A uniform atmospheric laser radar background noise determination method

Abstract

The application discloses a kind of uniform atmospheric laser radar background noise determination methods, belong to involve laser radar atmospheric detection technical field, based on the derivative of extreme point position of uniform atmospheric laser radar distance square correction signal, obtain the accurate value of uniform atmospheric laser radar signal background noise.First, according to the original signal of uniform atmospheric laser radar, make the waveform shape of corresponding distance square correction signal, determine the extreme point position of distance square correction signal;Then at extreme point position, distance square correction signal is differentiated to distance position coordinate, make derivative zero and establish equation;Then based on uniform atmospheric extinction, obtain the atmospheric extinction coefficient at extreme value;Finally, combine the numerical size of extreme point position distance square correction signal, and the extinction coefficient at extreme point position, the size of background noise is calculated out.The method of the application can determine the accurate value of laser radar echo background noise, and provide convenience for further analyzing laser radar data method.

Description

Technical Field

[0001] This invention relates to the field of lidar atmospheric detection technology, and in particular to a method for determining background noise in uniform atmospheric lidar. Background Technology

[0002] LiDAR, as an active remote sensing technology, has wide applications in atmospheric environment monitoring, meteorological observation, and target identification. Background noise is one of the most common types of LiDAR noise and a significant issue affecting the quality of LiDAR detection data.

[0003] The presence of background noise in lidar introduces significant uncertainty and error into lidar data inversion. Excessive error leads to distorted echo signals and inaccurate detection data, making it difficult to ensure the accuracy, representativeness, and reliability of observation data, which has consistently impacted lidar data quality. This is a major challenge or problem in the field of lidar atmospheric detection research. Especially during daytime experiments, where background light is always present, determining the magnitude of background noise is a crucial step in noise removal.

[0004] Therefore, accurately acquiring the background noise of lidar, further removing noise, solving noise problems, and improving lidar data quality have always been issues of concern and research for researchers engaged in lidar detection. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for determining the background noise of a uniform atmospheric lidar, which accurately obtains the background noise value of a uniform atmospheric lidar by combining the derivative at the extreme point of the uniform atmospheric distance square correction signal, the distance square correction signal value at the extreme point, and the extinction coefficient at the extreme point.

[0006] This invention adopts the following technical solution: a method for determining background noise in a uniform atmospheric lidar, comprising the following steps:

[0007] Step 1: Based on the lidar equation, obtain the range squared correction signal equation containing background noise from the uniform atmospheric lidar echo signal.

[0008] Step 2: Differentiate the distance squared correction signal equation containing background noise at the extreme point location, and make the derivative zero to obtain the differentiated distance squared correction signal equation. Substitute the value of the distance squared correction signal into the equation to obtain the distance squared correction signal equation with the extreme point location added.

[0009] Step 3: Based on uniform atmospheric extinction, obtain the atmospheric extinction coefficient at the extreme point;

[0010] Step 4: Substitute the atmospheric extinction coefficient at the extreme point obtained in Step 3 into the distance squared correction signal equation at the extreme point location obtained in Step 2 to obtain uniform atmospheric background noise.

[0011] Step 5: Based on the actual uniform atmospheric lidar echo signal to be measured, find the extreme point location of the distance squared correction signal containing uniform atmospheric background noise. Calculate the magnitude of the distance squared correction signal based on the extreme point location, obtain the smallest cell, and calculate the atmospheric extinction and uniform atmospheric background noise at the actual extreme point location.

[0012] Specifically, in step 1, the lidar equation is expressed as follows:

[0013]

[0014] Where σ is the background noise, α(r) is the atmospheric extinction, β(r) is the backscattering coefficient, P0 is the initial laser energy, r is the distance, k is the instrument constant, dr is the distance derivative, and P(r) is the lidar echo signal.

[0015] The formula for the squared range correction signal of the lidar containing background noise is obtained, which is a function of distance, and is expressed as follows:

[0016] F(r)=P(r)r 2

[0017]

[0018] Where F(r) is a noisy distance-squared corrected signal (function), and K is a constant, K = kk'.

[0019] For a uniform atmosphere, the following holds:

[0020] α(r)=α

[0021] The equation for the squared distance corrected signal containing background noise under uniform atmospheric conditions is obtained as follows:

[0022]

[0023] Where α represents atmospheric extinction.

[0024] Specifically, in step 2, at the extreme point location, the distance squared correction signal equation containing background noise is differentiated with respect to the position coordinates, and the derivative is made zero to obtain the differentiated distance squared correction signal equation:

[0025] P0Kexp[-2αr](1-2α 2 )+2σr=0

[0026] At the extreme point, the value of the squared distance corrected signal is:

[0027] F(r)=P0Kαexp(-2αr)+σr 2

[0028] get:

[0029]

[0030] Substituting the derivative of the distance-squared correction signal equation, we obtain the distance-squared correction signal equation with the extreme point locations added:

[0031]

[0032] Specifically, in step 3, S is defined as lnpr. 2 ,exist:

[0033]

[0034] Where S is the logarithmic function of the range squared correction signal, p is the echo signal of the lidar, and dp and dS are the differentials of the lidar echo signal and the logarithmic function of the range squared correction signal, respectively.

[0035] For a uniform atmosphere, atmospheric extinction α satisfies:

[0036]

[0037] The atmospheric extinction coefficient at the extreme point is obtained as follows:

[0038]

[0039] Specifically, in step 5, the atmospheric extinction and uniform atmospheric background noise at the actual extreme point location are calculated using the following method:

[0040] Step 5.1: Based on the waveform characteristics of the actual uniform atmospheric lidar echo signal to be measured, find the extreme point position r;

[0041] Step 5.2: Based on the distance-squared corrected signal equation containing background noise from Step 1, obtain the magnitude F(r) of the distance-squared corrected signal at the extreme point position r. Then, according to F(r) = P(r)r... 2 The value of the original laser radar echo signal P(r) at the extreme point position r is obtained;

[0042] Step 5.3: Based on the magnitude P(r) of the squared distance correction signal at the extreme point location r, find the smallest cell:

[0043] Δp=dp

[0044] Where Δp represents a tiny quantity of the lidar echo signal, used for differential calculations;

[0045] Step 5.4: Calculate the atmospheric extinction coefficient α at the extreme value according to the formula for the atmospheric extinction coefficient at the extreme value in Step 4.

[0046] Step 5.5: Substitute the atmospheric extinction coefficient at the extreme point, the position r of the extreme point, and the magnitude F(r) of the distance squared correction signal into the distance squared correction signal equation with the position of the extreme point obtained in Step 2 to obtain the uniform atmospheric background noise σ.

[0047] The present invention also provides: an electronic device, comprising:

[0048] One or more processors;

[0049] A storage device on which one or more programs are stored;

[0050] When the one or more programs are executed by the one or more processors, the one or more processors implement any of the above-described methods for determining the background noise of a uniform atmospheric lidar.

[0051] The present invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps in any of the above-mentioned methods for determining background noise in uniform atmospheric lidar.

[0052] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0053] The present invention provides a method for determining background noise in uniform atmospheric lidar. Based on the derivative (which is zero) at the extreme point of the uniform atmospheric distance-squared correction signal, combined with the distance-squared correction signal value at the extreme point and the extinction coefficient at the extreme point, the method accurately obtains the background noise value of the uniform atmospheric lidar, providing necessary support for subsequent noise removal and noise problem solving. Attached Figure Description

[0054] Figure 1 This is a flowchart of the steps in the uniform atmospheric lidar background noise determination method of the present invention.

[0055] Figure 2 An embodiment of the present invention: the location of the extreme point of the distance squared correction signal and the lidar echo signal at the extreme point location;

[0056] Figure 3 This is an embodiment of the present invention: a graph showing the variation of the extreme points and their positions with noise levels in the distance squared correction signal. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0058] In one embodiment of the present invention, a method for determining background noise in a uniform atmospheric lidar is provided, such as... Figure 1 As shown, it includes the following steps:

[0059] Step S1: Based on the lidar equation, obtain the range squared correction signal equation containing background noise according to the uniform atmospheric lidar echo signal;

[0060] Step S2: Differentiate the distance squared correction signal equation containing background noise at the extreme point location, make the derivative zero, and obtain the differentiated distance squared correction signal equation. Substitute the value of the distance squared correction signal into the equation of the distance squared correction signal with the extreme point location added.

[0061] Step S3: Based on uniform atmospheric extinction, obtain the atmospheric extinction coefficient at the extreme value;

[0062] Step S4: Substitute the atmospheric extinction coefficient at the extreme point obtained in Step 3 into the distance squared correction signal equation at the extreme point location obtained in Step 2 to obtain uniform atmospheric background noise.

[0063] Step S5: Based on the actual uniform atmospheric lidar echo signal to be measured, find the extreme point position of the distance squared correction signal containing uniform atmospheric background noise, calculate the magnitude of the distance squared correction signal based on the extreme point position, obtain the smallest cell, and calculate the atmospheric extinction and uniform atmospheric background noise at the actual extreme point position.

[0064] Specifically, in step S1, the actual lidar equation is expressed as follows:

[0065]

[0066] Where σ is the background noise, α(r) is the atmospheric extinction, β(r) is the backscattering coefficient, P0 is the initial laser energy, r is the distance, k is a constant, dr is the distance derivative, and P(r) is the lidar echo energy.

[0067] In this embodiment,

[0068] β(r)=k'α(r)

[0069]

[0070] K=kk'

[0071] Where K and k' are constants.

[0072] Furthermore, in step S1, the distance squared correction signal containing background noise is a function of distance, expressed as follows:

[0073] F(r)=P(r)r 2

[0074] Based on the echo signal of a uniform atmospheric lidar, construct the range correction signal of the uniform atmospheric lidar containing background noise, and write the equation for the range square correction signal containing background noise.

[0075]

[0076] For a uniform atmosphere, the following holds:

[0077] α(r)=α

[0078] In a uniform atmosphere, the actual distance squared correction signal containing background noise is shown in Equation (1):

[0079]

[0080] At the extreme position r, differentiate equation (1) with respect to the position coordinates using the squared distance correction signal, make the derivative zero, and establish the equation to obtain:

[0081] F'(r)=0

[0082]

[0083] The following formula (2) can be obtained:

[0084] P0Kexp[-2αr](1-2α 2 )+2σr=0 (2)

[0085] Specifically, in step S2, at the extreme point location, the measured value of the squared distance corrected signal is:

[0086] F(r)=P0Kαexp(-2αr)+σr 2

[0087] Based on the measured value F(r) of the squared distance correction signal at the extreme point, the following formula (3) can be obtained:

[0088]

[0089] Substituting formula (3) into formula (2), we obtain the equation for the distance squared correction signal at the extreme point location, which is expressed as formula (4) below:

[0090]

[0091] Specifically, in step S3, according to the definition S = ln pr 2 ,exist:

[0092]

[0093] Due to uniform atmospheric extinction, we have:

[0094]

[0095] The atmospheric extinction coefficient at the extreme value is obtained and expressed as the following formula (5):

[0096]

[0097] Specifically, in step S4, by substituting formula (5) into formula (4), the uniform atmospheric background noise σ can be obtained.

[0098] Further, in step S5, the magnitude of the actual background noise is calculated based on the actual uniform atmospheric lidar echo signal to be measured, as follows:

[0099] Based on the waveform characteristics of the actual uniform atmospheric lidar echo signal to be measured, find the extreme point position r of the range squared correction signal containing background noise;

[0100] Find the magnitude of the squared correction signal at position r:

[0101] F(r)=P(r)r 2 ;

[0102] Based on the value of the original echo signal P(r) from the lidar at the extreme point position r, the smallest cell Δp=dp is calculated for differential calculation;

[0103] According to formula (5), the atmospheric extinction α at the extreme point position r is calculated;

[0104] Substituting the extreme point unknown r, the magnitude of the squared distance correction signal F(r), and the atmospheric extinction α obtained in the above steps into formula (4), we can obtain the accurate value of the background noise of the actual uniform atmospheric lidar.

[0105] In this embodiment, as Figure 2As shown, the extreme points and positions of the range squared correction signal change with the noise level. The extreme point position of the range squared correction signal is r, and the corresponding noise is σ. When the noise level changes, the lidar echo signal and the range squared correction signal change accordingly.

[0106] Furthermore, such as Figure 3 As shown, the extreme point of the distance squared correction signal is located at r', and the corresponding noise is σ'.

[0107] In this embodiment of the invention, an electronic device is also provided, including: one or more processors; a storage device storing one or more programs thereon; when the one or more programs are executed by the one or more processors, the one or more processors implement the uniform atmospheric lidar background noise determination method described in the above embodiments.

[0108] In this embodiment of the invention, a computer-readable storage medium is also provided, on which a computer program is stored. When the program is executed by a processor, it implements the steps in the uniform atmospheric lidar background noise determination method in the above embodiments.

[0109] In summary, the uniform atmospheric lidar background noise determination method of the present invention can accurately determine the magnitude of uniform atmospheric background noise based on the derivative (which is zero) at the extreme value of the uniform atmospheric lidar range-squared correction signal, the magnitude of the range-squared correction signal at the extreme value, and the atmospheric extinction coefficient at the extreme value of the range-squared correction signal.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining background noise in a uniform atmospheric lidar system, characterized in that, Includes the following steps: Step 1: Based on the lidar equation, obtain the range squared correction signal equation containing background noise from the uniform atmospheric lidar echo signal. Step 2: At the extreme point, differentiate the distance squared correction signal equation with respect to the position coordinates based on the distance squared correction signal equation containing background noise, and make the derivative zero to obtain the differentiated distance squared correction signal equation. Substitute the value of the distance squared correction signal into the equation to obtain the distance squared correction signal equation added to the extreme point position. Step 3: Based on uniform atmospheric extinction, obtain the atmospheric extinction coefficient at the extreme point location; Step 4: Substitute the atmospheric extinction coefficient at the extreme point obtained in Step 3 into the distance squared correction signal equation at the extreme point location obtained in Step 2 to obtain uniform atmospheric background noise. Step 5: Based on the actual uniform atmospheric lidar echo signal to be measured, find the extreme point location of the distance squared correction signal containing uniform atmospheric background noise. Calculate the magnitude of the distance squared correction signal based on the extreme point location, obtain the smallest cell, and calculate the atmospheric extinction and uniform atmospheric background noise at the actual extreme point location.

2. The method for determining background noise of a uniform atmospheric lidar according to claim 1, characterized in that, In step 1, the lidar equation is expressed as follows: Where σ is the background noise, α(r) is the atmospheric extinction, β(r) is the backscattering coefficient, P0 is the initial laser energy, r is the distance, k is a constant, dr is the distance derivative, and P(r) is the lidar echo energy. The formula for the squared range correction signal of the lidar containing background noise is obtained, which is a function of distance, and is expressed as follows: F(r)=P(r)r 2 Where F(r) is the distance squared correction signal function containing noise, K is a constant, K = kk'.

3. The method for determining background noise of a uniform atmospheric lidar according to claim 2, characterized in that, In step 1, for a uniform atmosphere, the following holds true: α(r)＝α The equation for the squared distance corrected signal containing background noise under uniform atmospheric conditions is obtained as follows: Where α represents atmospheric extinction.

4. The method for determining background noise of a uniform atmospheric lidar according to claim 3, characterized in that, In step 2, at the extreme point, the distance squared correction signal equation containing background noise is differentiated with respect to the position coordinates, and the derivative is made zero to obtain the differentiated distance squared correction signal equation: P0Kexp[-2αr](1-2α 2 )+2σr=0 At the extreme point, the value of the squared distance corrected signal is: F(r)=P0Kαexp(-2αr)+σr 2 get: Substituting the derivative of the distance-squared correction signal equation, we obtain the distance-squared correction signal equation with the extreme point locations added:

5. The method for determining background noise of a uniform atmospheric lidar according to claim 4, characterized in that, In step 3, the parameter S is defined as ln pr. 2 ,exist: Where p is the lidar echo signal, and dp and dS are the derivatives of p and S, respectively; For a uniform atmosphere, atmospheric extinction α satisfies: The atmospheric extinction coefficient at the extreme point is obtained as follows:

6. The method for determining background noise of a uniform atmospheric lidar according to claim 5, characterized in that, In step 5, the atmospheric extinction and uniform atmospheric background noise at the actual extreme point location are calculated using the following method: Step 5.1: Based on the waveform characteristics of the actual uniform atmospheric lidar echo signal to be measured, find the extreme point position r; Step 5.2: Based on the distance-squared corrected signal equation containing background noise from Step 1, obtain the magnitude F(r) of the distance-squared corrected signal at the extreme point position r. Then, according to F(r) = P(r)r... 2 The value of the original laser radar echo signal P(r) at the extreme point position r is obtained; Step 5.3: Based on the magnitude P(r) of the squared distance correction signal at the extreme point location r, find the smallest cell: Δp=dp Where Δp represents the smallest unit value of the lidar echo signal, used for differential calculation of the lidar echo signal; Step 5.4: Calculate the atmospheric extinction coefficient α at the extreme value according to the formula for the atmospheric extinction coefficient at the extreme value in Step 4. Step 5.5: Substitute the atmospheric extinction coefficient at the extreme point, the position r of the extreme point, and the magnitude F(r) of the distance squared correction signal into the distance squared correction signal equation with the position of the extreme point obtained in Step 2 to obtain the uniform atmospheric background noise σ.

7. An electronic device, characterized in that, include: One or more processors; A storage device on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors implement the uniform atmospheric lidar background noise determination method as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, It stores a computer program, which, when executed by a processor, implements the steps in the uniform atmospheric lidar background noise determination method according to any one of claims 1 to 6.

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