KR20110129561A

KR20110129561A - Method for correcting error of gps

Info

Publication number: KR20110129561A
Application number: KR1020100049004A
Authority: KR
Inventors: 윤병윤
Original assignee: 한국단자공업 주식회사
Priority date: 2010-05-26
Filing date: 2010-05-26
Publication date: 2011-12-02

Abstract

The present invention discloses a method of improving a GPS error by selecting a satellite existing in a visible region among a plurality of GPS satellites and using the satellite signal.
The present invention receives satellite signals transmitted from a plurality of GPS satellites, and calculates information including elevation, azimuth, and carrier-to-noise ratio (C / No) for each GPS satellite from the received satellite signals. In addition, the present invention provides a GPS error improvement method for selecting GPS satellites present in the visible region using the calculated information and processing the signals using satellite signals transmitted from the selected GPS satellites.

Description

How to improve GPS error {METHOD FOR CORRECTING ERROR OF GPS}

The present invention relates to a method for improving an error of a global positioning system (hereinafter, referred to as a GPS), and in particular, by selecting satellites in a visible region among a plurality of GPS satellites and using satellite signals of the selected satellites. The present invention relates to a method for improving GPS error.

The development of GPS using satellites has begun under the leadership of the US Department of Defense and consists of a satellite group, a ground control group and a user group that monitor and control satellites. The satellite group consists of 24 NAVSTAR (navigation satellite timing and ranging) satellites and is distributed like an atomic model in six circular orbits over 20,200 km of Earth.

GPS is applied in a wide range of fields from simple location information to automatic navigation and traffic control of aircraft, ships and automobiles, collision prevention of oil tankers, precise surveying of large-scale civil engineering works, and mapping. It is developed variously. Such GPS is implemented in a module form and mounted on various devices.

The GPS module, including the GPS receiver, can measure the exact time and distance from three or more satellites and accurately calculate the current position according to triangulation methods of three different distances. Nowadays, it is widely used to obtain distance and time information from three satellites and to correct the error with one satellite. In addition, GPS can obtain accurate time with latitude, longitude, and altitude as well as three-dimensional speed information.

Since the conventional GPS module includes a lot of errors by itself, it must be canceled or minimized. The errors of the GPS module can be classified into satellite-related errors such as satellite orbit and satellite time errors, receiver-related errors such as receiver noise and multipath, and propagation errors caused by the troposphere and ionospheric layers. Most of these errors can be canceled or minimized by differential methods or mathematical algorithms, but multipath is almost impossible to eliminate mathematically because it changes with the environment of the GPS module.

1 is an exemplary view showing a multipath of a general GPS module.

Referring to FIG. 1, a satellite signal transmitted from a GPS satellite received by the GPS module 10 is received. These satellite signals are received through various paths 12 to 15. These multipaths 12-15 are due to the reflection of satellite signals, for example, in towers, buildings, trees, the surface of the water, the earth's surface, etc., which cause interference with each other and cause GPS errors. Ideally, the GPS module 10 receives a straight signal transmitted directly from the GPS satellites, such as the satellite signal 12, but the actual surrounding environment is inevitably caused by multipaths 12 to 15 by the satellite signal of the reflected signal. It is true.

However, since the surrounding environment of the GPS module 10 continuously changes according to the movement of the vehicle 11 or the portable terminal in which the conventional GPS module 10 is mounted, the GPS error caused by the multipath is continuously generated. I have a problem.

Therefore, there is a continuing need in the art to develop a technology that can improve the GPS error due to multipath by minimizing the influence of the reflected signal in the GPS module.

The present invention is proposed to solve the above problems of the prior art, GPS error by selecting a satellite in the visible region when viewed from the GPS module of the plurality of GPS satellites and using only the satellite signal transmitted from the selected satellite It is an object of the present invention to provide a method for improving the GPS error that can be improved.

Another object of the present invention is to provide a GPS error improvement method for selecting at least four GPS satellites according to altitude, azimuth, and C / No calculated from a plurality of GPS satellite signals and using satellite signals from the GPS satellites. There is this.

The present invention for achieving the above object,

Receiving satellite signals transmitted from a plurality of GPS satellites, respectively; Calculating information including elevation, azimuth, and carrier-to-noise ratio (C / No) for each GPS satellite from the received satellite signals; Selecting GPS satellites in a visible region by using the calculated information; And it provides a GPS error improvement method comprising the step of processing the signal using the satellite signal transmitted from the selected GPS satellite.

In an embodiment of the present disclosure, the selecting of the GPS satellites existing in the visible region may include selecting at least four GPS satellites in which the altitude, azimuth, and carrier noise ratio (C / No) are respectively within a preset reference range. It is preferable.

In an embodiment of the present disclosure, the signal processing may include performing positioning using satellite signals transmitted from the selected GPS satellite signals.

In an embodiment of the present invention, the reference range for the azimuth angle is preferably determined to be outside the azimuth range of an obstacle located between the GPS module receiving the satellite signal and the GPS satellite transmitting the satellite signal.

According to the present invention, the GPS satellites in the visible area are selected from a plurality of GPS satellites in the sky, and the GPS satellite signals are multipathed by performing positioning using the satellite signal of the straight signal received from the satellites. Can improve the measurement error.

1 is an exemplary view showing a multipath of a general GPS module.
2 is an exemplary view illustrating GPS satellites in a visible region and an invisible region according to an embodiment of the present invention.
3 is a block diagram of a GPS module according to an embodiment of the present invention.
4 is a view showing a view of a GPS satellite received according to an embodiment of the present invention.
5 is a diagram illustrating information of a GPS satellite signal according to an experimental example of the present invention.
6 is a flowchart illustrating a GPS error improving method according to an exemplary embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

2 is an exemplary view illustrating GPS satellites in a visible region and an invisible region according to an embodiment of the present invention.

Referring to FIG. 2, a number of GPS satellites exist over the earth. Of course, there are 24 GPS satellites, but in the present embodiment, only four satellites 110 to 140 are shown for convenience of description. The GPS module 150 according to the present invention is mounted on a movable means 160 such as a vehicle, a ship, a mobile communication terminal, and receives a GPS satellite signal transmitted from a plurality of GPS satellites 110 to 140 through signal processing. Perform various functions such as positioning. To this end, the GPS module 150 includes a GPS receiver (not shown) for receiving a GPS satellite signal therein.

In the present invention, GPS satellites are divided into two types. That is, it may be classified into a GPS satellite existing in the visible region and a GPS satellite existing in the invisible region. In this case, the visible area refers to an open-sky area that is directly open to the GPS module 130 without being obstructed by the obstacles 170 and 180, and the invisible area is directly due to the obstacles 170 and 180. It means the area of Non Open-Sky which is not open to be seen.

Thus, in the example of FIG. 2, the GPS satellites 110 and 120 on the left are in the visible region when viewed from the GPS module 150 and the GPS satellites 130 and 140 on the right are due to the obstacle 180 when viewed from the GPS module 150. It exists in the invisible region. The obstacles 170 and 180 may be in various forms such as buildings, towers, forests, and the like.

In this case, the GPS module 150 may directly receive satellite signals from the two GPS satellites 110 and 120 on the left side, and may not directly receive the satellite signals from the two GPS satellites 130 and 140 on the right side to receive the reflected signal. . Therefore, the satellite signals of the left GPS satellites 110 and 120 received by the GPS module 150 are straight signals and the satellite signals of the right GPS satellites 130 and 140 are reflected signals. As the GPS satellites in the invisible region, such as the GPS satellites 130 and 140 on the right side, the more signals are reflected, the more multipaths are generated. In this case, the signal delay and error are caused by the reflection and interference of the satellite signals. Will occur. Therefore, the GPS error may be reduced by using the satellite signal of the straight signal such as the GPS satellite 220.230 existing on the left side.

The present invention utilizes this principle to improve the GPS error by selecting the GPS satellites present in the visible region and using only the satellite signal of the straight signal received from the satellites.

3 is a block diagram of a GPS module according to an embodiment of the present invention.

Referring to FIG. 3, the GPS module 150 according to the present invention includes a GPS receiver 151, an information extractor 152, a satellite selector 153, a signal processor 154, and a controller 155.

The GPS receiver 151 receives GPS satellite signals transmitted from a plurality of GPS satellites, converts them into IF signals, and converts the converted IF signals into baseband signals.

The information extracting unit 152 calculates a carrier-to-noise ratio (C / No: Carrier to Noise Ratio) for each GPS satellite by using a correlation between the converted baseband signal and a preset reference code. In addition, the information extracting unit 152 calculates an elevation and azimuth for each GPS satellite from the received GPS satellite signal. These altitudes and azimuths are calculated from satellite signals using known calculation algorithms.

The satellite selector 153 selects the GPS satellites present in the visible region by using the altitude, azimuth, and carrier-to-noise ratio (C / No) information for each GPS satellite calculated by the information extractor 152. For example, at least four GPS satellites having an altitude of 50 degrees or more, an azimuth angle of 120 degrees or more, and a carrier-to-noise ratio of 35 dB / kHz or more are selected. The numerical values of the altitude, azimuth, and carrier-to-noise ratio, which are the selection criteria, are used to screen the GPS satellites present in the visible region as in the experimental example described later.

The signal processor 154 performs signal processing using satellite signals transmitted from the selected GPS satellites. Such signal processing includes not only inherent functions such as GPS positioning, but also application functions such as auto navigation and traffic control of cars, collision prevention of oil tankers, and precision surveying of large civil works.

The controller 155 controls the overall operation and function of the GPS module 150. In particular, in the present invention, the controller 155 may control the GPS receiver 151, the information extractor 152, the satellite selector 153, and the signal processor 154 to improve the GPS error through organic operations. Make sure

4 is a view showing a view of a GPS satellite received according to an embodiment of the present invention.

Referring to the view of the GPS satellites according to the embodiment of the present invention shown in FIG. Shows the value for. In the drawing, the reference point means a point where the GPS module 150 meets when drawing a virtual extension line in the vertical direction.

Such a view may be implemented by analyzing a GPS satellite signal currently received by the GPS module 150 using a predetermined program. In addition, the GPS module 150 may drive a known algorithm to extract satellite number, altitude, azimuth, and carrier-to-noise ratio information for each satellite from the satellite signal.

5 is a diagram illustrating information of a GPS satellite signal according to an experimental example of the present invention.

In the experimental example of FIG. 5, a total of 10 GPS satellites are extracted from information, and five GPS satellites exist within the visible range, and the remaining five GPS satellites are installed in an invisible region by installing artificial obstacles at an azimuth of 30 to 50 degrees. To exist. Therefore, satellite number, altitude, azimuth, and C / No information were extracted using satellite signals received for each GPS satellite.

The information thus extracted is shown in Table 1 below.

Satellite ID Elevation Azimuth Carrier-to-Noise Ratio (C / No) 27 72 153 49 09 61 178 21 15 55 040 50 24 54 213 50 21 51 271 50 18 43 311 46 05 22 114 30 26 16 258 37 22 10 303 32 28 07 048 37 10 03 117 14

Referring to FIG. 5 and Table 1, the satellite number (ID), elevation, azimuth, and carrier-to-noise ratio (C / No) are different for each GPS satellite, which is the time since the GPS satellite and the GPS move. The values change accordingly. In Table 1, for satellite 27, altitude is 72 degrees, azimuth is 153 degrees, and C / No is 49No / ㎐.

At this time, it is necessary to set a reference range of altitude, azimuth, and carrier-to-noise ratio (C / No) in order to select five GPS satellites existing in the visible region. As described above, this reference range should be determined according to the surrounding environment in which the GPS module 150 is located. In other words, if there is an obstacle such as a building in the vicinity, the range beyond the azimuth of the obstacle should be determined as the visible area. The higher the altitude, the better, and the higher the C / No, the better.

In this experiment, the installed obstacles have an azimuth of 30 to 50 degrees, so GPS satellites with an altitude of 50 degrees or more, azimuths of 0 to 30 degrees and 60 to 360 degrees, and C / No of 35 dB / ㏈ or more are selected. Therefore, as can be seen in Table 1, satellites satisfying this condition are satellite numbers 27, 24, 21 and 18, and these four GPS satellites are satellites in the visible range.

6 is a flowchart illustrating a GPS error improving method according to an exemplary embodiment of the present invention.

Looking at the GPS error improvement method according to the present invention with reference to FIG. 6, first, the GPS module 150 receives satellite signals from a plurality of GPS satellites in the air (S101). Subsequently, information including elevation, azimuth, and carrier-to-noise ratio (C / No) is extracted from each received satellite signal (S102).

Subsequently, GPS satellites existing in the visible region are selected using the extracted information as described above (S103). Here, since the higher the altitude, azimuth, and carrier noise ratios of the GPS satellites, the higher the probability of being present in the visible region, it is preferable to select a GPS satellite whose altitude, azimuth, and carrier noise ratios are larger than a preset reference value. It would be desirable to decide according to the surrounding environment. For example, in urban buildings, altitudes of 50 degrees or more, carrier-to-noise ratios (C / No) of 35 dB / ㏈ or more, and azimuth are determined according to the location of the building to select GPS satellites. At this time, at least four GPS satellites are selected to select at least three GPS satellites for positioning of the GPS module 150 and one satellite for error correction.

Thereafter, signal processing such as positioning is performed using the satellite signals received from the GPS satellites selected as described above (S104).

While the invention has been shown and described with reference to certain preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the appended claims, The genius will be so self-evident. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

110,120,130,140: GPS satellite 150: GPS module
151: GPS receiver 152: information extraction unit
153: satellite selection unit 154: signal processing unit
160: means of movement 170,180: obstacles

Claims

Receiving satellite signals transmitted from a plurality of GPS satellites, respectively;
Calculating information including elevation, azimuth, and carrier-to-noise ratio (C / No) for each GPS satellite from the received satellite signals;
Selecting GPS satellites in a visible region by using the calculated information; And
Signal processing using the satellite signals transmitted from the selected GPS satellites; GPS error improvement method comprising a.

The method of claim 1,
Selecting a GPS satellite existing in the visible region,
And at least four GPS satellites in which the altitude, azimuth, and carrier-to-noise ratio (C / No) are within a preset reference range, respectively.

The method of claim 2,
The signal processing step,
GPS positioning method comprising the step of performing the positioning using the satellite signal transmitted from the selected GPS satellite signal.

The method of claim 2,
The reference range for the azimuth angle is determined to be out of the azimuth range of the obstacle located between the GPS module receiving the satellite signal and the GPS satellite transmitting the satellite signal.