KR20020074267A - Half Cycle Ambiguity Resolution Method for GPS, and GPS Attitude Determination System and Method using the same - Google Patents

Abstract

PURPOSE: A GPS(Global Positioning System) receiver system for attitude measurement is provided which comprises a unit capable of measuring a half cycle ambiguity of a GPS satellite signal phase for a short time, and a method is provided which measures the half cycle ambiguity rapidly by comparing GPS satellite data for attitude measurement received from at least two antennas in a bit unit. CONSTITUTION: The GPS receiver system for attitude measurement comprises at least two antennas, and a satellite signal tracking part receiving a signal from a satellite by tracking at least one GPS satellite, and a demodulator part demodulating the received satellite signal into digital data stream, and a measurement part determining a position and a speed and an attitude of a signal receiving body on the basis of the demodulated data. The GPS receiver system further comprises a half cycle ambiguity detection unit. According to the half cycle ambiguity detection unit, the first storing unit stores data bit above 1 received/demodulated from the first antenna temporarily. The second storing unit stores corresponding data bit above 1 temporarily which is received/demodulated from the second antenna and corresponds to the bits stored in the first storing unit, as to the same satellite as that received by the first antenna. A comparator unit compares the data bit stored in the first storing unit with the corresponding data bit stored in the second storing unit. And a judgement part judges a half cycle ambiguity of a received carrier wave according to the comparison result of the comparator unit.

Description

Half Cycle Ambiguity Resolution Method for GPS, and GPS Attitude Determination System and Method using the same

The present invention relates to a half-cycle ambiguity detection method in a GPS (Global Positioning System) receiver, a GPS attitude measurement system and method using the same, and more particularly, two or more GPS. The present invention relates to a GPS receiving system capable of detecting and solving half-wave ambiguity within several tens of m seconds in a GPS system for attitude measurement having a signal receiving antenna, and a method of using the same.

GPS (Global Positioning System) is a radio navigation system that can find out user's location, speed, and time information anywhere in the world using navigation satellite. In general, the field where GPS is used is mainly used to determine the absolute position of the earth using C / A (Coarse / Acquistion) or P (Precision) code by connecting one antenna to one receiver. The A code has an error of approximately 10m (2dRMS (Root Mean Square)) under the influence of SA (Selective Availability) by the US Department of Defense.

For more precise positioning, it is possible to offset the errors in SA, ionospheric delay, tropospheric delay and satellite orbits by estimating the errors contained in the measurements of each satellite at known locations (reference stations) and propagating them to other receivers around them. Differential GPS (DGPS), which can achieve accuracy of several meters or less, is also widely used.

In order to obtain a more precise position using GPS, a carrier wave phase signal may be used instead of a code signal. In the case of C / A code, the length of one chip (the interval of transmitting O or 1 in binary pulse code: 1㎲) is 300m, and if it is measured at 1% resolution, it is regarded as having a resolution of about 3m. Can be. However, one wavelength of the carrier phase (L1 band; based on 1575.42 MHz) is 19 cm, and when measured at a resolution of 1%, the wavelength is 1.9 mm, and thus the carrier phase can be used to obtain an extremely accurate position.

On the other hand, by using two or more antennas for the attitude measurement GPS receiver, in addition to providing a position measurement value using the C / A code, etc., the attitude information of the antibody using the carrier phase measurement value can be provided. If two antennas are installed in the direction of the antibody, the posture may be determined by pitch and yaw, and when three or more antennas are installed, the three-dimensional posture of the antibody may be determined. . At this time, the error of the attitude information obtained from the GPS receiver for attitude measurement is independent of the speed of the antibody, and the magnitude of the attitude error is determined only by the length of the baseline vector, the vector between the antennas, and the size of the receiver noise. The posture measuring method of the antibody using the GPS receiver for posture measurement is described in detail in Korean Patent Specification No. 1997-057696.

In the GPS receiver for attitude measurement, the Integer Ambiguity included in the double-differencing carrier wave information must first be calculated to calculate the attitude. Integer Ambuity is the initial bias of the carrier phase observed with an arbitrary number of cycles. Initial satellite observations are made when the GPS receiver first picks up the GPS signal, where the exact number of cycles between the satellite and the receiver is unknown. As a result, there is an ambiguity component for cycle integers, which is called unknown. In other words, the unknown constant refers to the sine wave (phase constant) of the carrier existing between the satellite and the receiver, and even the double difference does not eliminate the initial unknown in the carrier measurement, so it is necessary to calculate it accurately to increase the high position accuracy. .

In addition, an initial unknown constant occurs when a satellite signal is first received, and once a value is obtained, it is not necessary to obtain it again while continuously receiving a satellite signal. That is, the initial unknown may have a constant value that does not change with time, but may be treated as a random constant that changes each time a satellite signal is first received. Therefore, in the geodetic field where there is less demand to obtain the location in real time, the method of using the carrier phase has been studied early. In order to use the carrier phase to determine the pose of the antibody in the GPS system, the unknown constant included therein is determined in real time. Should be.

However, it is impossible to find an unknown integer analytically because it has more unknowns than the measured value and has an integer constraint. In addition, since convexity is not guaranteed in the integer region, the solution cannot be solved by nonlinear programming. Therefore, a method of searching an area in which an unknown integer exists is mainly used. Unlike the geodetic field, which requires precise position measurement, the problem of determining the unknown constant in the attitude measurement requires attention to the study of finding the unknown constant with one measurement because it requires real-time processing.

The unknown is determined by the search in integer condition. On-the-fly techniques based on the integer least squares method use only the carrier phase and require an estimate of the unknown in the real area. Collect and use Therefore, the shorter the collection time of the measurement value, the larger the search range of the unknown integer, and the calculation amount required for the search increases, while the longer the measurement time, the smaller the search range but the calculation amount at each search point increases. In addition, there is no consideration of satellite changes during the search for unknown integers, which makes it difficult to apply them in real time. In particular, even when the unknown signal is determined, if the satellite signal is disconnected, all unknown constants have to be obtained again.

If the length of the baseline vector is 1m and the L1 frequency is used, there are hundreds of unknown integer candidates in the search range. In this case, when the number of unknowns is large, a large amount of computation is required, and the probability of finding an incorrect unknown is also increased.

In addition, half cycle ambiguity, which is an error having half the wavelength due to phase inversion during satellite signal tracking, has to be solved. Once the half-wave ambiguity is also determined, it does not need to be solved again until the satellite signal is lost. However, as described below, the half-wave ambiguity has a problem of waiting up to about 12 seconds after the satellite signal is acquired. Therefore, in order to measure the pose of an antibody using GPS, it is a key to improve system performance not only to determine an unknown but also to solve half-wave ambiguity quickly.

In the conventional GPS system, the half-wave ambiguity solution is performed by comparing demodulated data with a known data sequence in the process of obtaining frame synchronization.

FIG. 1 illustrates a conventional half-wave ambiguity solution and requires a frame synchronization acquisition process comparing with a known preamble at the start of each subframe. That is, when the demodulated data is stored in the memory and compared with the preamble "0011001" or the inverted preamble "1100110", the inverted bit sequence is also inverted and the subframe synchronization is finally confirmed through a parity check. At the same time, half-wave ambiguity is detected. In other words, after receiving one subframe (6 seconds) data from the satellite and performing a parity check to synchronize the frame, if the preamble of the received frame is the same as the known preamble sequence, it is determined that there is no half-wave ambiguity, and inverted. If it is the same as the preamble sequence, it is determined that there is half-wave ambiguity. The half-wave ambiguity information, that is, data inversion information obtained in this process, is transmitted to the measurement value obtaining unit, and the measurement obtaining unit generates the carrier phase measurement value in consideration of the half-wave ambiguity. A method of generating a carrier phase measurement value in a GPS receiver is expressed as an equation based on a principle that calculates and integrates Doppler from a time point of tracking a carrier.

Where t ₀ is the initial time at which the carrier starts to be integrated and ICP (t ₀ ) represents the initial value of integration. In Equation 1, if the received satellite signal has no half-wave ambiguity, ICP (t ₀ ) is 0, and if there is half-wave ambiguity, it has a value of 0.5.

Once the phase ambiguity is determined, there is no need to recheck unless the tracking loop (PLL) loses phase or a cycle slip occurs, and if this occurs, the ambiguity must be checked again. In this case, when the half-wave ambiguity is rechecked, frame synchronization must be realigned. Therefore, even after acquiring a carrier, bit synchronization and frame synchronization must be obtained before the half-wave ambiguity is confirmed and the carrier phase measurement can be used for positioning. do. Therefore, the half-wave ambiguity can only be detected after at least 6 seconds (time required for subframe synchronization) has elapsed from the time at which the half-wave ambiguity needs to be judged again.

In particular, when a cycle slip occurs, even if a cycle slip is detected, a phase inversion occurs due to the cycle slip, and the measurement value can be used only when a complete frame is received. 2 illustrates a half-wave ambiguity detection process when a cycle slip occurs (t _s ) according to the conventional method. Tracking may occur. In this case, in order to obtain the inversion information again, all of the next subframe data must be demodulated, which takes a maximum time of 12 seconds (t _r ). Therefore, even if the cycle slip is detected, the measured value cannot be used for precise positioning or posture measurement for up to 12 seconds.

This problem, which takes more than 10 seconds to solve the half-wave ambiguity, is a performance degrading factor in applications that determine attitude in real time.

The present invention was conceived to overcome the shortcomings of the conventional half-wave ambiguity solution. In the GPS system for attitude measurement having two or more antennas, the same data sequence is obtained when the same satellite signal is obtained from each antenna. The basic principle is to compare the satellite data received from each antenna bit by bit using. Using this method, half-wave ambiguity can be solved within 20m seconds to hundreds of ms after satellite signal acquisition.

SUMMARY OF THE INVENTION An object of the present invention is to provide a GPS reception system for posture measurement having means for detecting half cycle ambiguity of GPS satellite signal phase for a short time of several tens of ms.

Another object of the present invention is to provide a method for quickly detecting half-wave ambiguity by comparing bitwise GPS satellite data received from two or more antennas in units of bits.

It is yet another object of the present invention to employ a method for detecting half-wave ambiguities that compares one or more data bits, whereby the position, velocity and / or position using GPS for pose measurement can be quickly determined. It provides a posture method.

1 illustrates a conventional half-wave ambiguity solution.

2 illustrates a half-wave ambiguity detection process when a cycle slip occurs (t _s ) in the conventional method.

3 is a schematic diagram showing, in block units, the entire configuration of a GPS receiving system including a half-wave ambiguity detecting means according to the present invention.

Fig. 4 shows the configuration of the half-wave ambiguity detecting means in block units according to the present invention.

5 shows a hardware configuration of a specific GPS receiver used in the present invention.

6 shows the flow of the half-wave ambiguity detection method according to the first embodiment of the present invention.

7 is a flowchart of a half-wave ambiguity detection method according to a second embodiment of the present invention.

Fig. 8 is a diagram showing the time taken to perform attitude measurement by re-determining the half-wave ambiguity and the unknown constant when the cycle slip occurs in the conventional method and the method of the present invention.

The half-wave ambiguity-detectable GPS system according to the present invention for achieving the above object has the following configuration.

Two or more antennas, a satellite signal tracker for tracking one or more GPS satellites to receive signals from the satellites, a demodulator for demodulating the received satellite signals into a digital data stream, and a signal receiver based on the demodulated data. An attitude measuring GPS receiving system comprising a measuring unit for determining position, speed, and attitude, comprising: first storage means for temporarily storing one or more data bits received and demodulated by a first antenna; Second storage means for temporarily storing one or more corresponding data bits corresponding to the bits received and demodulated in the second antenna and stored in the first storage means for the same satellite as received by the first antenna; Comparison means for comparing the data bits stored in the first storage means with the corresponding data bits stored in the second storage means; And a half-wave ambiguity detecting means comprising: means for determining half-wave ambiguity of the received carrier wave according to the comparison result of the comparison means.

The above-described half-wave ambiguity detecting means compares one or more corresponding bits of the same satellite data stream received from two spatially separated antennas to determine whether there is no half-wave ambiguity (corresponding bit matches) or ambiguity (the corresponding bit is inverted). ) Function to check.

The measurement unit gives the integral initial value as shown in Equation 1 above and integrates it from the determined half-wave ambiguity detection result and the frame-based satellite data stream, and accurately calculates the carrier phase measurement value by using Equations 3 to 5 to be described later. Calculate.

The half-wave ambiguity detection method in the GPS system according to the present invention uses the above-described system, and includes the following steps.

A bit storing step of storing, by the aforementioned half-wave ambiguity detecting means, data bits received and demodulated by the first antenna in the first storage means; A corresponding bit storing step of storing corresponding data bits corresponding to the data bits received and demodulated by the second antenna from the same satellite and stored in the first storage means in the second storage means; At the point where half-wave ambiguity detection is required, the comparing means compares the data bits stored in the first storage means with the corresponding data bits stored in the second storage means and inverts whether the bits match (if there is no half-wave ambiguity). A half-wave ambiguity detecting step of checking whether there is a half-wave ambiguity; And a result transmission step of transmitting the half-wave ambiguity detection result to the measurement unit.

In addition, the method according to the modified form of the present invention for the more precise half-wave ambiguity detection consists of the following steps.

A bit storing step of storing, by the aforementioned half-wave ambiguity detecting means, data bits received and demodulated by the first antenna in the first storage means; A corresponding bit storing step of storing corresponding data bits in the second storage means corresponding to data bits received and demodulated by the second antenna from the same satellite and stored in the first storage means; At the point where half-wave ambiguity detection is needed, the comparison means compares the bits stored in the first storage means with the corresponding bits to see if the bits match or inverts and stores the result (half-wave index value) and A result storing step; Compare the comparison result in the bit comparison and result storage step with the comparison result for the previous bit, and if the result is identical, increase the count number by one and store the bit or the bit comparison and result for the bit following the previously compared bit. A result change detection step of repeating the storing step, otherwise resetting the count number and proceeding before the bit storing step; A half-wave ambiguity detecting step of detecting half-wave ambiguity only when the count number exceeds a predetermined threshold value; And a result transmission step of transmitting the half-wave ambiguity detection result detected in the half-wave ambiguity detection step to the measurement unit.

In the modified embodiment of the present invention, when a bit error may occur due to a small satellite signal or the like, a comparison of two or more bits is performed by giving a threshold value of two or more to improve the accuracy of the half-wave ambiguity detection result. You can.

In addition, the position, velocity, and pose measurement method of the antibody using the GPS receiver system for pose measurement using the half-wave ambiguity detection method according to the present invention, using two or more antennas spaced apart from the target antibody from three or more GPS satellites Receiving and demodulating satellite signals to generate a data stream, and determining the half-wave ambiguity and unknown constants in the dual-differential carrier phase measurements using the two specified antennas and satellite signals to determine baseline vectors between one or more antennas. And determining information about one or more of the position, velocity, and pose of the antibody using the data stream and the calculated baseline vector, wherein the half-wave ambiguity determination is determined for two identical satellites. By comparing one or more corresponding data bits received and demodulated by more than one antenna It is characterized by being performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic diagram showing, in block units, the entire configuration of a GPS receiving system including a half-wave ambiguity detecting means according to the present invention.

The GPS receiving system according to the present invention is largely divided into two or more antennas 31 and 31 ', a signal tracking unit 32 and 32' for tracking one or more specific satellite signals using each antenna and receiving a signal. Half-wave ambiguity detected by demodulators 33 and 33 'for generating a data stream by demodulating the received signal, half-wave ambiguity detection means 40, and data streams and half-wave ambiguity detection means generated in the demodulator. It consists of the measuring part 34 which determines and calculates the required measurement value according to a judgment result.

The GPS receiver for posture measurement should include two or more receiving antennas spaced apart from the antibody in order to use the dual difference, and the illustrated GPS receiving system includes two antennas (antenna A 31 and antenna B 31 '). ).

The signal tracking part (32, 32 ') is a function that tracks a particular satellite according to the unique C / A code of each satellite transmitted from the satellite, the demodulator is a proper data Through processing steps, it converts into a decipherable digital data stream.

The measuring unit 34 functions to determine the position, velocity, and posture of the antibody based on the demodulated data stream and the half-wave ambiguity result detected by the present invention. It can be subdivided into a navigation solution calculator for calculating speed and time.

Each of the above-mentioned parts of the GPS receiving system may be implemented in hardware and / or software. However, in the embodiment of the present invention, hardware and software are combined and implemented as described below.

4 is a block-by-block configuration of the half-wave ambiguity detecting means according to the present invention, and includes: a first temporary buffer (storing means) 41 for temporarily storing one or more data bits received and demodulated from the first antenna; A second temporary buffer (storing means; 41 ') for storing one or more corresponding bits corresponding to (synchronized) with the bits stored in the first temporary buffer among the data received from the second antenna and demodulated; A bit comparison / storing means for comparing two bits stored in a string to see if they match (i.e., have no half-wave ambiguity) or not match (i.e., have half-wave ambiguity), and store the result as needed. (42) and the half-wave ambiguity determining means 43 for determining the half-wave ambiguity in accordance with the comparison result of the bit comparison / storing means.

Each means constituting the half-wave ambiguity detecting means may be implemented using appropriate software installed in a GPS receiver (FIG. 5) to be described later, and hardware such as a central processing unit and a memory.

5 shows a hardware configuration of a specific GPS receiver used in the present invention.

Attitude GPS receiver is divided into hardware part and software part. The hardware part is divided into RF part, correlator part, central processing part and so on, and the software part can be divided into satellite tracking part, measurement acquisition part, navigation analysis part, and posture measuring part. As shown in Fig. 6, the hardware section of the GPS receiver includes a correlator section comprising two or more antennas (four in the figure), four RF / IF sections, four DSPs for attitude measurement, It is divided into central processing unit, memory unit and input / output unit.

Each RF / IF unit uses Mitel GP2010. 10 MHz of TCXO (Temperature Compensated Crystal Oscillator) was used as a reference clock. The RF / IF unit provides an operating frequency (40 MHz) to the correlator units DSP1, DSP2, DSP3, and DSP4 in a differential form, receives the GPS satellite signals from four antennas, and multiplies the frequency three times to create an IF signal. Also, the discrete output signals (MAG, SIGN) are sent to the correlator by using the sample clock (5.714MHz) provided by each DSP of the correlator.

The correlator base consists of four GP2021s from Mitel. GP2021 includes twelve channels of tracking modules, each of which uses a discrete signal from the RF / IF unit to generate correlation values and track satellite signals. The use of four DSPs enables signal tracking on 48 channels simultaneously and allows acquisition of code and carrier measurements.

The central processor used StrongARM (model name: SA-1100), which is an ARM CPU. StrongARM has a built-in DUART, memory management unit (MMU) and cache for communication with the outside of the receiver, and has a processing speed of about 268 MIPS when using a 220MHz crystal oscillator. The central processing unit calculates the navigation solution and performs the posture measurement using the measured values obtained from the correlator.

The memory part consists of ROM / RAM, and the ROM has a capacity of 512KByte using 4 1Mbits and the RAM has a capacity of 2Mbytes using 4 4Mbits.

The input / output section consists of two asynchronous communication ports and one synchronous communication port. The asynchronous communication port is for communicating with the receiver monitor and command and receiving DGPS signals, and the synchronous communication port is for communicating with other sensors such as IMU.

Such a GPS reception system may be implemented in a form different from that shown, and may be any hardware provided with hardware or software capable of utilizing the half-wave ambiguity detection method according to the present invention.

Hereinafter, the half-wave ambiguity detection method according to the present invention will be described in detail.

The GPS receiver for attitude measurement is provided with two or more antennas spaced apart from the antibody, and each antenna can track the same satellite signal. In this case, data received and demodulated from each antenna is expected to be the same as long as there is no error in reception and demodulation, and thus it is possible to provide bit information to each other.

As can be seen in Figure 4, the data signal received at the first antenna is used as the reference data, provided that the satellite signal is received from two antennas that are relatively close to a few meters to several tens of meters, and at the second antenna The basic principle is to determine the half-wave ambiguity by comparing the received data bit by bit.

FIG. 6 illustrates a flow of the half-wave ambiguity detection method according to the first embodiment of the present invention, and is implemented to determine half-wave ambiguity by comparing only one corresponding bit based on the above-described basic principle.

After receiving and demodulating satellite signals by tracking the same satellite in the first antenna and the second antenna (S61), data bits from the first antenna are extracted and stored in the first temporary buffer, and among the data from the second antenna. The corresponding bit is extracted and stored in the second temporary buffer (S62 and S62 ').

After comparing the two bits by the bit comparison means (S63), if the two bits are the same, the HC (Half Cycle) index is set to 0 (S65), otherwise, the HC index is set to 0.5 (S66). The half-wave ambiguity determining means detects whether there is half-wave ambiguity (with data inversion; HC index = 0.5) and whether there is no half-wave ambiguity (without data inversion; HC index = 0) according to the set HC index value. After that (S67), the result is transmitted to the measurement unit (S68).

In this method, only the relative inversion of the reference data (data from the first antenna) can be known and only half-wave ambiguity is known, but this is not a problem in attitude measurement using the dual differential carrier phase measurement. This will be described in detail in the description of the test results of the present invention.

Carrier phase measurement equation used for the attitude measurement using GPS is represented by the following equation (2). This carrier phase measurement includes the half-wave ambiguity detection result.

Where r is the actual distance between the satellite and the receiver, B is the clock error, c is the speed of the GPS carrier, N is the magnitude of the GPS carrier wavelength, N is the integer ambiguity, and HC is the half-wave ambiguity index value. Have Is the pseudorange measurement error due to ionospheric delay, Is the pseudorange measurement error due to tropospheric delay, Denotes pseudorange measurement error due to satellite orbit error, δm represents pseudorange measurement error due to multipath, and ω denotes measurement noise.

Double difference of the carrier phase measurement (Double Differencing) is the difference between the receiver and the difference between the satellites are shown in equations (3) to (5), respectively.

Where the subscript is the antenna identifier and the superscript is the satellite identifier. In Equation 3 and Equation 4 And Has a value of 0, 0.5 or -0.5. That is, if the two measurements have no phase reversal or both occur, 0, or if one of the two satellites is reversed, it will have a value of 0.5 or -0.5. and Still has an integer value.

Similarly, in double difference measurements Has the value -1, -0.5, 0, 0.5 or 1 Will still have an integer value. Therefore, whether the data is inverted with respect to the first antenna used as a reference has no effect on detecting the half-wave ambiguity in the GPS receiver for attitude measurement.

In summary, in the method proposed in the present invention, when multiple antennas are used and each antenna tracks the same satellite, the half-wave ambiguity is compared by comparing the demodulated satellite data received by two or more antennas in bit units. Detecting is the basic principle. That is, when the antennas A and B receive the signal of the satellite i, the demodulated data streams are compared bit by bit, and when the first bit of the half-wave ambiguity determination process is matched, the HC index is set to 0 and different from each other. In this case, the HC index is set to 0.5. Therefore, under the assumption that there is no bit error in the satellite signal, only one bit of the data stream of the same satellite received from two or more antennas is compared, and if the HC index is 0, it is determined that there is no half-wave ambiguity, and the HC index is 0.5. It can be judged that half-wave ambiguity exists.

Once the half-wave ambiguity (data inversion) is detected, the received data along with the ambiguity detection result is passed to the measurement part, and the measurement unit calculates the carrier phase measurement value using the detected half-wave ambiguity information. do.

However, in special cases, such as when the elevation angle of the satellite is small, a bit error may occur due to a small signal strength. Therefore, when ambiguity is determined by comparing only one bit, an ambiguity result is obtained when there is an error in the detected bit information. An error may occur.

In order to solve this problem, a second embodiment of the present invention as shown in Fig. 7 is provided, the basic principle of which is to compare two or more data bits sequentially input to confirm whether the detected half-wave ambiguity is maintained. It is. That is, the half-wave ambiguity, once solved, uses a characteristic that does not change while maintaining the signal.

FIG. 7 is a flowchart of a method according to a second embodiment of the present invention for accurately detecting half-wave ambiguity by comparing T bits of data, the user-defined threshold value.

After receiving and demodulating satellite signals by tracking the same satellite in the first antenna and the second antenna (S71), data bits from the first antenna are extracted and stored in the first temporary buffer, and among the data from the second antenna. The corresponding bit is extracted and stored in the second temporary buffer (S72 and S72 ').

After comparing the two bits by the bit comparison means (S73), if the two bits are the same, the current HC (Half Cycle) index is set to 0 and stored (S75), otherwise, the current HC index is set to 0.5. Save (S75 ').

Compare the current HC index with the HC index (previous HC index) for the previous bit (S76), and if it is the same, the previous data inversion (i.e. half-wave ambiguity) is still maintained. Increment one (S77), otherwise reset the count value to zero (S82). That is, when the previous HC index and the current HC index are different, the cycle slip or the bit error occurs, so that a matched half-wave ambiguity detection result cannot be derived. Therefore, the half-wave ambiguity detection process is performed again from the beginning.

If the previous HC index and the current HC index are the same, since 2 bits of data inversion is coincident, the count value is increased and the previous HC index value is updated with the current HC index value extracted and stored (S78). It is determined whether the count value exceeds the threshold value T (S79). If the count value is less than or equal to the threshold value, additional data reversal confirmation is required. Therefore, the process proceeds to the previous signal tracking step and continues the comparison of subsequent data bits.

Thus, for half-wave ambiguity detection, for the first bit of data to be compared, the comparison with the previous HC index is omitted, the count is increased immediately, and then the comparison is made for subsequent data bits. In the subsequent comparison of the second bit, the HC index comparison step S76 is performed by using the HC index for the first bit stored as the previous HC index.

If the count value exceeds a predetermined threshold, it is determined that data inversion is sufficiently confirmed (S80), the half-wave ambiguity detection is completed, and the result is transmitted to the measurement unit (S81).

That is, since half-wave ambiguity detection is not perfect when there is an error in one data bit, by setting the threshold value T and the initial value of count appropriately, it is possible to confirm whether data is inverted for two or more bits. Is the feature of the second embodiment.

The threshold T, which can be arbitrarily determined by the user, is a value that determines the number of data bits to be compared. If the threshold value is small, the time required to detect half-wave ambiguity is shortened, but the inaccuracy due to bit error increases. The larger the value, the longer the half-wave ambiguity detection time is, but the accuracy of the half-wave ambiguity detection result is higher. Therefore, the threshold can be appropriately adjusted according to the required half-wave ambiguity detection time and accuracy.

In order to verify the effect of the half-wave ambiguity detection method according to the present invention, the half-wave ambiguity detection was carried out using the conventional method and the method according to the present invention, respectively, and the results were confirmed to be identical.

To this end, half-wave ambiguity was detected for six satellites (the number of traced SV (Satellite Vechile) is 22, 29, 20, 30, 25, 6), and the results are shown in Tables 1 and 2.

Table 1 below shows the half-wave ambiguity detection result performed by the conventional method, and Table 2 shows the result performed by the method according to the present invention with respect to the same satellite.

Satellite Number (SV) Half Cycle Index Antenna A Antenna B 22 0.5 0.5 29 0.5 0,5 20 0.5 0 30 0.5 0.5 25 0.5 0.5 6 0 0.5

Satellite Number (SV) Half Cycle Index Antenna A Antenna B 22 0 0 29 0 0 20 0 0.5 30 0 0 25 0 0 6 0 0.5

As shown in Table 1, the data from antenna A is inverted except for SV6, and the data from antenna B is inverted except for SV20. It can be seen that the HC index value (Table 2) performed by the method according to the present invention is different from the value according to the conventional method (Table 1). In the present invention, the data from the antenna A is referred to as reference data. This is because the indexes are all set to 0, and as a result, phase reversal occurs only in SV6 and SV20. In addition, even in the results according to the conventional method (Table 1), it can be seen that SV having half-wave ambiguity between antennas A and B is the same as the result according to the present invention as SV6 and SV20.

Although the results of the conventional method and the method according to the present invention show different results, as will be discussed in connection with Tables 3 and 4 below, a correction combined with an unknown integer in a posture GPS system using Double Differencing is performed. In both cases, the same result is achieved.

Table 3 below shows Integer Ambiguity due to double difference.

Satellite Number (SV) Double difference unknown (N) Conventional method Invention method 22,29 -4 -4 29,20 -3 -2 20,30 One 0 30,25 One One 25,6 3 3

According to Table 3, it can be seen that the value of the double difference unknown constant obtained using the method according to the present invention is different from that obtained by the conventional method. However, this difference is only caused by the difference in half-wavelength index. Therefore, the resulting correction, i.e., the sum of the half-wave ambiguity result and the unknown, Has the same value in the conventional method and the method of the present invention, as shown in Table 4 below.

Satellite Number (SV) Conventional method Invention method N + HC N HC N HC 22,29 -4 0 -4 0 -4 29,20 -3 0.5 -2 -0.5 -2.5 20,30 One -0.5 0 0.5 0.5 30,25 One 0 One 0 One 25,6 3 -0.5 3 -0.5 2.5

The following test is to determine the time taken to perform the posture measurement by re-determining the half-wave ambiguity and the unknown constant when the cycle slip occurs in the conventional method and the method of the present invention. The following experiments were carried out by Van test, and posture measurements were obtained by post-processing. Six or more satellites were tracked during the test and were based on yaw information from the attitude information.

As shown in FIG. 8, when cycle slip occurs in the sixth epoch, the posture measured by the conventional method is the 25th epoch, and the total 19 epochs are determined for half-wave ambiguity and unknown constant after the cycle slip occurs. On the other hand, when the method according to the present invention is used, the posture measurement is completed at the 12th epoch, and it can be seen that only 6 epochs are required.

Indeed, when the method of the present invention is used, half-wave ambiguity is detected and resolved at the epoch immediately after the cycle slip has occurred, and the remaining time (5 epochs) is spent in determining an undefined integer. Therefore, in the above two cases, if the same unknown constant determination method is used, the half-wave ambiguity detection by the conventional method takes about 14 epochs, whereas in the present invention, only one epoch is required, so that the half-wave is much faster It can be seen that ambiguity could be detected and resolved.

Claims (7)

Two or more antennas, a satellite signal tracker for tracking one or more GPS satellites to receive signals from the satellites, a demodulator for demodulating the received satellite signals into a digital data stream, and a signal receiver based on the demodulated data. A GPS reception system for attitude measurement, comprising a measurement unit for determining position, speed, and attitude, First storage means for temporarily storing one or more data bits received and demodulated by the first antenna; Second storage means for temporarily storing one or more corresponding data bits corresponding to the bits received and demodulated in the second antenna and stored in the first storage means for the same satellite as received by the first antenna; Comparison means for comparing the data bits stored in the first storage means with the corresponding data bits stored in the second storage means; Determination means for determining the half-wave ambiguity of the received carrier wave (carrier wave) according to the comparison result of the comparison means; GPS receiving system for attitude measurement, further comprising a half-wave ambiguity detection means. Two or more antennas; A satellite signal tracking unit for tracking one or more GPS satellites and receiving a signal from the satellites; A demodulator for demodulating the received satellite signal into a digital data stream; A measuring unit determining a position, a speed, and an attitude of the signal receiver based on the demodulated data; And a half-wave ambiguity detecting means comprising first and second data bit storing means, a data bit comparing means, and a half-wave ambiguity determining means, comprising: a half-wave ambiguity detecting method using a GPS receiver system for posture measurement; By the half-wave ambiguity detecting means, A bit storing step of storing the data bits received and demodulated by the first antenna in the first storage means; A corresponding bit storing step of storing corresponding data bits corresponding to the data bits received and demodulated by the second antenna from the same satellite and stored in the first storage means in the second storage means; At the point where half-wave ambiguity detection is required, the comparing means compares the data bits stored in the first storage means with the corresponding data bits stored in the second storage means to see if the bits match (if there is no half-wave ambiguity). A half-wave ambiguity detecting step of checking whether there is inversion (if there is half-wave ambiguity); And, And a result transmission step of transmitting a half-wave ambiguity detection result to the measurement unit. The method of claim 2, If the bits match in the half-wave ambiguity detection step, the half-wave ambiguity index Is set to 0, and if it does not match Set to -0.5 or 0.5, In the measurement unit, a double-differencing carrier phase measurement value ( ) Is a half-wave ambiguity detection method of the GPS system for posture measurement, characterized by obtaining the following equation. The subscript is the antenna identifier, the superscript is the satellite identifier, r is the actual distance between the satellite and the receiver, B is the clock error, c is the speed of light, GPS is the magnitude of the GPS carrier wavelength, N is Integer Ambiguity, and HC is half The wavelength ambiguity index value, δm, is pseudorange measurement error due to multipath, and ω is measurement noise. Two or more antennas; A satellite signal tracking unit for tracking one or more GPS satellites and receiving a signal from the satellites; A demodulator for demodulating the received satellite signal into a digital data stream; A measuring unit determining a position, a speed, and an attitude of the signal receiver based on the demodulated data; And a half-wave ambiguity detecting means comprising first and second data bit storing means, a data bit comparing means, and a half-wave ambiguity determining means, comprising: a half-wave ambiguity detecting method using a GPS receiver system for posture measurement; By the half-wave ambiguity detecting means, A bit storing step of storing the data bits received and demodulated by the first antenna in the first storage means; A corresponding bit storing step of storing corresponding data bits corresponding to the data bits received and demodulated by the second antenna from the same satellite and stored in the first storage means in the second storage means; At the point where half-wave ambiguity detection is needed, the comparison means compares the bits stored in the first storage means with the corresponding bits to check whether the bits match or invert and store the result (half-wave index value) accordingly. And storing the result; Compare the comparison result in the bit comparison and result storage step with the comparison result for the previous bit, and if the result matches, increase the count number by one, and store the bit to the bit comparison step for the bit following the compared bit. A result change detecting step of repeating the result storing step, otherwise resetting the count number and proceeding before the bit storing step; A half-wave ambiguity detecting step of detecting half-wave ambiguity only when the count number exceeds a predetermined threshold value; And a result transmission step of transmitting the half-wave ambiguity detection result detected in the half-wave ambiguity detection step to a measurement unit. The method of claim 4, wherein Half-wave ambiguity index when the bits match in the bit comparison and result storage Is set to 0, and if it does not match Set to -0.5 or 0.5, In the measurement unit, a double-differencing carrier phase measurement value ( ) Is a half-wave ambiguity detection method of the GPS system for posture measurement, characterized by obtaining the following equation. The subscript is the antenna identifier, the superscript is the satellite identifier, r is the actual distance between the satellite and the receiver, B is the clock error, c is the speed of light, GPS is the magnitude of the GPS carrier wavelength, N is Integer Ambiguity, and HC is half The wavelength ambiguity index value, δm, is pseudorange measurement error due to multipath, and ω is measurement noise. Receiving and demodulating satellite signals from three or more GPS satellites using two or more antennas spaced apart from the subject antibody to generate a data stream; Calculating baseline vectors between one or more antennas by determining half-wave ambiguities and unknown constants in the dual differential carrier phase measurements using the signals of the two specified antennas and satellites; Determining information on at least one of the position, velocity, and position of the antibody using the data stream and the calculated baseline vector; In The half-wave ambiguity determination is performed by comparing one or more corresponding data bits received and demodulated by two or more antennas with respect to the same satellite, and the position, velocity, and attitude measuring method of the antibody using the GPS receiver system for attitude measurement. . The method of claim 6, A half-wave ambiguity index if the bits match, as a result of comparing the one or more corresponding data bits Is set to 0, and if it does not match Set to -0.5 or 0.5, The double-differencing carrier phase measurement ( ), The position, velocity, and posture measuring method of an antibody using a GPS receiver system for posture measurement, characterized by obtaining the following equation. The subscript is the antenna identifier, the superscript is the satellite identifier, r is the actual distance between the satellite and the receiver, B is the clock error, c is the speed of light, GPS is the magnitude of the GPS carrier wavelength, N is Integer Ambiguity, and HC is half The wavelength ambiguity index value, δm, is pseudorange measurement error due to multipath, and ω is measurement noise.