JPH0412287A - Satellite utilizing position measuring instrument using highly stable clock - Google Patents

Abstract

PURPOSE:To continuously measure the position in the case of trouble of a GPS satellite or the use in a city or a mountain region by providing a time reference keeping means, a range finding means, a position measuring operation means, and a range error correcting means. CONSTITUTION:Radio waves transmitted from plural satellites are received, amplified, and subjected to frequency conversion by a range finding radio wave reception part 1. This range finding radio wave signal is inputted to a reception radio wave processing part 2, and the time origin of the range finding radio wave is acquired, and navigation data from satellites which are superposed on the range finding radio wave is read. Since the time reference offered by a highly stable clock part 3 is deviated from that of transmission of the satellite range finding radio wave, a range error correcting part 4 stores the measured range error and corrects the error characteristic of the clock part 3 at the time of receiving range finding radio waves from satellites at three points or using a communication satellite. A position measuring operation processing part 5 calculates the output of the correcting part 4 and the two-dimensional position of a user inputted from a control display part 6 and displays the output on a display part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application) The present invention relates to a satellite-based positioning device using a highly stable clock. More specifically, for example, a small number of satellites will be deployed using NAVSTAR GPS (Global Positioning System) satellites, whose technical feasibility has already been demonstrated in the United States and whose operation is currently being promoted in stages. Utilization of satellites with highly stable clocks that enable highly accurate and continuous positioning even in remote areas or mountainous areas where ranging radio waves from three or more GPS satellites cannot be received due to the time of year or obstacles. Regarding positioning devices.

(Prior Art) Various systems have been developed and operated in order to measure the position of moving vehicles such as ships, aircraft, and vehicles. Among these, the systems currently in use, such as Loran, Omega, and Detsuka, which have radio stations on the ground, have advantages and disadvantages in terms of positioning accuracy and positioning service area. In addition, NSS (Navy NSS) using satellites
avigation S atell-ite S
system) uses the principle that the frequency of radio waves transmitted from a satellite changes due to the Doppler effect when the satellite passes, so positioning is possible only once every 90 minutes. For this reason, it has not been widely used in fields such as car navigation, for example.

For this reason, the United States has spent nearly 20 years and a huge amount of development costs to develop NAVST and ARGPS (hereinafter referred to as GPS), which are perfect in terms of positioning frequency, positioning accuracy, and positioning service area.
In 1992, there was an urgent need to deploy GPS satellites to enable global positioning services.

Since GPS is being developed under the leadership of the U.S. Department of Defense, it achieves sufficient positioning performance even for aircraft that move vigorously such as fighter jets, but it requires at least four systems to perform three-dimensional positioning. It is necessary to be able to directly receive ranging radio waves from three GPS satellites, and even if the user's altitude information, that is, the distance from the ground surface is available and two-dimensional positioning is performed, it is necessary to receive ranging radio waves from three satellites. There is a need to.

When used on aircraft or ships, there are few obstructions to the view, so once the 24 GPS satellites have been placed, four or more satellites will always be within view, even excluding satellites located at elevation angles of 20 degrees or less. So, there seems to be no problem. However, if one of the GPS satellites malfunctions, it is sometimes impossible to receive the required number of ranging radio waves for the time being.

Furthermore, even if four or more satellites are within sight, positioning may not be possible with sufficient accuracy due to the positional relationship of the satellites (see Figure 6.7).

This situation is particularly noticeable when used in land vehicles such as automobiles. In other words, the field of view from a subcommittee or a car driving in a mountainous area has an elevation angle of 20 degrees or more (this is about 65% of the total field of view on the ground).
) is unreasonable. For example, on a mountain road with a cliff on one side, visibility is expected to be at most 50%, and on roads adjacent to high-rise buildings, visibility is expected to frequently drop to 30% or less. Therefore, with the GPS positioning method that requires the reception of ranging radio waves from at least three satellites, there is a high possibility that the positioning function will temporarily stop in sub-districts or mountainous areas, so the number of users using this method is high. It is expected that its convenience will be impaired in the field of land vehicles, where the largest number of vehicles are located.

(Problem to be solved by the invention) As mentioned above, even though GPS is the most powerful positioning system in the future, when it is used for land vehicles, there are problems with the visibility of GPS satellites in sub-stations and mountainous areas. Therefore, there was a problem that the positioning function temporarily stopped. Also, G.P.
Even if an S-satellite fails, it is not easy to restore its functionality in a short period of time because it requires the launch of a new satellite to quickly deploy a new one. do not have.

This invention was devised in view of the above circumstances,
Achieve the following objectives. The purpose of this invention is to reduce the number of ranging radio waves from GPS satellites that must be constantly received, and to provide highly accurate and uninterrupted positioning even when GPS satellites fail or when used in subcommittees or mountainous areas. The goal is to provide functionality.

(Means for solving the problem) Measure the position of the point where the ranging radio waves are received by using multiple satellites that transmit ranging radio waves at the same time or in synchronization with the predetermined timing of the reference time. In the satellite positioning method, the time reference maintaining means accurately identifies the transmission time of a signal indicating the time reference of a ranging radio wave transmitted by a satellite and the reception time of the signal indicating the time reference; a range measuring means for calculating a time difference between the transmission time and the reception time of the signal indicating the time reference, and measuring the range between the transmission point and the reception point of the ranging radio wave; and at least two of the satellites. The receiving point of the ranging radio wave is based on the range measured by the range measuring means, the position data of the satellite at the time of transmitting the ranging radio wave, and the altitude data of the receiving point from the earth's surface. a positioning calculation means for calculating the position of the satellite, and when the ranging radio waves from three or more satellites can be received,
or the position of the receiving point of the ranging radio wave is known and 1
When the ranging radio waves from more than one satellite can be received, the range error is caused by a clock offset, which is a difference in the time reference between the time reference maintenance means and the satellite, which is generated and accumulated due to inherent error factors. range error correction means that calculates the range error and holds the range error value and corrects the range measured by the range measurement means as long as the range error matches the actual range error within a predetermined error range. A satellite-based positioning device using a highly stable clock, characterized in that it is capable of continuous positioning at a receiving point by continuously receiving ranging radio waves from two or more satellites. .

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the usage of a satellite-based positioning device (hereinafter referred to as this device) using a highly stable clock according to an embodiment of the present invention. By being mounted on a vehicle or carried by a person (hereinafter a vehicle or person having this device is referred to as a user) and receiving ranging radio waves transmitted from a GP8 satellite, etc.
It has the function of determining the user's location. When using this device, the user uses a storage device that stores map data, a barometric altimeter, etc.) to locate two points in his or her horizontal plane.
If the user has a function that allows him to constantly read his altitude relative to his dimensional position, his two-dimensional position can usually be determined by receiving ranging radio waves from two satellites, as will be described later. This device also has a built-in highly stable lock to measure the propagation time of ranging radio waves sent from the satellite to the user and determine the distance between the satellite and the user. The deviation in the transmission time reference (hereinafter referred to as clock offset or simply offset) diverges over time. Therefore, during the time period when ranging radio waves can be received from the three satellites, it has a function of updating the range error caused by the clock offset as well as the user's two-dimensional position to maintain positioning accuracy. Further, as shown in FIG. 1, if the user can use the communication line of the communication satellite, it is possible to update the range error due to the above-mentioned offset through communication with the user/ground main station.

FIG. 2 shows the functional configuration of this device according to an embodiment of the present invention. Radio waves transmitted from multiple satellites are
Reception, amplification, and frequency conversion are performed in the ranging radio wave receiving section 1. The ranging radio wave signal frequency-converted by the ranging radio wave receiving unit 1 is input to the received radio wave processing unit 2, which captures the epoch, which is the time origin of the ranging radio wave, and Reads navigation data from satellites superimposed on radio waves. The circuits and functions of the ranging radio wave receiving section 1 and the received radio wave processing section 2 are well-known techniques, and will not be described in detail here. The difference between the time when the above epoch is transmitted from the satellite and the time when it reaches the user is the propagation time T sui of the ranging radio wave between the satellite and the user, and when this is multiplied by the speed of light, the distance between the satellite and the user (hereinafter referred to as This time reference is provided by the highly stable clock section 3. However, the highly stable clock unit 3 is normally offset from the time reference for transmitting satellite ranging radio waves, and this offset is defined as ΔTbu (taken as a positive value when the time reference of this device is behind the time reference of the satellite). Then, since the above pseudo range Q-110-ji includes a range error equivalent to △S - △TbuXC (C: speed of light), △S is added to the above pseudo range. It is necessary to calculate the actual range (hereinafter referred to as the actual range) by correcting it. The range error correction unit 4 performs this correction, and also stores the range error measured when receiving ranging radio waves from three satellites or using a communication satellite, and the error characteristics of the highly stable clock unit 3. For example, range errors caused by clock errors depending on the rate of change of clock offset over time or ambient temperature are corrected. However, in this embodiment, communication satellites are not necessarily required, and even if they are not available, GP
Highly accurate positioning is possible using only S satellites. The positioning calculation processing unit 5 calculates the user's two-dimensional position using the actual range that is the output of the range error correction unit 4 and the user altitude information input via the operation panel of the control operation unit 6 or the input/output device. is calculated and output and displayed on the control display unit 6 as necessary. In addition to the above-mentioned functions, the control display unit 6 has functions of instructing the operating mode of the device and monitoring the operating status, and also serves as an interface with map display equipment that displays road maps and other user equipment. I do.

FIG. 3 clarifies the basic positioning calculation-related processing executed by the positioning calculation processing section 5 in the form of a flowchart. First, the number of satellites that can receive ranging radio waves (
In the following, the number of satellites that can receive ranging radio waves excluding satellites in positions that cannot be applied due to positioning calculation accuracy is referred to as the number of visible satellites) is 1, and if the user's location is known,
Calculate the range error ΔS according to relational expression 1 on page 18,
The range error stored in the range error correction section 4 is updated.

However, R1 indicates that the absolute value of the vector is taken. That is, TstN is the propagation time of the ranging radio wave of satellite #1 measured based on the time reference of the user equipment, and this includes the clock offset ΔTbu of the user equipment.
is included, so the range error due to this offset is △
This means that S can be determined using Relational Expression 1 on page 18.

When the number of visible satellites is two, the user's two-dimensional position is calculated and updated by process 1 in FIG. If the user altitude is known, the distance between the user and the center of the earth is calculated using the user altitude and the earth's shape model (known geophysical data), so the third fictitious satellite is located at the center of the earth. considered to be a thing. Therefore, since the distance Sx from the earth's center at the position of latitude λ and altitude is determined by relational expression 2 on page 18, this is set as the third range, and the position vector h of this imaginary satellite is set as the zero vector. Therefore, the user's three-dimensional position can be calculated using relational expression 3 on page 18. However, since the user's altitude was already known, the actual positioning was two-dimensional. In addition, in this calculation, the propagation time T5ui (i = 1.2) of the ranging radio waves from the two satellites includes the clock offset of the user equipment, and the measured pseudo range has a range error due to this offset. However, the range error correction section 4 eliminates this range error using the latest range error value ΔS.

In addition, in order to obtain the user's latitude λ and longitude μ, the 18th
It can be calculated by substituting the user number calculated using Relational Expression 3 on page 19 into Relational Expression 4 on the 19th page and performing the reverse calculation.

When the number of visible satellites is three or more, the ranging radio waves from the three satellites in positions that are advantageous in terms of positioning calculation accuracy are selected, and the user's three-dimensional position vector and the above-mentioned Calculate the range error △S and set it as the latest range error △
Record S. Strictly speaking, the range error ΔS calculated here corresponds to the initial value of the range error used for correction in the range error correction section 4 in FIG. 2, and until the range error ΔS is updated again, The range error △S recorded here includes a calibration method related to correcting the inherent error of the highly stable clock section 2 shown in FIG.
266375) to enable more accurate range error correction. Also, when calculating the user position vector and range error ΔS using ranging radio waves from three satellites and user altitude, the concept of user altitude is the same as in the case where two satellites are visible.
The positioning calculation algorithm uses relational expression 5 on page 19 since the range error ΔS is added as a variable to be determined. Furthermore, the procedure for determining the user's latitude λ and longitude μ from the user position vector is the same as in the case where two satellites are visible, and the relational expression 4 on page 19 is applied.

The satellite-based positioning device using the highly stable clock configured in this way has the following features compared to the conventional positioning device for GPS satellites:
Since the positioning function can be achieved even when the number of visible satellites is small, continuous positioning is not only possible even in areas with many high-rise buildings or mountainous areas that cause radio wave interference, but also even when there are many visible satellites. Since the positioning accuracy is closely related to the position of the selected satellite, it is possible to perform positioning with higher accuracy than conventional positioning devices.

The feature of this device is that it has a built-in highly stable lock that maintains the deviation of the time reference between the satellite and the user equipment as accurately as possible for a long period of time as described above. The purpose of this is to correct the range error caused by the error. Therefore, the range error is caused by three or more GPS
Since it is only necessary to take measurements intermittently during times when the satellite is visible, restrictions on its use are greatly reduced.

Furthermore, if a communication satellite or the like capable of two-way communication between the user and the ground station that measures and maintains the time reference of the GPS satellite is available, the measurement of the range error described above may be achieved with the support of the ground station. It is possible.

The highly stable clock used in this device does not require the level of stability of an atomic clock mounted on a GPS satellite. IQ-I measures the stability of the clock built into this device.
Assuming Q~IQ-I+, the position error caused by this is about 20m to 200m per hour.For example, if ranging radio waves can be received from three or more satellites every 15 minutes, the divergence during this time The position error will be 5m to 50m. With a clock as small as this level, it is possible to achieve the above performance with a crystal clock instead of an atomic clock, and the cost can be kept extremely low through mass production and training in calibration methods.

(Effects of the Invention) As detailed above, according to the present invention, the reception of ranging radio waves from multiple satellites is uncertain, and the reception of ranging radio waves from three or four or more satellites is difficult. Requires an operational environment where conventional positioning methods tend to be interrupted (see Figure 6.7)
Also, it is possible to provide a satellite-based positioning device using a highly stable clock that enables continuous and highly accurate positioning.

・Relational expression 1: Calculation formula for range error △S △S=I L, -Rl -Tsu, The distance radio wave propagation time 11 indicates the absolute value of the vector.・Relational expression 2: Relationship between altitude and distance Sx to the center of the earth 5
x = Rx + h = Re (I E2SIN2λ)
++h However, the definition of the symbol is the same as in relational expression 4, = satellite position vector (+-+, 2)L8=O P =S +△S (+-+ 2)P8=S
()1 indicates the conversion of a vertical vector to a horizontal vector. ・Equation 4: Relationship between position vector and latitude, longitude μ, and altitude, = satellite position vector (+-+, 2.3 )L4=
O P, =S, +△S (+-+, 2.3)P4=Sx ()7 shows the conversion of the vertical vector to the horizontal vector

[Brief explanation of the drawing]

FIG. 1 is a diagram showing how a satellite-based positioning device using a high-stability clock is used according to an embodiment of the present invention, and FIG. 2 is a diagram showing a satellite-based positioning device using a high-stability clock according to an embodiment of the present invention. The block diagram shown in FIG. 3 is a flowchart of the main positioning calculations of the positioning calculation processing unit 5 shown in FIG. 1, which is the core of the method of the present invention, and FIG. Figure 5 is a flowchart of position calculation in the case of 3 when the number of visible satellites in Figure 3 is 3.
Flowchart of position and range error calculation for cases greater than or equal to base, Part 6
The figure shows the relationship between the visible cone angle and the average number of visible satellites, and FIG. 7 shows an example of visibility when 24 GPS satellites are deployed. 1... Distance measurement radio wave receiving section 2... Received radio wave processing section 3... Highly stable clock section 4... Range error correction section 5... Positioning calculation processing section 6... Control display section -20 = Procedural amendment (scissors) 8. Contents of the amendment June 72, 1990 (1) The section from the first line of page 19 of the specification to the last line of the same page of the specification is amended as per the attached document, Commissioner of the License Agency. 1. Display of the incident (2) Figures 3 and 5 of the drawings should be amended as shown in the attached sheet. 1990 Patent Application No. 111672 2, Title of Invention Relationship with the case of a person who corrects a satellite-based positioning device using a high-stability clock

Claims (1)

[Claims] 1. Measuring the position of a point where ranging radio waves are received by using a plurality of satellites that transmit ranging radio waves at the same time or in synchronization with a predetermined timing of a reference time. In the satellite positioning system, a time reference maintenance means for accurately identifying a transmission time of a signal indicating a time reference of a ranging radio wave transmitted by a satellite and a reception time of a signal indicating the time reference; Calculating the time difference between the transmission time and the reception time of the signal indicating the time reference,
a range measuring means for measuring the range between the transmitting point and the receiving point of the ranging radio wave; the range measured by the range measuring means for at least two of the satellites; and the range measured by the range measuring means at the time of transmitting the ranging radio wave. positioning calculation means for calculating the position of the receiving point of the ranging radio wave based on the position data of the satellite and the altitude data of the receiving point from the earth's surface; If it is possible to receive
or the position of the receiving point of the ranging radio wave is known and 1
When the ranging radio waves from more than one satellite can be received, the clock offset is caused by a clock offset, which is a difference in the time reference between the time reference maintaining means and the satellite, which is generated and accumulated due to inherent error factors. a range error that calculates a range error, holds the value of the range error and corrects the range measured by the range measuring means as long as the range error matches the actual range error within a predetermined error range; A satellite-based positioning device using a highly stable clock, characterized in that it is equipped with a correction means and enables continuous positioning at a receiving point by continuously receiving ranging radio waves from two or more satellites. .