JP2003149315A - Gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GPS receiver capable of improving positioning accuracy by eliminating a signal which includes a multipath having an adverse effect on the positioning calculation without relying on the setting environment, by adaptively changing a threshold for a reception level of a signal to be used in a positioning calculation. SOLUTION: The GPS receiver is provided with means for determining the threshold for selecting the reception signal to be used in the positioning calculation according to the reception signal level of a signal from a GPS satellite with an elevation angle greater than the predetermined elevation angle selected from transmitting satellites. The threshold is determined by referring to a table in which an optimal threshold is correlated with each reception signal level of the satellite with high elevation angle. The satellite with reception signal level higher than the predetermined threshold is selected for use in the positioning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS receiver, and more particularly to setting a threshold value for selecting a reception signal used for positioning calculation.

[0002]

2. Description of the Related Art A GPS receiver is a GPS receiver that tracks GPS signals transmitted from GPS satellites.
The distance between the satellite and the GPS receiving device itself is measured (this is called a pseudo distance), and the position of itself is calculated by geometrical calculation based on the pseudo distances of a plurality of GPS satellites measured at the same time. Furthermore, the GPS receiver measures the rate of change of the carrier frequency of each satellite (Doppler measurement), calculates the moving speed and the heading of the satellite itself, and calculates these results as GP.
Output as S output data.

At this time, when the number of GPS satellites tracked by the GPS receiver is three, two-dimensional positioning, 4
When there are three or more, three-dimensional positioning is performed. The data calculated by the two-dimensional positioning is “latitude, longitude”, and the three-dimensional positioning is “latitude, longitude, altitude”. The number of signals (satellite) that can be simultaneously captured by the GPS receiving device is determined by the number of channels of the GPS receiving device. Generally, the number of channels is 8c.
It is about h to 12 ch.

FIG. 8 shows the configuration of a general GPS receiver 1. The GPS receiving device 1 includes an RF unit 2, a digital correlation processing unit 3, and a positioning calculation unit 4. RF unit 2
Converts the RF signal input from the GPS antenna 5 into an intermediate frequency signal, digitizes it, and outputs it to the digital correlation processing unit 3. The digital correlation processing unit 3 is a functional block for despreading the spread spectrum GPS signal (carrier correlation unit 31, PRN code correlation unit 3).
2, a carrier NCO 33, a PRN code generator 34, and a code NCO 35)
It has a plurality of.

The carrier tracking loop 42 and the code tracking loop 41 acquire GPS signals.
In tracking and tracking, carrier NCO
The (NCO; Numerically controlled oscillator) 33 and the code NCO 35 are controlled. The positioning calculation unit 4 determines the PRN code generation timing and the carrier NCO 33 in each channel.
The position, speed, azimuth, etc. of the GPS receiving device 1 itself are calculated based on the amount of phase change. The positioning calculation for obtaining the positioning solution is usually executed at regular time intervals (for example, every one second). The obtained positioning solution can be passed to the host system as the input / output data 43.

The GPS antenna 5 is roughly classified into two types: an active antenna and a passive antenna. FIG. 9 shows the configuration of the active antenna. The active antenna is equipped with a signal amplifier 52 after the antenna element 51, while the passive antenna is equipped with a signal amplifier 5.
A type that does not have 2. The GPS receiving device 1 is mounted on various application devices such as a car navigation system and a personal digital assistant, but due to the difference in these applications, the RF signal input terminal of the GPS receiving device from the GPS antenna (reference numeral 2a in FIG. 8). There will be a big difference in the route to. In general, the antenna cable 6 uses a coaxial line of 1 to 5 m for car navigation, and the antenna element is G for mobile information terminals.
It is either attached directly to the PS receiver board or a coaxial line of several cm is used.

Therefore, the active antenna is GP
The GPS signal radiated from the S satellite is weak, the gain of the antenna element 51 is small, and the GPS receiver 1
It is used in a car navigation system or the like for the purpose of keeping the signal level at the RF signal input end 2a of the GPS receiver 1 at a certain level or higher in consideration of the transmission loss up to. On the other hand, the passive antenna is used in a mobile information terminal or the like that does not require a signal amplifier because of a small transmission loss up to the GPS receiver 1.

As described above, depending on the application,
Since the type of antenna used (whether it is an active antenna or a passive antenna) and the presence / absence / length of an antenna cable exist, the GPS receiver 1
The signal level (intensity) input to the signal will have a difference of several tens of dB.

In the car navigation system, the GPS antenna 5 may be installed outside the vehicle compartment or inside the vehicle compartment, or even when installed in the vehicle compartment, it may be installed on the dashboard or the rear shelf or inside. The RF signal input end 2a of the GPS receiver 1 has a difference in signal level of several dB to several tens of dB depending on whether or not it is installed.

[0010]

The positioning calculation section 4 of the GPS receiving apparatus 1 includes each channel 3 of the digital correlation processing section 3.
The received signal level of each channel 39 can be known from the correlation processing output 36 in 9. Therefore, when the positioning calculation unit 4 performs positioning calculation, by selecting and using a signal having a received signal level equal to or higher than the set threshold value, the signal affected by multipath or noise is eliminated and positioning is performed. Will be able to do. This means that multipath signals generally have lower signal strength than direct waves, so signals with relatively low received signal levels may be affected by multipath, and signal input It is based on the fact that signals with low levels are relatively likely to be affected by noise.

Here, the above-mentioned threshold is the GPS receiver 1
It is necessary to consider that the optimum value greatly differs depending on the level of the received signal input to the. About this
This will be described with reference to the graph of FIG. 10 (a) and 10 (c) show "an example of the optimum threshold in the case of a high received signal level" and "an example of the optimum threshold in the case of a low received signal level".
Respectively. Note that in FIG. 10, each of the satellites A to H on the horizontal axis represents the satellite being received, and the vertical axis represents the received signal level of each satellite. In the examples of FIGS. 10A and 10C, the optimum threshold value is applied to the received signal level input to the GPS receiver, so that both signals (satellites) that may include multipath are included. B and satellite E)
It can be seen that only one is controlled so that it is not used for positioning calculations.

FIGS. 10 (b) and 10 (d) show "an example in which a threshold is applied on the assumption that a low received signal is input when a high received signal level is input" and "a low received signal level is input. Examples of applying a threshold value on the assumption that a high received signal is input ”are shown. In the example of FIG. 10B, since the threshold value A0 which is premised on inputting a low received signal level is applied despite inputting a high received signal level, multipath is included. It can be seen that the received signals (satellite B and satellite E) that may exist are included in the positioning calculation. This leads to an adverse effect of deterioration of positioning accuracy.

Further, in the example of FIG. 10 (d), the threshold value A1 which is premised on the input of a high received signal is applied in spite of inputting a low received signal level, It can be seen that the received signals (satellite D and satellite F) that should originally be used for positioning calculation are excluded. As a result, the GPS positioning rate is lowered, and the positioning performance is significantly adversely affected.

As described above, if the threshold value for selecting the signal used for the positioning calculation does not properly correspond to the received signal level input to the GPS receiver 1, the positioning performance will be significantly impaired. . Generally, a measure that can be taken to keep the positioning performance in a good state is to set a threshold value according to an application to the greatest common denominator and set the threshold value in the GPS receiving device in advance.

However, in the car navigation system, for example, the received signal level input to the GPS receiver 1 varies greatly depending on where the user installs the GPS antenna 5. In this case, the optimum threshold value is not set according to the usage (place of installation of the antenna), and the positioning performance may deteriorate.

The present invention has been made in view of such circumstances. That is, the present invention adaptively changes the threshold value of the reception level of the signal used for the positioning calculation according to the level of the reception signal input to the GPS receiving device, thereby performing the positioning without depending on the installation environment. An object of the present invention is to provide a GPS receiving device capable of excluding signals including multipaths that adversely affect calculation and improving positioning accuracy.

[0017]

In order to achieve the above object, the GPS receiving apparatus is configured so that the GPS receiving apparatus is based on the received signal level of a signal from a GPS satellite with a high elevation angle of which the elevation angle is a predetermined angle or more among the satellites being received. A means for deciding a threshold value for selecting a received signal used for positioning calculation is added (claim 1). The received signal level of a satellite with a high elevation angle and the optimum threshold value can be associated with each other in a fixed correspondence relationship. Therefore, the optimum threshold value can be obtained based on the received signal level from the satellite with a high elevation angle.

There may be one or more satellites whose elevation angle is equal to or greater than a predetermined angle. In this case, an average value may be obtained and used as the reception signal level of the high elevation satellite (claim 2).

Regarding the received signal level of the satellite of high elevation angle,
It is preferable that a moving average, which is an average of a predetermined number of data, is obtained and the threshold value is determined based on the moving average (claim 3). As a result, it is possible to prevent the optimum threshold value from sensitively changing in response to the reception state.

The threshold value can be continuously updated by continuously obtaining the average value or the moving average (claim 4). By continuously updating the threshold,
It is possible to continuously achieve positioning by eliminating signals affected by multipath.

The received signal level of the satellite of high elevation angle and the optimum threshold have a correspondence relationship uniquely associated with each other as a function, so that the optimum threshold can be obtained from the received signal level of the satellite of high elevation angle. Item 5). Alternatively, it is also possible to store the correspondence relationship as a table and obtain the optimum threshold value by referring to the table (claim 6).

The default value of the threshold is stored, and the GP
The default value may be used as the threshold value until the optimum threshold value is obtained, such as immediately after the S receiver is started up (claim 7).

The probability of capturing a satellite with a high elevation angle at the observation point becomes lower as the predetermined angle as the definition of the high elevation angle becomes higher. Therefore, the predetermined angle for considering it as a high elevation angle is an angle determined so that the probability that the GPS satellites can be captured becomes a predetermined value or more in consideration of the elevation angle transitions of all the GPS satellites at the observation point. Preferred (Claim 8).

Further, in order to achieve the above-mentioned object, claim 9
The invention described in (3) is a GPS receiving device that receives GPS signals from a plurality of GPS satellites and performs positioning, and is a G receiving device.
Of the PS satellites, G with a high elevation angle where the elevation angle is more than a predetermined angle
A first storage area capable of storing a plurality of PS satellite reception signal levels and a high elevation angle GPS satellite reception signal level are stored in the first storage area and averaged from a predetermined number of data stored in the first storage area. First control means for calculating a value,
A second storage area for storing a table in which a threshold value for selecting a reception signal used for positioning is stored for each reception signal level of a GPS satellite with a high elevation angle, and a threshold value used for selecting a reception signal for positioning. Is stored, and a threshold value corresponding to the average value obtained by the first control means is acquired by referring to the table stored in the second storage area and written in the third storage area. Second control means,
Positioning calculation means for performing positioning calculation by selecting a GPS satellite to be used for positioning using the threshold value stored in the third storage area. The optimum threshold value obtained by referring to the table based on the received signal level of the satellite of high elevation angle is stored in the third storage area. The positioning calculation means can acquire the optimum threshold value by referring to the third storage area, and can use this optimum threshold value to select the GPS satellite to be used for positioning.

Further, in order to achieve the above-mentioned object, claim 1
The invention described in 0 is a GPS receiving device that receives GPS signals from a plurality of GPS satellites and performs positioning, and G of a high elevation angle in which the elevation angle is a predetermined angle or more among the GPS satellites being received.
A first storage area capable of storing a plurality of PS satellite reception signal levels and a high elevation angle GPS satellite reception signal level are stored in the first storage area and averaged from a predetermined number of data stored in the first storage area. First control means for calculating a value,
A second storage area for storing a threshold value for selecting a reception signal used for positioning, and a second storage area for calculating a threshold value corresponding to the average value obtained by the first control means using a predetermined function. And a positioning calculation unit that selects a GPS satellite to be used for positioning and performs positioning calculation by using a threshold value stored in the second storage area. The received signal level of a satellite with a high elevation angle and the optimum threshold value can be uniquely associated with each other. By having this correspondence relationship as a function in the second control means, the optimum threshold value can be obtained from the received signal level of the satellite with a high elevation angle. Therefore, the positioning calculation means can acquire the optimum threshold value by referring to the second storage area, and can use this optimum threshold value to select the satellite to be used for positioning.

[0026]

FIG. 1 shows the configuration of a GPS receiver 101 of the present invention. The GPS receiving device 101 includes an RF unit 2, a digital correlation processing unit 3, and a positioning calculation unit 94. In FIG. 1, parts that are the same as the constituent elements of the GPS receiver 1 (FIG. 8) are given the same reference numerals, and detailed description of these parts is omitted. That is,
In the GPS receiver 101, the RF signal input from the GPS antenna 5 is converted into an intermediate frequency signal by the RF unit 2 and digitized, and then despread in the channel 39 of the digital correlation processing unit 3.

The positioning calculation section 94 determines the PRN code generation timing in each channel 39 and the carrier NCO3.
The position, speed, azimuth, etc. of the GPS receiving device 101 itself are calculated based on the phase change amount of 3. Furthermore, the positioning calculation unit 9
4 is provided with a threshold value determining means 95 for determining a threshold value for selecting a signal used for positioning calculation according to the received signal level of a signal from a satellite with a high elevation angle. The threshold value determined here is used when selecting a satellite in the process of positioning. Note that the positioning calculation unit 94 is composed of a processor and has a ROM, a RAM, a non-volatile memory and the like (not shown) necessary for executing the program therein.

FIG. 2A shows the elevation angle of each GPS satellite viewed from the GPS antenna 5 when a high reception signal level is input to the GPS receiver 101 (corresponding to FIGS. 10A and 10B). The receiving satellites are rearranged in order. Similarly, FIG. 2B shows the elevation angle of each GPS satellite viewed from the GPS antenna 5 when a low reception signal level is input to the GPS receiver 101 (corresponding to (c) and (d) in FIG. 10). The receiving satellites are rearranged in order. 2A and 2B, the horizontal axis represents the elevation angle and the vertical axis represents the received signal level.

In FIG. 2, the received signal levels of the GPS satellites are arranged substantially in the order of elevation angle because the antenna element 51 of the GPS antenna 5 has antenna beam characteristics having a peak elevation angle of 90 degrees. Is. In FIG. 2, the reception signal level of the satellite E is lower than the reception signal level of the satellite D whose elevation angle is lower than this because the satellite E is receiving multipath.

It can be understood from FIG. 2 that the elevation angle of the GPS satellite being received and the received signal level have a fixed relationship as shown in FIGS. 2 (a) and 2 (b). From this, the threshold value for excluding signals (satellite E and satellite B in FIG. 2) that may include multipath is determined from the received signal level of the high elevation satellites (satellite C, G, etc. in FIG. 2). It can be regarded as existing at a level obtained by subtracting a certain value. Therefore, if the received signal of a high-elevation satellite (for example, defined as an elevation angle of 70 degrees or more) is above a certain level, the optimum threshold value should be uniquely determined with respect to the average level of the received signal of the high-elevation satellite. You can

As an example, FIG. 3 shows a relationship in which a received signal level of a high elevation satellite is uniquely associated with an optimum threshold value. In FIG. 3, the horizontal axis is the received signal level of the high elevation satellite, and the vertical axis is the threshold value.

Incidentally, the correspondence relationship of FIG.
If it is a signal received at 1, the gain (amplification / attenuation) of the circuit or line that is passed until it is input to the GPS receiver 101
Are equal, and the signals of high elevation satellites are unlikely to be affected by multipath. The correspondence shown in FIG. 3 is an example in the case of simplification.
It should be noted that it is possible to consider a more detailed correspondence relationship based on the beam characteristics of the S antenna, the demodulation means in the GPS receiving device, and the configuration of the reception level calculation means. Actually, the correspondence relationship between the reception signal level and the optimum threshold value is uniquely determined by combining the characteristics of the GPS antenna 5 and the GPS receiving device 101, so an example is shown in FIG. It is possible to know such correspondence. The correspondence obtained in this way is stored in a non-volatile memory (not shown) in the positioning calculation unit 94 as a function or a table.

FIGS. 4A and 4B are respectively shown in FIG.
In the cases of (a) and (b), it is an example in which the optimum threshold value is obtained using the correspondence relationship of FIG. Here, the definition of the high elevation satellite is defined as "elevation angle of 70 degrees or more". Therefore, FIG.
In the cases of (a) and (b), the satellite C and the satellite G correspond to high elevation satellites. When the threshold value TH ₁ obtained from the correspondence relationship of FIG. 3 is applied to the average value P ₁ of the reception signal levels of the satellites C and G in FIG. 4A, the result is as shown in FIG. 4A. Similarly, when the threshold value TH ₂ obtained from the correspondence relationship of FIG. 3 is applied to the average value P ₂ of the reception signal levels of the satellites C and G in FIG. 4B, the result is as shown in FIG. 4B. . As described above, as shown in FIG. 3, regarding “the characteristic of the optimum threshold value with respect to the average received signal level of the high elevation satellite”,
If the system as a whole of the GPS receiving device 101 including the PS antenna 5 is understood, it is possible to optimally set the threshold value of the reception level of the reception signal used for the positioning calculation.

It is possible to obtain a highly accurate threshold value by setting the elevation angle for defining the high elevation satellite as high as possible. However, the opportunity to receive the satellite satisfying the definition of the high elevation angle is Since the higher the defined elevation angle is, the smaller it is, it is desirable to determine the optimum value in consideration of such a trade-off relationship. FIG. 5 is an example showing how each GPS satellite changes in elevation angle when the GPS satellite is observed for 24 hours in Tokyo. From FIG. 5, considering the above trade-off, it is reasonable to set the definition of the high elevation satellite to about 70 ± 10 degrees so that the probability of receiving a satellite satisfying the definition of the high elevation angle becomes a predetermined value or more. Target. However, the definition of high elevation satellites is not limited to this value.

In the positioning calculation unit 94, as described above, the threshold value is updated from the average received signal level of the high elevation angle satellites among the received satellites by using the correspondence relationship (FIG. 3) stored in the non-volatile memory. By continuously performing the operation, the threshold value can always be kept at the optimum value. In the positioning calculation process executed by the positioning calculation unit 94 at predetermined time intervals, a threshold is used as the satellite selection process, and only satellites with a received signal level exceeding the threshold are used in the positioning calculation. Therefore, it is possible to avoid using the signal including the influence of multipath and the like for the positioning calculation and always maintain the positioning accuracy in a high state.

As described above, the higher the elevation angle as the definition of the high-elevation angle satellite, the less chance of receiving a signal from the satellite satisfying the definition, and the optimum relationship determined according to the correspondence relationship in FIG. Considering that it is not desirable for the threshold to be sensitive to the reception condition, it is desirable to store the received signal level of the high elevation satellite in the nonvolatile memory etc. by a predetermined number of data and take the moving average. It is realistic.

FIG. 6 is a flowchart corresponding to the operation of the threshold value determining means 95 and showing a process of obtaining the received signal level of the high elevation satellite by the moving average and updating the optimum threshold value. It is assumed that this processing is executed at predetermined time intervals as a part of the positioning calculation processing. Further, in FIG. 6, “memory” refers to a non-volatile memory in the positioning calculation unit 94,
The “table” is a table that is stored in advance in the non-volatile memory and represents the correspondence relationship illustrated in FIG.

First, it is determined whether or not the satellites captured by the ordinary positioning calculation processing include those with a high elevation angle (elevation angle 70 ± 10 degrees or more) (S1). When the satellites with a high elevation angle are included in the captured satellites (S1: YES), the reception signal level of the satellite (if there are a plurality of high elevation angle satellites, their average value) is stored in the memory (S2). ). Here, the data of the high-elevation-angle satellite is stored in the memory by increasing n every time the process of step S2 is performed in a predetermined data storage area 96 in the memory as shown in FIG. 7A. , In order d
_It stores from ₁ to _{dn + 1} . In addition, from the n + 2nd data after the data storage area 96 is completely filled,
Data is sequentially stored again from the beginning of the data storage area 96 (see FIG. 7B). Data is updated in the so-called ring buffer format.

Next, it is determined whether a predetermined number of data (n + 1) has been stored in the data storage area 96 (S3). If the number of data stored in the data storage area 96 has not reached the predetermined number (S3: NO), this process is terminated without updating the threshold value. When the number has reached the predetermined number (S3: Y
ES), the data stored in the data storage area 96 is read (S4), and their average value, that is, the moving average is calculated (S5). Next, based on the calculated moving average,
The table stored in the memory is referred to (or the correspondence between the received signal level and the optimum threshold stored in the memory as a function is used) to obtain the optimum threshold corresponding to the received signal level as a moving average ( S6). The acquired optimum threshold value is then updated by overwriting the storage location of the positioning calculation threshold value in the memory (S7). Note that, as the initial value of the optimum threshold value, a value determined in consideration of the application is stored in the storage location of the positioning calculation threshold value when the GPS receiving apparatus 101 is initially powered on. In this case, the satellite can be selected using the initially set threshold until the optimum threshold is determined by this processing.

By the threshold updating process of FIG. 6 described above, the optimum threshold can be obtained using the moving average of the received signal level of the high elevation satellite in a predetermined time window. Therefore, it is possible to prevent the optimum threshold value from sensitively changing in response to the reception state.

[0041]

As described above, according to the present invention,
It is possible to adaptively change the optimum threshold value for selecting the signal used for the positioning calculation according to the level of the received signal input to the GPS receiving device. The threshold value can be automatically controlled to an optimum value without depending on the installation location of the antenna, the type of antenna (whether it is an active antenna or a passive antenna), and the like. As a result, it becomes possible to always improve the positioning accuracy by eliminating the signal including the multipath which adversely affects the positioning calculation, without depending on the installation environment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a GPS receiving device as an embodiment of the present invention.

FIG. 2 (a) shows the GP when the reception level is high.
FIG. 2B is a graph in which the reception levels of the GPS satellites received by the S reception device are arranged in the order of elevation angle. FIG. 2B is a graph showing the reception levels of the GPS satellites received by the GPS reception device in the order of elevation angle when the reception level is low. It is a rearranged graph.

FIG. 3 is a graph showing an example of a relationship that uniquely associates a received signal level of a high elevation satellite with an optimum threshold value.

FIG. 4 is a graph showing a state in which a threshold value obtained by using the correspondence relationship shown in FIG. 3 is applied to the graphs shown in FIGS. 2A and 2B.

FIG. 5 is a graph showing changes in elevation angle of each GPS satellite in Tokyo.

FIG. 6 is a flowchart showing a process of obtaining a reception signal level of a high elevation satellite by a moving average and updating an optimum threshold value.

FIG. 7 is a diagram for explaining a state in which a received signal level of a high elevation satellite is stored in a predetermined data storage area in a nonvolatile memory.

FIG. 8 is a block diagram showing a configuration of a conventional GPS receiver.

FIG. 9 is a diagram illustrating a configuration of an active antenna.

FIG. 10 is a diagram for explaining a relationship between a received signal level of a GPS satellite and an optimum threshold value.

[Explanation of symbols]

2 RF section 3 Digital correlation processor 5 GPS antenna 21 Down Converter 22 A / D converter 31 Carrier correlation unit 32 PRN code generator 33 Carrier NCO 34 PRN code generator 35 code NCO 36 Correlation output 39 channels 41 code tracking loop 42 Carrier tracking loop 94 Positioning calculator 95 threshold value determining means 101 GPS receiver

Claims (10)

[Claims] 1. A GPS receiving apparatus for receiving GPS signals from a plurality of GPS satellites and performing positioning, wherein the reception signal level of a GPS satellite with a high elevation angle of which the elevation angle is a predetermined angle or more among the GPS satellites being received. Based on the threshold value, a threshold value determining means for determining a threshold value for selecting a reception signal used for the positioning calculation, and a satellite selection for selecting a GPS satellite used for the positioning calculation by comparing the determined threshold value with the reception signal. A GPS receiving apparatus comprising: 2. The threshold value determining means is the GP being received.
The average value of the reception signal levels of GPS satellites of which the elevation angle is equal to or more than the predetermined angle among the S satellites is determined, and the threshold value is determined based on the reception signal level obtained as the average value. The GPS receiver according to 1. 3. The GP of high elevation angle is determined by the threshold value determining means.
Obtaining a moving average of the received signal level of the S satellite or the received signal level obtained as the average value, and determining the threshold value based on the obtained moving average.
The GPS receiver according to claim 1 or 2, characterized in that. 4. The threshold value determining means obtains a received signal level of the GPS satellite with the high elevation angle as the average value or the moving average, and determines the threshold value based on the average value or the moving average. The GPS receiving device according to claim 2 or 3, wherein the above is continuously executed and the threshold value is continuously updated. 5. The GP of high elevation angle is determined by the threshold value determining means.
Having a function that associates the received signal level of the S satellite with an optimum threshold value, and determining the threshold value using the function.
The GPS receiver according to any one of claims 1 to 4, characterized in that. 6. A storage unit that stores in advance a table in which an optimum threshold value is associated with each received signal level of the GPS satellite with a high elevation angle is further stored, and the threshold value determination unit is a table stored in the storage unit. The GPS receiver according to any one of claims 1 to 4, wherein the threshold value is determined with reference to. 7. The storage unit further stores a default value as the threshold value in advance, and the satellite selecting unit sets the threshold value as the threshold value when the threshold value has not yet been determined by the threshold value determining unit.
The GPS receiving device according to any one of claims 1 to 6, wherein the default value stored in the storage means is used. 8. The method according to claim 1, wherein the predetermined angle satisfies a condition that a probability that a GPS satellite having the predetermined angle or more can be received is a predetermined value or more. GPS receiver. 9. A GPS receiving apparatus for receiving GPS signals from a plurality of GPS satellites and performing positioning, wherein the received signal level of a GPS satellite having a high elevation angle of which the elevation angle is a predetermined angle or more among the GPS satellites being received. A first storage area capable of storing a plurality of data, a reception signal level of the GPS satellite having a high elevation angle is stored in the first storage area, and an average value is calculated from a predetermined number of data stored in the first storage area. A second storage area for storing a table in which a threshold value for selecting a reception signal to be used for the positioning is stored for each reception signal level of the GPS satellite with a high elevation angle; In the second storage area, a third storage area for storing the threshold value used when selecting the received signal in the above, and a threshold value corresponding to the average value obtained by the first control means are stored in the second storage area. Using the second control means, which is acquired by referring to the table and written in the third storage area, and the threshold value stored in the third storage area, the GPS satellite used for the positioning is selected and the positioning calculation is performed. A GPS receiving device comprising: a positioning calculation means for performing. 10. A GPS receiving device for receiving GPS signals from a plurality of GPS satellites and performing positioning, wherein a received signal level of a GPS satellite having a high elevation angle of elevation angles of a predetermined angle or more is received. A first storage area in which a plurality of storage areas can be stored, reception signal levels of the GPS satellites with high elevation angles are stored in the first storage area, and an average value is calculated from a predetermined number of data stored in the first storage area. A first control unit, a second storage area for storing a threshold value for selecting a reception signal used for the positioning, and a threshold value corresponding to the average value obtained by the first control unit are set to a predetermined function. Positioning calculation for selecting a GPS satellite to be used for the positioning and performing positioning calculation using a second control means calculated by using the above and writing to the second storage area, and a threshold value stored in the second storage area. GPS receiver, characterized in that it comprises a stage, a.