JP2014219204A - Mobile information terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile information terminal capable of controlling a calculation load of positioning processing while ensuring positioning accuracy of multi-global navigation satellite system (GNSS)-based positioning.SOLUTION: A mobile information terminal 100 comprises: a multi-GNSS-based positioning control unit 130 for selecting a combination of satellites to be used when performing multi-GNSS-based positioning; and a positioning calculation unit 120 for performing the positioning by using the combination of satellites selected by the multi-GNSS-based positioning control unit 130. When the multi-GNSS-based positioning is performed, the multi-GNSS-based positioning control unit 130 controls the combination of satellites used by the positioning calculation unit 120 for the positioning or frequency for outputting a positioning result by the positioning calculation unit 120 so that a positioning calculation load of the positioning calculation unit 120 becomes smaller than a predetermined value.

Description

  The present invention relates to a mobile information terminal that performs position measurement using a GNSS (Global Navigation Satellite System).

  A mobile information terminal such as a car navigation device has a function of measuring (positioning) the position of a mobile body (for example, a vehicle) on which the mobile information terminal is mounted. Conventionally, GPS (Global Positioning System) has been widely used as a GNSS used for positioning of mobile information terminals. In recent years, mobile information terminals that perform positioning using a GNSS other than GPS have been put into practical use. For example, the positioning can be dynamically switched between positioning by GLONASS (GLObal NAvigation Satellite System) operated by Russia and positioning by GPS. In addition, there are those that perform positioning by combining GPS and GLONASS.

  Patent Document 1 below proposes a technique for dynamically switching between positioning using only GPS and high-accuracy positioning using a combination of a quasi-zenith satellite and GPS based on determination conditions such as moving object speed. Has been.

JP 2004-144893 A

  As described above, in recent years, GNSSs other than GPS have been put into practical use, and technical development of positioning using a combination of two or more GNSSs (multi-GNSS based positioning) is progressing. Multi-GNSS-based positioning can be expected to improve positioning accuracy due to an increase in the number of satellites used for positioning, but there is a concern that the calculation load increases. In Patent Document 1, the calculation load is reduced by performing positioning using a combination of the quasi-zenith satellite and GPS only when necessary. For example, the calculation load is reduced while maintaining the positioning accuracy above a certain level. Or fine control that reduces the number of satellites used for smoothing the computation load.

  Conventionally, positioning processing in a mobile information terminal has been generally performed using dedicated hardware. However, due to high performance of CPU (Central Processing Unit), positioning processing has recently been performed by software. It is in. In addition, as the mobile information terminals become more multifunctional, various processes are required for the CPU. Therefore, it is important to smooth the calculation load due to the positioning process so that the CPU is not occupied by the positioning process. It becomes.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a mobile information terminal capable of controlling the calculation load of positioning processing while ensuring the positioning accuracy by multi-GNSS-based positioning. To do.

  A mobile information terminal according to the present invention includes a satellite receiver that receives satellite signals from a plurality of GNSS satellites, and a multi-GNSS that selects one or more of the plurality of GNSSs based on predetermined positioning switching conditions. A base positioning control unit, and a positioning calculation unit that performs positioning based on a GNSS satellite signal selected by the multi-GNSS base positioning control unit, and the multi-GNSS base positioning control unit selects two or more GNSSs, The number of satellites used for positioning by the positioning calculation unit or the frequency at which the positioning calculation unit outputs the positioning result is controlled so that the positioning calculation load of the positioning calculation unit is smaller than a predetermined value.

  According to the present invention, in multi-GNSS-based positioning, for example, positioning is performed by smoothing the positioning calculation load while maintaining high positioning accuracy, or by reducing the number of satellites used or decreasing the output frequency of positioning results. Fine control such as suppression of computation load is possible. That is, by appropriately switching the number of satellites used for positioning and the output frequency of positioning results, it is possible to improve both positioning accuracy and smooth the positioning calculation load.

It is a figure which shows the example of GNSS with which application to this invention is assumed. It is a figure which shows the satellite arrangement | positioning example of GPS and QZSS. It is a figure which shows the satellite arrangement | positioning example of GPS, QZSS, GLONSS, Galileo, and BDS. It is a block diagram of the mobile information terminal which concerns on embodiment. It is a figure which shows the example of the management table of a multi-GNSS satellite. It is a figure for demonstrating the calculation method of the stay time in the sky. It is a flowchart which shows the operation | movement of the positioning process in the mobile information terminal which concerns on embodiment. It is a flowchart which shows the update process of the management table in the mobile information terminal which concerns on embodiment. It is a figure which shows the example of a transition of the positioning calculation load in the multi-GNSS base positioning of this invention.

  First, an outline of multi-GNSS-based positioning will be described. FIG. 1 is a diagram showing an example of GNSS assumed to be applied to the present invention. In addition to the conventional GPS operated and managed by the US, for example, QZSS (Quasi-Zenith Satellite), which aims to supplement / reinforce GPS with four systems in 2019, and Russia operates with 24 systems from 2011 GLONASS, which EU started operating in 30 units in 2019, and BDS (Bei Dou System) in which China started operation in 2012 from 2012. In 2019, the number of satellites that can be used for positioning will be 104 or more.

  2 and 3 are diagrams showing examples of GNSS satellite arrangements. In these figures, the position immediately above the current position (elevation angle 90 degrees) is positioned at the center of the circle, the outermost circle is the horizon (elevation angle 0 degrees), and a circle with elevation angles of 30 and 60 degrees is drawn between them. Yes. N, E, S, and W represent north, east, south, and west directions, respectively. 2 and 3, each satellite is represented by the symbols shown in FIG.

  FIG. 2 shows an arrangement example of GPS and QZSS satellites, and shows a state where 11 GPS satellites and three QZSS satellites can be used for positioning in open sky. On the other hand, FIG. 3 is a satellite arrangement example of GPS, QZSS, GLONSS, Galileo, and BDS. In addition to GPS satellites (11 units) and QZSS satellites (3 units) in the open sky, A total of 42 satellites including the base Galileo satellite and the 8 BDS satellites can be used for positioning.

  If multi-GNSS-based positioning using many satellites shown in FIG. 3 is performed, highly accurate positioning is possible, but the calculation processing load of positioning processing increases. Therefore, in the present embodiment, a mobile information terminal is proposed that selects an appropriate combination from available satellites in consideration of maintaining positioning accuracy and smoothing the calculation load of the CPU.

  FIG. 4 is a configuration diagram of the mobile information terminal 100 according to the embodiment of the present invention. In the present embodiment, the mobile information terminal 100 is described as a car navigation device mounted on a vehicle. However, the present invention can be applied to any mobile information terminal that can move with a mobile object. Hereinafter, a vehicle equipped with the mobile information terminal 100 may be referred to as “own vehicle”.

  The mobile information terminal 100 includes a multi-GNSS base positioning unit 101, a navigation unit 102, a video image control unit 103, and a vehicle sensor unit 104. A camera 105 is connected to the video image control unit 103. The camera 105 may be built in the mobile information terminal 100, or may be an external camera attached to the mobile information terminal 100, for example.

  Each element constituting the multi-GNSS base positioning unit 101, the navigation unit 102, and the video image control unit 103 is realized mainly by the CPU operating according to a program. However, the positioning control information storage unit 134 of the multi-GNSS base positioning control unit 130 and the map information storage unit 144 of the navigation unit 102 are configured by a hard disk, a removable disk, a memory, and the like.

  The navigation unit 102 has a function of performing route guidance from the current position to the destination set by the user, and includes a locator unit 141, a route search unit 142, a video display unit 143, and a map information storage unit that stores map data 144.

  The locator unit 141 is a map based on information such as the position of the mobile information terminal 100 (position of the own vehicle) measured by the multi-GNSS base positioning unit 101 and the speed and angular velocity of the own vehicle acquired by the vehicle sensor unit 104. A map matching process for estimating the position of the vehicle on the map read from the information storage unit 144 is performed. The route search unit 142 searches for a route from the position of the vehicle to the destination. The video display unit 143 performs route guidance for the user while displaying the route to the destination and the position of the vehicle in real time on the map.

  The multi-GNSS base positioning unit 101 receives a signal (satellite signal) from a GNSS satellite and extracts information necessary for the positioning calculation, and performs a positioning calculation based on the information extracted by the satellite receiving unit 110. A positioning calculation unit 120 is provided, and a multi-GNSS-based positioning control unit 130 that selects a GNSS and a satellite used for positioning and adjusts the output frequency of the positioning result when performing multi-GNSS-based positioning.

  The satellite reception unit 110 is connected to the multi-GNSS antenna 111 and includes a satellite acquisition / tracking unit 112, a navigation message decoding unit 113, and a satellite selection control unit 114.

The satellite acquisition / tracking unit 112 performs satellite acquisition / tracking processing based on the satellite signal received from the GNSS satellite through the multi-GNSS antenna 111. At this time, the C / N ₀ value (carrier-to-noise ratio) and the code delay time from the reference time, which are characteristics of the satellite signal, are calculated.

The calculated C / N ₀ value is sent to the multi-GNSS base positioning control unit 130 as information on the satellite (satellite information). The satellite signal also includes information on the type of GNSS (GNSS type) to which the transmission source satellite belongs and the satellite number, which is a unique number assigned to each satellite. Sends them to the multi-GNSS-based positioning control unit 130 as satellite information. On the other hand, the code delay time is sent to the positioning calculation unit 120.

  The navigation message decoding unit 113 extracts a navigation message from data acquired as a result of tracking the satellite. The navigation message includes satellite orbit information necessary for calculating the satellite position. The extracted navigation message is sent to the positioning calculation unit 120.

  The satellite selection control unit 114 acquires a satellite selection result from the multi-GNSS base positioning control unit 130, and specifies the satellite to be captured and tracked by the satellite capturing / tracking unit 112 accordingly. Thereby, the number of satellites used for positioning is controlled.

  The positioning calculation unit 120 includes a pseudo distance calculation unit 121, a positioning unit 122, and an output frequency control unit 123.

  The pseudo distance calculating unit 121 calculates a pseudo distance between the mobile information terminal 100 and the satellite based on the code delay time acquired from the satellite receiving unit 110. The positioning unit 122 extracts a satellite orbit from the navigation message acquired from the satellite receiving unit 110, and performs a positioning calculation for determining the position of the mobile information terminal 100 from the extracted satellite orbit and the pseudo distance obtained by the pseudo distance calculating unit 121. I do. In addition, the positioning unit 122 sends the satellite orbit and information on the elevation angle and direction of the satellite obtained from the satellite orbit to the multi-GNSS-based positioning control unit 130 as satellite information.

  The output frequency control unit 123 controls the frequency at which the positioning calculation unit 120 outputs the positioning result (the calculation result of the position of the mobile information terminal 100 by the positioning unit 122) to the navigation unit 102. Specifically, the output frequency of the positioning result is specified by the multi-GNSS base positioning control unit 130, and the output frequency control unit 123 has a period according to the output frequency specified by the multi-GNSS base positioning control unit 130, and the positioning calculation unit The positioning result is output from 120.

  The multi-GNSS base positioning control unit 130 includes a satellite selection unit 131, a positioning switching condition setting unit 132, a satellite selection management unit 133, and a positioning control information storage unit 134.

  The satellite selection unit 131 determines whether to perform a GPS-based positioning using only GPS satellites or a multi-GNSS-based positioning method using two or more GNSS satellites, and performs multi-GNSS-based positioning. When performing, a combination of satellites used for positioning is selected from various GNSS satellites (this determines the number of satellites used for positioning). The determination result of the positioning method and the satellite selection result are sent to the satellite receiver 110.

  The determination of the positioning method is performed based on the positioning switching condition that is input in advance to the positioning switching condition setting unit 132 and stored in the positioning control information storage unit 134. For example, when the condition “less than 80 km / h” is set as the positioning switching condition, the satellite selection unit 131 acquires the speed of the own vehicle from the vehicle sensor unit 104, and performs multi-GNSS based positioning when the speed is less than 80 km / h. When the speed is 80 km / h or more, it is determined to perform GPS-based positioning. In general, high-precision positioning by multi-GNSS-based positioning is desired when driving at low speeds on back roads, etc., but GPS-based positioning is available when driving on highways at speeds of 80 km / h or higher. This is because the obtained positioning accuracy is sufficient.

  The positioning switching condition is not limited to the speed condition of the host vehicle, and may be, for example, the condition of the area where the host vehicle is located. For example, if the location of your vehicle is a snowy or foggy region, a region covered with deep forest, a region where roads are complicated and the prospect is poor, or a region where many accidents have occurred in the past, Therefore, multi-GNSS-based positioning is preferably performed.

  Further, the positioning switching condition may be a distance condition from the current position to the destination set in the navigation unit 102. For example, when the vehicle is close to the destination, high-precision positioning by multi-GNSS-based positioning is desired, so that multi-GNSS-based positioning may be performed. In that case, the satellite selection unit 131 compares the destination set in the navigation unit 102 with the position of the host vehicle calculated by the positioning unit 122. If this distance is equal to or less than a specific value, the multi-GNSS based positioning is performed. A determination is made to select a process.

  The satellite selection by the satellite selection unit 131 is performed based on a multi-GNSS satellite management table (hereinafter simply referred to as “management table”) created by the satellite selection management unit 133.

FIG. 5 is a diagram illustrating an example of a management table. In the management table, satellite information such as the GNSS type, satellite number, priority, C / N ₀ value, elevation angle, azimuth, satellite orbit, and sky stay time of each satellite is registered. In FIG. 5, the azimuth represents N as 0 degrees, E as 90 degrees, S as 180 degrees, and W as 270 degrees.

The GNSS type, satellite number, and C / N ₀ value registered in the management table are obtained from the satellite capturing / tracking unit 112 of the satellite receiving unit 110. The elevation angle, direction, and satellite orbit are acquired from the positioning unit 122 of the positioning calculation unit 120.

  The priority is a priority when a satellite is selected. For example, when the user sets the GLONASS preferentially, the priority of the GLONASS satellite is set high. Also, for example, when the position of the vehicle is in a high latitude area where there are many GLONASS satellites, the priority of the GLONASS satellite is high, and when it is in the area around China where there are many BDS satellites, the priority of the BDS satellite is high. May be set automatically.

  The staying time in the sky is determined by the satellite selection management unit 133 based on the video over the host vehicle captured by the video image control unit 103 using the camera 105 and the elevation angle, direction, and satellite orbit of each satellite registered in the management table. Is calculated.

  For example, it is assumed that the sky image as shown in FIG. Focusing on the GPS satellite position 200 shown in FIG. 6, the position of the GPS satellite position 200 can be found by referring to the elevation angle and direction of the GPS satellite position 200 registered in the management table. Further, from the satellite orbit of the GPS satellite position 200 registered in the management table, a point 201 where the GPS satellite position 200 rises from the horizon and a point 202 where the GPS satellite position 200 sinks to the horizon are known. Furthermore, a straight line connecting the position of the GPS satellite position 200 and the point 201 and a point 201a where the outline of the building (shield) intersects, and a straight line connecting the position of the GPS satellite position 200 and the point 202 and the building The point 202a at which the contour line intersects is obtained. A broken line reaching from the point 201a through the position of the GPS satellite position 200 to the point 202a is an approximate orbit when the GPS satellite position 200 stays in the sky, and the time when the GPS satellite position 200 rises and sinks to the horizon and the present The approximate stay in the sky can be calculated from the time.

  Returning to FIG. 5, candidates (satellite combination candidates) of satellite combinations (that is, GNSS combinations) used for positioning are specified in the management table (the satellites used have the code “A” (Applicable)). A combination number is assigned to each of the satellite combination candidates. Each of the satellite combination candidates is associated with DOP (Dilution of precision) value, positioning calculation load, and output frequency information calculated by the satellite selection management unit 133. The DOP value is an index representing the positioning accuracy, and is calculated from the position of the satellite used for positioning. The positioning calculation load is the value of the calculation load when the positioning processing is performed using the satellite combination candidate satellites, and an approximate value is known from the number of satellites used for positioning and the type of GNSS to which each satellite belongs. The output frequency represents an interval at which the positioning calculation unit 120 outputs the positioning result. If the output frequency is increased, positioning calculation load becomes high because it is necessary to perform positioning calculation at high speed, but in this embodiment, in order not to exceed the maximum value (maximum positioning calculation load) of the predetermined positioning calculation load, The satellite selection management unit 133 sets an output frequency value.

  For example, in the management table of FIG. 5, the satellite combination candidate with the combination number “01” is a combination when performing GPS-based positioning, so that the maximum positioning calculation load 100 has a margin and the calculation load becomes 80. The output frequency is set to 1 Hz (1 second interval).

  The satellite combination candidate of the combination number “02” is a combination in the case of performing multi-GNSS-based positioning by adding QZSS and GLONASS satellites to GPS satellites. In this case, the DOP value is improved (the DOP value becomes smaller) and the positioning accuracy is higher than when only the GPS satellite is used, but the calculation load increases and the positioning calculation load becomes 100.

The satellite combination candidate with the combination number “03” is obtained by adding QZSS, GLONASS, and Galileo satellites to GPS satellites, and intentionally excluding GPS and GLONASS satellites having low C / N ₀ values (exclusions). (N / A) (Not Applicable) is attached to the satellites. In this case, the DOP value is worse than the satellite combination candidate of the combination number “02”, but the calculation load is suppressed to 90 by reducing the number of satellites used for positioning, and a margin for the maximum positioning calculation load is secured.

  The satellite combination candidate with the combination number “04” is a combination when multi-GNSS-based positioning is performed by adding QZSS, GLONASS, Galileo, and BDS satellites to a GPS satellite. In this case, the DOP value becomes 1 and high positioning accuracy is obtained, but the calculation load exceeds 100 when the output frequency is 1 Hz. Therefore, in the satellite combination candidate of the combination number “04”, the calculation load is suppressed to 90 by setting the output frequency to 0.5 Hz (2 second intervals), and a margin for the maximum positioning calculation load is secured.

  Each piece of information registered in the management table is stored in the positioning control information storage unit 134 and is centrally managed by the satellite selection management unit 133.

  Here, the operation of mobile information terminal 100 according to the present embodiment will be described. FIG. 7 is a flowchart showing an operation of positioning processing in the mobile information terminal 100.

  When the multi-GNSS base positioning unit 101 starts the positioning process (step S100), the satellite selection control unit 114 first selects to perform GPS base positioning (step S101). Therefore, the positioning calculation unit 120 performs GPS-based positioning (step S102) and outputs the positioning result to the navigation unit 102 (step S109).

  The positioning accuracy and calculation load in this GPS-based positioning are a reference when performing switching processing to multi-GNSS-based positioning and satellite selection. Depending on the combination of satellites, multi-GNSS-based positioning may be less accurate than GPS-based positioning. However, such a combination of satellites should not be selected, and a combination of satellites that has higher accuracy than GPS-based positioning. This is because it is reasonable not to perform multi-GNSS-based positioning if is not present.

  Next, the satellite selection unit 131 checks the positioning switching condition set by the positioning switching condition setting unit 132 and stored in the positioning switching condition setting unit 132 (step S103), and determines whether multi-GNSS based positioning is necessary. (Step S104). If it is determined that multi-GNSS-based positioning is unnecessary (NO in step S104), the process returns to step S101, and GPS-based positioning is continued.

  On the other hand, for example, when it is determined that multi-GNSS-based positioning is necessary because the vehicle speed exceeds 80 km / h (YES in step S104), the satellite selection unit 131 selects to perform multi-GNSS-based positioning (step S105). ).

  Then, the satellite selection unit 131 refers to the management table and selects a combination of satellites used in the multi-GNSS-based positioning from among the combination candidates (step S106). The method for selecting the combination of satellites may be arbitrary. For example, a method of selecting a combination with the smallest DOP value with an emphasis on positioning accuracy, a method of selecting a combination including many satellites with high priority, and the like are conceivable.

  The satellite selection unit 131 sends information on the combination of selected satellites to the satellite selection control unit 114 of the satellite reception unit 110. Based on the combination, the satellite selection control unit 114 specifies a satellite used for positioning (a satellite that the satellite capturing / tracking unit 112 captures and tracks). In this case, when the satellite used for positioning is changed, the command is output from the satellite selection unit 131 to the satellite selection control unit 114, and the satellite selection control unit 114 selects the satellite to be captured and tracked by the satellite capture / tracking unit 112. change.

  Which satellite is used for positioning affects the positioning processing by the positioning calculation unit 120. Therefore, when the satellite selection unit 131 selects the combination of the satellites, it is possible to control the calculation load of the positioning process and the positioning accuracy in the positioning calculation unit 120.

  Further, the satellite selection unit 131 sends the output frequency associated with the selected satellite combination candidate to the output frequency control unit 123 of the positioning calculation unit 120. The output frequency control unit 123 sets the positioning result to be output from the positioning calculation unit 120 at a frequency according to the output frequency (step S107).

  Increasing the output frequency of the positioning results in the positioning calculation unit 120 increases the positioning calculation load because it is necessary to perform positioning calculation at high speed. Conversely, if the output frequency is reduced and the calculation speed is also suppressed, the positioning calculation load can be reduced. Therefore, the positioning calculation load in the positioning calculation unit 120 can be controlled by the satellite selection unit 131 controlling the output frequency.

  When the combination of satellites used for multi-GNSS-based positioning and the output frequency of positioning results are determined, the positioning calculation unit 120 performs multi-GNSS-based positioning (step S108) and outputs the positioning results to the navigation unit 102 (step). S109).

  Thereafter, the process returns to step S103, and after confirming whether or not the positioning switching condition has been changed, it is determined again whether multi-GNSS-based positioning is necessary (step S104). At this time, if it is determined that multi-GNSS base positioning is necessary (YES in step S104), multi-GNSS base positioning is continued, but if it is determined that multi-GNSS base positioning is not required (NO in step S104), GPS base Return to positioning.

  Here, since the position of the own vehicle and the position of the satellite move, the management table needs to be updated periodically. FIG. 8 is a flowchart showing management table update processing performed by the satellite selection management unit 133.

  When the satellite selection management unit 133 starts update processing of the management table (step S200), the satellite selection management unit 133 first checks the positioning switching condition stored in the positioning control information storage unit 134 (step S201).

Next, the satellite selection management unit 133 acquires and generates satellite information to be registered in the management table (step S202). Specifically, the priority order of the satellites is set, or the C / N ₀ value of each satellite is acquired and registered from the satellite receiving unit 110 (the GNSS type and the satellite number are unchanged, so updating is unnecessary). In addition, the elevation angle, direction, and satellite orbit of each satellite are acquired from the positioning calculation unit 120 and registered. Furthermore, the sky stay time of each satellite is calculated and registered based on the image of the vehicle over the camera 105.

Next, a temporary satellite combination candidate for newly registering in the management table based on the satellite information such as priority, C / N ₀ value, elevation angle, heading, satellite orbit, and sky stay time registered in the management table Is determined (step S203). When tentative satellite combination candidates are determined, GNSS satellites with higher priority are selected with priority over other satellites. In addition, a GNSS satellite having a high C / N ₀ value and a high elevation angle has a small pseudo-range error, and thus is preferentially selected over other satellites. In addition, since the GNSS satellite with a long stay in the sky can receive a direct wave for a long time, it is preferentially selected over other satellites.

  When the temporary satellite combination candidate is determined, the satellite selection management unit 133 calculates a DOP value and a positioning calculation load corresponding to the temporary satellite combination candidate (step S204). The DOP value is calculated based on the position of the satellite obtained from the elevation angle and direction of the satellite information, and the positioning calculation load is calculated based on the number of satellites and the type of GNSS to which the satellite belongs.

  Then, based on the DOP value of the temporary satellite combination candidate and the satellite information of each satellite, it is determined whether positioning accuracy is improved over GPS-based positioning if positioning is performed using the temporary satellite combination candidate satellites (step S205). . If it is determined that the positioning accuracy does not improve compared with the GPS-based positioning (NO in step S205), the process returns to step S203 to reexamine the temporary satellite combination candidates.

  If it is determined that the positioning accuracy is improved over the GPS-based positioning (YES in step S205), it is determined whether the positioning calculation load of the temporary satellite combination candidate obtained in step S204 is equal to or less than the maximum positioning calculation load ( Step S206). For example, when a margin for the maximum positioning calculation load is given at the time of GPS-based positioning, it is determined whether the load that increases when switching to multi-GNSS-based positioning can be absorbed by the margin. If it is determined that the positioning calculation load is equal to or less than the maximum positioning calculation load (YES in step S206), a combination number is assigned to the temporary satellite combination candidate and registered as a formal satellite combination candidate in the management table.

  If it is determined that the positioning calculation load of the temporary satellite combination candidate exceeds the large positioning calculation load (NO in step S206), the output frequency is adjusted based on the positioning switching condition and the positioning calculation load of the temporary satellite combination candidate. It is determined whether or not it is possible (step S207). If the output frequency can be adjusted (YES in step S207), the output frequency value is adjusted so that the positioning calculation load of the temporary satellite combination candidate is smaller than the maximum positioning calculation load (step S208). A number is assigned to the combination, and it is registered in the management table as an official satellite combination candidate (step S209). If the output frequency cannot be adjusted (NO in step S207), the process returns to step S203 to reexamine the provisional satellite combination candidates.

In the update process of the management table, the priority order, C / N ₀ value, elevation angle, and azimuth that can be calculated with a small calculation load may be updated with a relatively high frequency. It is desirable to update the stay time in the sky, the DOP value, and the positioning calculation load at a relatively low frequency. The registration process of the satellite combination candidates is also performed periodically according to the update.

  FIG. 9 is a diagram showing a transition example of the positioning calculation load in the mobile information terminal 100 according to the present embodiment. In this example, GPS-based positioning is performed using a combination of satellites with the combination number “01” in the management table of FIG. 5, and the output frequency of positioning results is 1 Hz so as to have a margin for the maximum positioning calculation load. (1 second interval) is set.

At time t _0, the multi-GNSS based positioning is to have been determined to be necessary based on the positioning switch condition. In this case, the mobile information terminal 100 switches the positioning method to multi-GNSS based positioning. In the example of FIG. 9, from time t _0, a multi-GNSS-based positioning using a combination of satellite combination number of the management table "02" in FIG. 5 is started. In the combination of satellites with the combination number “02”, the output frequency of the positioning result is maintained at 1 Hz, but the positioning calculation load is equal to the maximum positioning calculation load.

Thereafter, the management table is updated, and it is determined that the desired positioning accuracy cannot be obtained with the combination of the satellites with the combination number “02” at time t ₁ . In the example of FIG. 9, the time t _1, to start the multi-GNSS-based positioning unit 101 using a combination of satellite management combination number "04" in the table of FIG. 5, and maintain a high positioning accuracy. The combination of satellites with the combination number “04” uses GPS, QZSS, GLONASS, Galileo, and BDS satellites, which increases the positioning calculation load. However, by reducing the output frequency to 0.5 Hz (2 second intervals) The increase in positioning calculation load is suppressed, and a margin for the maximum positioning calculation load is secured.

  According to the present embodiment, in multi-GNSS-based positioning, for example, as shown in FIG. 9, the positioning calculation load is smoothed while maintaining high positioning accuracy, or the positioning calculation load is suppressed without reducing the output frequency. In addition, fine control can be performed, such as suppressing the positioning calculation load by intentionally reducing the number of satellites as in the satellite combination candidate of the combination number “03” in FIG. That is, by appropriately switching the satellite used for positioning and the output frequency of the positioning result, it is possible to achieve both improvement in positioning accuracy and smoothing of the positioning calculation load.

  In the present invention, the embodiments can be appropriately modified and omitted within the scope of the invention.

  DESCRIPTION OF SYMBOLS 100 Mobile information terminal, 101 Multi-GNSS base positioning part, 102 Navigation part, 103 Video image control part, 104 Vehicle sensor part, 105 Camera, 110 Satellite receiver part, 111 Multi-GNSS antenna, 112 Satellite acquisition and tracking part, 113 Navigation Message decoding unit, 114 satellite selection control unit, 120 positioning calculation unit, 121 pseudorange calculation unit, 122 positioning unit, 123 output frequency control unit, 130 multi-GNSS base positioning control unit, 131 satellite selection unit, 132 positioning switching condition setting unit , 133 satellite selection management unit, 134 positioning control information storage unit, 141 locator unit, 142 route search unit, 143 video display unit, 144 map information storage unit.

Claims (11)

A satellite receiver for receiving satellite signals from a plurality of GNSS (Global Navigation Satellite System) satellites;
A multi-GNSS-based positioning control unit that selects one or more of the plurality of GNSSs based on a predetermined positioning switching condition;
A positioning calculation unit for positioning based on a GNSS satellite signal selected by the multi-GNSS base positioning control unit;
With
The multi-GNSS-based positioning control unit, when selecting two or more GNSS, the number of satellites used for positioning by the positioning calculation unit so that the positioning calculation load of the positioning calculation unit is smaller than a predetermined value or the A mobile information terminal characterized by controlling the frequency with which a positioning calculation unit outputs positioning results. The multi-GNSS-based positioning control unit selects a combination of satellites used for positioning by the positioning calculation unit based on a management table described in association with a combination of satellites and a positioning calculation load when positioning is performed with the combination. The mobile information terminal according to claim 1. In the management table, the positioning calculation load is further associated with an output frequency of a positioning result for obtaining the positioning calculation load,
The mobile information terminal according to claim 2, wherein the multi-GNSS-based positioning control unit determines a frequency at which the positioning calculation unit outputs a positioning result based on the management table. In the management table, the combination of satellites is further associated with a DOP value determined by the combination,
4. The multi-GNSS-based positioning control unit controls the number of satellites used for positioning by the positioning calculation unit and the frequency at which the positioning calculation unit outputs a positioning result in addition to the DOP value. Mobile information terminal. 5. The multi-GNSS-based positioning control unit determines a combination of satellites to be described in the management table based on a C / N ₀ value of a satellite signal of each satellite. Mobile information terminal. The mobile information terminal according to any one of claims 2 to 5, wherein the multi-GNSS-based positioning control unit determines a combination of satellites described in the management table based on a position of each satellite. 7. The multi-GNSS-based positioning control unit determines a combination of satellites described in the management table based on a stay time in the sky region obtained from an orbit of each satellite. Mobile information terminal. The mobile information according to any one of claims 2 to 7, wherein the multi-GNSS-based positioning control unit determines a combination of satellites described in the management table based on priority order information of each GNSS satellite. Terminal. The mobile information terminal according to any one of claims 1 to 8, wherein the positioning switching condition is a speed condition of a mobile object equipped with the mobile information terminal. The mobile information terminal according to any one of claims 1 to 8, wherein the positioning switching condition is a condition of a region where a mobile object equipped with the mobile object information terminal is located. The mobile information terminal according to any one of claims 1 to 8, wherein the positioning switching condition is a condition of a distance to a destination set in the mobile information terminal.