count before the reduction, not necessarily equal to the bit count between <NUM> % and <NUM> % of the bit count before the reduction.

A reinforcement information output unit <NUM> outputs, to an output destination, the reinforcement information on the order of decimeters being the reinforcement information after the amount of information is reduced.

The output destination of the reinforcement information output unit <NUM> is an interface of the transmitter <NUM> or an interface of the wireless LAN network <NUM>, for example.

Next, an operational example of the information processing device <NUM> according to the present embodiment will be described.

<FIG> is a flowchart illustrating an operational example of the information processing device <NUM> according to the present embodiment.

First, in step S101, the reinforcement information generation unit <NUM> generates the reinforcement information on the order of centimeters.

Then in step S102, the reinforcement information adjustment unit <NUM> degrades the reinforcement information on the order of centimeters to generate the reinforcement information on the order of decimeters.

Finally, in step S103, the reinforcement information output unit <NUM> outputs the reinforcement information on the order of decimeters generated by the reinforcement information adjustment unit <NUM> to the output destination.

The output destination of the reinforcement information output unit <NUM> is the interface of the transmitter <NUM> or the interface of the wireless LAN network <NUM> as described above, for example.

Next, there will be described in detail the operation in step S102 illustrated in <FIG>.

<FIG> is a flowchart illustrating the details of step S102.

First, in step S1021, the reinforcement information adjustment unit <NUM> performs the update cycle adjustment processing.

The update cycle adjustment processing will be described in detail with reference to <FIG>.

A data stream of the reinforcement information on the order of centimeters is illustrated in (a) of <FIG>.

As illustrated in (a) of <FIG>, the update cycle of the reinforcement information on the order of centimeters is <NUM> seconds.

Reinforcement information (t = <NUM>) is the reinforcement information on the order of centimeters transmitted from the quasi-zenith satellite <NUM> or the wireless LAN network <NUM> between time t = <NUM> and time t = <NUM>.

The same applies to time t = <NUM> onward.

During <NUM> seconds from time t = <NUM> to time t = <NUM>, the satellite clock error, the satellite orbit error, the inter-frequency bias, the ionospheric delay error at each grid point, and the tropospheric delay error at each grid point at a measurement timing T0 (T0 < (t = <NUM>)) are transmitted as the reinforcement information (t = <NUM>).

Then, during <NUM> seconds from time t = <NUM> to time t = <NUM>, the satellite clock error, the satellite orbit error, the inter-frequency bias, the ionospheric delay error at each grid point, and the tropospheric delay error at each grid point at a new measurement timing T1 (T1 < (t = <NUM>)) are transmitted as the reinforcement information (t = <NUM>).

Note that, strictly speaking, the satellite clock error is transmitted five times during <NUM> seconds since a satellite clock error is updated every five seconds, but the reinforcement information as a whole is updated in the cycle of <NUM> seconds.

As illustrated in (a) of <FIG>, the reinforcement information generation unit <NUM> repeatedly generates the reinforcement information on the order of centimeters in increments of <NUM> seconds and inputs the information to the reinforcement information adjustment unit <NUM>.

As illustrated in (b) of <FIG>, the reinforcement information adjustment unit <NUM> selects the reinforcement information on the order of centimeters in increments of <NUM> seconds.

In an example illustrated in (b) of <FIG>, the reinforcement information adjustment unit <NUM> selects the reinforcement information (t = <NUM>) between time t = <NUM> and time t = <NUM>, and spends <NUM> seconds transmitting the reinforcement information (t = <NUM>).

That is, the reinforcement information adjustment unit <NUM> transmits the reinforcement information (t = <NUM>) at a rate half the transmission rate in (a) of <FIG>.

The reinforcement information adjustment unit <NUM> does not select the following reinforcement information (t = <NUM>) between time t = <NUM> and time t = <NUM>.

Moreover, the reinforcement information adjustment unit <NUM> selects the reinforcement information (t = <NUM>) between time t = <NUM> and time t = <NUM>, and spends <NUM> seconds transmitting the reinforcement information (t = <NUM>).

Only the reinforcement information on the order of centimeters selected in the update cycle adjustment processing (step S1021) is subjected to the processing from step S1022 onward.

The number of pieces of reinforcement information on the order of centimeters to be subjected to the processing in step S1022 is reduced by half when the update cycle adjustment processing (step S1021) is performed by the method illustrated in (b) of <FIG>.

Referring back to <FIG>, the reinforcement information adjustment unit <NUM> performs the geographic interval error value adjustment processing in step S1022.

The reinforcement information adjustment unit <NUM> performs the geographic interval error value adjustment processing on each reinforcement information on the order of centimeters selected in step S <NUM>.

The geographic interval error value adjustment processing will be described in detail with reference to <FIG>.

Each point in <FIG> indicates the grid point.

The reinforcement information on the order of centimeters selected in step S1021 each includes the ionospheric delay error and the tropospheric delay error of all the grid points.

In step S1022, the reinforcement information adjustment unit <NUM> reduces the number of each of the ionospheric delay errors and the tropospheric delay errors by selecting the ionospheric delay error and the tropospheric delay error every three grid points (<NUM>) in each of the latitude direction and the longitude direction from among the ionospheric delay errors and the tropospheric delay errors of all the grid points included in the reinforcement information on the order of centimeters.

As a result of the reduction, only the ionospheric delay error and the tropospheric delay error corresponding to the grid point filled in with black in <FIG> are selected to be subjected to the processing in step S1023.

The number of each of the ionospheric delay errors and the tropospheric delay errors to be subjected to the processing in step S1023 is reduced to one ninth when the geographic interval error value adjustment processing (step S1022) is performed by the method illustrated in <FIG>.

That is, a multiplication of one third in the latitude direction by one third in the longitude direction gives one ninth overall.

Note that a reference numeral <NUM> and a reference numeral <NUM> in <FIG> indicate the ionospheric delay error and the tropospheric delay error included in the reinforcement information on the order of centimeters.

The positioning device <NUM> can calculate estimated values (a reference numeral <NUM> and a reference numeral <NUM>) of the ionospheric delay error and the tropospheric delay error at a grid point not included in the reinforcement information on the order of centimeters by performing linear interpolation between the ionospheric delay errors and the tropospheric delay errors (the reference numeral <NUM> and the reference numeral <NUM>) included in the reinforcement information on the order of centimeters.

However, actual ionospheric delay error and tropospheric delay error can possibly have errors (a reference numeral <NUM> and a reference numeral <NUM>) with respect to the estimated values (the reference numeral <NUM> and the reference numeral <NUM>).

The reinforcement information adjustment unit <NUM> notifies of a decrease in reliability caused by the errors (the reference numeral <NUM> and the reference numeral <NUM>) with respect to the estimated values at the grid point not included in the reinforcement information on the order of centimeters in the form of integrity information to be described later.

Referring back to <FIG>, the reinforcement information adjustment unit <NUM> performs the bit count adjustment processing in step S1023.

The bit count adjustment processing will be described in detail with reference to <FIG>.

In <FIG>, a reference numeral <NUM> denotes an error value on the order of centimeters and a reference numeral <NUM> denotes an error value on the order of decimeters.

The error value on the order of centimeters <NUM> is each error value included in the reinforcement information on the order of centimeters.

The error value on the order of decimeters <NUM> is an error value obtained after reducing the bit count of the error value on the order of centimeters <NUM>.

In the bit count adjustment processing (step S1023), the reinforcement information adjustment unit <NUM> reduces the bit count, for each error value relevant to the carrier wave, starting from the least significant bit (LSB), such that the bit count of the error value on the order of decimeters <NUM> is equal to any bit count between <NUM> % and <NUM> % of the bit count of the error value on the order of centimeters <NUM>.

When the error value on the order of centimeters <NUM> has <NUM> bits, for example, the reinforcement information adjustment unit <NUM> reduces the bit count such that the bit count of the error value on the order of decimeters <NUM> is equal to any value between <NUM> bits and <NUM> bits.

The reinforcement information adjustment unit <NUM> reduces the satellite clock error, the satellite orbit error, and the inter-frequency bias included in the reinforcement information on the order of centimeters selected in step S1021 and the bit count of each of the ionospheric delay error and the tropospheric delay error (the ionospheric delay error and the tropospheric delay error corresponding to the grid point filled in with black in <FIG>) included in the reinforcement information on the order of centimeters and selected in step S1022.

Note that the reinforcement information adjustment unit <NUM> notifies of the decrease in reliability caused by reducing the bit count in the form of the integrity information to be described later.

Through step S1021 to step S1023 described above, the amount of information in the reinforcement information on the order of centimeters is reduced to be the reinforcement information on the order of decimeters.

A bandwidth of <NUM> kbps is required to transmit the reinforcement information on the order of centimeters, while a bandwidth at a level of <NUM> bps is sufficient to transmit the reinforcement information on the order of decimeters.

As a result, the data volume can be reduced to approximately one eighth by converting the reinforcement information on the order of centimeters into the reinforcement information on the order of decimeters.

Moreover, the reinforcement information adjustment unit <NUM> uses the reduced bit count and information on the reduced grid point to be able to calculate reliability of the reinforcement information when the amount of information therein is reduced, on the basis of reliability of the reinforcement information obtained from the reinforcement information on the order of centimeters.

The reinforcement information adjustment unit <NUM> can find the reliability of the reinforcement information on the order of decimeters by obtaining a root sum square (RSS) of the reliability of the reinforcement information on the order of centimeters, the decrease in the reliability caused by the bit reduction, and the decrease in the reliability caused by reducing the grid point.

That is, the reinforcement information adjustment unit <NUM> calculates a root sum square RSS of the error <NUM> and the error <NUM> illustrated in <FIG> and calculates a root sum square RSS of an error corresponding to the bit count reduced as illustrated in <FIG> to find the reliability of the reinforcement information on the order of decimeters.

The reinforcement information adjustment unit <NUM> then includes the reliability as the integrity information into the reinforcement information.

The reinforcement information adjustment unit <NUM> thus generates the integrity information notifying of the decrease in reliability of the positioning accuracy caused by the geographic interval error value adjustment processing and the bit count adjustment processing and includes the integrity information being generated into the reinforcement information on the order of decimeters.

The reinforcement information output unit <NUM> transmits the reinforcement information including the integrity information.

The integrity information allows a user who uses the reinforcement information on the order of decimeters to find reliability of a measurement result from the basis of the reinforcement information in real time and is an essential piece of information in controlling a moving body.

According to the present embodiment described above, the reinforcement information on the order of centimeters is converted to the reinforcement information on the order of decimeters to be able to compress the data volume of the reinforcement information down to approximately one eighth and allow the communication bandwidth to be used effectively.

Moreover, as the reinforcement information on the order of centimeters requires <NUM> kbps to be transmitted, an L6 frequency needs to be used when the information is transmitted from the quasi-zenith satellite or the like.

The reinforcement information on the order of decimeters can be transmitted at the level of <NUM> bps so that the L1, L2, or L5 frequency can be used when the information is transmitted from the quasi-zenith satellite or the like.

The smart phone, mobile phone, tablet terminal, and car navigation system generally support the L1, L2, or L5 frequency and can thus realize positioning with relatively high accuracy on the order of decimeters even without a circuit or the like for the L6 frequency.

There has been described the method of reducing the number of each of the ionospheric delay errors and the tropospheric delay errors in the first embodiment.

In the present embodiment, there will be described a method of generating reinforcement information on the order of decimeters without reducing the number of each of the ionospheric delay errors and the tropospheric delay errors.

In the present embodiment as well, a positioning system has an overall configuration as illustrated in <FIG>, and an information processing device <NUM> has an internal configuration as illustrated in <FIG>.

Note, however, that an operation of a reinforcement information adjustment unit <NUM> differs in the present embodiment.

As geographic interval error value adjustment processing <NUM>, the reinforcement information adjustment unit <NUM> of the present embodiment analyzes a plurality of geographic interval error values, calculates a coefficient value of a coefficient included in an approximate expression used to calculate an approximate value of the geographic interval error value for each geographic interval, and includes the coefficient value for each geographic interval into reinforcement information in place of the plurality of geographic interval error values.

That is, the reinforcement information adjustment unit <NUM> analyzes a plurality of ionospheric delay errors included in reinforcement information on the order of centimeters that is selected in S <NUM> of <FIG> and calculates, for each grid point, a coefficient value of a coefficient included in an approximate expression used to calculate an approximate value of the ionospheric delay error at each grid point.

The reinforcement information adjustment unit <NUM> further analyzes a plurality of tropospheric delay errors included in the reinforcement information on the order of centimeters that is selected in step S1021 and calculates, for each grid point, a coefficient value of a coefficient included in an approximate expression used to calculate an approximate value of the tropospheric delay error at each grid point.

The reinforcement information adjustment unit <NUM> then includes, in place of the ionospheric delay error, the calculated coefficient value for each grid point into the reinforcement information on the order of centimeters that is selected in step S <NUM>.

Moreover, the reinforcement information adjustment unit <NUM> includes, in place of the tropospheric delay error, the calculated coefficient value for each grid point into the reinforcement information on the order of centimeters that is selected in step S1021.

Note that in the present embodiment, what is different from the first embodiment will mainly be described.

Matters not described below are the same as those of the first embodiment.

In the present embodiment as well, an operation of the information processing device <NUM> is as illustrated in <FIG> and <FIG> except for a point described below.

Processing in step S1022 in <FIG> is different in the present embodiment.

The operation of the reinforcement information adjustment unit <NUM> according to the present embodiment will be described with reference to <FIG>.

Processing in step S1021 of <FIG> is the same as that of the first embodiment.

That is, as illustrated in <FIG>, the reinforcement information adjustment unit <NUM> selects the reinforcement information on the order of centimeters to be subjected to the processing in step S1022 from among pieces of reinforcement information on the order of centimeters input from a reinforcement information generation unit <NUM>.

In step S1022, the reinforcement information adjustment unit <NUM> analyzes the plurality of ionospheric delay errors included in the reinforcement information on the order of centimeters that is selected in step S1021 and calculates, for each grid point, the coefficient value of the coefficient included in the approximate expression used to calculate the approximate value of the ionospheric delay error at each grid point.

The reinforcement information adjustment unit <NUM> further analyzes the plurality of tropospheric delay errors included in the reinforcement information on the order of centimeters that is selected in step S1021 and calculates, for each grid point, the coefficient value of the coefficient included in the approximate expression used to calculate the approximate value of the tropospheric delay error at each grid point.

The reinforcement information adjustment unit <NUM> then includes the calculated coefficient value for each grid point into the reinforcement information on the order of centimeters that is selected in step S1021, in place of the ionospheric delay error at each grid point included in the reinforcement information on the order of centimeters that is selected in step S1021.

Moreover, the reinforcement information adjustment unit <NUM> includes the calculated coefficient value for each grid point into the reinforcement information on the order of centimeters that is selected in step S1021, in place of the tropospheric delay error at each grid point included in the reinforcement information on the order of centimeters that is selected in step S1021.

A positioning device <NUM> is notified of the approximate expression for each of an ionospheric delay error and the tropospheric delay error in advance and applies, to the approximate expression, a coefficient value included in reinforcement information on the order of decimeters <NUM> received from a quasi-zenith satellite <NUM> or a wireless LAN network <NUM> to be able to obtain the approximate value of each of the ionospheric delay error and the tropospheric delay error at each grid point.

<FIG> is a diagram illustrating the operation of the reinforcement information adjustment unit <NUM> according to the present embodiment.

Each circle (∘) in <FIG> indicates the error value (the ionospheric delay error and the tropospheric delay error) at each grid point.

The positioning device <NUM> uses an approximate expression: <MAT> to be able to calculate the approximate value for the error value at each grid point.

In the approximate expression, x denotes a latitude of the position of the grid point, y denotes a longitude of the position of the grid point, each of a, b, c, d, and e denotes the coefficient value calculated for each grid by the reinforcement information adjustment unit <NUM>, and f denotes a constant.

Note that while a second-order polynomial is illustrated as an example of the approximate expression, the approximate expression is not limited to a second-order expression.

The reinforcement information adjustment unit <NUM> analyzes the error value for each grid point and calculates the value of each of the coefficients a, b, c, d, and e in the approximate expression by a least squares method, for example.

The reinforcement information adjustment unit <NUM> then includes the value of each of the coefficients a, b, c, d, and e for each grid point into the reinforcement information on the order of centimeters that is selected in step S1021, in place of the ionospheric delay error at each grid point included in the reinforcement information on the order of centimeters that is selected in step S1021.

Moreover, the reinforcement information adjustment unit <NUM> includes the value of each of the coefficients a, b, c, d, and e for each grid point into the reinforcement information on the order of centimeters that is selected in step S1021, in place of the tropospheric delay error at each grid point included in the reinforcement information on the order of centimeters that is selected in step S1021.

While the positioning device <NUM> can calculate an estimated value of each of the ionospheric delay error and the tropospheric delay error for each grid point by the approximate expression, there is an error as illustrated in <FIG> between the estimated value and each of actual ionospheric delay error and tropospheric delay error.

The error is illustrated for only several grid points by reason of drawing in <FIG>, but a difference between a graph of the approximate expression and each circle is the error.

The reinforcement information adjustment unit <NUM> notifies of a decrease in reliability caused by using the approximate expression in the form of integrity information to be described later.

Next, in step S1023 of <FIG>, the reinforcement information adjustment unit <NUM> reduces a bit count for each error value included in the reinforcement information on the order of centimeters after the processing in step S1022.

The processing in step S <NUM> is performed as illustrated in the first embodiment.

Note that the reinforcement information adjustment unit <NUM> does not reduce a bit count of the coefficient value (the value of each of the coefficients a, b, c, d, and e) included in the reinforcement information on the order of centimeters in step S1022.

The conversion into the reinforcement information on the order of decimeters by the method according to the present embodiment can also reduce the data volume to approximately one eighth compared to the reinforcement information on the order of centimeters.

Moreover, the reinforcement information adjustment unit <NUM> uses the reduced bit count and the approximate expression for the geographic interval error value to be able to calculate reliability of the reinforcement information when the amount of information therein is reduced, on the basis of reliability of the reinforcement information obtained from the reinforcement information on the order of centimeters.

The reinforcement information adjustment unit <NUM> can find the reliability of the reinforcement information on the order of decimeters by obtaining a root sum square (RSS) of the reliability of the reinforcement information on the order of centimeters, the decrease in the reliability caused by the bit reduction, and the decrease in the reliability caused by using the approximate expression.

That is, the reinforcement information adjustment unit <NUM> calculates a root sum square RSS of each error illustrated in <FIG> and calculates a root sum square RSS of an error corresponding to the bit count reduced as illustrated in <FIG> to find the reliability of the reinforcement information on the order of decimeters.

A reinforcement information output unit <NUM> transmits the reinforcement information including the integrity information.

The integrity information allows a user who uses the reinforcement information on the order of decimeters to find reliability of a measurement result from the reinforcement information in real time and is an essential piece of information in controlling a moving body.

According to the present embodiment as well, the reinforcement information on the order of centimeters is converted to the reinforcement information on the order of decimeters to be able to compress the data volume of the reinforcement information down to approximately one eighth and allow a communication bandwidth to be used effectively.

Moreover, a smart phone, a mobile phone, a tablet terminal, a car navigation system or the like can realize positioning with relatively high accuracy on the order of decimeters even without a circuit or the like for an L6 frequency.

Note that while there has been described in the first and second embodiments that the processing of generating the reinforcement information on the order of decimeters is performed in the order of the update cycle adjustment processing step S1021, the geographic interval error value adjustment processing step S1022 and the bit count adjustment processing step S1023 as illustrated in <FIG>, the processing need not be performed in this order but may be performed in a different order such that, for example, the update cycle adjustment processing step S1021 is performed after the geographic interval error value adjustment processing step S1022, followed by the bit adjustment processing step S1023.

A positioning device <NUM> illustrated in <FIG> will be described in detail in the present embodiment.

Note that while there will be described an example in the present embodiment that the positioning device <NUM> receives reinforcement information on the order of decimeters <NUM> and uses the reinforcement information on the order of decimeters <NUM> to perform satellite positioning, the reinforcement information on the order of decimeters <NUM> may be replaced by reinforcement information on the order of centimeters when the reinforcement information on the order of centimeters can be received to thus allow the positioning device to perform satellite positioning by using the reinforcement information on the order of centimeters.

<FIG> illustrates a configuration example of the positioning device <NUM> according to the present embodiment.

Moreover, <FIG> illustrates a brief description of each component illustrated in <FIG>, and <FIG> illustrates a brief description of intermediate data.

An approximate position/satellite position calculation unit <NUM> receives observed data <NUM> and a broadcast ephemeris <NUM> from a GPS satellite <NUM> and calculates an approximate position of a positioning point and a position of each GPS satellite <NUM>.

An approximate position <NUM> and a satellite position <NUM> are calculation results of the approximate position/satellite position calculation unit <NUM>.

The approximate position <NUM> is a position of the positioning point that is calculated by independent positioning and accurate on the order of meters.

The satellite position <NUM> is a position of each GPS satellite <NUM> from which the positioning device <NUM> receives the observed data.

A correction data generation unit <NUM> receives the reinforcement information on the order of decimeters <NUM> from a quasi-zenith satellite <NUM> as well as acquires the approximate position <NUM> and the satellite position <NUM> to calculate correction data <NUM> from the reinforcement information on the order of decimeters <NUM>, the approximate position <NUM> and the satellite position <NUM>.

The correction data <NUM> indicates an error expected to be included in the observed data <NUM> that is received at the positioning point from each GPS satellite <NUM>.

An observed data screening unit <NUM> eliminates the observed data <NUM> that is expected to be degraded in quality.

More specifically, the observed data screening unit <NUM> selects the observed data <NUM> to be used in positioning calculation from among the plurality of pieces of observed data <NUM> on the basis of an angle of elevation of the GPS satellite <NUM> being a positioning satellite from which the observed data <NUM> is transmitted as well as received signal strength of the observed data <NUM>.

The observed data screening unit <NUM> for example has a threshold table in which a plurality of ranges of the angle of elevation is indicated and, for each range of the angle of elevation, a threshold of the received signal strength is defined.

The observed data screening unit <NUM> then refers to the threshold table and selects a piece of observed data <NUM> when the received signal strength of the observed data <NUM> is higher than or equal to a threshold of the received signal strength defined in association with a range of the angle of elevation corresponding to the angle of elevation of the GPS satellite <NUM> from which the observed data is transmitted.

An observed data error correction unit <NUM> performs double difference calculation to output double difference data <NUM> of the observed data.

The double difference data <NUM> indicates a value obtained by subtracting observed data of a master satellite (observed data already corrected by using the correction data <NUM>) from observed data of a slave satellite (observed data already corrected by using the correction data <NUM>).

A time extrapolation calculation unit <NUM> performs time extrapolation calculation to estimate a state quantity X (t) of a current epoch from a state quantity X^ (t - Δt) of a previous epoch.

More specifically, the time extrapolation calculation unit <NUM> estimates the state quantity X (t) by using process noise adjusted by a process noise adjustment unit <NUM> to be described later.

Note that notation in which "^" lies directly above "X" in <FIG> is identical in meaning to the notation in which "^" lies at the upper right of "X" ("X^").

Moreover, "^" indicates a state quantity after being updated by an observation update calculation unit <NUM> to be described.

Note that the state quantity X (t) corresponds to the position and speed of the positioning device <NUM>.

A geometric distance calculation unit <NUM> calculates a geometric distance <NUM> from the GPS satellite <NUM> to the positioning point on the basis of the satellite position <NUM>.

A residual calculation unit <NUM> calculates a double difference residual <NUM> from the double difference data <NUM> and the geometric distance <NUM>.

The observation update calculation unit <NUM> updates the state quantity X (t) such that the state quantity X (t) has the smallest estimated error.

More specifically, the observation update calculation unit <NUM> updates the state quantity X (t) by using observation noise calculated by an observation noise calculation unit <NUM> to be described later.

The state quantity X (t) after being updated by the observation update calculation unit <NUM> is denoted as a state quantity X^ (t).

Note that a range enclosed with a dashed line in <FIG> is called a positioning calculation unit <NUM>.

The positioning calculation unit <NUM> performs positioning calculation by using the process noise adjusted by the process noise adjustment unit <NUM> and the observation noise calculated by the observation noise calculation unit <NUM>.

A carrier smoothing processing unit <NUM> performs carrier smoothing on the observed data <NUM> (a pseudorange and a carrier phase).

The process noise adjustment unit <NUM> adjusts the process noise used in the positioning calculation by the positioning calculation unit <NUM> (more specifically the time extrapolation calculation unit <NUM>) according to the type of a moving body in which the positioning device <NUM> is arranged.

The process noise adjustment unit <NUM> selects process noise smaller in the altitude direction than a default value when the moving body in which the positioning device <NUM> is arranged is any of a vehicle, a train and a ship, for example.

The observation noise calculation unit <NUM> uses integrity information included in the reinforcement information to calculate the observation noise used in the positioning calculation.

The integrity information is a piece of information presenting "certainty" of a positioning signal and is used at the time of determining whether a positioning result can be used safely.

In the present embodiment, there will be described the operation of mainly the observed data screening unit <NUM>, the time extrapolation calculation unit <NUM>, the observation update calculation unit <NUM>, the process noise adjustment unit <NUM> and the observation noise calculation unit <NUM>.

The observed data screening unit <NUM> selects the observed data <NUM> to be subjected to the processing by the observed data error correction unit <NUM> and beyond, from among the pieces of the observed data <NUM> on which the carrier smoothing is already performed by the carrier smoothing processing unit <NUM>.

The observed data screening unit <NUM> selects the observed data <NUM> to be subjected to the processing by the observed data error correction unit <NUM> and beyond from among the plurality of pieces of the observed data <NUM> on the basis of the angle of elevation of the GPS satellite <NUM> from which the observed data <NUM> is transmitted as well as the received signal strength of the observed data <NUM>.

A positioning device has conventionally performed screening on observed data used in positioning calculation on the basis of received signal strength, where there has been uniformly applied a common threshold of the received signal strength regardless of the angle of elevation between the GPS satellite <NUM> and the positioning device.

There is a correlation between the angle of elevation of a satellite and the received signal strength where, in general, the received signal strength of the observed data increases as the angle of elevation of the satellite increases.

When the received signal strength of observed data from a certain GPS satellite <NUM> largely falls below the received signal strength from another GPS satellite <NUM> when the another GPS satellite <NUM> is at an equal angle of elevation, for example, it is presumed that quality of the observed data from the GPS satellite <NUM> is not very good even when the received signal strength of the GPS satellite <NUM> exceeds the uniform threshold.

Therefore, in the present embodiment, the observed data screening unit <NUM> considers the correlation between the angle of elevation between the positioning device <NUM> and the GPS satellite <NUM> and the received signal strength of the observed data to select the observed data <NUM> to be used in the positioning calculation.

The observed data screening unit <NUM> holds a threshold table illustrated in <FIG>, for example.

In the threshold table of <FIG>, a plurality of ranges of the angle of elevation is indicated and, for each range of the angle of elevation, a threshold of the received signal strength is defined.

That is, in <FIG>, as the ranges of the angle of elevation, ranges of <NUM> to <NUM> degrees and <NUM> to <NUM> degrees are described, for example.

Note that in <FIG>, the range of <NUM> to <NUM> degrees means <NUM> to <NUM> degrees while the range of <NUM> to <NUM> degrees means <NUM> to <NUM> degrees.

The threshold table in <FIG> is generated by analyzing the correlation between the angle of elevation of the satellite and the received signal strength of the observed data for a plurality of the GPS satellites <NUM>.

The observed data screening unit <NUM> calculates the angle of elevation of the GPS satellite <NUM> from which the observed data <NUM> is transmitted, on the basis of the satellite position <NUM> calculated by the approximate position/satellite position calculation unit <NUM>.

The observed data screening unit <NUM> then refers to the threshold table in <FIG> and selects the observed data <NUM> with the received signal strength higher than or equal to a threshold of the received signal strength defined in association with a range of the angle of elevation corresponding to the calculated angle of elevation of the satellite, from among the plurality of pieces of the observed data <NUM> on which the carrier smoothing is already performed.

The observed data screening unit <NUM> outputs only the selected observed data <NUM> to the observed data error correction unit <NUM>.

In order for the positioning calculation unit <NUM> to perform positioning calculation, the observed data screening unit <NUM> needs to select four or more of the observed data <NUM>.

Next, there will be described a Kalman filter realizing the time extrapolation calculation unit <NUM> and the observation update calculation unit <NUM>.

<FIG> illustrates a processing flow of the Kalman filter.

<FIG> illustrates a description of a variable used in the processing of the Kalman filter.

The time extrapolation calculation unit <NUM> performs time extrapolation calculation of the Kalman filter illustrated in <FIG>.

Moreover, the observation update calculation unit <NUM> performs observation update calculation of the Kalman filter illustrated in <FIG>.

The time extrapolation calculation and the observation update calculation form a single loop, the loop formed by the time extrapolation calculation and the observation update calculation is executed repeatedly.

The Kalman filter estimates a state quantity such that a diagonal element of an error variance (error variance matrix Pij = E <xixj>, where E <a> is a variance of "a") of the estimated state quantity (state quantity X) is the smallest in each loop being repeated.

Processing performed in the Kalman filter will be described in due order.

In the time extrapolation calculation, from a state quantity (x^ (-)) and an error covariance matrix (P^ (-)) of a previous time, a state quantity (x (+)) and an error covariance matrix (P (+)) of a following time are estimated based on a transition matrix φ determined according to a dynamic model being adopted.

At this time, process noise Q that is an error expected between the dynamic model and an actual phenomenon is added to the error covariance matrix (P^ (-)).

The process noise Q is also determined according to the dynamic model and design being adopted.

From the estimated state quantity (x (+)), an amount y- equivalent to an observation amount(y- represents that "-" lies directly above "y"; the same applies hereinafter) is obtained, the amount y- being estimated by an observation model (y- = f (x)) expressing a relationship between the state quantity and the observation amount.

In the observation update calculation, a residual (dz = y - y-) being a difference between an actual observation amount and the estimated observation amount is obtained and converted into a difference in the state quantity (dx = K · dz) by using Kalman gain K expressed in an expression in <FIG>, whereby the state quantity is updated.

An observation matrix used in the observation update calculation expresses the observation model and is obtained by the following expression.

Moreover, R included in the denominator of the expression of the Kalman gain K represents observation noise expected to be included in the observation amount.

The process noise adjustment unit <NUM> adjusts the process noise provided to the time extrapolation calculation unit <NUM>.

<FIG> illustrates default process noise and process noise obtained after being adjusted by the process noise adjustment unit <NUM>.

Default process noise Q<NUM> has an X component (east-west direction), a Y component (north-south direction) and a Z component (altitude direction) that are equal to one another with no anisotropy as illustrated in (a) of <FIG>.

However, a vehicle, train or ship shifts in the altitude direction in a gentle manner.

It is thus desired to set the process noise in the altitude direction smaller than a default value when the vehicle, train or ship is the moving body in which the positioning device <NUM> is arranged.

Accordingly, in the present embodiment, the process noise adjustment unit <NUM> selects f⊥ (<NUM> < f⊥ << <NUM>) as the value of the process noise in the altitude direction when the moving body is any of the vehicle, train and ship (when the positioning device <NUM> is mounted in any of the vehicle, train and ship).

The process noise adjustment unit <NUM> then outputs process noise Q⊥ including f⊥ to the time extrapolation calculation unit <NUM>, which uses Q⊥ to perform the time extrapolation calculation illustrated in <FIG>.

On the other hand, when the moving body in which the positioning device <NUM> is arranged is a user (human), namely when the user carrying the positioning device <NUM> is on the move on foot (when the positioning device <NUM> is not mounted in the vehicle, train or ship), the process noise adjustment unit <NUM> outputs the default process noise Q<NUM> to the time extrapolation calculation unit <NUM>, which uses Q<NUM> to perform the time extrapolation calculation illustrated in <FIG>.

Moreover, when the moving body in which the positioning device <NUM> is arranged is an airplane, the process noise adjustment unit <NUM> outputs the default process noise Q<NUM> to the time extrapolation calculation unit <NUM>, which uses Q<NUM> to perform the time extrapolation calculation illustrated in <FIG>.

Note that the type of the moving body in which the positioning device <NUM> is arranged is input to the positioning device <NUM> by the user, for example, the type being the vehicle, train or ship, the user (human), or the airplane.

Moreover, in <FIG>, Tecefenu is a matrix converting an ecef coordinate system into an enu coordinate system.

Furthermore, each of Q<NUM> and Q⊥ is a matrix (process noise) in the enu coordinate system, and f⊥ is the value of the process noise in the altitude direction when the moving body is any of the vehicle, train and ship.

The observation noise calculation unit <NUM> calculates the observation noise provided to the observation update calculation unit <NUM>.

<FIG> illustrates conventional observation noise and the observation noise calculated by the observation noise calculation unit <NUM>.

The smaller the angle of elevation, the higher the possibility that a satellite signal is affected by an obstacle such as a building or mountain and the longer the distance for which the signal passes through the atmosphere and ionosphere causing a signal delay, so that the observation noise of the satellite signal with the small angle of elevation is conventionally large as illustrated in (a) of <FIG>.

Low weighting is set to the observed data from a satellite having a large value of the observation noise in the observation update calculation performed by the observation update calculation unit <NUM> and, as a result, the data is reflected in a measurement result with a small ratio.

The reinforcement information includes the integrity information.

In the integrity information, a high value is set to observed data from a satellite that is considered low in quality, whereas a low value is set to observed data from a satellite that is considered high in quality.

As described above, the observed data from the satellite with the small angle of elevation is likely to be low in quality so that the observed data from the satellite having the small angle of elevation and considered low in quality is desirably reflected in the positioning result with a small ratio.

The observation noise calculation unit <NUM> according to the present embodiment uses the integrity information in calculating the observation noise to set the observation noise more properly.

More specifically, as illustrated in (b) of <FIG>, the observation noise calculation unit <NUM> reflects the value of the integrity information of a target GPS satellite in a formula of the observation noise.

The observation noise calculation unit <NUM> outputs observation noise R being a matrix of observation noise σi calculated by the formula illustrated in (b) of <FIG> to the observation update calculation unit <NUM>, which uses the observation noise R to perform the observation update calculation illustrated in <FIG>.

Note that in <FIG>, i denotes a satellite number, σi denotes the observation noise of a satellite i, and σpr denotes a design constant.

Moreover, n denotes the number of satellites captured by the positioning device <NUM>, and el; denotes the angle of elevation of the satellite i.

Furthermore, Ii denotes the integrity information of the satellite i.

The observation noise calculation unit <NUM> calculates the angle of elevation of the satellite i on the basis of the satellite position <NUM> calculated by the approximate position/satellite position calculation unit <NUM>.

Therefore, according to the present embodiment, the observed data screening unit <NUM> selects the observed data used in the positioning calculation while considering the angle of elevation of the satellite, whereby the observed data with good quality can be selected more accurately.

Moreover, according to the present embodiment, the process noise adjustment unit <NUM> selects the process noise according to the type of the moving body, whereby the positioning accuracy can be improved by using the process noise appropriate for the type of the moving body.

Furthermore, according to the present embodiment, the observation noise calculation unit <NUM> uses the integrity information to calculate the observation noise, whereby the positioning accuracy can be improved by increasing the weighting on the observed data with high quality and decreasing the weighting on the observed data with low quality.

These effects can then compensate for a decrease in the positioning accuracy caused by the use of the reinforcement information on the order of decimeters.

Another embodiment of a positioning device <NUM> will be described in the present embodiment.

In the present embodiment as well, an example of the configuration of the positioning device <NUM> is as illustrated in <FIG>.

However, in the present embodiment, when n (n ≥ <NUM>) pieces of observed data is selected on the basis of an angle of elevation of a satellite and received signal strength, an observed data screening unit <NUM> repeats an operation of selecting m (m ≥ <NUM> and m < n) pieces of observed data from among the n pieces of observed data. The observed data screening unit <NUM> then generates k (k ≥ <NUM> and k ≤ n) data sets, each of which is a data set formed of the m pieces of observed data and has a different combination of the m pieces of observed data.

Moreover, in the present embodiment, an observation update calculation unit <NUM> of a positioning calculation unit <NUM> performs observation update calculation on the m pieces of observed data making up the data set for each data set, and selects any data set from among the k data sets on the basis of a variance of a residual (double difference residual) before the observation update calculation of each data set and a variance of a residual (double difference residual) after the observation update calculation of each data set.

More specifically, the observation update calculation unit <NUM> extracts a data set having the smallest variance of the residual after the observation update calculation, and compares the variance of the residual after the observation update calculation of the extracted data set with a variance of a residual after update calculation of a data set having the second smallest variance of a residual after the observation update calculation.

When there is a significant difference between the variances, the observation update calculation unit <NUM> determines whether or not a variance of a residual before the observation update calculation of the extracted data set is equal to or smaller than a threshold, and selects the extracted data set when the variance of the residual before the observation update calculation of the extracted data set is equal to or smaller than the threshold.

The observation update calculation unit <NUM> then handles the residual (double difference residual) in the extracted data set being selected as a state quantity X^ (t).

An operation of each of a process noise adjustment unit <NUM> and an observation noise calculation unit <NUM> is the same as that illustrated in the third embodiment.

Moreover, in the third embodiment, an approximate position/satellite position calculation unit <NUM>, a correction data generation unit <NUM>, an observed data error correction unit <NUM>, a time extrapolation calculation unit <NUM>, a geometric distance calculation unit <NUM> and a residual calculation unit <NUM> perform processing on the four or more pieces of observed data selected by the observed data screening unit <NUM> whereas, in the present embodiment, the k data sets each formed of the m pieces of observed data is subjected to the processing.

However, except for the k data sets being subjected to the processing, an operation of each of the approximate position/satellite position calculation unit <NUM>, the correction data generation unit <NUM>, the observed data error correction unit <NUM>, the time extrapolation calculation unit <NUM>, the geometric distance calculation unit <NUM> and the residual calculation unit <NUM> is the same as that illustrated in the third embodiment.

That is, each of the approximate position/satellite position calculation unit <NUM>, the correction data generation unit <NUM>, the observed data error correction unit <NUM>, the time extrapolation calculation unit <NUM>, the geometric distance calculation unit <NUM> and the residual calculation unit <NUM> performs processing identical to that of the third embodiment on each data set.

Next, an example of the operation of the positioning device <NUM> according to the present embodiment will be described with reference to <FIG>.

Since the operation of each of the observed data screening unit <NUM> and the observation update calculation unit <NUM> of the present embodiment is different from that of the third embodiment, there will be described an example of the operation of mainly the observed data screening unit <NUM> and the observation update calculation unit <NUM>.

<FIG> illustrates an example where n = <NUM>, m = <NUM>, and k = <NUM>.

That is, <FIG> illustrates an example where the observed data screening unit <NUM> selects six pieces of observed data from six GPS satellites <NUM> on the basis of the angle of elevation of the satellite and the received signal strength.

The observed data screening unit <NUM> generates a data set by selecting five pieces of observed data from among the six pieces of observed data.

Here, the data set generated first is referred to as a data set #<NUM>.

In the example of <FIG>, the data set #<NUM> is formed of observed data from satellite <NUM>, observed data from satellite <NUM>, observed data from satellite <NUM>, observed data from satellite <NUM>, and observed data from satellite <NUM>.

The observed data screening unit <NUM> outputs the generated data set #<NUM> to the observed data error correction unit <NUM>.

The observed data error correction unit <NUM> performs double difference calculation on the data set #<NUM> as with the third embodiment and generates double difference data <NUM>.

Moreover, the residual calculation unit <NUM> calculates a double difference residual <NUM> as with the third embodiment on the basis of the double difference data <NUM> generated from the data set #<NUM> and a geometric distance <NUM>.

The observation update calculation unit <NUM> performs the observation update calculation on the double difference residual <NUM> for the data set #<NUM>.

The observation update calculation unit <NUM> further calculates a variance of the double difference residual <NUM> before the observation update calculation for the data set #<NUM> and a variance of the double difference residual <NUM> after the observation update calculation for the data set #<NUM>.

The processing performed up to this point corresponds to a first round of loop.

Next, as processing performed in a second round of loop, the observed data screening unit <NUM> generates a new data set by selecting five pieces of observed data with a combination different from that of the data set #<NUM>, from among the six pieces of observed data.

Here, the data set generated in the second round of loop is referred to as a data set #<NUM>.

In the example of <FIG>, the data set #<NUM> is formed of the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, and observed data from satellite <NUM>.

The processing identical to that performed on the data set #<NUM> is performed on the data set #<NUM>. The observation update calculation unit <NUM> calculates a variance of the double difference residual <NUM> before the observation update calculation for the data set #<NUM> and a variance of the double difference residual <NUM> after the observation update calculation for the data set #<NUM>.

The processing performed up to this point corresponds to the second round of loop.

Likewise, processing from a third round of loop to a sixth round of loop is performed from then on such that the observed data screening unit <NUM> generates data sets #<NUM> to #<NUM> while the observation update calculation unit <NUM> calculates a variance of the double difference residual <NUM> before the observation update calculation and a variance of the double difference residual <NUM> after the observation update calculation with respect to each of the data sets #<NUM> to #<NUM>.

Although the data sets #<NUM> and #<NUM> are omitted from <FIG> due to a restriction on drawing space, the data set #<NUM> is formed of the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, and the observed data from satellite <NUM> while the data set #<NUM> is formed of the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, the observed data from satellite <NUM>, and the observed data from satellite <NUM>.

Moreover, in <FIG>, a residual before observation update means a double difference residual before the observation update calculation is performed by the observation update calculation unit <NUM> while a residual after observation update means a double difference residual after the observation update calculation is performed by the observation update calculation unit <NUM>.

Furthermore, in each of the residual before observation update and the residual after observation update, a variance of a residual in loop <NUM> corresponds to the variance of the residual in the data set #<NUM>.

The same applies to loop <NUM> and onward.

Once the processing on the sixth round of loop is completed with the variance of the residual in each of loop <NUM> to loop <NUM> obtained for both before and after the observation update, the observation update calculation unit <NUM> extracts a data set with the smallest variance after the observation update and a data set with the second smallest variance.

Here, it is assumed that the variance of the data set #<NUM> is the smallest and that the variance of the data set #<NUM> is the second smallest.

The observation update calculation unit <NUM> determines whether or not there is a significant difference between the variance of the data set #<NUM> and the variance of the data set #<NUM>.

There may be prepared, for example, a threshold for the difference in the variance (a difference threshold) so that the observation update calculation unit <NUM> determines there is the significant difference when the difference between the variance of the data set #<NUM> and the variance of the data set #<NUM> exceeds the difference threshold.

When there is the significant difference between the variance of the data set #<NUM> and the variance of the data set #<NUM>, the observation update calculation unit <NUM> determines whether or not the variance before the observation update of the data set #<NUM> is small enough.

There may be prepared, for example, a threshold for the variance before the observation update (a variance threshold before observation update), so that the observation update calculation unit <NUM> determines the variance before the observation update is small enough when the variance before the observation update of the data set #<NUM> is smaller than or equal to the variance threshold before observation update.

When the variance before the observation update is small enough, the observation update calculation unit <NUM> selects the data set #<NUM> and handles the double difference residual <NUM> after the observation update of the data set #<NUM> as the state quantity X^ (t) in <FIG>.

Therefore, according to the present embodiment, there can be obtained the combination of the observed data with which a more accurate positioning result can be obtained.

Note that while the operation of each of the process noise adjustment unit <NUM> and the observation noise calculation unit <NUM> is the same as that of the third embodiment, the operation of each of the process noise adjustment unit <NUM> and the observation noise calculation unit <NUM> need not be the same as that of the third embodiment.

That is, the process noise adjustment unit <NUM> may be adapted to output default process noise Q<NUM> illustrated in (a) of <FIG> to the time extrapolation calculation unit <NUM> regardless of the type of a moving body in which the positioning device <NUM> is arranged.

Moreover, the observation noise calculation unit <NUM> may be adapted to calculate observation noise σi according to the expression illustrated in (a) of <FIG> without using integrity information.

Furthermore, while the observed data screening unit <NUM> described above selects the n pieces of observed data by using the threshold of the received signal strength for each angle of elevation of a satellite as with the third embodiment, the n pieces of observed data may be selected by using a uniform threshold for the received signal strength not involving the angle of elevation of a satellite.

Moreover, while there has been described in the third and fourth embodiments the example of operation of the positioning device <NUM> that receives the reinforcement information on the order of decimeters <NUM>, a positioning device receiving reinforcement information on the order of centimeters may be adapted to perform the same operation.

That is, the positioning device receiving the reinforcement information on the order of centimeters may select observed data to be used in positioning calculation from among a plurality of pieces of observed data on the basis of the angle of elevation of a satellite and the received signal strength of the observed data.

The integrity information included in the reinforcement information on the order of centimeters may also be used to calculate the observation noise.

The positioning device receiving the reinforcement information on the order of centimeters may also be adapted to adjust the process noise according to the type of the moving body.

Moreover, the positioning device receiving the reinforcement information on the order of centimeters may be adapted to generate k data sets from the n pieces of observed data and select any data set from among the k data sets on the basis of a variance of a residual before the observation update calculation of each data set and a variance of a residual after the observation update calculation of each data set.

Furthermore, while there has been described in the third and fourth embodiments the example where the positioning device <NUM> receives the reinforcement information on the order of decimeters <NUM> from the quasi-zenith satellite <NUM>, the reinforcement information on the order of decimeters <NUM> may be received from a satellite other than the quasi-zenith satellite <NUM> or from the wireless LAN network <NUM> providing a wireless LAN environment.

Specifically, where the positioning device <NUM> receives the reinforcement information on the order of decimeters <NUM> from a satellite other than the quasi-zenith satellite <NUM>, the positioning device <NUM> may include a receiver used to receive a signal from the satellite and input, to the correction data generation unit <NUM>, the reinforcement information on the order of decimeters <NUM> received by the receiver.

Alternatively, where the positioning device <NUM> receives the reinforcement information on the order of decimeters <NUM> from the wireless LAN network <NUM>, the positioning device <NUM> may include a wireless LAN receiver and input, to the correction data generation unit <NUM>, the reinforcement information on the order of decimeters <NUM> received by the wireless LAN receiver.

Lastly, an example of a hardware configuration of each of the information processing device <NUM> and the positioning device <NUM> according to the first to fourth embodiments will be described with reference to <FIG>.

Each of the information processing device <NUM> and the positioning device <NUM> is a computer that can implement each component in each of the information processing device <NUM> and the positioning device <NUM> by a program.

Each of the information processing device <NUM> and the positioning device <NUM> has the hardware configuration in which an arithmetic unit <NUM>, an external storage <NUM>, a main storage <NUM>, a communication unit <NUM> and an input/output unit <NUM> are connected to a bus.

The arithmetic unit <NUM> is a CPU (Central Processing Unit) executing the program.

The external storage <NUM> is a ROM (Read Only Memory), a flash memory and/or a hard disk device, for example.

The main storage <NUM> is a RAM (Random Access Memory).

In the positioning device <NUM>, the communication unit <NUM> receives the observed data and the broadcast ephemeris from the GPS satellite and receives the reinforcement information from the quasi-zenith satellite or the wireless LAN network.

Moreover, the communication unit <NUM> in the positioning device <NUM> includes an AD (analog-digital) conversion function.

The input/output unit <NUM> is a touch panel display, for example.

The program usually stored in the external storage <NUM> is sequentially read into the arithmetic unit <NUM> and executed while loaded to the main storage <NUM>.

The program is a program implementing the function that is described as ". unit" in <FIG> and <FIG>.

Moreover, the external storage <NUM> stores an operating system (OS), at least a part of which is loaded to the main storage <NUM> so that the arithmetic unit <NUM> executes the program implementing the function of the ". unit" illustrated in <FIG> and <FIG> while executing the OS.

Furthermore, the main storage <NUM> stores as a file a piece of information, data, a signal value and a variable value representing the result of the processing described as "correction of. ", "generation of. ", "creation of. ", "computation of. ", "calculation of. ", "adjustment of. ", "determination of. ", "evaluation of. ", "update of. ", "estimation of. ", "extraction of. ", "selection of. ", "reception of. " and the like in the first to fourth embodiments.

Note that the configuration in <FIG> merely illustrates an example of the hardware configuration of each of the information processing device <NUM> and the positioning device <NUM>, which may thus have the hardware configuration that is not necessarily the configuration illustrated in <FIG> but another configuration.

While the embodiments of the present invention have been described, two or more of those embodiments may be combined and implemented.

Alternatively, one of those embodiments may be partially implemented.

Yet alternatively, two or more of those embodiments may be partially combined and implemented.

Claim 1:
A positioning device (<NUM>) comprising:
- a correction data generation unit (<NUM>) to receive reinforcement information including integrity information;
- an observation noise calculation unit (<NUM>) to calculate observation noise (R) used in positioning calculation by using integrity information included in reinforcement information that is used to correct a satellite positioning error;
- a positioning calculation unit (<NUM>) to perform positioning calculation by using the observation noise (R) calculated by the observation noise calculation unit (<NUM>); and
- an observed data screening unit (<NUM>) to repeat an operation of selecting m, m ≥ <NUM> and m < n, pieces of observed data from among n, n ≥ <NUM>, pieces of observed data, each piece of observed data transmitted from a corresponding positioning satellite, and generate k, k ≥ <NUM> and k ≤ n, data sets each of which is formed of the m pieces of observed data selected at different repetition, and that has a different combination of the m pieces of observed data,
wherein the positioning calculation unit (<NUM>) is adapted to perform, for each data set, observation update calculation on the m pieces of observed data making up the data set as a part of the positioning calculation, and to select any data set from among the k data sets on the basis of a variance of a residual before the observation update calculation of each data set and a variance of a residual after the observation update calculation of each data set,
wherein the residual for each data set is a difference between an actual observation amount and an estimated observation amount;
wherein the observation update calculation includes applying a Kalman gain (K) to the residual for each data set; and
wherein the observation noise (R) is included in a denominator of a Kalman gain.