JPH01152384A - Radio wave speedometer - Google Patents

Abstract

PURPOSE:To enhance measuring accuracy, by forming an equation of observation wherein the value, which is obtained by adding N differences indicated on every N data of the data obtained by continuously measuring the time difference of an arrival radio wave to a reference pulse at a definite time interval, is set as data. CONSTITUTION:The azimuth of a radio wave emitting station looked from a receiving point is calculated. At first, when the geodetic longitude and latitude of the radio wave emitting station are set to lambda1, PHI1 and those of the receiving point are set to lambda2, PHI2, the cosine of the angle distance X between both points is represented by formulae I-III and an azimuth Z is represented by formulae IV, IV' from said formulae I-III. An equation for resolving the data concerned into latitude and longitude components becomes formula V using said azimuth Z. The time difference data of the receiver 2 of loran C and the geodetic longitude and latitude calculated therefrom are outputted. A microcomputer calculates a speed using the formula V.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radio wave velocity meter in which special measures are taken to measure the amount of change in a measurement medium due to a change in speed to improve speed measurement accuracy.

Roland, Detsuka, Omega, etc. are radio navigation aid systems that are received by ships and used to determine their own position. They receive these radio waves, measure the time difference or phase difference, convert this data into a geodetic position, and then calculate the position. The conventional speed measurement method is to calculate the speed from a geodetic position, but in this invention, the time difference measurement data is directly converted to the ship speed without the roundabout process of converting the measured data to a geodetic position. Special measures have also been taken to detect velocity components from the data.

This eliminates the loss of accuracy that occurs during the complicated calculation procedure required for geodetic position conversion of data, and since only the changes in data are handled, the number of significant digits to be handled is reduced, making it possible to improve calculation speed and accuracy. Become.

Measurement data: Receive radio waves from the radio navigation aid system, and continuously measure arrival time differences for all master and slave stations at regular intervals with respect to the reference pulse at the receiving point.

The data for each lap of a, b, c... are thus measured as a + , gt , 6 m'', b, respectively.
, bz , @@ ' , (l , (16# II
Then, the next interval difference (an++-at)+(an+t-az),・”(a
n+1-ai) (bn++-b+)+(bn+z-bz
)s” (bn÷1-bi) (Cn÷+-C+), (Cn
+2-Cz),"(Cn+1-Ci).

Here, this calculated value includes the change that occurs when the receiving point moves in the line-of-sight direction with respect to the transmitting station, so it has the property of being O1' if the receiving point does not move. Furthermore, calculate the sum of the differences using the following formula.

Da=(an++-aI)+(an+z-at)+”・
+(an+*-ar) (D1=1~n Same method, D b + D c for each station c
seek. Da, Db, and Dc thus obtained correspond to nXn of the measured phase change caused by the movement of the receiving point relative to the transmitting station. This will be explained using more specific numerical values.

Now, suppose that there are two pulse generators A and B that generate exactly the same repeating pulse train. Therefore, when the phase difference between A and B is measured at the B generator point via radio waves, the value is constant when the two are not in relative motion, and constant when A moves away from B at a constant speed in the line of sight direction. , and the velocity component in that direction can be detected. In other words, radio waves travel 300 meters in 1 microsecond, so the receiving point travels 300 meters per second.
If you move away by m, the measured value of 18 m will increase by 1 microsecond. This increment per unit time is the velocity component.

Therefore, the numerical sequence of measured values measured every 18 is 1.2, 34.
5... Let φ◆04 and calculate the formula 0) for this.

If n=3 in equation (1), al=l, an++=4
It is clear from the above sequence that . The first term (in parentheses) is the difference between every third column in the second row of the sequence, and is 3, as in the first row. Similarly, the second term is also 3. Therefore, 1=n=3 means that the sum of these three is naturally 9. Also, n=4
Then, each term in the (+) equation is 4, as shown in the third row of the numerical sequence, and the sum is 16. As described above, it can be seen that according to the equation (+), the measured value of the phase change corresponding to the speed is magnified by nXn times. The velocity component measured in this way has a measurement unit of μS (?Ita 0 seconds), and the radio wave propagation velocity is m/μ.
S), where the measurement time interval is t seconds, the velocity component is V (knn shoes), and the measured quantity calculated by formula (+) is D, then Vi = (D ・v X3600) / ((nt)
LX 1852) (2) (1: Corresponding to the station in question) Therefore, expanding the measured amount for a unit speed change means improving resolution. Next, since the data obtained in this way is a velocity component taken in the direction of the station from the receiving point, it can be expressed in the usual velocity expression format (azimuth and velocity kn taken from north to east on the geodetic coordinate system). ).

Creation of observation equation: From the geodetic latitude and latitude of each radio wave emission and the receiving point used, calculate the direction between the radio wave emission as seen from the receiving point using the following formula. The geodetic latitude and latitude between radio wave emission is λl+φ1. If the geodetic latitude and latitude of the receiving point are λ and φ2, then the cosine of the angular distance χ between the two points is cosχ=sinφ(sinφL+ cosφl CO8φz cos(in1−λz) (
3) sinχ=7 (4) θ=co
s”((sinφ, -5inφ, cosχ)/(sin
z cosφ, )) (5) From now on, the direction Z will be S group (λ included l) ≧ 0, Z = θ (6) s
When in(λI−λ,)〈0, Z=2rt−θ (6
)' Using this direction, the equation for decomposing the data into latitude and longitude components is as follows: (See Figure 1) Va = Δφcos
Z a÷Δλ5inZa+Δtvb=ΔφcosZb
+Δ input 5inZ b÷Δt(7)Vi=ΔφcosZ
i+Δλ5inZ i+Δt (1 corresponds to each station) where Δφ: velocity component in the latitude direction Δλ: velocity component in the longitudinal direction Δt: phase drift of the reference pulse. One equation corresponds to one station's data. If we can solve this and determine the unknown, we can find the ship's speed. In this case, the unknowns included in the equation are Δφ, Δλ
, Δt, a solution to the unknown can be obtained if there is data from three stations with different directions.

Although the earth's ellipsoid correction is ignored in the calculations of equations (3) to (5), if the distance between the radio wave emission and the radio wave receiving point is sufficiently far (in general, it is far enough), the relative position of the transmitting and receiving points will change somewhat. The difference has little effect on accuracy. Therefore, it is usually sufficient to have a calculation accuracy of four digits.

Therefore, if there is continuous data, it is not necessary to perform this calculation every time.

How to solve the equation: As mentioned above, this equation has three unknowns, so it can be solved if you have data from three stations acquired at the same time and in different directions, but if there are four or more stations, there will be less loss of accuracy due to data variations, resulting in better results. is obtained. Here, we will explain the least squares method when there is a large amount of data.

The coefficients and constants of the equation are ai=cosZ i , bi=
sinZ i.

ci=1. di= 'J i and these 1=a-
The following sum of products [aiai], [aibi] [ai
cico, [aidi], [bibi] + [bici],
Calculate [bidiL[ciciL[:cidi]. From this calculated value, the normal equation becomes. Once a normal equation is created in this way, its solution can be calculated completely mechanically from the determinant of the coefficients.

In this way, the time difference measurement data of each station can be converted into velocity components in the latitude and longitude directions. The absolute value V of the speed and the direction of travel Z to be obtained from this are v=, /r噌组Tτ丙 (13) θ= c
os””(Δφ/v) (+4) If the direction of movement taken from north to east is 2, when Δλ≧0, Z=θ (15) When Δλ<0, Z=2π−θ (15)'Δt is the phase change of the receiving point reference pulse with respect to the utilized radio wave emission system reference. The introduction of this Δt separates the drift error of the reference oscillator.

By the way, in the explanation so far, data obtained by measuring the phase of the received wave with respect to the reference pulse at the reception point has been described. However, in the method of the invention, the problem can be solved directly using time difference or phase difference data obtained with a conventional hyperbolic navigation receiver. The reason is that Δt is introduced in equation (7). Since this value can take any value, the reference pulse at the receiving point in this explanation may be synchronized with the arrival of the main station radio wave. In other words, this means that it is equivalent to replacing the reference pulse when the main station radio wave arrives. Therefore, in this case, create the following equation with the main station corresponding data Dm as :0'' (
Solve in addition to the simultaneous equations in 7).

0=Δφcoszm+Δλsinzm+Δt (1
6) Practical example: To put this method into practical use, it is possible to design the head part that receives radio waves and measures the time difference or phase difference, but since there is already a high-performance commercial product for this part, we cannot use this part. It is easiest to use . FIG. 2 shows a block diagram of an embodiment designed using some of these commercially available products. 1 is the receiving antenna,
2 is the Loran C receiver, which outputs time difference data and geodetic latitude and latitude calculated from this data. 3 is an electronic computer which receives the data of 2 and performs calculations from formula (+) to formula (16) of the present invention; and 4 is a recording or display device for measurement results.

Application example 1: In equation (1), al + al + ... a5 is the reference point (λ.

, φ0), (10),
Since Δλ and Δφ determined by the equation (11) give latitude and longitude deviations with respect to the reference point, it can be used as is as a highly accurate relative positioning device with respect to the reference point (isthmus area near the reference point).

In this case, the geodetic position of the sought point (λχ, φχ) is input χ = λ.

+Δ input φ8 = φ. +Δφ Application example 2: In other words, Δt obtained by equation (12) is the deviation of the standard oscillator frequency used as the standard for creating the reference pulse at the receiving point from the standard oscillator frequency of the radio wave emission system. Therefore, the present invention can be used as is as a highly accurate frequency stability measuring device that can measure even in a moving state. The frequency deviation Δf in this case is calculated by considering the unit conversion constant in equation (2) and the measurement unit being μS, and calculating the frequency deviation Δf=Δt(vX3600XIO6/1852) (
Hz) (18), Δf at the fixed point is simply Δf without solving the equation or converting the unit in equation (2).
= D / (nt)" / 10' (
H2) (19). Frequency measurements made with this method are measured relative to the average frequency of the system, not a single station. The most important feature is that the accuracy improves in proportion to the square of the measurement time.

[Brief explanation of the drawing]

Figure 1 is an illustration of the observation equation for received data from radio wave emitting station a. FIG. 2 shows an embodiment. that's all

Claims (1)

[Claims] ``Create an observation equation whose data is the sum of every N specified differences of the data continuously measured at a fixed time interval for the time difference of the incoming radio wave with respect to the reference pulse, and solve this equation to calculate the speed. What we were looking for was a differential integration type radio wave speed meter.”