JP2001074824A - Apparatus for monitoring cycle slip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge whether a cycle slip is generated or not by a method wherein a positioned result at an integer-value bias which is found previously is compared with a positioned result at an integer-value bias which is found recently and a display content which expresses the decision state of an integer-value bias is changed according to the difference between both. SOLUTION: A reference antenna 10 is connected to a reference-antenna reception circuit 11, and a measuring antenna 20 is connected to a measuring- antenna reception circuit 21. A processor 24 outputs, through an interface 25, data on the carrier phases of respective satellites in the position of the antenna 20. A processor 14 receives the data through an interface 15. When the satelites in the number whose integer-value bias can be decided are tracked at present, an integer-value-bias decision-state display means uses one out of them as a reference satellite, and it finds the observed double phase difference between the carrier phases regarding a set of other satellites. Then, regarding a set of two satellites each, the integer-value bias of every double phase difference is found. Then, the difference between every double-phase integer-value bias which is found previously and every double-phase integer-value bias which is found recently is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device for receiving a radio wave transmitted from a positioning satellite such as a GPS satellite and performing positioning of a receiving point and for monitoring a cycle slip.

[0002]

2. Description of the Related Art Conventionally, in GPS, when high positioning accuracy that cannot be obtained by independent positioning is required,
Interference positioning using the carrier phase is performed. In particular, real-time kinematic positioning (hereinafter referred to as RTK) for performing interference positioning in real time is performed. This RT
If the K method is used, positioning can be performed in real time with positioning accuracy on the order of cm, so that it is used for various purposes in fields other than surveying. For example, by arranging a reference antenna and a measurement antenna at a predetermined position on a ship, and by measuring the relative position of the measurement antenna with respect to the position of the reference antenna, the direction of the measurement antenna viewed from the reference antenna is obtained, thereby measuring the heading. Things have also been done.

In this RTK positioning, first, a difference (single phase difference) between a carrier phase of a reference satellite observed by a reference antenna and a carrier phase of a reference satellite observed by a measurement antenna is obtained, and observation is performed by the reference antenna. The difference (single phase difference) between the carrier phase of another satellite and the carrier phase of those satellites observed by the measurement antenna is determined, and the difference between them (double phase difference) is determined. Then, based on these double phase differences and the positions of the satellites, an equation is set with the position of the receiving point as an unknown number, and the equation is solved to find the position of the receiving point. However, the above-mentioned double phase difference is only obtained correctly only for the value after the decimal point of the carrier phase,
The amount of clogging (integer value bias) of the integer wavelength is initially unknown. Therefore, an initialization process for obtaining an integer value bias of the carrier phase called OTF is performed, and thereafter, the position of the receiving point is obtained based on the value of the integer part and the value of the decimal part of the double phase difference.

[0004]

However, in such interference positioning, reception may be momentarily interrupted due to the influence of obstacles, multiple reflections, and noise radio waves on satellite radio waves. Even if the interruption is instantaneous interruption of 0.1 seconds or less, the carrier phase locked loop of the receiver loses synchronization,
Information about the increase / decrease of the integer part of the carrier wave number is lost. This state is a cycle slip.

Therefore, conventionally, after the integer value bias of the carrier phase is determined, the difference (residual) between the double phase difference (observed) used for positioning and the double phase difference calculated backward from the positioning result. The magnitude was constantly checked, and when the residual exceeded a certain threshold, it was assumed that a cycle slip had occurred.

However, in a situation where only two satellites other than the reference satellite can be received, only one receiving point is obtained and no residual occurs, so that it is not possible to determine whether or not a cycle slip has occurred. Was.

Further, even in a situation where a residual is required,
It was not possible to unambiguously determine when the residual was considered to have caused a cycle slip, and in some cases it was difficult to determine.

An object of the present invention is to provide a cycle slip monitoring device which can easily determine whether or not a cycle slip has occurred.

[0009]

According to the present invention, regardless of the relative movement of the measurement position with respect to the reference position, if a cycle slip does not occur, the integer bias of the carrier phase of the radio wave from each satellite is constant, This utilizes the relationship that if the cycle slip occurs, the integer value bias changes. Alternatively, the relationship that the positioning result is constant when the relative position of the measurement position with respect to the reference position does not change and no cycle slip occurs, and the positioning result changes when the cycle slip occurs, is used. .

That is, the cycle slip monitoring device of the present invention receives radio waves from a plurality of positioning satellites with a reference antenna provided at a reference position and a measurement antenna provided at a measurement position, respectively. The difference between the carrier phase at the position of the antenna and the measurement antenna is determined, and the integer bias of the carrier phase difference is repeatedly determined, and the measured antenna relative to the reference antenna is determined using the determined integer bias of the carrier phase difference. In a positioning device equipped with a means for calculating a relative position, the previously obtained integer value bias is compared with the currently obtained integer value bias, or the positioning result with the previously obtained integer value bias and the currently obtained integer value are compared. Compare with the positioning result with bias,
There is provided an integer bias determination state display means for changing the display content indicating the determination state of the integer bias in accordance with the difference between the two.

In the cycle slip monitoring device according to the present invention, as the integer value bias determination state display means, the value of a counter is increased or decreased in accordance with the presence or absence of the difference between the two and the magnitude of the difference. Shall be displayed.

For example, if the counter value is increased or decreased so that the counter is counted up when there is no change in the integer value bias and the counter is counted down when the change occurs, the counter value tends to increase. , It can be determined that positioning has been performed correctly without the occurrence of cycle slips, and conversely, when the value of the counter is decreasing, it is determined that cycle slips have occurred and the positioning results may be incorrect. it can. Of course, it is usually difficult to immediately and reliably determine the presence or absence of a cycle slip based on the value of such a counter or its tendency to change, but it is possible to provide an observer with at least a guide for determining the presence or absence of a cycle slip. .

[0013] Further, when the difference between the positioning result obtained by the integer value bias obtained last time and the positioning result obtained by the integer value bias obtained this time is within a predetermined value and when the difference exceeds the predetermined value,
The count direction of the counter is changed, and an increase or decrease in the value of the counter is displayed.

As described above, by changing the counting direction of the counter in accordance with the presence or absence of a change in the positioning result, it is possible to provide the observer with an indication of whether or not there is a cycle slip based on the increasing or decreasing tendency of the counter value. Can be.

[0015]

FIG. 1 is a block diagram showing a configuration of a positioning device. This positioning device is provided, for example, on a work boat such as a dredger and used for measuring the heading of the work boat. In FIG. 1, reference numeral 10 denotes a reference antenna;
Is a measurement antenna. The receiver connected to the reference antenna 10 is a reference antenna receiver, and the receiver connected to the measurement antenna 20 is a measurement antenna receiver.

The receiving circuits 11 and 21 amplify the signal received from the antenna and convert it to an intermediate frequency signal. The AD converters 12 and 22 sample the received signal and convert it into digital data. Digital signal processing circuit 1
Numerals 3 and 23 perform arithmetic processing on the digital data strings converted by the AD converters 12 and 22. Specifically, the input data sequence is multiplied by the C / A code to remove the C / A code component, and the carrier N
An I correlation value and a Q correlation value are obtained by integrating the result of multiplying the I signal and the Q signal generated by the CO.
Further, a correlation with the C / A code shifted by ± 0.5 chip is obtained, and the difference is obtained as an EL correlation value.

Processors 14 and 24 are CPU, RO
M, RAM, etc., detecting the carrier phase of the received signal from the I correlation value and the Q correlation value, detecting the phase of the C / A code included in the received signal from the EL correlation value, The tracking of the carrier phase and the C / A code phase is performed. This carrier phase is actually detected not from the phase of the carrier frequency of the radio wave transmitted from the GPS satellite but from the signal converted into the intermediate frequency signal, but the phase information of the intermediate frequency signal is determined by the GPS satellite and the receiving point. Since the information on the distance from the GPS satellite is stored as it is, this is equivalent to detecting the phase of the carrier frequency of the radio wave transmitted from the GPS satellite.

The processor 24 outputs the data of the carrier phase of each satellite at the position of the measurement antenna 20 via the interface 25, and the processor 14 receives the data via the interface 15. Further, the processor 14 obtains the observed single phase difference at the measurement antenna position, and obtains the observation double phase difference from the data of the observation single phase difference and the data of the observation single phase difference at the reference antenna position. Further, the processor 14 displays a display indicating the state of the relative positioning on the display device 18 by a procedure described later. In addition, the azimuth of the measurement antenna with respect to the reference antenna is obtained, and this is converted into the heading azimuth and displayed on the display device 18.

FIG. 2 is a flowchart showing the procedure of the observation process. First, search and tracking of radio waves from satellites are performed to determine the carrier phase of each satellite. In addition, it decodes the navigation message of each satellite, performs independent positioning with the reference antenna, and outputs the PDOP (Position Dilution of Precision).
n: Geometric positioning accuracy reduction rate determined by satellite arrangement), etc. are calculated.

FIG. 3 is a flowchart showing a processing procedure for determining an integer value bias. First, OTF (On The
Fly calibration) If tracking is currently possible for a number that can be processed, that is, an integer value bias can be determined, one of the satellites is used as a reference satellite and the observed double phase difference of the carrier phase for the pair with another satellite is calculated. Ask. Then, an integer bias of each double phase difference is obtained for each set of two satellites. This corresponds to determining a true solution among points (three-dimensional lattice points) where multiple hyperboloids due to three sets of observed double phase differences intersect.

Then, the difference between the previously obtained integer bias of each double phase difference and the integer bias of each double phase difference obtained this time is obtained. Here, "previously obtained... Integer value bias" refers to an integer value bias which is obtained in the previous time or in the past and is regarded as a correct value and used. If there is no change in the bias of the integer value of the double phase difference for all the sets, a predetermined value d is added to the value C of the counter. As a result, if the value of the counter is the maximum value C
When it exceeds max (for example, 100), it is reduced by Cmax and set within a predetermined range. If there is a difference in the integer value bias for any pair of double phase differences, a certain number d is subtracted from the counter value C. When the value C of the counter falls below the lowest possible value Cmin (for example, -100), the value of the counter is added within the predetermined range by adding Cmin. The above processing is repeated. It should be noted that the time required to determine the integer value bias is usually not constant, so that the cycle at which the value C of the counter changes is usually not constant.

FIG. 4 is a flowchart showing a procedure of a display process for the value of the counter. As described later, the value C of the counter is graphically displayed with the horizontal axis representing time and the vertical axis representing the counter value. Therefore, first, the position of the horizontal axis is determined according to the elapsed time from the start of the display, and the dot is plotted at the corresponding horizontal axis position at the vertical axis position according to the counter value C. However, when the position of the 1/5 unit break is reached, the display contents of 1/5 ahead of the position are erased. This process is repeated with the passage of time, and the change in the counter value C is graphically displayed.

FIG. 5 is a diagram showing a display example regarding the state of relative positioning. Here, the “status” indicates the current processing state. For example, if the value is 3, during the OTF,
If it is 4, it indicates the OTF completion state. "Number of satellites" is the number of satellites currently being tracked, and "PDOP" is the rate of decrease in geometrical positioning accuracy due to the satellite arrangement. “BL” is the length of the baseline from the reference antenna to the measurement antenna. “C” is the value C of the counter.

The horizontal axis of these graphs is time, and in the initial state, the graphs extend from left to right on the screen.
After reaching the right end, the 1/5 part from the left disappears, and the graph extends from the left end to the right. After that, 1 from left
When it extends to / 5, the portion of 1/5 to 2/5 disappears, and the graph extends to this 1/5 to 2/5. In the same manner, the display content is sequentially updated while securing a display space in front of the expanding graph.

As shown in FIG. 5, every time the OTF is completed, ie, every time a new integer bias is determined, C
Changes, but if the value of the integer bias does not change, the graph shows a tendency to rise to the right. If the integer bias changes from the previously obtained value, C decreases and the integer bias When the change is repeated, C shows a tendency of falling to the right. The graphic display of the value of C can be used as information for determining the presence or absence of a cycle slip.

The easier the determination of the integer value bias is, for example, when the number of satellites is large, the shorter the cycle of determining the integer value bias becomes, so that the slope of C to the right rises steeply. Therefore, it is possible to estimate the determination state of the integer bias based on the slope of the change of C.

The above "status", "number of satellites",
The display of “PDOP” and “BL” is not essential, and only the change of the counter value C may be displayed. However, if the changes in the “number of satellites”, “PDOP”, and “BL” are also displayed, these pieces of information can be used as information for determining whether a cycle slip has occurred. For example, when C is decreasing, the number of satellites is decreasing at the same time,
If P is large, it can be estimated that the determination of the integer bias has failed due to them. If the value of BL changes rapidly, it can be estimated that a cycle slip has occurred at that time.

Next, a processing procedure of the positioning device according to the second embodiment will be described with reference to FIG. FIG. 6 shows a processing procedure relating to relative positioning. First, an observed double phase difference of the carrier phase of each satellite is obtained, and an integer bias of each double phase difference is determined from these. Then, the position of the measurement antenna relative to the reference antenna is measured. When the difference between the positioning result obtained with the integer value bias obtained this time and the positioning result obtained with the integer value bias obtained previously is equal to or less than a predetermined threshold value Lmax, a predetermined value d is added to the counter value C. . As a result, if the value of the counter exceeds the maximum value Cmax,
The value is reduced by Cmax and set within a predetermined range. When the difference exceeds Lmax, a certain number d is subtracted from the counter value C. Then, the minimum value Cm that the counter value C can take
When the value falls below in, the value of the counter is added within a predetermined range by adding Cmin. This process is repeated.

Assuming that the relative position of the measurement antenna with respect to the reference antenna is constant, if no cycle slip occurs, the positioning result of the relative position of the measurement antenna with respect to the reference antenna falls within a predetermined error range.
The value C of the counter indicates an increasing tendency. If a cycle slip occurs, the result of the relative positioning greatly deviates from the previous positioning result, and the value of the counter decreases. If the cycle slip continues, the value of the counter shows a decreasing tendency.
If the increase / decrease of the counter is graphically displayed, it will be displayed in the same manner as that shown in FIG.

Next, FIG. 7 shows a processing procedure for azimuth observation in the relative positioning device according to the third embodiment. Here, the reference antenna and the measurement antenna are in the same horizontal plane, the relative positioning of the measurement antenna with respect to the reference antenna is performed, and the azimuth of the measurement antenna as viewed from the reference antenna is obtained. Unlike the example shown in FIG. 6, here, attention is paid to a change in azimuth. That is, as shown in FIG. 7, the difference between the azimuth obtained by positioning with the previously obtained integer bias and the azimuth obtained by positioning with the obtained integer bias is equal to or less than a predetermined threshold value Dmax. , The predetermined value d is added to the value C of the counter. As a result, if the value of the counter exceeds the maximum value Cmax, the value is reduced by Cmax to fall within a predetermined range. When the difference exceeds Dmax, a certain number d is subtracted from the counter value C. When the value C of the counter falls below the lowest possible value Cmin, Cmin
And the value of the counter falls within a predetermined range. This process is repeated.

As described above, the relative position of the measurement antenna with respect to the reference antenna may be obtained not as a three-dimensional position but as an azimuth in a horizontal plane.

Next, FIG. 8 is a block diagram showing a configuration of a positioning device according to a fourth embodiment. Unlike the positioning device shown in FIG. 1 as the first embodiment, the reference antenna receiver connected to the reference antenna 10 and the measurement antenna receiver connected to the measurement antenna 20 perform frequency conversion based on the common oscillator 9. , A local oscillation signal for the A / D converters 12, 22 and the digital signal processing circuit 13,
23 is supplied with a reference clock signal. Divider 17,
27 supplies a clock signal to the processors 14 and 24.

As described above, by synchronizing a local oscillation signal for converting a received signal into an intermediate frequency signal and a system clock signal serving as a reference for signal processing timing, a carrier phase of a certain satellite observed by a reference antenna can be adjusted. , The difference from the carrier phase of the satellite observed by the measurement antenna (single phase difference) is obtained, and the integer bias can be determined from the single phase difference obtained for each satellite. That is, the number of required satellites is reduced by one as compared with the case of obtaining the double phase difference as in the above embodiment. Even in such a case, if the value of the counter is increased or decreased in accordance with a change in the integer value bias or a change in the positioning result due to the occurrence of the cycle slip in the same manner as in the embodiment described above. Thus, the occurrence of cycle slip can be monitored.

[0034]

According to the first and second aspects of the present invention, the display content indicating the determination state of the integer bias changes depending on whether or not a cycle slip has occurred. Can be determined.

In particular, according to the second aspect of the present invention, the direction in which the value of the counter changes varies depending on whether or not a cycle slip has occurred. Therefore, whether or not a cycle slip has occurred can be easily estimated from the tendency of the change in the value. Become like

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a positioning device according to a first embodiment.

FIG. 2 is a flowchart showing a processing procedure relating to observation by the positioning device;

FIG. 3 is a flowchart showing a processing procedure for determining an integer value bias of the positioning device.

FIG. 4 is a flowchart showing a processing procedure regarding display processing of the positioning device.

FIG. 5 is a diagram showing a display example of the positioning device.

FIG. 6 is a flowchart showing a processing procedure regarding positioning processing of the positioning device according to the second embodiment.

FIG. 7 is a flowchart showing a processing procedure relating to azimuth measurement of the positioning device according to the third embodiment;

FIG. 8 is a block diagram illustrating a configuration of a positioning device according to a fourth embodiment.

Claims (2)

[Claims] 1. A reference antenna provided at a reference position,
With a measurement antenna provided at the measurement position, radio waves from a plurality of positioning satellites are respectively received to determine a carrier phase difference between the reference antenna and the measurement antenna, and an integer bias of the carrier phase difference. Is repeatedly determined, and a positioning device having means for calculating the relative position of the measurement antenna with respect to the reference antenna using the determined integer value bias of the carrier phase difference is used. By comparing the numerical value bias or the positioning result with the previously obtained integer value bias and the positioning result with the current integer value bias, the determination state of the integer value bias is determined according to the difference between the two. A cycle slip monitoring device comprising an integer value bias determination state display means for changing the displayed content. 2. The method according to claim 1, wherein the integer value bias determination state display means increases or decreases the value of the counter in accordance with the presence or absence of the difference between the two or the magnitude of the difference, and displays the increase / decrease tendency of the counter. 2. The cycle slip monitoring device according to item 1.