JP3825580B2 - Portable distance / speed meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable distance / speed meter that presents the measured travel distance and the reliability of the travel speed using a small device such as a wristwatch, particularly when a distance / speed meter is configured with a GPS receiver. .
[0002]
[Prior art]
The GPS (Global Positioning System) is the most easily received among 24 GPS satellites that orbit around 6 orbits of about 20,200km on the earth and an inclination angle of 55 degrees in about 12 hours. The navigation data necessary for positioning is received from four or more satellites by a receiver on the earth, and the propagation delay time is measured to perform positioning calculation such as the user's position and moving direction.
[0003]
Here, there are two transmission frequencies of GPS satellites, frequency L1 (1.57542 GHz) and frequency L2 (1.276060 GHz), and the C / A code whose code is publicly released for private use is 1.57542 GHz (frequency The frequency L1 is used for general positioning because it is transmitted at L1). The frequency L1 is PSK (phase shift keying) modulated by a pseudo-noise code (a C / A code for identifying a satellite, a combined wave of navigation data such as satellite orbit information, satellite orbit information, and time information), and spread spectrum. To be sent.
[0004]
FIG. 7 is a diagram showing a schematic configuration of a GPS receiver for receiving radio waves (frequency L1) transmitted from GPS satellites. In FIG. 7, a GPS receiver 200 is generated by a receiving antenna 201 that receives GPS radio waves from a GPS satellite, an L-band amplifier circuit 202 that amplifies the received L-band signal, and a received signal and a local oscillation circuit 107. A down converter circuit 203 that performs signal conversion by multiplying the signal, a voltage comparison circuit 204 that digitally converts the signal from the down converter circuit 203, and a signal input from the voltage comparison circuit 204 is converted into a C / A code generation circuit 208. The generated C / A code is multiplied to obtain navigation data and carrier phase information corresponding to the pseudorange, and the positioning data is calculated using the navigation data and carrier phase information input from the message decoding circuit 205. A positioning operation circuit 206. The local oscillation circuit 107 is a circuit that generates a signal for converting a received signal into a signal having a desired frequency.
[0005]
Next, the receiving operation of the GPS receiver 200 will be described. In FIG. 7, first, the L-band amplifier circuit 202 selectively amplifies a 1.57542 GHz signal received by the receiving antenna 201. The signal amplified in the L-band amplifier circuit is input to the down-converter circuit 203. The down-converter circuit 203 uses the signal generated by the local oscillation circuit 107 as the first signal of several tens to 200 MHz. To an IF (intermediate frequency) signal, and further to a second IF signal of about 2 MHz to 5 MHz. Then, the voltage comparison circuit 204 inputs this second IF signal, and digitally converts this signal using a clock several times the input second IF signal. Here, the digitally converted signal becomes spread spectrum data (digital signal).
[0006]
The digital signal output from the voltage comparison circuit 204 is input to the message decoding circuit 205. The message decoding circuit 205 generates a C / A code (generated by the C / A code generation circuit 208) with respect to the input digital signal. The carrier noise phase information corresponding to the navigation data and the pseudorange is acquired by despreading the same pseudo-noise code as the GPS satellite).
[0007]
The above operation is performed for each of a plurality of GPS satellites. Usually, navigation data and carrier phase information of four satellites are acquired, and the positioning calculation circuit 206 obtains positioning data based on these information. The positioning data obtained in the positioning calculation circuit 206 is output to a CPU (not shown) that controls the operation of the entire device, or is output to the outside as a digital signal. Such a GPS receiver is used as a car navigation system by combining GPS position information and map information using a CD-ROM.
[0008]
The GPS receiver 200 described above is supplied as a digital ASIC (Application Specific IC) due to recent technological progress including semiconductors, and is low in cost, small size, and light weight by basic high frequency technology and GPS software technology. The modularization that features is.
[0009]
In such a background, a portable GPS receiver capable of measuring a moving speed and a moving distance of a person using a GPS receiver has been proposed. For example, the “portable GPS receiver” disclosed in Japanese Patent Application Laid-Open No. 10-325735 discloses an accurate measurement by a GPS receiver of a moving distance and a moving speed required in accordance with the realization of miniaturization, and supplementation of a GPS satellite. The number of steps of the user calculated based on the movement distance obtained by receiving GPS radio waves only at a predetermined timing and the signal detected by the walking detection means in order to realize continuous measurement avoiding the impossible state Then, the user's stride (stride) is calculated and the moving distance of the user is obtained by multiplying the stride data by the number of steps.
[0010]
[Problems to be solved by the invention]
However, the movement distance and movement speed measured using a GPS receiver like the above-mentioned “portable GPS receiver” include errors that are generally unavoidable due to GPS positioning. The error factors include (1) time error of the atomic clock (satellite clock) mounted on the satellite, (2) error due to SA (Selective Availability), (3) radio propagation error in the ionosphere or troposphere, and (4) disturbance. Examples include multipath errors due to multiple reflections from objects. Usually, the measurement accuracy of a GPS receiver is represented by the sum of these errors.
[0011]
In particular, the largest one of these error factors is (2) an error due to SA (Selective Availability), and a ranging error of about 10 times occurs as compared with other error factors. SA is a signal intentionally added by the US Department of Defense to degrade navigation data measured by a GPS receiver, and introduces an error that varies in the fundamental frequency of a satellite clock. Since the pseudo distance is obtained from the difference between the arrival time of the GPS radio wave measured by the time of the satellite clock and the clock of the GPS receiver, SA appears as a direct error in the pseudo distance, and the moving distance calculated using the pseudo distance and This error also appears in the moving speed.
[0012]
In particular, the above-mentioned error due to SA cannot be ignored for measuring the moving speed and moving distance of a small range of movement at a relatively low speed such as walking or running of a person. On the other hand, since SA is generated on the transmission side, it has a spatial correlation, and an error occurring in a certain place is observed as a similar error in the vicinity. Since SA has such properties, its influence can be removed by adopting DGPS (Differential GPS). DGPS is a technique for removing a common error in both the GPS receiver of the reference station and the GPS receiver of the user, and is used when surveying a relatively wide range.
[0013]
However, in DGPS, it is necessary to install a reference station in the area to be surveyed, and considering the infrastructure maintenance and operation costs, portable distance / It is difficult to adopt this DGPS for a speedometer.
[0014]
In view of the above problems, the present invention calculates and presents the average moving speed and moving distance of the user measured by the GPS receiver, and also affects the above-described error included in the presented average moving speed and moving distance, that is, The purpose is to provide a portable distance / speedometer that presents the average travel speed and the reliability of the travel distance.
[0015]
[Means for Solving the Problems]
FIG. 1 is a principle diagram of a portable distance meter or a portable distance / speed meter according to the present invention. In FIG. 1, a portable distance / speed meter according to the present invention receives a GPS radio wave transmitted from a GPS satellite and achieves the above object, and a user's position or moving speed based on the received GPS radio wave. A GPS receiver 10 for calculating the movement distance, a moving distance calculation means 11 for calculating the moving distance of the user based on the calculation result in the GPS receiver 10, a timing means 14 for measuring the moving time of the user at the moving distance, Based on the moving distance calculated by the distance calculating means 11 and the moving time measured by the time measuring means 14, the moving speed calculating means 12 for calculating the moving speed of the user, and the moving speed calculated by the moving speed calculating means 12 Average moving speed calculating means 13 for calculating the average moving speed of the user based on the average, and the average calculated in the average moving speed calculating means 13 Variation within a predetermined time dynamic speed includes a measurement evaluating means 15 for evaluating whether within a predetermined amplitude range, and display means 16 for displaying the evaluation results of measurement evaluating means 15.
[0016]
According to the present invention, the average moving speed calculating means 13 calculates the average moving speed from the moving speed calculated by the moving speed calculating means 12, so that the SA or the like can be obtained when the actual moving speed of the user is constant. While the movement speed including the fluctuation due to the positioning error is converged to the actual movement speed as the average movement speed, the convergence state of the average movement speed is evaluated by the measurement evaluation means 15 and evaluated by the display means 16. Since the result is displayed, the user determines whether, for example, the moving distance and the average moving speed displayed on the same display means 16 are greatly affected by the positioning error, that is, whether they are reliable. It becomes possible.
[0017]
In the portable distance / speed meter according to the present invention, a plurality of predetermined times for determining the convergence state of the average moving speed are further set in the measurement evaluation unit 15, and the fluctuations in the average moving speed are set to the predetermined numbers. While evaluating whether or not it is within a predetermined amplitude range every time, the display means 16 displays the evaluation results corresponding to each of the plurality of predetermined times in multiple stages. It is possible to determine in a multi-step manner how much the moving distance and the average moving speed displayed in 16 are affected by the positioning error, that is, how reliable the moving distance and average moving speed are.
[0018]
In addition, the portable distance / speed meter according to the present invention displays on the display means 16 a graph showing fluctuations in the average moving speed calculated by the average moving speed calculating means 13, so that the user can use the graph as an average. The convergence state of the movement speed can be visually confirmed. For example, whether the movement distance and the average movement speed displayed on the same display means 16 are greatly affected by the positioning error, that is, whether the movement speed is reliable. It becomes possible to judge.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a portable distance / speed meter according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.
[0020]
FIG. 2 is a block diagram showing a configuration of the portable distance / speed meter according to the embodiment. The portable distance / velocity meter shown in FIG. 2 receives a radio wave transmitted from a plurality of GPS satellites 20 and measures the longitude / latitude, and will be described later. The CPU 24 that calculates the movement distance, movement speed, and average movement speed of the user by performing various calculation processes, and the display panel 27 that includes an LCD (liquid crystal display), etc. are controlled, and the movement distance, average movement calculated by the CPU 24 And an LCD driving circuit 28 for displaying the speed and an evaluation level, which will be described later, on the display panel 27.
[0021]
In FIG. 2, 26 is a ROM storing an operation program for the CPU 24, 25 is a RAM used as a work area for the CPU 24, 22 is an input switch for instructing start of distance / speed measurement, and the like. Reference numeral 23 denotes an OSC (oscillation circuit) that generates a reference frequency signal.
[0022]
Next, the operation of the portable distance / speed meter configured as described above will be described. FIG. 3 is a flowchart showing the operation of the portable distance / speed meter according to the embodiment. In FIG. 3, first, measurement of a user's moving distance, moving speed, average moving speed, etc. is started by the user operating the input switch 22 or the like (step S101). Then, initialization is performed by substituting an initial value 0 for a comparison target average speed va0 described later (step S102).
[0023]
Next, a time counter corresponding to the time measuring unit 14 shown in FIG. 1 is also used or another time counter is used to start time T (step S103). Then, the velocity is calculated from the Doppler frequency of the GPS radio wave obtained in the GPS receiver 10 (step S104), and the distance d is calculated by accumulating the velocity (step S105). More specifically, the distance d is measured by the CPU 24 using a clock counter corresponding to the clock means 14 shown in FIG. 1 for a predetermined time, and the predetermined time measured at the speed obtained from the Doppler shift. Calculated by multiplying time. In addition to using the Doppler shift, position information is acquired at each time point corresponding to the start time and end time of the predetermined time, and the distance d is calculated from the difference between the two acquired position information. May be.
[0024]
Therefore, when calculating the distance d, since the predetermined time is counted as described above, the speed v can be calculated by dividing the calculated distance d by the measured predetermined time ( Step S106). Next, the average speed va of the speed v calculated in step S106 is calculated (step S107). Specifically, this step S107 is performed by integrating the speed v calculated in step S106 this time with the speed v calculated in step S106 until the previous time, and dividing the integration result by the number of integrations.
[0025]
The distance d and the average speed va calculated in steps S105 and S107 are displayed on the display panel 27 through the control by the LCD drive circuit 28 (step S108). Next, it is determined whether or not the average speed va calculated in step S107 is equal to the comparison target average speed va0 (step S109). In this determination, in practice, a predetermined range width (amplitude due to fluctuation of the average speed va) is set in advance, and the average speed va0 to be compared is determined by the predetermined range width and the average speed va calculated in step S109. This is done depending on whether or not it is within the range of the upper and lower thresholds centered on.
[0026]
That is, the process of step S109 is to determine the state of fluctuation of the average speed va calculated in step S107. When this fluctuation is within a predetermined range, that is, when the fluctuation is small, the average speed va is This is regarded as a starting point that starts to converge to the actual movement speed of the user.
[0027]
If it is not determined in step S109 that the average speed va is equal to the comparison target average speed va0, the average speed va calculated in step S109 is substituted for the comparison target average speed va0 (step S112), and the process is started in step S103. The time T of the time counter is reset (step S113), the process is returned to step S103 again, and the process for calculating the distance d, the speed v, and the average speed va described above is repeated.
[0028]
If it is determined in step S109 that the average speed va is equal to the comparison target average speed va0, a measurement evaluation process described later is performed (step S110). After the process of step S110, it is determined whether or not the end of measurement is instructed by the user operating the input switch 22 or the like (step S111). If the end of measurement is instructed in step S111, the process shown in FIG. 3 is ended. If the end of measurement is not instructed, the process from step S103 is repeated again.
[0029]
(Measurement evaluation process)
Next, the measurement evaluation process in step S110 described above will be described. FIG. 4 is a flowchart showing the measurement evaluation process. In this measurement evaluation process, it is determined whether the time T of the time counter started in step S103 of FIG. 3 has elapsed, and according to the determination, the distance d and the distance d displayed on the display panel 27 in step S108. An evaluation is made as to whether or not the speed v is greatly affected by the GPS positioning error. In particular, in FIG. 4, the predetermined time set in advance for use in the determination of the time T described above is divided into three stages T0, T1, and T2 (T0 <T1 <T2), and according to the value indicated by the time T. The evaluation results are represented by three evaluation levels 1 to 3.
[0030]
In FIG. 4, first, it is determined whether or not the time T started to be measured in step S103 in FIG. 3 is greater than a predetermined time T2 (step S121). In step S121, if the time T is less than or equal to the predetermined time T2, it is determined whether or not the time T is greater than the predetermined time T1 (step S122). In step S122, if the time T is less than or equal to the predetermined time T1, it is determined whether or not the time T is greater than the predetermined time T0 (step S123). Furthermore, if the time T is equal to or shorter than the predetermined time T0 in step S123, it is determined that the average speed va has not converged, and the process returns to step S111 in FIG. Continue counting time T.
[0031]
If the time T is greater than the predetermined time T0 in step S123, display indicating the evaluation level 1 is performed on the display panel 27 (step S126). After the process of step S126, the process returns to step S111 of FIG. 3 again, and when the end of measurement is not instructed, the time T is continuously counted.
[0032]
If the time T is greater than the predetermined time T1 in step S122, display indicating the evaluation level 2 is performed on the display panel 27 (step S125). After the process of step S125, the process returns to step S111 of FIG. 3 again, and when the end of measurement is not instructed, the time T is continuously counted.
[0033]
When the time T is larger than the predetermined time T2 in step S121, display indicating the evaluation level 3 is performed on the display panel 27 (step S124). After the process of step S124, the process returns to step S111 of FIG. 3 again, and when the end of measurement is not instructed, the time T is continuously counted.
[0034]
FIG. 5 is a graph showing the relationship between the speed v (referred to herein as the instantaneous speed) calculated after the start of measurement and the elapsed time, and the relationship between the average speed va and the elapsed time. In addition, this graph is an experimental result when a user walks at about 0.40 m / s. As shown in FIG. 5, the calculated instantaneous speed fluctuates with an irregular amplitude centering on a speed of 0.40 m / s, and this fluctuation is based on the positioning error mainly due to the above-mentioned SA.
[0035]
In FIG. 5, the average speed va starts to converge starting from the time point when the elapsed time is around 1250 seconds. Therefore, in this experimental result, the time T measured by the time counter after the elapsed time from the start of measurement becomes 1250 seconds is an important factor in the measurement evaluation process shown in FIG. For example, if the predetermined times T0, T1, and T2 are set to 50 seconds, 150 seconds, and 450 seconds in the measurement evaluation process shown in FIG. 4, when the elapsed time becomes 1300 seconds in the graph of FIG. When the evaluation level 1 is displayed and the elapsed time is 1400 seconds, the evaluation level 2 is displayed. When the elapsed time is 1700 seconds, the evaluation level 3 is displayed. Become.
[0036]
In other words, an increase in the period during which the average speed variation is small means that the average speed is closer to the convergence speed, that is, the averaging effect becomes remarkable, and the GPS positioning error included in the obtained average speed It shows that the influence of is small. Therefore, the display of the evaluation levels 1 to 3 shows the degree of influence of the GPS positioning error step by step, and presents the reliability of the distance d and the average speed va displayed on the display panel 27 to the user. is there.
[0037]
FIG. 6 is a diagram illustrating an example of display of evaluation levels 1 to 3 on the display panel 27. In FIG. 6, the display panel 27 displays the average speed va calculated in step S107 in FIG. 3 in the area M1, and the distance d calculated in step S105 in FIG. 3 in the area M2. . Furthermore, the above-described evaluation levels 1 to 3 are displayed in stages as level bars L1 to L3.
[0038]
Therefore, according to the embodiment of the present invention, the user's moving distance, moving speed, and average moving speed are calculated based on the GPS radio wave obtained by the GPS receiver 10, and the calculated average moving speed is a predetermined time. When the fluctuation within the predetermined range is sustained, it is determined that the average moving speed has converged in the vicinity of the actual user moving speed, and the calculated average moving speed is greatly influenced by positioning errors such as SA. Since the display indicating that it is not included is performed, the user visually recognizes this display, so that the moving distance and the average moving speed currently displayed on the display panel 27 are greatly affected by the positioning error. It can be determined whether it is a thing, that is, whether it is trustworthy.
[0039]
In the above-described embodiment, the distance d calculated by calculating the velocity from the Doppler frequency of the GPS radio wave obtained by the GPS receiver 10 in step S104 and step S105 in FIG. 3 and accumulating the velocity. Is displayed as a moving distance on the display panel 27, but a new distance is calculated using the average speed va calculated in step S107 in FIG. 3, and this distance is displayed on the display panel 27 as the moving distance of the user. You may do it.
[0040]
In the above description, the evaluation result in the measurement evaluation process is represented by three evaluation levels 1 to 3. However, the evaluation result may be displayed by an evaluation level in another number of stages. For example, in addition to the display such as the level bars L1 to L3 in FIG. 6, an evaluation mark as indicated by M3 in FIG. 6 can be displayed or blinked.
[0041]
【The invention's effect】
As described above, according to the present invention, the user's moving distance, moving speed, and average moving speed are measured based on GPS radio waves transmitted from GPS satellites, and the average is calculated based on fluctuations in the average moving speed. While evaluating the influence of GPS positioning error on the moving speed and presenting the evaluation result, the user is greatly affected by the influence of the GPS positioning error on the moving distance and average moving speed displayed on the display means such as the display panel. It is possible to determine whether it is a reliable one, that is, whether it is reliable.
[0042]
Further, according to the present invention, a plurality of predetermined times for determining the convergence state of the average moving speed are set, and whether or not the fluctuation of the average moving speed is within a predetermined amplitude range for each of the plurality of predetermined times. Since the display means displays the evaluation results corresponding to each of the plurality of predetermined times in multiple stages, the user can determine whether the movement distance or the average movement speed displayed on the same display means is, for example, It is possible to determine in a multi-step manner how much the influence of the error is received, that is, how reliable it is.
[0043]
Further, according to the present invention, since the graph showing the fluctuation of the calculated average moving speed is displayed on the display means, the user can visually recognize the convergence state of the average moving speed, for example, the same. It is possible to determine whether the moving distance and the average moving speed displayed on the display means are greatly affected by the positioning error, that is, whether the moving distance and the average moving speed are reliable.
[Brief description of the drawings]
FIG. 1 is a principle diagram of a portable distance / speed meter according to the present invention.
FIG. 2 is a block diagram showing a configuration of a portable distance / speed meter according to the embodiment.
FIG. 3 is a flowchart showing the operation of the portable distance / speed meter according to the embodiment.
FIG. 4 is a flowchart showing measurement evaluation processing according to the embodiment.
FIG. 5 is a graph showing the relationship between instantaneous speed and elapsed time and the relationship between average speed and elapsed time.
FIG. 6 is a diagram showing an example of an evaluation level display according to the embodiment.
FIG. 7 is a diagram showing a schematic configuration of a conventional GPS receiver.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10, 21 GPS receiver 11 Movement distance calculation means 12 Movement speed calculation means 13 Average movement speed calculation means 14 Timekeeping means 15 Measurement evaluation means 16 Display means 20 GPS satellite 22 Input switch 23 OSC
24 CPU
25 RAM
26 ROM
27 Display panel 28 LCD drive circuit

Claims (1)

In a portable distance / speed meter equipped with a GPS receiver that receives GPS radio waves transmitted from GPS satellites and calculates the user's position or moving speed based on the received GPS radio waves ,
And moving distance calculating means for calculating a movement distance of the user based on the calculation result in the GPS receiver,
Clocking means for clocking the movement time of the user at the movement distance;
A moving speed calculating means for calculating the moving speed of the user based on the moving distance calculated by the moving distance calculating means and the moving time calculated by the time measuring means;
Average moving speed calculating means for calculating the average moving speed of the user based on the moving speed calculated by the moving speed calculating means;
In order to evaluate whether or not the fluctuation within the predetermined time of the average moving speed calculated by the moving speed calculating means is within a predetermined amplitude range, a plurality of the predetermined times are set, and the fluctuation of the average moving speed is Measurement evaluation means for evaluating whether or not the predetermined amplitude range is within the predetermined time intervals;
A portable distance / speed meter comprising: display means for displaying the evaluation results in the measurement evaluation means in multiple stages according to each of the plurality of predetermined times .

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