JP5901177B2 - Positioning device, observation device and positioning method - Google Patents

Description

  The present invention relates to a technology for suppressing power consumption when performing positioning using a global positioning system.

  A global navigation satellite system (GNSS) is known as a technique for acquiring the position of a moving body, and GPS (Global Positioning System) is particularly well-known in GNSS. In GPS, a plurality of satellites fly while broadcasting transmission time (clocks of all satellites coincide with high accuracy) and information (ephemeris) indicating their own orbits as GPS signals. These GPS signals are transmitted by a CDMA (Code Division Multiple Access) method in which all satellites use the same frequency. A GPS receiver that observes information necessary for positioning is attached to (or integrated with) a moving body, and is configured to obtain the position of the moving body by receiving such a GPS signal.

  A general method for obtaining a positioning position by receiving a signal transmitted from a GPS satellite is described in Patent Document 1, for example. In GPS, as described in Patent Document 1, a GPS receiver is obtained by solving an equation of a sphere centered on a satellite whose position is specified by an ephemeris and having a radius of the distance between the satellite and the GPS receiver. Identify the location. The radius is obtained by measuring the time (propagation time) from when the radio wave propagating at the speed of light is actually transmitted until it is received by the GPS receiver.

  However, the timepiece built in the GPS receiver is less accurate than the satellite timepiece and has errors. Therefore, if the time when the radio wave transmitted from the satellite reaches the GPS receiver is recorded by the GPS receiver, an error occurs in the propagation time. That is, in GPS, it is necessary to correct the GPS receiver clock in order to match the clock of the satellite. Therefore, in GPS, as described in Patent Document 1, the GPS receiver clock error is added as one unknown, and the four satellites whose positions are specified by the ephemeris and the three-dimensional positions are unknown (three unknowns). ), The position of the GPS receiver is specified while correcting the clock of the GPS receiver by solving each of the above equations.

  Patent Document 2 describes a technique for obtaining a pseudo distance between a satellite and a GPS receiver at high speed.

JP 2003-057327 A Japanese Patent No. 3912172

As described above, in the technique described in Patent Document 1, in order to synchronize the GPS receiver clock with the satellite clock with high accuracy, the positioning must be continued, and power consumption is reduced. There was a problem of intenseness. In particular, the fact that the position needs to be obtained by performing positioning means that the position is frequently changed. In other words, in most cases, GPS technology is not a stationary device, but a portable device (notebook computer, digital camera, mobile phone, PDA (Personal Digital Assistant) , smart phone, various music players, portable game. Machine). And since many portable devices are driven by batteries, there is a particular demand for reducing power consumption. Therefore, the positioning technology using GPS is originally a technology that is highly necessary to suppress power consumption.

  The technique described in Patent Document 2 is a technique for obtaining a pseudo distance without waiting for information indicating a transmission time from a satellite to arrive, and is not a technique for suppressing power consumption.

  The present invention has been made in view of the above problems, and provides a technique for suppressing power consumption when specifying a position by receiving radio waves from a satellite in a global positioning system.

In order to solve the above problems, the invention of claim 1 is a positioning device for receiving radio waves transmitted from a plurality of satellites in a global positioning system, wherein a reference satellite and the reference satellite are selected from the plurality of satellites. A selecting means for selecting a satellite other than the receiving means, an acquiring means for acquiring the propagation time of the reference satellite, and a timing for measuring the arrival time of each bit included in a signal transmitted from each of the plurality of satellites Means for interpolating a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means for at least satellites other than the reference satellite, and storage means for storing the arrival time measured by the time measuring means. , the number of arrival bits of the reference satellite at the arrival time of the reference bit of the selected reference satellite by said selecting means, the reference bit of the reference satellites selected by said selection means A bit operation means for obtaining the number of arrival bits being the difference between the number of arriving bits of the satellite as a target of the interpolation in wearing time, based on the number of arriving bits determined difference by said bit operation means, other than the reference satellite A time difference calculating means for obtaining a propagation time difference between the satellites, and a propagation time of the plurality of satellites based on the propagation time of the reference satellite obtained by the obtaining means and the propagation time difference obtained by the time difference calculating means. Propagation time calculation means.

  The invention according to claim 2 is the positioning apparatus according to the invention of claim 1, wherein the selecting means selects the satellite that the reference bit has reached earliest as the reference satellite.

  The invention according to claim 3 is the positioning apparatus according to claim 1 or 2, wherein the selecting means selects a satellite predicted to be present in the nearest vicinity as the reference satellite.

  A fourth aspect of the present invention is the positioning apparatus according to any one of the first to third aspects of the invention, wherein the interpolation is an interpolation based on a least square method.

  The invention of claim 5 is the positioning apparatus according to any one of claims 1 to 4, wherein the plurality of satellites are based on the propagation times of the plurality of satellites obtained by the propagation time calculating means. Pseudo distance calculating means for calculating a pseudo distance from the satellite is further provided.

  The invention according to claim 6 is the positioning device according to any one of claims 1 to 5, wherein the receiver processor causes at least the time measurement by the time measurement means to be stored in the storage means. And a navigation processor having at least the bit operation means.

Further, the invention of claim 7 is an observation device, comprising observation data acquisition means for acquiring observation data expressing the surrounding environment, a reference satellite and a satellite other than the reference satellite among the plurality of satellites. Selecting means for selecting; acquisition means for acquiring a propagation time of the reference satellite; timing means for timing the arrival time of each bit included in a signal transmitted from each of the plurality of satellites; Interpolating a graph indicating the relationship between the arrival time and the number of arrival bits stored in the storage means for at least satellites other than the reference satellite, and selecting the selection time; the number of arriving bits of the reference satellite at the arrival time of the reference bit of the selected reference satellite by means before the arrival time of the reference bit of the reference satellites selected by said selection means Bit calculation means for determining the arrival bit number difference that is the difference from the arrival bit number of the satellite subject to interpolation, and propagation of satellites other than the reference satellite based on the arrival bit number difference obtained by the bit calculation means Time difference calculating means for obtaining a time difference, and propagation time calculating means for obtaining the propagation times of the plurality of satellites based on the propagation time of the reference satellite obtained by the obtaining means and the propagation time difference obtained by the time difference calculating means. And a pseudo-range computing means for computing pseudo distances from the plurality of satellites based on the propagation times of the plurality of satellites obtained by the propagation time computing means, and the plurality obtained by the pseudo-range computing means. Position information generating means for generating position information indicating the position of the observation device based on a pseudo-distance from the satellite, the observation data and the position information And a second storage means for association with memory.

The invention of claim 8 is a positioning method for specifying a position by receiving radio waves transmitted from a plurality of satellites in the global positioning system, wherein the signals transmitted from each of the plurality of satellites Selecting a reference satellite and a satellite other than the reference satellite from the plurality of satellites by selecting the arrival time of each bit included in the step, storing the measured arrival time in a storage means, And interpolating a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means for at least satellites other than the reference satellite, and arrival of reference bits of the reference satellite selected by the selection means the number of arriving bits of the reference satellite at the time, the number of arrival bits of the satellite as a target of the interpolation in the arrival time of the reference bit of the reference satellites selected by said selection means A step of determining the number of arrival bits being the difference, based on the number of arriving bits calculated difference, a step of determining the time difference calculating means the propagation time difference between the satellite other than the reference satellite, and acquires the propagation time of the reference satellite And a step of obtaining the propagation times of the plurality of satellites by the propagation time calculation means based on the acquired propagation time of the reference satellite and the propagation time difference obtained by the time difference calculation means .

For at least a satellite other than the reference satellite, a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means is interpolated, and the reference in the arrival time of the reference bit of the reference satellite selected by the selection means Bit calculating means for obtaining a difference in arrival bits, which is a difference between the arrival bits of the satellites and the arrival bits of the reference bits of the reference satellites selected by the selection means; A time difference calculating means for obtaining a propagation time difference of satellites other than the reference satellite based on the difference in the number of arrival bits obtained by the bit calculating means, and a propagation time obtained by the time difference calculating means of the reference satellite obtained by the obtaining means. Providing propagation time calculation means to obtain the propagation time of multiple satellites based on the time difference, so that positioning is not continued at all times Also, it is possible to determine the propagation time of each satellite with sufficient accuracy.

It is a block diagram of a digital camera. It is a figure which shows the functional block which a positioning part has with the flow of data. It is a figure explaining the function of a bit calculating part. It is a flowchart which shows the operation | movement in the power saving mode of a digital camera. It is a flowchart which shows the detail of the positioning process performed by the positioning part.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

<1. Embodiment>
FIG. 1 is a block diagram of the digital camera 1. As shown in FIG. 1, the digital camera 1 as a recording apparatus according to the present invention is designed as an apparatus that can be carried by a user, and records imaging data 91.

  As shown in FIG. 1, a digital camera 1 includes a CPU 10 that performs various data operations, a ROM 11 that can only read data stored in advance, a RAM 12 that can both read and write data, an operation unit 13, and a display unit. 14 is provided. The digital camera 1 also includes a card slot 15 into which a memory card 90 can be inserted, an imaging unit 16 that acquires image data 160, and a positioning unit 17 that acquires position information 84.

  The CPU 10 reads out the program 80 stored in the ROM 11 and controls the components included in the digital camera 1 by executing the program 80 while using the RAM 12 as a working area. Thus, the digital camera 1 has a function as a general computer.

  In particular, the CPU 10 in the present embodiment appropriately requests the position information 84 from the positioning unit 17, associates the position information 84 acquired from the positioning unit 17 with the image data 160 acquired from the imaging unit 16, and Imaging data 91 is created and stored in the memory card 90. The function and operation of the CPU 10 will be described later as appropriate.

  The operation unit 13 corresponds to various buttons, keys, switches, and the like. The user can input various information to the digital camera 1 by operating the operation unit 13. In particular, the digital camera 1 includes a shutter button that is operated to instruct the imaging unit 16 to perform imaging, a power switch for inputting an instruction to switch the power state of the digital camera 1, and the like as the operation unit 13.

  The display unit 14 includes various lamps, LEDs, liquid crystal panels, and the like, and has a function of presenting various data to the user. In particular, the display unit 14 has a function of displaying the imaging range of the imaging unit 16 and displaying the imaging data 91 to the user. The digital camera 1 may realize the functions of the operation unit 13 and the display unit 14 by including a device such as a touch panel display.

  The card slot 15 provides a function of detachably storing a memory card 90 that is a portable storage medium with respect to the digital camera 1. Thus, the digital camera 1 (CPU 10) can use the memory card 90 as its own storage device, and can store a relatively large amount of data such as the imaging data 91.

  The memory card 90 removed from the digital camera 1 is configured so that it can be attached to an external computer or the like (not shown). Therefore, the user can read and use the imaging data 91 stored in the memory card 90 on an external computer.

  The digital camera 1 may have a function for performing data communication with an external computer (not shown). As a configuration for realizing such a function, a USB terminal, an infrared communication unit, or the like is assumed. If the digital camera 1 has such a configuration, the user can transfer and use the imaging data 91 stored in the memory card 90 to an external computer without removing the memory card 90. .

  The imaging unit 16 performs a correction process or a compression process on an optical system including a lens, an optical filter, a motor that drives the lens, a photoelectric conversion element such as a CCD, a flash that illuminates a subject, and acquired data. It consists of an image processing unit and the like. The imaging unit 16 has a function of capturing a subject in accordance with a user instruction (for example, pressing a shutter button) and acquiring digital data (image data 160) representing the subject (ambient environment). That is, the imaging unit 16 mainly has a function as observation data acquisition means.

  The positioning unit 17 has a function as a positioning device that receives radio waves transmitted from a plurality of satellites in a global navigation system (GNSS) and identifies a position.

  As shown in FIG. 1, the positioning unit 17 includes an antenna 170 that receives radio waves transmitted from satellites in the global positioning system, an RFIC 171 that converts an input signal from the antenna 170 into a digital signal, and a replica signal that generates a replica signal. A generation circuit 172 and a correlation processing unit 173 that takes a correlation between the digital signal converted by the RFIC 171 and the replica signal generated by the replica signal generation circuit 172 are provided. The positioning unit 17 includes a receiver processor 174 that mainly executes processing in real time, a ROM 175 that stores a program 81 that is executed by the receiver processor 174, a RAM 176 that is used as a temporary working area of the receiver processor 174, and A timer unit 177 is provided.

  Since the receiver processor 174 controls the replica signal generation circuit 172 and the correlation processing unit 173, the conventional technique can be used for the process of continuously capturing the satellite and demodulating the signal transmitted from the satellite. Briefly described below.

  The antenna 170 receives radio waves from satellites in the global positioning system and transmits analog signals to the RFIC 171. In the following, an example in which a GPS (Global Positioning System) provided by the United States as a global positioning system is employed unless otherwise specified will be described.

  The RFIC 171 converts the analog signal input from the antenna 170 into a digital signal while down-converting it, and outputs it to the correlation processing unit 173.

  The replica signal generation circuit 172 generates a replica signal based on a control signal (a signal indicating a control parameter) from the receiver processor 174 and outputs the replica signal to the correlation processing unit 173.

  Although not shown in detail in FIG. 1, the replica signal generation circuit 172 includes a carrier generation circuit that generates a carrier replica signal corresponding to a carrier for transmitting data from the satellite, and a spread code (PN code unique to the satellite). And a code generation circuit for generating a code replica signal corresponding to (1).

  The carrier generation circuit generates a carrier replica signal that is correlated with the I signal of the IF signal by a correlation processing unit 173, which will be described later, and a carrier replica signal that is correlated with the Q signal of the IF signal by the correlation processing unit 173. .

  A control parameter from the receiver processor 174 (more specifically, a control parameter corresponding to a frequency error; hereinafter referred to as “frequency control parameter”) is input to the carrier generation circuit. The carrier generation circuit changes the frequency of the carrier replica signal according to the frequency control parameter input from the receiver processor 174. In other words, the carrier generation circuit generates a carrier replica signal having a frequency corresponding to the frequency control parameter input from the receiver processor 174.

  The code generation circuit selects a PN code specific to the satellite to be captured and generates a code replica signal corresponding to the PN code. When the satellite to be captured is switched, the code generation circuit generates a new code replica signal using a PN code unique to the switching destination satellite. Further, the code generation circuit changes the phase of the code replica signal in accordance with a control parameter from the receiver processor 174 (more specifically, a control parameter corresponding to the code phase difference, hereinafter referred to as “code control parameter”). Is possible.

  More specifically, the code generation circuit includes a prompt code replica signal (P signal), an early code replica signal (E signal) advanced by ½ chip with respect to the prompt code replica signal, and Then, a rate code replica signal (L signal) delayed by ½ chip with respect to the prompt code replica signal is generated.

  Although not shown in detail, the correlation processing unit 173 includes a plurality of channel circuits, and each channel circuit captures and tracks a satellite. In other words, the positioning unit 17 can simultaneously observe as many satellites as the number of channel circuits included in the correlation processing unit 173.

  Each channel circuit of the correlation processing unit 173 down-converts the input signal (IF signal) from the RFIC 171 to the baseband frequency by the carrier replica signal input from the replica signal generation circuit 172 (carrier generation circuit). Further, each channel circuit of the correlation processing unit 173 includes the down-converted digital signal (I signal and Q signal) and a code replica signal (E signal, P signal) input from the replica signal generation circuit 172 (code generation circuit). Signal and L signal). That is, by each channel circuit of the correlation processing unit 173, correlation signals (IE signal, IP signal, IL signal, QE signal, QP signal, and the like corresponding to the input signal from the RFIC 171 and the replica signal from the replica signal generation circuit 172 are displayed. QL signal) is generated and output.

  The receiver processor 174 reads the program 81 stored in the ROM 175, and executes the program 81 while using the RAM 176 as a working area. That is, the receiver processor 174 has a function as a microcomputer.

  The receiver processor 174 transmits the satellite (captured satellite) selected by the navigation processor 178 to the code generation circuit of the replica signal generation circuit 172. Thereby, as described above, the code generation circuit generates a code replica signal corresponding to the PN code unique to the selected satellite.

  Further, the receiver processor 174 performs the control parameter for the replica signal generation circuit 172 according to the correlation signal (IE signal, IP signal, IL signal, QE signal, QP signal, and QL signal) output from the correlation processing unit 173. The replica signal generation circuit 172 is controlled.

  For example, since satellites fly at high speeds on their orbits, radio waves transmitted from the satellites have a frequency error with respect to the original frequency due to the Doppler effect. Furthermore, the relative speed between the satellite in flight and the digital camera 1 (positioning unit 17) moving due to the rotation of the earth is almost always changing, and the frequency error due to the Doppler effect is also almost always changing. .

  Therefore, the receiver processor 174 obtains a correlation between the digital signal down-converted by the carrier replica signal and the replica signal from the replica signal generation circuit 172 while monitoring the correlation signal output from the correlation processing unit 173 ( The carrier replica signal generation circuit (carrier replica signal) is feedback controlled by changing the frequency control parameter so that both signals can be synchronized.

  That is, the receiver processor 174 monitors the correlation signal from the correlation processing unit 173 while changing the frequency control parameter, and captures the frequency of the carrier wave in which the frequency error has occurred. Thereafter, while monitoring the correlation signal from the correlation processing unit 173, the frequency control parameter is changed so that the synchronized state is maintained, and the frequency of the carrier wave whose frequency error is changed is tracked. Such control can be realized using conventional techniques (for example, Phase Locked Loop, Frequency Locked Loop, etc.).

  Furthermore, the IF signal input from the RFIC 171 and the code replica signal generated by the replica signal generation circuit 172 due to the distance between the satellite and the digital camera 1 (positioning unit 17), the error between the satellite clock and the time measuring unit 177, and the like. There is a code phase difference between. Since the satellite and the digital camera 1 are moving, the distance between the satellite and the digital camera 1 is almost always changing, and the code phase difference is also almost always changing.

  Therefore, the receiver processor 174 monitors the output signal from the correlation processing unit 173, and detects the down-converted digital signal (more specifically, the I signal and the Q signal) and the code replica signal from the replica signal generation circuit 172. Thus, the code control parameter is changed so that the correlation between the two is obtained (synchronization of both signals is obtained), and the code replica signal generation circuit (code replica signal) is feedback-controlled.

  That is, the receiver processor 174 monitors the output signal from the correlation processing unit 173 while changing the code control parameter, and ensures synchronization between the down-converted digital signal and the code replica signal. Thereafter, the receiver processor 174 changes the code control parameter and tracks the phase so that the synchronized state is maintained while monitoring the output signal from the correlation processing unit 173. Such control can be realized by using a conventional technique (for example, Delay Locked Loop).

  The receiver processor 174 in the present embodiment has a function of creating arrival time information 83 and storing it in the RAM 176 in addition to the above demodulation processing.

  In GPS, data transmitted from each satellite is represented by a bit string. The receiver processor 174 monitors the output signal (correlation signal) from the correlation processing unit 173 (each channel circuit), measures the arrival time of each bit included in the data transmitted from each satellite by the time measuring unit 177, and arrives. Time information 83 is created. Therefore, the arrival time information 83 exists in each corresponding to the observed (captured) satellite.

  That is, the receiver processor 174 and the timer unit 177 implement the timer unit in the present invention. In GPS, the transfer rate of data transmitted from a satellite is 50 [bps]. Therefore, since 20 [ms] is required to transmit 1 bit, the arrival time information 83 is a record plotted at intervals of about 20 [ms].

  As shown in FIG. 1, the positioning unit 17 includes a navigation processor 178, a ROM 179 that stores a program 82 that is executed by the navigation processor 178, and a RAM 180 that is used as a temporary working area of the navigation processor. That is, the navigation processor 178 has a function as a microcomputer.

  The navigation processor 178 determines which satellite's code replica signal is to be generated by the replica signal generation circuit 172 (which satellite is to be captured) and provides an instruction via the receiver processor 174. Once a satellite that has been determined to be acquired cannot actually be acquired (or the acquired satellite can no longer be acquired), a new satellite to be acquired is selected and transmitted to the receiver processor 174. .

  In addition, the navigation processor 178 acquires data transmitted from the satellite based on the correlation signal output from the correlation processing unit 173 and outputs the data to the RAM 180. Although not described in detail, the navigation processor 178 detects, based on the correlation signal, that the acquisition of the satellite has been completed and the satellite has been tracked, and the correlation signal ( That is, the data transmitted from the satellite is decoded from the demodulated transmission signal.

  For example, a satellite in GPS transmits data including transmission time of data to be transmitted (PN code), ephemeris data expressing a satellite orbit unique to the satellite, almanac data expressing an approximate orbit of all satellites, and the like. Flying. The navigation processor 178 obtains this data by decoding and stores it in the RAM 180. Each ephemeris data and almanac data has an expiration date. It is preferable that the navigation processor 178 appropriately monitors the expiration date of the transmitted data and acquires the information again before the expiration date expires.

  In addition, the navigation processor 178 calculates the position of the digital camera 1 (positioning unit 17) at a predetermined timing and creates position information 84. Note that the navigation processor 178 in the present embodiment can continuously perform positioning processing in the same manner as the conventional method to create the same information as the position information 84, but here the conventional method is described. Will not be described.

  FIG. 2 is a diagram showing the functional blocks of the positioning unit 17 together with the data flow. The reference satellite selection unit 181, the bit calculation unit 182, the time difference calculation unit 183, the propagation time calculation unit 184, the pseudo distance calculation unit 185, and the position calculation unit 186 in FIG. 2 are operated by the navigation processor 178 operating according to the program 82. It is a functional block that is realized.

  The reference satellite selection unit 181 selects a reference satellite and a satellite other than the reference satellite from a plurality of observed (tracked) satellites. In other words, one reference satellite is selected from a plurality of satellites being tracked (determined by the navigation processor 178), and classified into the selected reference satellite and the other satellites.

  The reference satellite selection unit 181 in the present embodiment selects a satellite that is predicted to exist in the nearest vicinity as a reference satellite. Specifically, according to the demodulated signal input from each channel circuit of the correlation processing unit 173, the satellite assigned to the channel circuit where the specific bit (reference bit) arrives earliest (demodulated) is used as a reference. Select as satellite.

  The bit calculation unit 182 obtains the arrival time information 83 stored in the RAM 176 from the receiver processor 174 and interpolates to obtain the difference in the number of arrival bits in the arrival time of the reference bit of the reference satellite selected by the reference satellite selection unit 181. The arrival bit number difference information 85 is created.

  FIG. 3 is a diagram illustrating the function of the bit calculation unit 182. In FIG. 3, points indicated by black circles are arrival time information 83 of the reference satellite. A black square indicates arrival time information 83 of one of the observed satellites that is not the reference satellite (hereinafter referred to as “non-reference satellite”).

  In FIG. 3, the time when the first bit of the data transmitted from the reference satellite (more specifically, the first bit of the first subframe) arrives is shown as the origin. As described above, the arrival time information 83 is created for each observed (tracking) satellite, and the arrival time of each bit is plotted approximately every 20 [ms].

  Here, attention is paid to the n-th arriving bit. Each satellite in the GPS transmits the same number of bits simultaneously. Therefore, the nth bit is also transmitted simultaneously from each satellite. However, the nth bit transmitted from the reference satellite arrives at time T1, while the nth bit transmitted from a non-reference satellite located farther than the reference satellite arrives at time T2. .

  Therefore, if there is no error in the timer 177 (local clock), the propagation time difference between the reference satellite and the non-reference satellite is “T2−T1”. However, since the actual time measuring unit 177 has a larger error than the atomic clock mounted on the satellite, and the positioning unit 17 moves (especially due to the rotation of the earth) while the signal arrives late, The distance difference cannot be obtained as it is from the above propagation time difference.

  Now, a case will be described as an example where at time T3, the shutter button is operated to create image data 160 and the CPU 10 requests the positioning unit 17 to output the position information 84.

  The bit calculation unit 182 interpolates the arrival time information 83 of the reference satellite by the least square method, and creates a solid line L1 shown in FIG. Then, the reference bit is determined by the intersection of the solid line L1 and time T3. In the example illustrated in FIG. 3, the reference bit is “q”. It should be noted that the bit value is an integer at the point plotted in the arrival time information 83, but the value of the reference bit is not necessarily an integer, and is generally a positive number.

  Next, the bit calculation unit 182 interpolates the arrival time information 83 of the non-reference satellite by the least square method, and creates a one-dot chain line L2 shown in FIG. Then, the arrival bit of the non-reference satellite at the arrival time of the reference bit of the reference satellite (that is, time T3) is obtained from the intersection of the alternate long and short dash line L2 and time T3. In the example illustrated in FIG. 3, the arrival bit is “p”. The value of the arrival bit of the non-reference satellite is also generally a positive number.

  Further, the bit calculation unit 182 obtains the arrival bit number difference (“ΔBit” shown in FIG. 3) based on the difference between the reference bit and the arrival bit. In the example shown in FIG. 3, the arrival bit number difference can be obtained by the following Expression 1.

  ΔBit = q−p Equation 1

  The obtained arrival bit number difference is stored in the RAM 180 as arrival bit number difference information 85. Here, the method of creating the arrival bit number difference information 85 for one non-reference satellite has been described. However, the bit calculation unit 182 excludes all non-reference satellites (excluding the reference satellite among the observed satellites). Satellite). In the following, the case where m non-reference satellites are observed is taken as an example, and the values corresponding to the non-reference satellites are distinguished by attaching a subscript of 1 to m (m is a positive integer). That is, Expression 1 for the mth non-reference satellite is expressed as ΔBit (m) = q−p (m).

  Returning to FIG. 2, the time difference calculation unit 183 obtains the propagation time difference “ΔCT (m)” of the satellites other than the reference satellite based on the arrival bit number difference information 85 obtained by the bit calculation unit 182, and the propagation time difference information 86. Create As described above, in GPS, 20 [ms] is required to transmit 1 bit, and therefore the propagation time difference “ΔCT (m)” can be obtained by Equation 2.

  ΔCT (m) = 20 × ΔBit (m) Equation 2

  The propagation time calculation unit 184 calculates and acquires the propagation time of the reference satellite by referring to the average distance information 87 (information indicating the average distance of the satellite) stored in advance and multiplying this by the speed of light. . That is, the propagation time calculation unit 184 has a function as acquisition means of the present invention. Here, when calculating based on the average distance of the satellite, the propagation time of the reference satellite is 68 [ms]. The propagation time of the reference satellite is obtained based on the data (ephemeris or almanac) transmitted from the reference satellite already acquired and the predicted position of the positioning unit 17 based on the position information 84 acquired so far. May be.

  Next, based on the propagation time (CT) of the reference satellite and the propagation time difference (ΔCT (m)) obtained by the time difference calculation unit 183, the propagation time calculation unit 184 calculates the propagation time of each non-reference satellite as follows: It calculates | requires by Formula 3, respectively.

  CT (m) = CT + ΔCT (m) Equation 3

  That is, the propagation time information 88 created by the propagation time calculation unit 184 includes the propagation time CT of the reference satellite and the propagation times CT (1) to CT (m) of each non-reference satellite.

  Based on the propagation time (propagation time information 88) of the tracking satellite obtained by the propagation time calculation unit 184, the pseudo distance calculation unit 185 calculates the pseudo distance from the tracking satellite. More specifically, the pseudorange for each satellite is obtained by multiplying the propagation time obtained for each satellite by the speed of light. The obtained pseudo distance is stored in the RAM 180 as the pseudo distance information 89.

  The position calculation unit 186 creates position information 84 indicating the position of the positioning unit 17 based on the pseudo distance information 89. A conventional technique can be applied to the process of creating the position information 84 based on the pseudo distance (pseudo distance information 89) from each satellite.

  The above is the description of the configuration and functions of the digital camera 1 in the present embodiment. As described above, in the positioning unit 17 according to the present embodiment, it is not necessary to perform the positioning processing (processing for creating the position information 84) until the CPU 10 requests the position information 84. The power can be kept off and power consumption can be suppressed. As described above, in more detail, the navigation processor 178 is turned on until an observable satellite is captured and the tracking state is entered. It is also preferable that the navigation processor 178 is turned on when the expiration date of the transmitted data for each satellite is approaching or when the observable satellite is switched.

  Next, a positioning method in which the digital camera 1 receives radio waves transmitted from a satellite and specifies the position information 84 will be described.

  FIG. 4 is a flowchart showing the operation of the digital camera 1 in the power saving mode. The power saving mode is one of operation modes selected mainly by a user instruction, and is a mode in which control is performed to suppress power consumption. However, the shift to the power saving mode is not limited to the user's instruction, and may be shifted due to, for example, a decrease in battery capacity or a long time non-operation.

  In the power saving mode, the receiver processor 174 of the positioning unit 17 monitors whether a satellite is being acquired (step S1). The determination in step S1 is based on, for example, whether correlation signals are obtained from all channel circuits in the correlation processing unit 173, or whether satellite acquisition processing described later has been executed for all satellites in flight. can do.

  If the satellite is not being acquired (No in step S1), the receiver processor 174 turns on the navigation processor 178 and cooperates to execute the satellite acquisition process (step S2). Note that the satellite acquisition process can be executed by appropriately applying conventional techniques, and thus detailed description thereof is omitted here.

  When the satellite is being captured (tracked) (Yes in step S1), the receiver processor 174 starts the satellite tracking process while monitoring the correlation signal output from the correlation processing unit 173 (step S3). Note that the satellite tracking process can be executed by appropriately applying conventional techniques, and thus detailed description thereof is omitted here. If the satellite tracking process has already been started, the satellite tracking process is continued. In addition, the satellite tracking process is continued until the satellite is lost in principle. However, for example, the satellite tracking process is also ended when the user gives an instruction to end and the power is turned off.

  When each channel circuit included in the correlation processing unit 173 includes a satellite that is capturing a satellite and a channel circuit that is not capturing a satellite, the processing of step S2 or the processing of steps S3 to S5 is performed for each channel circuit. Is executed. When all the observable satellites are acquired or when all the channel circuits are acquiring the satellites, it is not determined No in step S1, and the navigation processor 178 is once in the off state. It becomes.

  While the satellite tracking process is started and the process is being executed, the receiver processor 174 monitors the correlation signal from the correlation processing unit 173, and each time a new bit of data transmitted from each satellite arrives, the clocking unit 177 , The arrival time of the bit is counted (step S4). Then, the measured arrival time is stored in the RAM 176 as arrival time information 83 (step S5).

In GPS, one bit of data transmitted from a satellite is spectrum-spread with a PRN code having a cycle of 1.023 [MHz]. Therefore, the 1 bit, ing from PRN code 20 that consists in 1023 chips. In other words, while the satellite tracking process is being performed, the receiver processor 174 performs the time counting unit 177 every time the first chip of a new bit transmitted from the tracking satellite arrives. , A process of storing the value (time) at that time as arrival time information 83 of the bit is executed. In addition, this process is executed simultaneously for all the satellites being acquired.

However, as described above, since this process only needs to be executed for the first PRN code constituting one bit, the load on the receiver processor 174 is not increased much.

  Further, since the navigation processor 178 is not required to perform any process during the period in which the satellite tracking process is simply executed, the power consumption can be suppressed by turning off the navigation processor 178 during this period.

  In the power saving mode, the CPU 10 monitors whether or not an imaging instruction has been given by the user (step S6) and whether or not to end the power saving mode has been instructed (step S12).

  When imaging is instructed by the user in the power saving mode, the CPU 10 instructs the imaging unit 16 to execute imaging. Thereby, the imaging unit 16 images the subject, and the image data 160 is acquired (step S7). The imaging instruction by the user is, for example, a pressing operation of a shutter button (operation unit 13). In the power saving mode, the CPU 10 may be turned off, and when the operation unit 13 is operated (for example, when the shutter button is pressed), an activation signal may be generated and the CPU 10 may be turned on. If comprised in this way, the electric power consumed by CPU10 can also be suppressed.

  In parallel with the process of step S <b> 7, the CPU 10 requests the position information 84 from the positioning unit 17. In response to this request, the navigation processor 178 is turned on, and positioning processing by the positioning unit 17 is executed (step S9).

  FIG. 5 is a flowchart showing details of the positioning process executed by the positioning unit 17.

  First, the reference satellite selection unit 181 selects the satellite in which the same bit arrives the earliest from the satellites being captured (tracked) as the reference satellite (step S20), and selects the bit calculation unit 182. Communicate the results.

  Next, the bit calculation unit 182 acquires the arrival time information 83 for each satellite stored in the RAM 176 from the receiver processor 174 and interpolates using the least square method (step S21). Then, the arrival bit number difference in the arrival time of the reference bit of the reference satellite selected by the reference satellite selection unit 181 (the time when the position information 84 is requested by the CPU 10) is obtained for each non-reference satellite, and the arrival bit number difference information 85 Is created (step S22).

  When the arrival bit number difference information 85 is created, the time difference calculation unit 183 obtains the propagation time difference “ΔCT (m)” of satellites other than the reference satellite based on the arrival bit number difference information 85, and the propagation time difference information 86. Is created (step S23).

  Next, the propagation time calculation unit 184 refers to the average distance information 87 stored in advance, and obtains the propagation time of the reference satellite by calculation by multiplying it by the speed of light. The propagation time calculation unit 184 obtains the propagation time of each non-reference satellite based on the propagation time of the reference satellite and the propagation time difference information 86 obtained by the time difference calculation unit 183. Thereby, the propagation time information 88 is created for all the satellites being acquired (step S24).

  Next, the pseudo distance calculation unit 185 calculates the pseudo distance from the tracking satellite based on the propagation time information 88 obtained by the propagation time calculation unit 184, and creates the pseudo distance information 89 (step S25). .

  When the pseudo distance information 89 is obtained for all the satellites being acquired, the position calculation unit 186 creates position information 84 indicating the position of the positioning unit 17 based on the pseudo distance information 89 (step S26). Then, the navigation processor 178 outputs the created position information 84 to the CPU 10 (step S27), ends the positioning process, and returns to the process shown in FIG.

  When the positioning process is completed, the navigation processor 178 is temporarily turned off (step S10). Thereby, power consumption is suppressed until the navigation processor 178 is turned on again.

  When the position information 84 is acquired from the positioning unit 17, the CPU 10 creates the imaging data 91 by associating the image data 160 acquired in step S7 with the position information 84 and stores it in the memory card 90 (step S11). . Therefore, in the imaging data 91, the position information 84 indicating the imaging position is associated with the image data 160. It should be noted that it is preferable to further reduce the power consumption by appropriately turning off the CPU 10 after executing Step S11.

  When the end is instructed by the user in the power saving mode, the CPU 10 determines Yes in step S12, ends the power saving mode, and shifts to the instructed mode (details are omitted).

  As described above, the digital camera 1 serving as the observation apparatus according to the first embodiment includes the imaging unit 16 that acquires the image data 160 representing the subject, the reference satellite among the plurality of tracking satellites, and the reference satellite. A reference satellite selection unit 181 that selects a satellite other than the satellite, a propagation time calculation unit 184 that acquires the propagation time of the reference satellite, and the arrival of each bit included in a signal transmitted from each of the plurality of satellites A time measuring unit 177 for measuring time, a RAM 176 for storing the arrival time measured by the time measuring unit 177, and at least satellites other than the reference satellite, the arrival time information 83 stored in the RAM 176 is interpolated, and the reference satellite selecting unit 181 is interpolated. The bit calculation unit 182 that obtains the difference in the number of arrival bits in the arrival time of the reference bit of the reference satellite selected by the On the basis of the arrival bit number difference information 85, the time difference calculation unit 183 that obtains the propagation time difference information 86 of satellites other than the reference satellite, and the propagation time and time difference calculation unit 183 of the reference satellite acquired by the propagation time calculation unit 184 Based on the obtained propagation time difference information 86, a propagation time calculation unit 184 that obtains propagation time information 88 of a plurality of satellites being tracked, and a plurality of propagation time information 88 obtained by the propagation time calculation unit 184, Based on the pseudo distance calculation unit 185 for calculating the pseudo distance information 89 from the satellite and the pseudo distance information 89 from the plurality of satellites obtained by the pseudo distance calculation unit 185, position information 84 indicating the position of the digital camera 1 is obtained. A position calculation unit 186 to be created, and a memory card 90 that stores image data 160 and position information 84 in association with each other are provided. As a result, the propagation time can be obtained with sufficient accuracy and the position information 84 can be obtained without continuously positioning. Further, since the difference in the number of arrival bits is obtained by interpolation, it is not necessary to manage the arrival time for all chips (one bit is composed of 1023 chips), and the load on the receiver processor 174 does not increase.

  Further, the bit calculation unit 182 can cancel the jitter and the like of the time measuring unit 177 by executing the interpolation by the least square method.

  In addition, by including a receiver processor 174 that causes at least time measurement by the time measurement unit 177 to store the arrival time information 83 in the RAM 176 and a navigation processor 178 having at least a bit calculation unit 182, the processing is distributed and the load is reduced. The navigation processor 178 can be turned off while it can be mitigated and the location need not be identified. That is, the navigation processor 178 can be operated intermittently, and the power consumption can be suppressed as compared with the case where the positioning is continuously performed.

<2. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, as described with reference to FIG. 3, in the above embodiment, the reference bit (q) at time T3 (imaging time) is obtained by interpolating the arrival time information 83 of the reference satellite. However, if there are only reference bits, the output signal from the correlation processing unit 173 may be analyzed to obtain the reference bit (q) at time T3. That is, the bit arriving at time T3 may be obtained by analysis.

  Further, the interpolation by the least square method may be performed only for points in the arrival time information 83 near the time T3 (for example, arrival times for several bits). Thereby, the information amount of the arrival time information 83 to be stored can be further suppressed, and the processing time required for the interpolation is shortened.

  Further, the interpolation is not limited to the least square method. For example, the solid line L1 and the alternate long and short dash line L2 may be created by simply connecting and extending two points plotted immediately before.

  In the above embodiment, it has been described that the time when a new bit arrives is recorded as the arrival time. However, if the receiver processor 174 has a sufficient specification, for example, the arrival time is recorded every half bit. May be. That is, the interval for recording the arrival time is not limited to each bit.

  Further, the observation apparatus in the present invention is not limited to a digital camera. For example, the present invention can be applied to a recording device that records wild bird calls when observing wild birds outdoors, an observation device that records fishing results and environmental information (such as temperature, water temperature, tidal current, and wind speed) at a fishing spot. Alternatively, it can be applied to a game machine in which a story changes depending on a place to play. Further, a device in which these functions are combined may be used.

  Further, although the observation apparatus has been described as an apparatus that does not have a function of performing data communication with a radio base station, it can be applied to an apparatus having such a function (for example, a mobile phone). In this case, for example, the propagation time of the reference satellite may be acquired from the radio base station.

  Further, although each functional block described in the above embodiment has been described as being realized by a program, a part or all of these functional blocks may be realized by a dedicated logic circuit (hardware).

  Moreover, each process shown to the said embodiment is an illustration to the last, and is not limited to such a content and order. That is, as long as the same effect can be obtained, the content and order may be changed as appropriate.

  Further, a functional block realized by the navigation processor 178 operating according to the program 82 may be realized by the CPU 10 operating according to the program 80. In that case, the navigation processor 178 need not be provided.

1 Digital camera 10 CPU
11,175,179 ROM
12,176,180 RAM
DESCRIPTION OF SYMBOLS 13 Operation part 14 Display part 15 Card slot 16 Image pick-up part 160 Image data 17 Positioning part 174 Receiver processor 177 Time measuring part 178 Navigation processor 181 Reference | standard satellite selection part 182 Bit calculating part 183 Time difference calculating part 184 Propagation time calculating part 185 Pseudo distance calculating part 186 Position calculator 80, 81, 82 Program 83 Arrival time information 84 Position information 85 Arrival bit number difference information 86 Propagation time difference information 87 Average distance information 88 Propagation time information 89 Pseudo distance information 90 Memory card 91 Imaging data

Claims (8)

A positioning device that receives radio waves transmitted from a plurality of satellites in a global positioning system,
Selecting means for selecting a reference satellite and a satellite other than the reference satellite from the plurality of satellites;
Obtaining means for obtaining a propagation time of the reference satellite;
Clocking means for timing the arrival time of each bit included in a signal transmitted from each of the plurality of satellites;
Storage means for storing the arrival time measured by the time measuring means;
For at least a satellite other than the reference satellite, a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means is interpolated, and the reference in the arrival time of the reference bit of the reference satellite selected by the selection means Bit calculating means for obtaining a difference in arrival bits, which is a difference between the arrival bits of the satellites and the arrival bits of the reference bits of the reference satellites selected by the selection means; ,
Based on the arrival bit number difference obtained by the bit computation means, a time difference computation means for obtaining a propagation time difference of satellites other than the reference satellite;
Based on the propagation time of the reference satellite obtained by the obtaining means and the propagation time difference obtained by the time difference computing means, a propagation time computing means for obtaining the propagation times of the plurality of satellites;
A positioning device comprising: The positioning device according to claim 1,
The positioning unit is a positioning device that selects the satellite that the reference bit reaches earliest as the reference satellite. The positioning device according to claim 1 or 2,
The positioning unit is a positioning device that selects a satellite predicted to exist in the nearest vicinity as the reference satellite. The positioning device according to any one of claims 1 to 3,
The positioning apparatus, wherein the interpolation is interpolation by a least square method. The positioning device according to any one of claims 1 to 4,
A positioning apparatus further comprising pseudorange computing means for computing pseudoranges from the plurality of satellites based on propagation times of the plurality of satellites obtained by the propagation time computing means. A positioning device according to any one of claims 1 to 5,
A receiver processor that causes at least time measurement by the time measuring means to be stored, and stores the arrival time in the storage means;
A positioning device comprising at least a navigation processor having the bit calculation means. Observation data acquisition means for acquiring observation data expressing the surrounding environment;
Selecting means for selecting a reference satellite and a satellite other than the reference satellite from the plurality of satellites;
Obtaining means for obtaining a propagation time of the reference satellite;
Clocking means for timing the arrival time of each bit included in a signal transmitted from each of the plurality of satellites;
First storage means for storing the arrival time measured by the time measuring means;
For at least a satellite other than the reference satellite, a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means is interpolated, and the reference in the arrival time of the reference bit of the reference satellite selected by the selection means Bit calculating means for obtaining a difference in arrival bits, which is a difference between the arrival bits of the satellites and the arrival bits of the reference bits of the reference satellites selected by the selection means; ,
Based on the arrival bit number difference obtained by the bit computation means, a time difference computation means for obtaining a propagation time difference of satellites other than the reference satellite;
Based on the propagation time of the reference satellite obtained by the obtaining means and the propagation time difference obtained by the time difference computing means, a propagation time computing means for obtaining the propagation times of the plurality of satellites;
Based on the propagation times of the plurality of satellites determined by the propagation time calculation means, pseudo distance calculation means for calculating pseudo distances from the plurality of satellites;
Position information creating means for creating position information indicating the position of the observation device based on pseudo distances from the plurality of satellites obtained by the pseudo distance calculating means;
Second storage means for storing the observation data and the position information in association with each other;
An observation device. A positioning method for identifying a position by receiving radio waves transmitted from a plurality of satellites in a global positioning system,
Timing the arrival time of each bit included in a signal transmitted from each of the plurality of satellites;
Storing the time of arrival in the storage means ;
Selecting a reference satellite and a satellite other than the reference satellite from the plurality of satellites by a selection means ;
For at least a satellite other than the reference satellite, a graph showing the relationship between the arrival time and the number of arrival bits stored in the storage means is interpolated, and the reference in the arrival time of the reference bit of the reference satellite selected by the selection means Obtaining an arrival bit number difference which is a difference between the arrival bit number of the satellite and the arrival bit number of the reference target satellite selected by the selection means at the interpolation target satellite time ;
Based on the obtained arrival bit number difference, obtaining a propagation time difference of satellites other than the reference satellite by a time difference calculation means ;
Obtaining a propagation time of the reference satellite;
Obtaining the propagation times of the plurality of satellites based on the obtained propagation time of the reference satellite and the propagation time difference obtained by the time difference calculating means;
A positioning method having

Images