JP3182198B2 - GPS receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a GPS (Global Posit
The present invention relates to a GPS receiver that receives a radio wave from a satellite and obtains a pseudorange to perform positioning.

[0002]

2. Description of the Related Art GPS is a system for launching a predetermined number of GPS satellites (hereinafter simply referred to as satellites) in orbit around the earth and positioning a mobile object. In this system, a GPS receiver is mounted on a moving object (such as a ship) to be positioned. Each GPS receiving device obtains its own position of a mounted mobile body through a series of operations of selecting a satellite to be used for positioning, measuring a pseudo distance to the selected satellite, and calculating its own position using the measured pseudo distance. .

As a method of selecting a satellite used for positioning, there is a method of selecting a combination that is expected to have the highest positioning accuracy among visible satellites. The visible satellite is a satellite at a position where radio waves can be received at present, and the positioning accuracy is, for example, GDOP.
(Geometrical Dilution Of Precision). By using such an index, it is possible to select an optimal combination of the number of satellites required for positioning from among the visible satellites.

If the distance to each satellite can be measured (without offset) from the propagation time of radio waves, 3
To determine the three-dimensional position, select three satellites,
In order to determine the two-dimensional position, two satellites one less than this may be selected. However, actually, the distance (pseudo distance) obtained by the measurement includes an offset due to a radio wave delay, a clock error, or the like. Therefore, actually, it is necessary to select three or four satellites as GPS satellites.

As the satellite moves in orbit,
The positional relationship between the GPS receiver and the satellite changes. In this case, the GPS receiver again selects a satellite to be used for positioning, and secures a suitable positioning accuracy by combining a newly selected satellite.

[0006]

However, the conventional GPS
In the receiving device, the own position obtained by positioning may change discontinuously. This occurs particularly when the combination of satellites used for positioning is changed.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a GPS which does not discontinuously change its own position obtained by positioning when the combination of satellites used for positioning is changed. It is intended to realize a receiving device.

[0008]

In order to achieve such an object, the present invention is characterized by having the structure shown in FIG. That is, according to the present invention, a satellite selection operation unit A selects a predetermined number of satellites to be used for positioning with predetermined logic, and outputs selected satellite information indicating a combination of the selected satellites.
And a receiving unit B that receives a signal from a satellite related to the selected satellite information, calculates a pseudorange with each satellite based on the signal, and outputs the pseudorange data as pseudorange data, and obtains its own position based on the selected satellite information and pseudorange data. A GPS receiving device comprising: a positioning operation unit C that outputs the position data; determining whether a combination of satellites used for positioning has changed based on the selected satellite information. , A distance correction value calculation unit D that calculates a pseudo distance correction amount based on the own position before the change and outputs the calculated pseudo distance correction amount as pseudo distance correction data. The distance data is corrected by the pseudo distance correction data, and the own position is calculated.

A second aspect of the present invention is characterized in that the pseudo distance correction amount is reduced with time.

[0010]

In the present invention, it is determined whether or not the combination of satellites used for positioning has changed, and when the combination has changed, the pseudorange data is corrected for the newly selected satellite. That is, for the newly selected satellite, a pseudo-range correction amount based on the own position before the change is obtained, and the pseudo-range correction data indicating the obtained pseudo-range correction amount provides pseudo-range data of the newly selected satellite. Is corrected. Thereby, the discontinuous change of the own position due to the use of the new satellite is suppressed.

Considering a point in time after a certain period of time has elapsed since the selection of a new satellite, the error included in the pseudorange relating to the new satellite at that point in time is determined by the pseudorange immediately after the selection. It has a correlation with the included error. This correlation decreases over time. Therefore, claim 2
In, the pseudo-range correction amount is reduced with time to match the reduction in correlation. Thereby, the positioning accuracy is maintained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a GPS according to an embodiment of the present invention.
The configuration of the receiving device is shown. This device comprises a receiving antenna 1, a receiving unit 2, a pseudo distance measuring unit 3, a positioning calculating unit 4, a distance calculating unit 5, a correction amount calculating unit 6, and a satellite selecting unit 7.

The receiving section 2 receives and demodulates a signal transmitted by radio from a satellite via the receiving antenna 1. Satellite selector 7
At this time, a combination of satellites to be received is selected, and the receiving unit 2 performs reception and demodulation in accordance with the combination. Receiver 2
The demodulated signal is supplied to the pseudorange measuring unit 3, and the pseudorange measuring unit 3 determines each satellite based on a difference between a clock (not shown) incorporated in the device and a signal timing obtained by the receiving unit 2. Is calculated. The obtained pseudo distance is supplied to the positioning calculation unit 4 as pseudo distance data.

FIG. 3 shows the operations of the positioning calculation unit 4, the distance calculation unit 5, and the correction amount calculation unit 6 in this embodiment. Among the operations shown in this figure, the correction of the pseudorange related to the newly selected satellite is a characteristic process of the present embodiment.

First, the distance calculation unit 5 determines whether or not the satellite selected by the satellite selection unit 7 has been switched, that is, whether or not the combination of satellites used for positioning has been switched, based on the output of the satellite selection unit 7. A determination is made (100).

If it is determined that the switching has been performed, the distance calculation unit 5 obtains its own position from the combination of the satellites before the switching (102). When three-dimensional positioning is performed, the obtained self-position includes a unique clock error ΔR in addition to the three-dimensional coordinates (X, Y, Z). The distance calculation unit 5 calculates a distance R from the own position obtained in this way to the newly selected satellite (104).

The correction amount calculator 6 calculates a pseudo distance R 'and a distance R
Then, a correction amount Δ is obtained from the inherent error ΔR (106). The pseudo distance R 'to the newly selected satellite is a numerical value obtained by the pseudo distance calculation unit 3, and is shown in FIG. The correction amount calculation unit 6 obtains a pseudo distance correction amount Δ by subtracting the pseudo distance R ′ (−specific error ΔR) from the distance R.

The positioning calculation unit 4 corrects the pseudo distance using the pseudo distance correction amount Δ (108). That is, the pseudo-range is corrected by adding the pseudo-range correction amount Δ to the pseudo-range sequentially obtained for the newly selected satellite. The positioning calculation section 4 performs positioning calculation using the corrected pseudorange to obtain its own position (110).

By such a correction, the own position does not change discontinuously even when the selection of the satellite is switched. That is, since the pseudo-range is corrected for the newly selected satellite so that the own position substantially matches before and after the switching, the problem of discontinuous change of the own position does not occur. This leads to the advantage that, when the GPS receiver is mounted on a fishing boat, the position of the own ship during operation can be continuously grasped.

In the above description, the case where only one satellite is newly selected when switching the selection of the satellite is considered. Usually, this is because one newly selected satellite is used. Although the own position is obtained again after the satellite is switched, the own position obtained by the previous positioning may be used in some cases. For example, when positioning is performed at one-second intervals, a low-speed ship does not move much in one second, so that the own position obtained by the previous positioning is sufficient.

Further, it is more preferable that the pseudo distance correction amount Δ is gradually reduced with time. This is because when errors included in the pseudorange of the newly selected satellite are observed in a time series, the correlation decreases as the elapsed time from the switching time increases. If the pseudo distance correction amount Δ is reduced correspondingly, the positioning accuracy becomes favorable. An exponential function or the like can be used as the decreasing curve.

[0023]

As described above, according to the present invention,
Since the pseudorange data is corrected for a newly selected satellite when the combination of satellites used for positioning changes, it is possible to prevent a discontinuous change in the own position.

Further, the positioning accuracy can be maintained and improved by decreasing the pseudo distance correction amount over time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a GPS receiver according to one embodiment of the present invention.

FIG. 3 is a flowchart showing a flow of the operation of the embodiment.

FIG. 4 is a diagram illustrating the meaning of a pseudo distance correction amount.

[Explanation of symbols]

 A satellite selection calculation unit B, 2 reception unit C, 4 positioning calculation unit D distance correction value calculation unit 3 pseudo distance measurement unit 5 distance calculation unit 6 correction amount calculation unit 7 satellite selection unit X, Y, Z, ΔR own position R Distance to newly selected satellite R 'Pseudo distance to newly selected satellite Δ Pseudo distance correction amount of newly selected satellite

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S 5/00-5/14

Claims (2)

(57) [Claims] 1. A satellite selection operation unit for selecting a predetermined number of GPS satellites to be used for positioning with a predetermined logic, outputting selected satellite information indicating a combination of the selected GPS satellites, and outputting a signal from the GPS satellite related to the selected satellite information. A receiving unit that receives and obtains a pseudo-range with each GPS satellite based on the received information and outputs the obtained pseudo-range data as a pseudo-range data; The provided GPS receiving device determines whether or not the combination of GPS satellites used for positioning has changed based on the selected satellite information. If the combination has changed, the newly selected GPS satellite is determined based on its own position before the change. A distance correction value calculation unit that calculates a pseudo distance correction amount and outputs the obtained pseudo distance correction data as pseudo distance correction data; The pseudorange data according to star corrected by pseudorange correction data, GPS receiving apparatus, characterized by calculating the current position. 2. The GPS receiving apparatus according to claim 1, wherein the pseudo distance correction amount is reduced with time.