JP3723492B2 - GPS receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a GPS receiver, and more particularly, to setting a threshold value for selecting a received signal used for positioning calculation.
[0002]
[Prior art]
The GPS receiver measures the distance between the GPS satellite and the GPS receiver itself by tracking a GPS signal transmitted from the GPS satellite (this is called a pseudorange), and relates to a plurality of GPS satellites measured simultaneously. Based on the pseudo distance, the position of itself is calculated by a geometric operation. Furthermore, the GPS receiver measures the change rate of the carrier frequency of each satellite (Doppler measurement), calculates its own moving speed and traveling direction, and outputs these calculation results as GPS output data.
[0003]
At this time, the GPS receiving device performs two-dimensional positioning when the number of GPS satellites being tracked is three, and three-dimensional positioning when four or more. Note that the data calculated by the two-dimensional positioning is “latitude, longitude”, and “latitude, longitude, altitude” is three-dimensional positioning. The number of signals (satellite) that can be captured simultaneously by the GPS receiver is determined by the number of channels of the GPS receiver, and the number of channels is generally about 8ch to 12ch.
[0004]
FIG. 8 shows a configuration of a general GPS receiver 1. The GPS receiver 1 includes an RF unit 2, a digital correlation processing unit 3, and a positioning calculation unit 4. The RF unit 2 converts the RF signal input from the GPS antenna 5 into a signal having an intermediate frequency, and then 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 (comprising a carrier correlation unit 31, a PRN code correlation unit 32, a carrier NCO 33, a PRN code generation unit 34, and a code NCO 35). A plurality of channels 39 are provided.
[0005]
The carrier tracking loop 42 and the code tracking loop 41 control the carrier NCO (NCO; numerically controlled oscillator) 33 and the code NCO 35 in the acquisition (tracking) and tracking (tracking) of the GPS signal. The positioning calculation unit 4 calculates the position, speed, direction, and the like of the GPS receiver 1 itself based on the PRN code generation timing in each channel and the phase change amount of the carrier NCO 33. The positioning calculation for obtaining the positioning solution is usually executed at regular time intervals (for example, every second). The obtained positioning solution can be transferred as input / output data 43 to the host system.
[0006]
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 provided with a signal amplifier 52 in the subsequent stage of the antenna element 51, while the passive antenna refers to a type that does not have the signal amplifier 52. The GPS receiver 1 is mounted on various application devices such as a car navigation system and a portable information terminal. Due to the difference in these applications, the RF signal input terminal of the GPS receiver from the GPS antenna (reference numeral 2a in FIG. 8). There will be a big difference in the route to reach. In general, the antenna cable 6 uses a 1 to 5 m coaxial line for car navigation, and an antenna element is directly attached to a GPS receiver board or a several cm coaxial line is used for a portable information terminal or the like. Degree.
[0007]
Therefore, the active antenna takes into account the fact that the GPS signal radiated from the GPS satellite is weak, the gain of the antenna element 51 is small, the transmission loss up to the GPS receiver 1, and the like. Is used in a car navigation system or the like for the purpose of keeping the signal level at the RF signal input terminal 2a at a certain level or higher. On the other hand, the passive antenna is used in a portable information terminal that does not require a signal amplifier because the transmission loss to the GPS receiver 1 is small.
[0008]
As described above, depending on the application, the type of antenna used (whether it is an active antenna or a passive antenna) and the presence / absence / absence of an antenna cable exist, so the signal input to the GPS receiver 1 The level (intensity) has a difference of several tens of dB.
[0009]
In the car navigation system, the GPS antenna 5 is installed on the dashboard or rear shelf or installed in the interior depending on the difference between the GPS antenna 5 being installed outside the vehicle interior or the vehicle interior. Due to this difference, a signal level difference of several dB to several tens of dB occurs at the RF signal input terminal 2a of the GPS receiver 1.
[0010]
[Problems to be solved by the invention]
The positioning calculation unit 4 of the GPS receiver 1 can know the received signal level of each channel 39 from the correlation processing output 36 of each channel 39 of the digital correlation processing unit 3. Therefore, when the positioning calculation unit 4 performs the positioning calculation, it selects and uses a signal having a reception signal level equal to or higher than the set threshold value, thereby eliminating the signal affected by multipath or noise. It becomes possible 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 This is based on the fact that a signal with a low level is relatively likely to be affected by noise.
[0011]
Here, it is necessary to consider that the above-described threshold value varies greatly depending on the level of the received signal input to the GPS receiver 1. This will be described with reference to the graph of FIG. FIGS. 10A and 10C respectively represent “an example of an optimum threshold for a high received signal level” and “an example of an optimum threshold for a low received signal level”. In FIG. 10, each of the satellites A to H on the horizontal axis represents a receiving satellite, and the vertical axis represents the received signal level of each satellite. In the examples of FIGS. 10A and 10C, since the optimum threshold is applied to the received signal level input to the GPS receiver, signals that may include multipath (satellite) It can be seen that only B and satellite E) are controlled so as not to be used for the positioning calculation.
[0012]
10B and 10D, “an example in which a threshold is applied on the assumption that a low reception signal is input when a high reception signal level is input” and “a high reception signal when a low reception signal level is input”. An example of applying a threshold based on the assumption that “ In the example of FIG. 10B, the threshold A0 is applied on the assumption that a low received signal level is input even though a high received signal level is input. It can be seen that the received signals (satellite B and satellite E) that may be present have been taken into the positioning calculation. This leads to an adverse effect of deterioration in positioning accuracy.
[0013]
In addition, in the example of FIG. 10D, since the threshold A1 is applied on the assumption that a high received signal is input even though a low received signal level is input, positioning is originally performed. It can be seen that the received signals (satellite D and satellite F) that can be used for computation are excluded. As a result, the GPS positioning rate is lowered, and the positioning performance is significantly affected.
[0014]
As described above, if the threshold for selecting a signal used for the positioning calculation does not appropriately correspond to the received signal level input to the GPS receiver 1, the positioning performance is significantly impaired. In general, a measure that can be taken in order to keep the positioning performance in a good state is to set a threshold according to the application in terms of the greatest common divisor and to set this threshold in the GPS receiver in advance.
[0015]
However, for example, in a car navigation system, a significant difference occurs in the received signal level input to the GPS receiver 1 depending on where the user installs the GPS antenna 5. In this case, an optimum threshold value is not set according to how it is used (placement location of the antenna), and positioning performance may be deteriorated.
[0016]
The present invention has been made in view of such circumstances. That is, according to the present invention, positioning can be performed without depending on the installation environment by adaptively changing the threshold of the reception level of the signal used for positioning calculation according to the level of the reception signal input to the GPS receiver. An object of the present invention is to provide a GPS receiver capable of eliminating a signal including a multipath that adversely affects an operation and improving positioning accuracy.
[0017]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, a reception signal used for positioning calculation is transmitted to a GPS receiver based on a reception signal level of a signal from a high-elevation GPS satellite whose elevation angle is equal to or greater than a predetermined angle among the satellites being received. A means for determining a threshold for selection is added (claim 1). The reception signal level of the high elevation satellite and the optimum threshold value can be associated with each other with a certain correspondence. Therefore, an optimum threshold value can be obtained based on the received signal level from the satellite having a high elevation angle.
[0018]
There may be one or more satellites whose elevation angle is greater than or equal to a predetermined angle, but in this case, the average value may be obtained as the reception signal level of the high elevation satellite (claim 2).
[0019]
It is preferable that a moving average that is an average of a predetermined number of data is obtained for a received signal level of a satellite having a high elevation angle, and a threshold value is determined based on the moving average. As a result, it is possible to prevent the optimum threshold from fluctuating in response to the reception state.
[0020]
The threshold value can be continuously updated by continuously obtaining the average value or the moving average (claim 4). By continuously updating the threshold value, it is possible to continuously achieve positioning by eliminating signals affected by multipath.
[0021]
The received signal level of the high-elevation satellite and the optimum threshold value have a correspondence that uniquely associates it as a function, so that the optimum threshold value can be acquired from the received signal level of the high-elevation angle satellite. . Alternatively, the correspondence relationship can be stored as a table, and an optimum threshold value can be obtained by referring to the table (claim 6).
[0022]
It is also possible to store the default value of the threshold value and use the default value as the threshold value until an optimal threshold value is obtained, for example, immediately after starting the GPS receiver (claim 7).
[0023]
The probability that a satellite with a high elevation angle can be captured at the observation point decreases as the predetermined angle as the definition of the high elevation angle increases. Therefore, the predetermined angle for considering the high elevation angle may be an angle determined so that the probability that the GPS satellite can be captured is a predetermined value or more in consideration of the elevation angle transition of all the GPS satellites at the observation point. Preferred (claim 8).
[0024]
In order to achieve the above object, the invention described in claim 9 is a GPS receiving device that receives GPS signals from a plurality of GPS satellites and performs positioning, and among the GPS satellites being received, the elevation angle is predetermined. A first storage area that can store a plurality of reception signal levels of GPS satellites with a high elevation angle that is equal to or greater than an angle, and a reception signal level of GPS satellites with a high elevation angle are stored in the first storage area and stored in the first storage area. A table in which a first control unit that calculates an average value from a predetermined number of data and a threshold value for selecting a received signal used for positioning is stored for each received signal level of a high-elevation GPS satellite is stored. A second storage area, a third storage area for storing a threshold used when selecting a received signal in positioning, and a threshold corresponding to the average value obtained by the first control means are stored in the second storage area. Is Positioning calculation that performs positioning calculation by selecting a GPS satellite to be used for positioning using the second control means that is obtained by referring to the table and that writes to the third storage area and the threshold value stored in the third storage area Means. The optimum threshold value obtained by referring to the table based on the received signal level of the high elevation satellite is stored in the third storage area. The positioning calculation means can acquire an optimum threshold value by referring to the third storage area, and can use this optimum threshold value to select a GPS satellite to be used for positioning.
[0025]
In order to achieve the above object, the invention according to claim 10 is a GPS receiving device that receives GPS signals from a plurality of GPS satellites and performs positioning, and the elevation angle of the GPS satellites being received is a predetermined angle. The first storage area that can store a plurality of received signal levels of GPS satellites with high elevation angles, and the received signal level of GPS satellites with high elevation angles are stored in the first storage area and stored in the first storage area. Corresponds to the first control means for calculating an average value from a predetermined number of data, a second storage area for storing a threshold value for selecting a reception signal used for positioning, and the average value obtained by the first control means A second control means that calculates a threshold value to be calculated using a predetermined function and writes it to the second storage area, and uses the threshold value stored in the second storage area to select a GPS satellite to be used for positioning and perform a positioning calculation. Positioning performance to be performed And means, the. The received signal level of the high elevation satellite can be uniquely associated with the optimum threshold value. By having this correspondence 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 an optimum threshold value by referring to the second storage area, and can select a satellite to be used for positioning using this optimum threshold value.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of the GPS receiver 101 of the present invention is shown in FIG. The GPS receiver 101 includes an RF unit 2, a digital correlation processing unit 3, and a positioning calculation unit 94. In FIG. 1, the same reference numerals are used for the same parts as the components of the GPS receiver 1 (FIG. 8), 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. .
[0027]
The positioning calculation unit 94 calculates the position, speed, direction, etc. of the GPS receiver 101 itself based on the PRN code generation timing in each channel 39 and the phase change amount of the carrier NCO 33. Further, the positioning calculation unit 94 is provided with threshold determination means 95 for determining a threshold for selecting a signal used for the positioning calculation according to the received signal level of the signal from the satellite at a high elevation angle. The threshold value determined here is used when selecting a satellite in the positioning process. Note that the positioning calculation unit 94 is composed of a processor, and has therein a ROM, a RAM, a non-volatile memory (not shown) necessary for executing the program.
[0028]
FIG. 2A shows a case where a high reception signal level is input to the GPS receiving apparatus 101 (corresponding to (a) and (b) of FIG. 10). Are rearranged. Similarly, FIG. 2B shows an elevation angle of each GPS satellite viewed from the GPS antenna 5 when a low received signal level is input to the GPS receiver 101 (corresponding to (c) and (d) of 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.
[0029]
In FIG. 2, the reason why the received signal levels of the GPS satellites are arranged in the order of elevation angle is that the antenna element 51 of the GPS antenna 5 has an antenna beam characteristic having a peak at an elevation angle of 90 degrees. In FIG. 2, the reason why the received signal level of the satellite E is lower than the received signal level of the satellite D having a lower elevation angle is that the satellite E has received a multipath.
[0030]
From FIG. 2, it can be understood that the elevation angle of the receiving GPS satellite and the received signal level have a certain relationship as shown in FIGS. 2 (a) and 2 (b). For this reason, the threshold for eliminating signals that would include multipath (satellite E and satellite B in FIG. 2) is based on the received signal level of 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 is uniquely determined with respect to the average level of the received signal of the high elevation satellite. Can do.
[0031]
As an example, FIG. 3 shows a relationship in which the received signal level of the high elevation satellite is uniquely associated with the optimum threshold value. In FIG. 3, the horizontal axis represents the received signal level of the high elevation satellite, and the vertical axis represents the threshold value.
[0032]
Note that the correspondence relationship in FIG. 3 is that if the signal is received by the antenna element 51, the influence of the gain (amplification / attenuation) of the circuit and line that is input to the GPS receiver 101 is equal, and the high elevation angle This is based on the fact that satellite signals are unlikely to be affected by multipath. Further, the correspondence shown in FIG. 3 is an example in a simplified case, and more detailed correspondence is considered based on the configuration of the beam characteristics of the GPS antenna, the demodulation means in the GPS receiver, and the reception level calculation means. It should be noted that it is also possible. Actually, the correspondence relationship between the received 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, and an example is shown in FIG. It is possible to know such correspondence. The correspondence relationship obtained in this manner is held in a nonvolatile memory (not shown) in the positioning calculation unit 94 as a function or a table.
[0033]
FIGS. 4A and 4B are examples in which the optimum threshold value is obtained using the correspondence relationship of FIG. 3 in the case of FIGS. 2A and 2B, respectively. Here, the definition of the high elevation satellite is defined as “elevation angle of 70 degrees or more”. Therefore, in the case of FIGS. 4A and 4B, the satellite C and the satellite G correspond to high elevation satellites. When the threshold value TH ₁ obtained from the correspondence relationship in FIG. 3 is applied to the average value P ₁ of the received signal levels of the satellites C and G in FIG. 4A, the result is as shown in FIG. 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 received signal levels of the satellites C and G in FIG. 4B, the result is as shown in FIG. . As described above, if the “optimum threshold characteristic with respect to the average received signal level of the high elevation satellite” as shown in FIG. 3 is grasped as the entire system of the GPS receiver 101 including the GPS antenna 5, the positioning calculation is performed. It is possible to optimally set the threshold of the reception level of the reception signal used for the above.
[0034]
Note that the elevation angle for defining a high elevation satellite can be obtained with a higher accuracy threshold if it is set as high as possible. However, the opportunity to receive a satellite that satisfies the definition of a high elevation angle is Therefore, it is desirable to determine the optimum value in consideration of such a trade-off relationship. FIG. 5 is an example showing how the elevation angle of each GPS satellite changes when the GPS satellites are observed for 24 hours in Tokyo. From FIG. 5, it is reasonable to set the definition of the high elevation satellite to about 70 ± 10 degrees so that the probability that a satellite satisfying the definition of the high elevation angle can be received is a predetermined value or more in consideration of the trade-off. Is. However, the definition of a high elevation satellite is not limited to this value.
[0035]
In the positioning calculation unit 94, as described above, the threshold value is updated from the average received signal level of the high elevation satellite among the received satellites using the correspondence relationship (FIG. 3) stored in the nonvolatile memory. By executing continuously, the threshold value can always be kept at an optimum value. In the positioning calculation process executed at predetermined time intervals in the positioning calculation unit 94, a threshold is used as the satellite selection process, and only satellites having a received signal level exceeding the threshold are used for the positioning calculation. Therefore, it is possible to avoid using a signal including the influence of multipath or the like for the positioning calculation, and to keep the positioning accuracy always high.
[0036]
As described above, the higher the elevation angle as a definition of a high elevation satellite, the smaller the opportunity to receive a signal from a satellite that satisfies the definition, and the optimum threshold value determined according to the correspondence relationship in FIG. Considering that it is not desirable to react sensitively to the reception state, it is desirable and practical to store the received signal level of the high elevation satellite in a non-volatile memory or the like for a predetermined number of data and take a moving average. is there.
[0037]
FIG. 6 is a flowchart corresponding to the operation of the threshold value determining means 95, showing the process of obtaining the received signal level of the high elevation satellite by moving average and updating the optimum threshold value. This process is executed at predetermined time intervals as part of the positioning calculation process. In FIG. 6, “memory” refers to a nonvolatile memory in the positioning calculation unit 94, and “table” is a table representing the correspondence illustrated in FIG. 3 stored in advance in the nonvolatile memory.
[0038]
First, it is determined whether satellites acquired by normal positioning calculation processing include those with a high elevation angle (elevation angle of 70 ± 10 degrees or more) (S1). When a satellite with a high elevation angle is included in the acquired satellite (S1: YES), the received signal level of the satellite (if there are a plurality of satellites with a high elevation angle, the average value thereof) is stored in the memory (S2). ). Here, as shown in FIG. 7A, the high elevation satellite data is stored in the memory while increasing n every time the process of step S2 is performed in the predetermined data storage area 96 in the memory. In this order, d ₁ to d _{n + 1 are} stored. Note that the n + 2th data after the data storage area 96 is completely filled is stored again in order from the top of the data storage area 96 (see FIG. 7B). Data is updated in a so-called ring buffer format.
[0039]
Next, it is determined whether a predetermined number of data (n + 1) is stored in the data storage area 96 (S3). If the data stored in the data storage area 96 has not reached the predetermined number (S3: NO), the process is terminated without updating the threshold value. If the predetermined number has been reached (S3: YES), the data stored in the data storage area 96 is read (S4), and an average value thereof, that is, a moving average is calculated (S5). Next, based on the calculated moving average, referring to the table stored in the memory (or using the correspondence relationship between the received signal level and the optimum threshold stored in the memory as a function), the moving average An optimum threshold value corresponding to the received signal level is acquired (S6). The acquired optimum threshold value is then updated by overwriting the storage location of the positioning calculation threshold value in the memory (S7). It should be noted that a value determined in consideration of the application is stored in the storage location of the positioning calculation threshold when the GPS receiver 101 is initially turned on as the initial value of the optimum threshold. In this case, the satellite can be selected using the initially set threshold until the optimum threshold is determined by this processing.
[0040]
By the threshold value updating process of FIG. 6 described above, the optimum threshold value can be obtained using the moving average over a predetermined time window for the received signal level of the high elevation satellite. Therefore, it can be avoided that the optimum threshold changes sensitively to the reception state.
[0041]
【The invention's effect】
As described above, according to the present invention, the optimum threshold value for selecting a signal used for positioning calculation can be adaptively changed according to the level of the received signal input to the GPS receiver. The threshold value can be automatically controlled to an optimum value without depending on the location of the antenna and the type of antenna (whether it is an active antenna or a passive antenna). This makes it possible to always improve positioning accuracy by eliminating signals including multipaths that adversely affect the positioning calculation without depending on the installation environment.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a GPS receiver as an embodiment of the present invention.
FIG. 2 (a) is a graph in which the reception levels of GPS satellites received by the GPS receiver when the reception level is high are arranged in order of elevation, and FIG. 2 (b) is a low reception level. It is the graph which rearranged the reception level of the GPS satellite received in the GPS receiver in order of elevation angle.
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.
4 is a graph showing a state in which a threshold obtained using the correspondence relationship shown in FIG. 3 is applied to the graphs shown in FIGS. 2 (a) and 2 (b).
FIG. 5 is a graph showing changes in elevation angle of each GPS satellite in Tokyo.
FIG. 6 is a flowchart showing a process for obtaining a received 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 unit 3 Digital correlation processing unit 5 GPS antenna 21 Down converter 22 A / D converter 31 Carrier correlation unit 32 PRN code generation unit 33 Carrier NCO
34 PRN code generator 35 Code NCO
36 Correlation Processing Output 39 Channel 41 Code Tracking Loop 42 Carrier Tracking Loop 94 Positioning Calculation Unit 95 Threshold Determination Means 101 GPS Receiver

Claims (10)

A GPS receiver that performs positioning by receiving GPS signals from a plurality of GPS satellites,
Threshold determining means for determining a threshold for selecting a received signal used for positioning calculation based on a received signal level of a GPS satellite with a high elevation angle whose elevation angle is equal to or greater than a predetermined angle among GPS satellites being received;
Satellite selection means for selecting a GPS satellite to be used for positioning calculation by comparing the determined threshold value with a received signal;
A GPS receiving device comprising: The threshold value determining means obtains an average value of received signal levels of GPS satellites having an elevation angle equal to or greater than the predetermined angle among the GPS satellites being received, and determines the threshold value based on the received signal level obtained as the average value. The GPS receiver according to claim 1, wherein: The threshold value determining means obtains a moving average for the received signal level of the GPS satellite at the high elevation angle or the received signal level obtained as the average value, and determines the threshold value based on the obtained moving average; The GPS receiver according to claim 1 or 2, characterized by the above-mentioned. The threshold value determination means continuously obtains a received signal level of the GPS satellite at 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, wherein the GPS receiving device is executed and the threshold value is continuously updated. The threshold determination means has a function in which a reception signal level of the GPS satellite at the high elevation angle is associated with an optimal threshold, and determines the threshold using the function. The GPS receiving device according to claim 4. A storage means for storing in advance a table in which an optimum threshold value is associated with each received signal level of the high-elevation GPS satellite;
The GPS receiving device according to any one of claims 1 to 4, wherein the threshold value determining unit determines the threshold value with reference to a table stored in the storage unit. The storage means further stores in advance a default value as the threshold value,
The said satellite selection means uses the said default value stored in the said memory | storage means as said threshold value, when the said threshold value is not yet determined by the said threshold value determination means, The said threshold value is used. Item 7. The GPS receiver according to any one of Items 6 to 7. The GPS receiving apparatus according to claim 1, wherein the predetermined angle satisfies a condition that a probability that a GPS satellite having a predetermined angle or more can be received is a predetermined value or more. A GPS receiver that performs positioning by receiving GPS signals from a plurality of GPS satellites,
A first storage area capable of storing a plurality of received signal levels of high-elevation GPS satellites whose elevation angle is equal to or greater than a predetermined angle among GPS satellites being received;
First control means for storing a received signal level of the high elevation GPS satellite in the first storage area and calculating an average value 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 used for positioning is stored for each reception signal level of the high-elevation GPS satellite;
A third storage area for storing the threshold value used when selecting a received signal in the positioning;
Second control means for acquiring a threshold value corresponding to the average value obtained by the first control means with reference to a table stored in the second storage area, and writing the threshold value in the third storage area;
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;
A GPS receiving device comprising: A GPS receiver that performs positioning by receiving GPS signals from a plurality of GPS satellites,
A first storage area capable of storing a plurality of received signal levels of high-elevation GPS satellites whose elevation angle is equal to or greater than a predetermined angle among GPS satellites being received;
First control means for storing a received signal level of the high elevation GPS satellite in the first storage area and calculating an average value from a predetermined number of data stored in the first storage area;
A second storage area for storing a threshold for selecting a reception signal used for the positioning;
A second control unit that calculates a threshold value corresponding to the average value obtained by the first control unit using a predetermined function and writes the threshold value in the second storage area;
Positioning calculation means for selecting a GPS satellite to be used for positioning and performing positioning calculation using the threshold value stored in the second storage area;
A GPS receiving device comprising:

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