CN111399012A - A method for monitoring reservoir water level using GNSS three-frequency phase combination data - Google Patents

Abstract

The invention discloses a method for monitoring reservoir water level by utilizing GNSS tri-frequency phase combined data, which is suitable for water level monitoring. The method comprises the steps of acquiring interference signals by utilizing three-frequency phase combination through data of a GNSS deformation monitoring receiver on a high slope near water surface of an erected reservoir dam, extracting three carrier signals, acquiring interference time sequence signals by eliminating a combination mode of geometric distance and ionosphere delay, performing spectrum analysis by utilizing wavelet analysis to acquire main frequency of the interference signals, corresponding the time sequence signals to satellite height angles one by one to form time sequence signals with the satellite height angles as variables, performing spectrum analysis on the non-equidistant signals to acquire the main frequency, establishing a model of the main frequency and known reservoir water level, and acquiring real-time reservoir water level through the model. The method has the advantages of simple steps, realization of real-time detection, high detection precision and realization of automatic detection without manual intervention.

Description

A method for monitoring reservoir water level using GNSS three-frequency phase combination data

technical field

The invention relates to a method for monitoring the water level of a reservoir, and is particularly suitable for a method for monitoring the water level of a reservoir by utilizing the GNSS data of a deformation monitoring system of a reservoir dam used in flood control and drought resistance.

Background technique

Water is a precious natural resource that human beings rely on, and it is also a source of disasters. Reasonable storage, utilization and monitoring of changes in water resources are important guarantees for sustainable economic and ecological development. As an important water conservancy infrastructure, reservoirs play a vital role in water transportation, hydropower generation, flood control and drought relief, and ecological environment. Their safety directly affects the safety of life and property of downstream people. At present, traditional reservoir water level monitoring is generally measured by artificial water gauge or ultrasonic measurement. The artificial method has certain limitations: continuous observation cannot be achieved, and the spatial and temporal resolution of the observation is not high, especially in the rainstorm and flood season, the observation is limited and there are potential safety hazards. Ultrasound and other means usually require the establishment of a complete monitoring system, and the monitoring cost is relatively high. Many domestic reservoir areas and dams have established GNSS deformation monitoring systems. The stations of the GNSS observation system for reservoir dam deformation monitoring are usually set on the exterior of the dam or on high slopes near the water. -IR) provides the possibility to measure the change of reservoir water level. The existing GNSS monitoring system can also become a reservoir water level monitoring method without additional monitoring cost while monitoring the dam deformation.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the above technologies, a method for monitoring the water level of a reservoir using GNSS three-frequency phase combination data is provided with simple steps and good detection effect, which can solve the problems and deficiencies of the existing reservoir water level monitoring methods and is economical.

In order to achieve the above-mentioned technical purpose, a method for monitoring the water level of a reservoir using GNSS three-frequency phase combination data of the present invention is provided with a receiver and an antenna for receiving GNSS signals at the high slope position of the dam, and the steps are: For the GNSS deformation monitoring receiver data on the high-slope water surface of the reservoir dam, the interference signal is obtained by three-frequency phase combination, and three carrier signals are extracted. Perform spectral analysis to obtain the main frequency of the interference signal, and correspond the time series signal with the satellite altitude angle one-to-one to form a time series signal with the satellite altitude angle as a variable, and perform spectrum analysis on the unequally spaced signal to obtain the main frequency and establish the main frequency. And the model of the known reservoir water level, and obtain the real-time reservoir water level through the model.

specific:

a First, extract the three-frequency phase observation data and the satellite elevation angle from the satellite observations;

计算出三频相位组合观测值M_1,2,5(t)，式中λ₁＝0.1902937m是GPS的L1信号波长，λ₂＝0.2442102m是GPS的L2信号波长，λ₅＝0.2548280m是GPS的L5信号波长；相位

为相位观测值；m为单位米；b. The three-frequency phase observation data is composed of three-frequency phase combined observations by dividing the geometric distance factor and the ionospheric influence, and the specific formula is:

Calculate the three-frequency phase combination observation value M _1,2,5 (t), where λ ₁ =0.1902937m is the L1 signal wavelength of GPS, λ ₂ =0.2442102m is the GPS L2 signal wavelength, λ ₅ =0.2548280m is L5 signal wavelength of GPS; phase

is the phase observation value; m is the unit meter;

c Replace the sequence of three-frequency phase combination observations M _1,2,5 (t) with time as a variable with a sequence M _1,2,5 (sinθ) of the sine of the satellite elevation angle corresponding to time as a variable;

d. Use wavelet transform to perform spectrum analysis on the three-frequency phase combination observation value M _1,2,5 (sinθ), and obtain the main frequency of the three-frequency phase combination observation value M _1,2,5 (sinθ) through the spectrum analysis;

e Use the main frequency of the three-frequency phase combination observation value M _1,2,5 (sinθ) and the known reservoir water level to establish a linear model, and use this model to obtain the vertical height from the receiver antenna phase center to the reservoir water surface;

f Use the difference between the vertical height and the standard water surface height to obtain the water level of the reservoir.

The water surface is regarded as a specular reflection, the reflected signal comes from the mirror point SP, the superimposed signal of the reflected signal and the direct signal, that is, the path delay of the interference signal relative to the direct signal is related to the vertical height h of the water surface from the receiver antenna phase center;

The signal received by the GNSS receiver is expressed as the superposition of the direct signal and the reflected signal:

叠加信号和直射信号之间的相位差即干涉信号β(t)表示为：in,

The phase difference between the superimposed signal and the direct signal, that is, the interference signal β(t), is expressed as:

代表直射信号，

代表反射信号，A_d代表直射信号的振幅，A_r代表反射信号的振幅，ω(t)代表直射信号相位，

代表反射信号与直射信号的相位差。

represents the direct signal,

represents the reflected signal, Ad represents the amplitude of the direct signal, _Ar represents the amplitude of the reflected signal, ω( _t ) represents the phase of the direct signal,

Represents the phase difference between the reflected signal and the direct signal.

且κ₁＝λ₁η₁，κ₂＝λ₂η₂，κ₅＝λ₅η₅，The interference signal β is obtained by using the three-frequency phase combination observation value, and the combination of the three-frequency phase combination observation value M _1,2,5 (t) is used to eliminate the geometric distance of signal propagation and the influence of the ionosphere, so that

and κ ₁ =λ ₁ η ₁ , κ ₂ =λ ₂ η ₂ , κ ₅ =λ ₅ η ₅ ,

The three-frequency phase combination observation value expression is obtained:

u＝κ₁N₁+κ₂N₂+κ₅N₅，λ₁为GPS信号的L1载波的波长，λ₂为GPS信号的L2载波的波长，λ₅为GPS信号的L5载波的波长，N₁为L1载波的相位模糊度，N₂为L2载波的相位模糊度，N₅为L5载波的相位模糊度；In the formula,

u=κ ₁ N ₁ +κ ₂ N ₂ +κ ₅ N ₅ , λ ₁ is the wavelength of the L1 carrier of the GPS signal, λ ₂ is the wavelength of the L2 carrier of the GPS signal, λ ₅ is the wavelength of the L5 carrier of the GPS signal, N ₁ is the phase ambiguity of the L1 carrier, N ₂ is the phase ambiguity of the L2 carrier, and N ₅ is the phase ambiguity of the L5 carrier;

其中，TEC为传播路径的电子含量，f为卫星信号的频率，延迟大小与信号频率呈反比；三频相位组合观测值M_1,2,5(t)为：M_1,2,5(t)＝M_1,2,5 ^d+M_1,2,5 ^r，其中：The navigation satellite signal passes through the ionosphere, and the phase delay is:

Among them, TEC is the electron content of the propagation path, f is the frequency of the satellite signal, and the delay is inversely proportional to the signal frequency; the three-frequency phase combination observation value M _1,2,5 (t) is: M _1,2,5 (t )=M _1,2,5 ^d +M _1,2,5 ^r , where:

M _1,2,5 ^r is only related to satellite altitude, signal wavelength and antenna height;

λ _i ψ _i (t)=d _i +δ _i +Δ,i=1,2,5

d _i is the geometric distance between the satellite and the receiver antenna phase center, δ _i is the ionospheric delay, and Δ is the clock error and noise;

Since the principle of phase combination is no geometric distance and elimination of ionosphere, the three-frequency phase combination is:

M _1,2,5 (t)=M _1,2,5 ^r =κ ₁ β ₁ (t)+κ ₂ β ₂ (t)+κ ₅ β ₅ (t)

The effective wavelength of the linear phase combination is:

A linear model is established based on the correspondence between the frequency and the vertical height between the water surface and the receiver antenna phase center:

h=kf+b

h is the vertical height between the water surface and the receiver antenna phase center, f is the main frequency of the time series, k and b are the model coefficients, and k and b are the model coefficients to be determined using the actual observation values.

Beneficial effects:

The technology utilizes the observation data of the deformation monitoring system that has been constructed and operated on the slope of the reservoir dam, and can realize the automatic monitoring of the water level of the reservoir without increasing additional facilities and construction costs. The use of the high-precision characteristics of the tri-frequency signal makes the reservoir water level inversion using the tri-frequency signal more accurate and more available data; since the data and equipment are already available, and related equipment is installed on the dam, there is no need to Additional hardware construction costs are required, and the method has high availability and economy; no manual monitoring is required and the amount of data is large, and near real-time reservoir water level monitoring can be realized.

Description of drawings

Fig. 1 is a schematic diagram of the method for monitoring the water level of a reservoir by utilizing the GNSS three-frequency phase combination data of dam deformation monitoring according to the present invention; Fig. 2 is an interference phase model used in the present invention.

Detailed ways

The embodiments of the present invention will be further described below with reference to the accompanying drawings.

The signal received by the traditional earth receiver antenna is the interference signal generated by the superposition of the direct signal from the satellite and the signal reflected from the water surface or the ground. Figure 1 shows the geometric figure of signal interference. Therefore, the water surface is regarded as a specular reflection. The three-frequency phase observation data and the satellite elevation angle are extracted from the three-frequency phase observation data; the reflected signal comes from the mirror point SP, and the path delay of the superimposed signal (ie the interference signal) of the reflected signal and the direct signal relative to the direct signal is the distance from the water surface to the receiver antenna phase center. The vertical height h is related.

代表直射信号，

代表反射信号，β代表叠加信号和直射信号之间的相位差。Figure 2 shows the phase relationship of the interference signal, the abscissa is the in-phase component of the signal, and the ordinate is the quadrature component of the signal.

represents the direct signal,

represents the reflected signal, and β represents the phase difference between the superimposed signal and the direct signal.

The signal received by the GNSS receiver is the superposition of the direct signal and the reflected signal:

in,

β _i (t) is the interference phase due to the interference of the reflected signal from the water surface.

且κ₁＝λ₁η₁，κ₂＝λ₂η₂，κ₅＝λ₅η₅，三频相位组合观测值M_1,2,5(t)的组合原则是消除信号传播的几何距离以及电离层的影响，就可以得到以下表达式：Then use the three-frequency phase combination observation value to obtain the interference signal β, specifically: the combination of the three-frequency phase combination observation value M _1,2,5 (t) is used to eliminate the geometric distance of signal propagation and the influence of the ionosphere, so that

And κ ₁ =λ ₁ η ₁ , κ ₂ =λ ₂ η ₂ , κ ₅ =λ ₅ η ₅ , the combination principle of the three-frequency phase combination observation value M _1,2,5 (t) is to eliminate the geometric distance of signal propagation and the influence of the ionosphere, the following expression can be obtained:

β_i(t)由于来自水面反射信号干扰而产生的干涉信号，其它参数表达如下：in,

β _i (t) is the interference signal due to the interference of the reflected signal from the water surface, and other parameters are expressed as follows:

u=κ ₁ N ₁ +κ ₂ N ₂ +κ ₅ N ₅

The navigation satellite signal passes through the ionosphere, and the phase delay is:

where TEC is the electron content of the propagation path, and f is the frequency of the satellite signal. The magnitude of the delay is inversely proportional to the signal frequency. The three-frequency phase combination observation value M _1,2,5 (t) is: M _1,2,5 (t)=M _1,2,5 ^d +M _1,2,5 ^r ,

in,

M _1,2,5 ^r is only related to satellite altitude, signal wavelength and antenna height;

λ _i ψ _i (t)=d _i +δ _i +Δ,i=1,2,5

d _i is the geometric distance between the satellite and the receiver antenna phase center, δ _i is the ionospheric delay, and Δ is the clock error and noise;

Since the principle of phase combination is no geometric distance and elimination of ionosphere, the three-frequency phase combination is expressed as:

M _1,2,5 (t)=M _1,2,5 ^r =κ ₁ β ₁ (t)+κ ₂ β ₂ (t)+κ ₅ β ₅ (t)

The effective wavelength of the linear phase combination is

Then select a suitable interference signal β:

In the case of a low satellite altitude angle, the reflected signal is strong, so when selecting the interference signal, generally select the data within the range of the satellite altitude angle of 10 to 30 degrees. And according to the azimuth of the observation receiver and the reservoir and the position of the mirror point, the value range of the azimuth angle is determined.

Then obtain the dominant frequency of the interference signal β

The acquired interference signal is converted into a time series with the sine of the satellite elevation angle as a variable. The sequence becomes an unequally spaced sequence, and it is no longer applicable to obtain the dominant frequency using the Fourier transform. Select the wavelet transform to obtain the dominant frequency of the time series.

A linear model is established based on the correspondence between frequency and antenna height (the vertical height between the reflector and the receiver antenna phase center):

h=kf+b

h is the height of the antenna, f is the main frequency of the time series, k and b are the model coefficients, and k and b are the model coefficients to be determined by using the actual observation values.

Obtain detection information of reservoir water level changes

At t ₁ , according to the time series frequency of the obtained interference signal, substitute the linear model to obtain the antenna height h ₁ . Calculate the antenna height h ₂ at t ₂ , and subtract the heights at different times to obtain the change of the reservoir water level. For the reference height h ₀ of the reservoir water level, the height of the reservoir water level can be obtained in real time by subtracting the antenna height _hi obtained at any time from the reference.

Claims (5)

1. a method utilizing GNSS three-frequency phase combination data monitoring reservoir water level, is provided with the receiver and the antenna that receives GNSS signal at the high slope position of dam, it is characterized in that step is as follows: Through the GNSS deformation monitoring receiver data on the high-slope water surface of the erected reservoir dam, the interference signal is obtained by three-frequency phase combination, three carrier signals are extracted, and the interference timing signal is obtained by eliminating the combination of geometric distance and ionospheric delay. Use wavelet analysis to perform spectral analysis to obtain the main frequency of the interference signal, and to correspond the time series signal with the satellite elevation angle one-to-one to form a time series signal with the satellite elevation angle as a variable, and perform spectrum analysis on the unequally spaced signal to obtain the main frequency, Build models of dominant frequencies and known reservoir water levels, and obtain real-time reservoir water levels through the model. 2. the method for utilizing GNSS three-frequency phase combination data to monitor reservoir water level according to claim 1 is characterized in that concrete steps are as follows: a First, extract the three-frequency phase observation data and the satellite elevation angle from the satellite observations; b. The three-frequency phase observation data is composed of three-frequency phase combined observations by dividing the geometric distance factor and the ionospheric influence, and the specific formula is:

Calculate the three-frequency phase combination observation value M _1,2,5 (t), where λ ₁ =0.1902937m is the L1 signal wavelength of GPS, λ ₂ =0.2442102m is the GPS L2 signal wavelength, λ ₅ =0.2548280m is L5 signal wavelength of GPS; phase

is the phase observation value; m is the unit meter; c Replace the sequence of three-frequency phase combination observations M _1,2,5 (t) with time as a variable with a sequence M _1,2,5 (sinθ) of the sine of the satellite elevation angle corresponding to time as a variable; d. Use wavelet transform to perform spectrum analysis on the three-frequency phase combination observation value M _1,2,5 (sinθ), and obtain the main frequency of the three-frequency phase combination observation value M _1,2,5 (sinθ) through the spectrum analysis; e Use the main frequency of the three-frequency phase combination observation value M _1,2,5 (sinθ) and the known reservoir water level to establish a linear model, and use this model to obtain the vertical height from the receiver antenna phase center to the reservoir water surface; f Use the difference between the vertical height and the standard water surface height to obtain the water level of the reservoir. 3. the method that utilizes GNSS three-frequency phase combination data to monitor reservoir water level according to claim 2, is characterized in that: water surface is regarded as specular reflection, reflected signal comes from mirror image point SP, the superposition signal of reflected signal and direct signal , that is, the path delay of the interference signal relative to the direct signal is related to the vertical height h of the water surface from the receiver antenna phase center; The signal received by the GNSS receiver is expressed as the superposition of the direct signal and the reflected signal:

in,

The phase difference between the superimposed signal and the direct signal, that is, the interference signal β(t), is expressed as:

represents the direct signal,

represents the reflected signal, Ad represents the amplitude of the direct signal, _Ar represents the amplitude of the reflected signal, ω( _t ) represents the phase of the direct signal,

Represents the phase difference between the reflected signal and the direct signal. 4. the method that utilizes GNSS three-frequency phase combination data to monitor reservoir water level according to claim 2, is characterized in that: utilizes three-frequency phase combination observation value to obtain interference signal β, three-frequency phase combination observation value M _1,2,5 The combination of (t) is used to eliminate the geometric distance of signal propagation and the influence of the ionosphere, so that

and κ ₁ =λ ₁ η ₁ , κ ₂ =λ ₂ η ₂ , κ ₅ =λ ₅ η ₅ , The three-frequency phase combination observation value expression is obtained:

In the formula,

u=κ ₁ N ₁ +κ ₂ N ₂ +κ ₅ N ₅ , λ ₁ is the wavelength of the L1 carrier of the GPS signal, λ ₂ is the wavelength of the L2 carrier of the GPS signal, λ ₅ is the wavelength of the L5 carrier of the GPS signal, N ₁ is the phase ambiguity of the L1 carrier, N ₂ is the phase ambiguity of the L2 carrier, and N ₅ is the phase ambiguity of the L5 carrier; The navigation satellite signal passes through the ionosphere, and the phase delay is:

Among them, TEC is the electron content of the propagation path, f is the frequency of the satellite signal, and the delay is inversely proportional to the signal frequency; the three-frequency phase combination observation value M _1,2,5 (t) is: M _1,2,5 (t )=M _1,2,5 ^d +M _1,2,5 ^r , where:

M _1,2,5 ^r is only related to satellite altitude, signal wavelength and antenna height; λ _i ψ _i (t)=d _i +δ _i +Δ,i=1,2,5 d _i is the geometric distance between the satellite and the receiver antenna phase center, δ _i is the ionospheric delay, and Δ is the clock error and noise; Since the principle of phase combination is no geometric distance and elimination of ionosphere, the three-frequency phase combination is: M _1,2,5 (t)=M _1,2,5 ^r =κ ₁ β ₁ (t)+κ ₂ β ₂ (t)+κ ₅ β ₅ (t) The effective wavelength of the linear phase combination is:

5. the method that utilizes GNSS three-frequency phase combination data to monitor reservoir water level according to claim 2, is characterized in that: according to the correspondence between the vertical height between frequency and water surface and receiver antenna phase center, establish linear model : h=kf+b h is the vertical height between the water surface and the receiver antenna phase center, f is the main frequency of the time series, k and b are the model coefficients, and k and b are the model coefficients to be determined using the actual observation values.

Images