JPH0618643A - GPS receiver - Google Patents

Abstract

(57) [Summary] [Purpose] Make the trajectory of the current position smoother. [Structure] The positioning use selection satellite check unit 5 restricts changes in satellite combinations. The positioning use selection satellite check unit 5 determines that the DOP value of the combination of satellites that has been used for positioning calculation does not exceed the limit value set by the DOP limit value setting unit 2 and belongs to this combination. Check if any of the above are ready to receive. When this condition is satisfied, control is transferred to the positioning calculation unit 4 without going through the satellite selection unit 3, and the combination of satellites up to that point is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to GPS (Global Position
ioning System) The present invention relates to a GPS receiver that receives orbital information from a satellite and calculates positioning.

[0002]

2. Description of the Related Art A GPS is a mobile unit in which a GPS satellite on the earth orbit transmits its orbit information and the like, and the GPS receiver on the earth receives the orbit information and the like. Etc. is a system for positioning. In this system, there are three in order to perform two-dimensional positioning,
In order to perform three-dimensional positioning, it is necessary to receive the orbit information from four satellites, and the positioning accuracy changes depending on the combination of satellites used. Therefore, the positioning accuracy can be improved by optimizing the combination of satellites used for the positioning calculation.

Positioning accuracy in GPS can be evaluated by a position accuracy deterioration index (DOP: Dilusion Of Precision). Several types of DOP are known, and for example, PDOP (Positional DOP) and HDOP (Horizontal DOP) are used. P
The DOP measures the position accuracy associated with the combination of four satellites using HDO.
P is an index for evaluating the position accuracy associated with the combination of the three satellites, and in each case, the smaller the value, the better the position accuracy.

FIG. 4 shows a schematic configuration of a GPS receiver according to a conventional example. The GPS receiver shown in this figure includes a DOP value calculation unit 1, a DOP limit value setting unit 2, a satellite selection unit 3, and a positioning calculation unit 4. The DOP value calculation unit 1 obtains PDOP values for all combinations of four satellites among visible satellites in a certain time zone, and also obtains HDOP values for all combinations of three satellites. The satellite selection unit 3 uses the DOP value calculated by the DOP value calculation unit 1.
The satellite combination having the smallest value and therefore the best position accuracy is selected, and the positioning calculation unit 4 moves based on the received data from the satellites related to the combination selected by the satellite selection unit 3, the movement in which the receiver is mounted. Perform body positioning calculations. The positioning calculation algorithm is well known and will not be described here.

Further, even if the DOP value obtained by the DOP value calculation unit 1 is the best, there are cases where the position accuracy sufficient to provide it to the operator of the moving body cannot be obtained. Therefore, the DOP limit value setting unit 2 sends the DOP limit value to the satellite selecting unit 3.
Set the limit value. The satellite selection unit 3 operates so as to select only a combination that does not exceed the limit value set by the DOP limit value setting unit 2, thereby ensuring the minimum position accuracy in the GPS receiver.

FIG. 5 shows an example of the operation in this conventional example. This figure shows the change over time of the DOP value. In the figure, (1) to (3) are the combinations of satellites selected by the satellite selection unit 3, and (4) is the DOP limit value setting unit 2
Indicates the limit value of the DOP value set by, and T _{0 to} T ₅ indicate the satellite selection change timing. In the example of this figure, the DOP value related to the satellite combination (1) at time T ₀ is the minimum, so the satellite selection unit 3 selects this combination (1), and the positioning calculation unit 4 selects this combination (1). The positioning calculation is executed based on the satellite received data. Further, if the radio wave from the satellite which constitutes the (1) is blocked, such as the radio wave from the GPS satellite is blocked, the positioning calculation cannot be executed by using the combination (1). Therefore, the satellite selector 3
The combination (2) having the next best DOP value is selected, and the positioning calculation unit 4 executes the positioning calculation based on the data received from the satellite according to this combination (2). Similarly, the combination of satellites selected by the satellite selection unit 3 and used for the positioning calculation by the positioning calculation unit 4 is changed to (3), (2), (1) ... Thus, in the past, D
Since the combination of satellites was selected using the OP value and the positioning calculation was executed, good position accuracy was always obtained.

[0007]

However, when the reception condition of the radio wave from the satellite changes and the combination related to the selection is changed as a result, the current position of the moving body obtained by the positioning calculation at the time when the combination is changed. Changes in steps. That is, as shown in FIG. 6, when the combination of satellites is changed with a change in the reception state, the track of the current position obtained by the positioning calculation changes stepwise.

The present invention has been made to solve the above problems, and a track obtained by a positioning calculation while changing the selection of the combination of satellites based on the DOP value to secure the position accuracy. It is an object of the present invention to provide a GPS receiver capable of smoothing.

[0009]

In order to achieve such an object, the GPS receiver of the present invention has a DOP value relating to a combination other than the combination selected until the reception state from the satellite changes. When it becomes the minimum, a means for maintaining the combination of satellites for positioning calculation is provided as long as the DOP value for the combination selected so far does not exceed the set limit value.

[0010]

In the present invention, even if the DOP value is not the minimum due to the combination of the satellites selected until then due to the change of the receiving state, the DOP value by the combination does not exceed the set limit value. As long as it is continuously used for positioning calculation. Therefore, changing the combination of satellites related to the positioning calculation is limited so that the track of the current position obtained by the positioning calculation does not change stepwise. In addition, since the condition that the DOP value does not exceed the set limit value is set as a condition for continuing the combination selected until then,
The lowest position accuracy is ensured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those in the conventional example shown in FIGS. 4 to 6 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows a GPS according to an embodiment of the present invention.
The configuration of the receiver is shown. In this embodiment, a positioning use selection satellite check unit 5 is added to the conventional example shown in FIG.

The DOP value calculation 1 calculates the PDOP value and the HDOP value depending on the combination of satellites, as in the conventional example.
The positioning use selection satellite check unit 5 confirms that data can be received from the satellites associated with the combination that has been used for the positioning calculation up to that point, and the DOP based on this combination is received.
Confirm that the value does not exceed the limit value set by the DOP limit value setting unit 2.

When the confirmation condition in the positioning use selection satellite check unit 5 is satisfied, that is, data can be received from the satellites associated with the combination used for the positioning calculation until then, and the DOP value due to this combination is limited. If the value does not exceed the value, the position accuracy will not be significantly deteriorated even if the positioning calculation is performed using the combination that has been used for the positioning calculation. Therefore, in this case, the control immediately shifts to the positioning calculation unit 4 without passing through the satellite selection unit 3, and the predetermined positioning calculation is executed using the combination of the satellites selected up to that point.

Further, when the positioning use selection satellite check unit 5 determines that one of the confirmation conditions is not satisfied, that is, whether or not the satellite associated with the combination used for positioning up to that point is in the unreceivable state. , Or when the DOP value due to the combination exceeds the limit value,
Control is transferred to the satellite selection unit 3. When the satellite is selected for the first time, the control shifts to the satellite selection unit 3. In the satellite selection unit 3, as in the conventional example, the combination of satellites having the minimum DOP value is selected, and this combination of satellites is used in the positioning calculation by the positioning calculation unit 4.

FIG. 2 shows an example of the operation of this embodiment. This figure is similar to FIG.
It is a figure which shows the time change of a value.

For example, it is assumed that the DOP value due to the satellite combination (1) at time T ₀ is the smallest value compared to the others. When the satellite belonging to the combination (1) becomes unreceivable at time T ₁ after this, this is checked by the positioning use selection satellite check unit 5, and the operation of the satellite selection unit 3 causes the next good DOP value. The combination (2) is selected as the combination for positioning calculation. Furthermore, when the satellites belonging to this combination (2) become unreceivable at time T ₂ , this is similarly checked by the positioning use selection satellite check unit 5, and the combination (3) with the next best DOP value is selected. The satellite selection unit 3 selects a combination related to positioning calculation.

Thereafter, at time T ₃ , the combination (2)
It is assumed that all the satellites according to (1) are ready to receive, and that the DOP value of this combination (2) is the best compared to the other combinations. In this case, in the conventional example, the combination (2) was selected as the combination relating to the positioning calculation, but in the present embodiment, the DOP value of the combination (3) at this time T ₃ becomes the limit value (4). Since it does not exceed, the combination (3) is continuously used as a combination for positioning calculation. That is, the positioning use selection satellite check unit 5 determines that at time T ₃ , the DOP value related to the combination (3) does not exceed the limit value set by the DOP limit value setting unit 2 and the combination (3) is concerned. It is confirmed that all the satellites are in the receivable state, and as a result, the control shifts to the positioning calculation section 4 without going through the satellite selection section 3. Therefore, although the combination (2) has the best DOP value, it is not selected as the combination for positioning calculation.

It is assumed that, at time T ₄ , all the satellites of the combination (1) are ready to receive, and the DOP value thereof is the best compared with the other combinations.
At this time T ₄ , the DOP value for combination (3) does not exceed the limit value (4), and any satellite belonging to combination (3) maintains the receivable state.
The control shifts from the positioning use selection satellite check unit 5 to the positioning calculation unit 4, and subsequently the combination (3) is selected as the combination related to the positioning calculation. The combination (1) is selected as a combination for positioning calculation because one of the satellites belonging to the combination (3) is in the unreceivable state or the combination (3) is selected.
This is the case where the DOP position due to exceeds the limit value (4).
In the example of FIG. 2, the combination (1) is selected as the combination for the positioning calculation at time T _{5 when the} DOP value of the combination (3) exceeds the limit value (4).

Therefore, according to this embodiment, as long as the DOP value of the combination of satellites that has been used for positioning calculation does not exceed the limit value (4) or any of the satellites belonging to the combination used for positioning calculation. Will be used for the positioning calculation by the positioning calculator 4 as long as it is not received. As a result, as can be understood from the comparison between FIG. 2 and FIG. 5, the frequency of changing satellite combinations is suppressed. Therefore, as shown in FIG. 3, the track of the current position obtained by the positioning calculation is smoother than that of the conventional example. In addition, since the limit by the limit value (4) is still ensured, the minimum position accuracy of the GPS receiver can still be ensured.

[0021]

As described above, according to the GPS receiver of the present invention, even if the reception state from the satellite changes and the DOP value related to the combination selected until then becomes the minimum, As long as the DOP value related to a combination other than the selected combination does not exceed the set limit value, it is used for the positioning calculation continuously. Therefore, the locus of the current position obtained by the positioning calculation becomes smoother and the minimum position accuracy is also obtained. Reserved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a GPS receiver according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an operation of changing a combination of satellite selections in this embodiment.

FIG. 3 is a diagram showing an effect of this embodiment.

FIG. 4 is a block diagram showing a configuration of a GPS receiver according to a conventional example.

FIG. 5 is a diagram showing an example of a satellite combination changing operation in this conventional example.

FIG. 6 is a diagram showing a problem in this conventional example.

[Explanation of symbols]

 1 DOP value calculation unit 2 DOP limit value setting unit 3 Satellite selection unit 4 Positioning calculation unit 5 Positioning use selection satellite check unit (1), (2), (3) Satellite combination (4) Limit value

Claims (1)

[Claims] 1. A means for calculating a DOP value for each combination of a predetermined number of visible satellites, a means for selecting a combination for which data is receivable and a calculated DOP value is minimum for all satellites, and the selected combination. In the GPS receiver including means for executing positioning calculation based on the received data from the satellite according to, the means for setting the limit value of the DOP value and the combination selected until then due to a change in the reception state from the satellite. When the DOP value related to a combination other than is the minimum, as long as the DOP value related to the combination selected until then does not exceed the set limit value, means for maintaining the combination of satellites related to positioning calculation, A GPS receiver, comprising: