A laser ranging method and system for field lines

Abstract

The present invention relates to the technical field of radio wave ranging processing, and in particular to a laser ranging method and system for a field line, the method comprising: performing wavelet transform processing on a first laser echo signal in a laser ranging process to obtain a plurality of wavelet coefficients, the wavelet coefficients comprising approximate coefficients and detail coefficients at each decomposition level; constructing a wavelet tree structure corresponding to the plurality of wavelet coefficients, the wavelet tree structure comprising a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, the first node and the second node in the wavelet tree structure being sorted according to the decomposition level respectively; selecting a third node that is not disturbed by noise in the second node according to noise characteristics; reconstructing a signal using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal; and performing laser ranging processing on the field line based on the second laser echo signal. The present application can solve the technical problem of low accuracy of laser ranging of field lines.

Description

Technical Field

[0001] The invention relates to the technical field of radio wave ranging processing, and in particular to a laser ranging method and system for an on-site line. Background Art

[0002] Laser ranging is a high-precision measurement technology that is widely used in the fields of construction, engineering, mining, etc. It mainly relies on the propagation speed and reflection characteristics of light. Laser pulses are emitted to the target to be measured. After the laser beam passes a certain distance, it is reflected back to the receiver by the target. By measuring the time from the emission to the reception of the laser pulse, combined with the speed of light, the distance to the target to be measured is calculated. In this way, on-site surveys can be carried out to accurately locate faults and the layout of the work site. The laser echo signal is a non-stationary signal, and the quality of the signal determines the ranging capability of the system.

[0003] In the process of using handheld devices to perform laser ranging of field lines, the laser ranging module is used to collect the distance information of the field lines. However, the laser beam is disturbed by environmental factors or the uneven surface of the target being measured during propagation, resulting in noise in the echo signal in the frequency domain and time domain, which affects the extraction of the echo signal. Wavelet transform is an effective signal processing technology, which is applied to signal processing in the laser ranging process. By decomposing the signal into components of different frequencies, the signal can be analyzed at different scales, and the information in the time domain and frequency domain can be provided at the same time. It can effectively remove noise, extract features and analyze the time-frequency characteristics of the signal, achieving the high precision and high resolution usually required by laser ranging technology to ensure the accuracy of measurement.

[0004] However, the characteristics of the laser ranging signal may have certain errors in the frequency domain and time domain due to changes in the environment and the measured object, which makes the use of the same denoising parameters in different situations not ideal. When using wavelet transform analysis to process laser ranging signals, the more decomposition layers there are, the more obvious the characteristic difference between the laser echo signal and the noise interference signal. However, as the number of decomposition layers increases, the difficulty of signal reconstruction will gradually increase, resulting in an increase in the error between the denoised signal and the original signal, affecting the accuracy of the measurement results. Summary of the invention

[0005] In order to solve the technical problem of low accuracy of laser ranging of field lines, the purpose of the present invention is to provide a laser ranging method and system for field lines, and the technical solutions adopted are as follows:

[0006] In a first aspect, the present invention provides a laser ranging method for a field line, comprising:

[0007] Performing wavelet transform processing on the first laser echo signal in the laser ranging process to obtain a plurality of wavelet coefficients, wherein the wavelet coefficients include approximate coefficients and detail coefficients at each decomposition level;

[0008] Constructing a wavelet tree structure corresponding to the plurality of wavelet coefficients, wherein the wavelet tree structure includes a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, and in the wavelet tree structure, the first node and the second node are respectively sorted according to the decomposition level;

[0009] selecting a third node that is not disturbed by noise from the second nodes according to the noise characteristics;

[0010] Reconstructing a signal using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal;

[0011] Laser ranging processing is performed on the field line based on the second laser echo signal.

[0012] Optionally, before performing wavelet transform processing on the first laser echo signal in the laser ranging process, the method further includes:

[0013] According to a preset sampling time and a preset sampling frequency, a laser receiver is used to collect a plurality of initial laser echo signals of the laser beam;

[0014] The initial laser echo signal is filtered, normalized, and signal enhanced to obtain a plurality of the first laser echo signals.

[0015] Optionally, the first laser echo signal in the laser ranging process is subjected to wavelet transform processing to obtain a plurality of wavelet coefficients, including:

[0016] Determining the number of decomposition layers of wavelet transform according to the signal length of the first laser echo signal;

[0017] The first laser echo signal is decomposed at multiple scales to obtain approximate coefficients and detail coefficients corresponding to each decomposition level under the number of decomposition levels.

[0018] Optionally, constructing a wavelet tree structure corresponding to the plurality of wavelet coefficients includes:

[0019] With the first laser echo signal as the vertex, the approximate coefficient as the first node, and the detail coefficient as the second node, a wavelet tree structure corresponding to the plurality of wavelet coefficients is constructed in descending order of the decomposition levels.

[0020] Optionally, screening a third node that is not interfered by noise from the second nodes according to the noise feature includes:

[0021] Determine frequency domain images and time domain images obtained after wavelet transform processing of a plurality of the first laser echo signals, wherein the frequency domain images are used to characterize frequency domain characteristics of the first laser echo signals, and the time domain images are used to characterize time domain characteristics of the first laser echo signals;

[0022] By analyzing the frequency domain image and the time domain image, calculating the noise standard deviation of the detail coefficient;

[0023] A third node that is not disturbed by noise is screened from among the second nodes based on the noise standard deviation.

[0024] Optionally, calculating the noise standard deviation of the detail coefficient by analyzing the frequency domain image and the time domain image includes:

[0025] Calculating environmental interference factors caused by climate and environmental changes based on the signal curve in the frequency domain image;

[0026] Determine a multipath interference factor caused by a multipath effect based on a signal curve in the time domain image;

[0027] The noise standard deviation of the detail coefficient is calculated according to the environmental interference factor and the multipath interference factor.

[0028] Optionally, the calculating the environmental interference factor caused by climate environment change based on the signal curve in the frequency domain image includes:

[0029] Determining the amplitude difference and phase difference between different first laser echo signals according to the signal curve in the frequency domain image;

[0030] Calculating the frequency energy of the first laser echo signal near the reference frequency according to the amplitude difference, the phase difference, the reference frequency and a preset statistical frequency range;

[0031] The environmental interference factor is calculated based on the frequency energy of the first laser echo signal near the reference frequency and the theoretical frequency domain energy.

[0032] Optionally, the determining a multipath interference factor caused by a multipath effect based on a signal curve in the time domain image includes:

[0033] Screening out similar laser echo signals from a plurality of first laser echo signals based on a signal curve in the time domain image;

[0034] Calculating the time delay difference between the similar laser echo signals using a cross-correlation function;

[0035] A multipath interference factor caused by the multipath effect is calculated based on the time delay difference.

[0036] Optionally, the selecting, from the second nodes, a third node that is not interfered by noise based on the noise standard deviation includes:

[0037] Calculate a screening threshold corresponding to the noise feature based on the noise standard deviation;

[0038] The second node corresponding to the detail coefficient greater than the screening threshold is screened as the third node not interfered by the noise.

[0039] In a second aspect, an embodiment of the present invention further provides a laser ranging system for a field line, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned methods when executing the computer program.

[0040] The present invention has the following beneficial effects: through the technical solution provided by the present invention, after obtaining the first laser echo signal in the laser ranging process, the first laser echo signal can be firstly subjected to wavelet transform processing to obtain multiple wavelet coefficients including approximate coefficients and detail coefficients at each decomposition level; then a wavelet tree structure corresponding to multiple wavelet coefficients can be constructed, the wavelet tree structure includes a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, and the first node and the second node in the wavelet tree structure are respectively sorted according to the decomposition level; further, a third node not disturbed by noise can be selected in the second node according to the noise characteristics; finally, the approximate coefficient and the detail coefficient corresponding to the third node are used to reconstruct the signal to obtain the second laser echo signal, and the laser ranging processing is performed on the field line based on the second laser echo signal. The present invention can deeply analyze the time domain and frequency domain characteristics of the laser echo signal through the combination of wavelet transform and tree structure, select the feature nodes not disturbed by noise according to the attributes of the nodes, and use the feature nodes not disturbed by noise to reconstruct the signal of the laser echo signal, which can remove the interference of noise on the laser echo signal, improve the accuracy of signal analysis, and make the data of line measurement more accurate and reliable.

[0041] It should be understood that the above general description and the following detailed description are only exemplary and explanatory and cannot limit the present invention. Other features and advantages of the present invention will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 A schematic flow chart of a laser ranging method for an on-site circuit provided by an embodiment of the present invention;

[0044] Figure 2 A schematic flow chart of a laser ranging method for an on-site circuit provided by another embodiment of the present invention;

[0045] Figure 3 A schematic diagram of a wavelet tree structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the laser ranging method and system for a field line proposed by the present invention, its specific implementation, structure, features and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0047] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0048] The specific scheme of a laser ranging method and system for an on-site line provided by the present invention is described in detail below with reference to the accompanying drawings.

[0049] See also Figure 1 , which shows a flow chart of the steps of a laser ranging method for a field line provided by an embodiment of the present invention, the method comprising the following steps:

[0050] Step 110: Perform wavelet transform processing on the first laser echo signal in the laser ranging process to obtain a plurality of wavelet coefficients, where the wavelet coefficients include approximate coefficients and detail coefficients at each decomposition level.

[0051] The specific scenario targeted by the present invention is: the pulsed laser rangefinder uses the characteristics of extremely short laser pulse duration, relatively concentrated energy in time, and large instantaneous power to measure distance. A pulsed laser with an extremely short duration is emitted by the laser emission system. After passing the distance L to be measured, it is reflected by the target object. The emitted pulsed laser signal is received by the photodetector in the laser receiving system. The time interval circuit calculates the time t between the laser emission and the arrival of the echo signal to obtain the distance L between the target object and the emission.

[0052] In the specific on-site line detection process, due to the interference of environmental climate and multipath effects, there is noise interference in the initial laser echo signal received by the photodetector, so it is necessary to process the collected initial laser echo signal to obtain a more accurate laser echo signal. The first laser echo signal is a more accurate laser echo signal obtained after data processing of the collected initial laser echo signal. Wavelet transform can analyze the signal at different time and frequency scales, effectively separate the low-frequency information (trend) and high-frequency information (details) of the signal, identify the basic mode and instantaneous changes of the signal, and more accurately show the local characteristics of non-stationary signals.

[0053] Step 120: construct a wavelet tree structure corresponding to multiple wavelet coefficients, wherein the wavelet tree structure includes a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient. In the wavelet tree structure, the first node and the second node are sorted according to the decomposition level.

[0054] During the propagation of laser echo signals, due to the multipath effect and environmental interference, the signal data exhibits different characteristics in the time domain and frequency domain after wavelet transformation. By further constructing a wavelet tree structure, characteristic statistics and coefficient analysis are performed on each node in the wavelet tree structure to identify the frequency mode in the laser echo signal, so as to remove noise interference and obtain accurate measurement data. The tree structure uses graphical tools to display the relationship between different frequencies and time scales of signal data after wavelet transformation, which is convenient for understanding the performance characteristics of laser echo signals at different levels and for further processing and reconstruction of laser echo signals. The tree structure combined with wavelet transformation can deeply analyze the time domain and frequency domain characteristics of laser echo signals, reduce the complexity of calculation, and enhance the real-time and accuracy of laser echo data processing.

[0055] Step 130: select a third node that is not disturbed by noise from the second nodes according to the noise characteristics.

[0056] During the propagation of laser echo signals, multipath effects are generated due to reflection, refraction and scattering, resulting in time delays in the time domain of laser echo signals. Environmental interference caused by factors such as climate change and electromagnetic interference from other equipment causes spectrum expansion, pulse broadening, frequency drift or attenuation of laser echo signals, and even waveform distortion affects the frequency characteristics of the signal. According to the Nyquist sampling theorem, when performing the n-th layer of decomposition, the range of each frequency band and the actual requirements need to be determined comprehensively. When the number of decomposition layers increases, the separation degree of noise and signal becomes more obvious, and the distortion of the signal becomes more serious. Therefore, after constructing the wavelet tree structure, the time domain and frequency domain characteristics of the laser echo signal can be analyzed according to the wavelet tree structure, and the third node that is not interfered by noise can be selected from the second node.

[0057] Step 140: Reconstruct the signal using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal.

[0058] For the embodiment of the present disclosure, the second laser echo signal can be reconstructed using the detail coefficients corresponding to the third node that removes noise interference and the approximate coefficients corresponding to the first node, which can remove the interference of noise on the laser echo signal, improve the accuracy of signal analysis, and make the line measurement data more accurate and reliable.

[0059] Step 150: Perform laser ranging processing on the field line based on the second laser echo signal.

[0060] For the embodiments of the present disclosure, the propagation time of the optical signal can be calculated by measuring the time difference between the laser emission signal and the second laser echo signal, and the line distance can be calculated in combination with the speed of light. The average value can be taken after multiple measurements to complete the laser ranging of the on-site line.

[0061] In summary, according to a laser ranging method for a field line provided by the present invention, after obtaining the first laser echo signal in the laser ranging process, the first laser echo signal can be firstly subjected to wavelet transform processing to obtain a plurality of wavelet coefficients including approximate coefficients and detail coefficients at each decomposition level; then a wavelet tree structure corresponding to the plurality of wavelet coefficients can be constructed, the wavelet tree structure including a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, and the first node and the second node in the wavelet tree structure are respectively sorted according to the decomposition level; further, a third node not disturbed by noise can be selected in the second node according to the noise characteristics; finally, the signal is reconstructed using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal, and the field line is subjected to laser ranging processing based on the second laser echo signal. The present invention can deeply analyze the time domain and frequency domain characteristics of the laser echo signal through the combination of wavelet transform and tree structure, select the feature nodes not disturbed by noise according to the attributes of the nodes, and use the feature nodes not disturbed by noise to reconstruct the signal of the laser echo signal, which can remove the interference of noise on the laser echo signal, improve the accuracy of signal analysis, and make the data of line measurement more accurate and reliable.

[0062] based on Figure 1 The embodiment shown is a refinement and extension of the above embodiment. In order to fully illustrate the specific implementation process of the method of this embodiment, this embodiment provides the following Figure 2 The specific method shown. Figure 2 based on Figure 1 As shown in 2, the method comprises the following steps:

[0063] Step 210: Perform wavelet transform processing on the first laser echo signal in the laser ranging process to obtain a plurality of wavelet coefficients, where the wavelet coefficients include approximate coefficients and detail coefficients at each decomposition level.

[0064] In a specific application scenario, before executing the steps of this embodiment, the initial laser echo signal of the laser ranging process can be first collected by a handheld laser rangefinder, and then the collected initial laser echo signal can be processed to obtain a more accurate first laser echo signal. During data processing, digital signal processing technology can be used to filter and normalize the received signal, enhance the signal, and extract an effective laser echo signal. For example, the received data signal is cleaned, the attention of the cleaned signal to the frequency band of interest is strengthened, and a suitable filter is selected to selectively enhance the frequency component. Accordingly, the steps of the embodiment may include: according to a preset sampling time and a preset sampling frequency, a laser receiver is used to collect multiple initial laser echo signals of the laser beam; the initial laser echo signal is filtered, normalized, and signal enhanced to obtain multiple first laser echo signals.

[0065] For the embodiment of the present disclosure, performing wavelet transform processing on the first laser echo signal in the laser ranging process to obtain multiple wavelet coefficients in step 210 may include the following steps:

[0066] Step 210 - 1 : Determine the number of decomposition levels of wavelet transform according to the signal length of the first laser echo signal.

[0067] In a specific application scenario, since the main components of the signal spectrum are concentrated in the low-frequency signal, the number of decomposition layers of the wavelet change is set to:

[0068]

[0069] In the formula, n represents the number of decomposition levels, It is expressed as a logarithm with base 2, where N represents the signal length of the first laser echo signal obtained, Indicates rounding down.

[0070] Step 210 - 2 , performing multi-scale decomposition on the first laser echo signal to obtain approximate coefficients and detail coefficients corresponding to each decomposition level under the number of decomposition levels.

[0071] For the embodiment of the present disclosure, the first laser echo signal is decomposed into components of different scales (the scale corresponds to the size of the time window) and frequencies by performing multi-scale decomposition on the first laser echo signal. Each decomposition level corresponds to a decomposition of the wavelet change, and the number of levels determines the degree of detail of the signal decomposition. Further, the approximate coefficients corresponding to each decomposition level under the multiple decomposition levels corresponding to the number of decomposition levels can be obtained. and detail factor , where j represents the jth decomposition level.

[0072] Step 220 , construct a wavelet tree structure corresponding to a plurality of wavelet coefficients in descending order of decomposition levels, with the first laser echo signal as the vertex, the approximate coefficient as the first node, and the detail coefficient as the second node.

[0073] For the embodiments of the present disclosure, Figure 3 As shown, Figure 3 In the above example, LPF (low pass filter) represents a low pass filter, and HPF (high pass filter) represents a high pass filter. The first laser echo signal S can be used as the vertex and the tree structure can be constructed by arranging them in a layer-by-layer decomposition order. Specifically, the approximate coefficients can be constructed as The corresponding first node , and the construction detail coefficient The corresponding second node , each decomposition level contains a detail coefficient and an approximate coefficient , each layer detail coefficient and approximate coefficients In the wavelet tree structure, only the low-frequency components in the signal are continuously decomposed, so the first node under the previous decomposition level can be gradually decomposed in the order of high to low decomposition levels. Divide. Figure 3 In the first decomposition level, the first laser echo signal S is first decomposed into the first node and the second node ; In the second decomposition level, for the first node Continue to decompose and get the first node and the second node ; In the third decomposition level, for the first node Continue to decompose and get the first node and the second node , so far the decomposition process is completed, and the wavelet tree structure corresponding to multiple wavelet coefficients is obtained.

[0074] Step 230: Determine a frequency domain image and a time domain image obtained after the plurality of first laser echo signals are processed by wavelet transform.

[0075] The frequency domain image is used to characterize the frequency domain characteristics of the first laser echo signal, and the time domain image is used to characterize the time domain characteristics of the first laser echo signal.

[0076] Step 240: Calculate the noise standard deviation of the detail coefficient by analyzing the frequency domain image and the time domain image.

[0077] For the embodiment of the present disclosure, calculating the noise standard deviation of the detail coefficient by analyzing the frequency domain image and the time domain image in step 240 may include the following steps:

[0078] Step 240 - 1 : Calculate the environmental interference factor caused by the climate environment change based on the signal curve in the frequency domain image.

[0079] Environmental interference components have higher energy within a specific frequency range. When the ambient temperature changes or there is electromagnetic interference, the laser echo signal may drift in the frequency domain spectrum, causing the signal position in the spectrum to move. In the frequency domain spectrum, the environmental interference factor caused by climate change is calculated based on the signal curve in the frequency domain image:

[0080]

[0081] In the formula, Indicates that the first laser echo signal is at the reference frequency nearby frequency energy; represents the amplitude difference between different first laser echo signals collected at frequency f, which can be the distance difference between the vertical coordinates of the signal curves on the spectrum image; The phase difference between different first laser echo signals collected at the frequency f may be the distance difference between the horizontal coordinates of the signal curves on the spectrum image; The frequency of the laser echo signal that should be collected by the emitted laser beam in theory is recorded as the reference frequency; is the signal fluctuation frequency difference, specifically, It can be 10; It is the preset statistical frequency range.

[0082] Furthermore, the environmental interference factor can be calculated by comparing the frequency energy of the collected multiple first laser echo signals near the reference frequency with the theoretical frequency domain energy:

[0083]

[0084] In the formula, Environmental interference factors; Indicates that the first laser echo signal is at the reference frequency The frequency energy nearby; E is the theoretical frequency domain energy that can be obtained according to the energy of the emitted laser beam.

[0085] Correspondingly, for the embodiments of the present disclosure, the embodiment steps may include: determining the amplitude difference and phase difference between different first laser echo signals based on the signal curve in the frequency domain image; calculating the frequency energy of the first laser echo signal near the reference frequency based on the amplitude difference, phase difference, reference frequency and a preset statistical frequency range; calculating the environmental interference factor based on the frequency energy of the first laser echo signal near the reference frequency and the theoretical frequency domain energy.

[0086] Step 240 - 2 : Determine a multipath interference factor caused by the multipath effect based on the signal curve in the time domain image.

[0087] Since the propagation time of different paths is different, the first laser echo signal received will be dislocated in time, forming multiple delayed signals in the time domain; and the overlap of multiple echo signals will cause the pulse broadening of the received signal and reduce the time resolution of the signal; but from the perspective of the signal frequency domain characteristics, the signal frequency of each echo is the same as the laser frequency, so the collected echo signal frequency should be the same or similar.

[0088] For the embodiment of the present disclosure, based on the signal curve in the time domain image, the bands with similar waveform changes in the time domain image can be extracted, and all similar waveform segments are arranged according to the collection time, and the multiple first laser echo signals are analyzed:

[0089] Use cosine similarity to calculate the vector similarity between two echo signals, so as to filter out similar echo signals:

[0090]

[0091] In the formula, represents the similarity between the Ath first laser echo signal and the Bth first laser echo signal on the time domain image; A vector representing the xth data point on the Ath first laser echo signal; represents the vector of the xth data point on the Bth first laser echo signal; N represents the number of data points on the time domain image; Indicates the length of the calculation vector; Representation vector Length; Representation vector Length.

[0092] The greater the similarity, the more detailed the peaks between different echo signals are, and the higher the possibility that they are caused by multipath effects. The results are between, when When , it means that the corresponding two first laser echo signals are not similar or even completely opposite, and the delay factor cannot be constructed based on the similarity between the two first laser echo signals; when , it indicates that the similarity between the corresponding two first laser echo signals is high, and therefore corresponding data correction can be performed according to the similar echo signals.

[0093] Calculate the multipath interference factor due to the multipath effect:

[0094]

[0095] In the formula, represents the multipath interference factor; argmax() is a function for finding the maximum value of the independent variable; The cross-correlation function represents the cross-correlation function of similar echo signals. The delay difference is calculated through the cross-correlation function, so as to correct the signal and offset the influence of multipath effect.

[0096] Correspondingly, for the embodiments of the present disclosure, the embodiment steps may include: screening out similar laser echo signals from multiple first laser echo signals based on the signal curve in the time domain image; calculating the time delay difference between similar laser echo signals using the cross-correlation function; and calculating the multipath interference factor caused by the multipath effect based on the time delay difference.

[0097] Step 240-3: Calculate the noise standard deviation of the detail coefficient according to the environmental interference factor and the multipath interference factor.

[0098] For the embodiment of the present disclosure, the noise standard deviation of the detail coefficient can be calculated by combining the environmental interference factor and the multipath interference factor:

[0099]

[0100]

[0101] In the formula, A weighting coefficient representing the signal characteristics; Environmental interference factors; represents the multipath interference factor; is the standard deviation of the detail coefficients of the jth layer in the wavelet tree structure, reflecting the noise level in the current node; Represents the detail coefficient of the jth layer in the wavelet tree structure; j is the jth decomposition level in the wavelet tree structure.

[0102] Step 250: Screen a third node that is not disturbed by noise from among the second nodes based on the noise standard deviation.

[0103] For the embodiment of the present disclosure, the screening of the third node that is not disturbed by noise in the second node based on the noise standard deviation in step 250 may include the following steps:

[0104] Step 250 - 1 : Calculate a screening threshold corresponding to the noise feature based on the noise standard deviation.

[0105] For the disclosed embodiment, a threshold construction formula for filtering nodes in the wavelet tree structure can be constructed according to the noise characteristics, the filtering threshold can be determined, and the second node in the wavelet tree structure can be filtered based on the filtering threshold. The construction formula for the filtering threshold is:

[0106]

[0107] Where, T represents the screening threshold constructed according to the noise characteristics; k represents the empirical coefficient, which is usually selected in the range of (0,3); Represents the standard deviation of the detail coefficients at the jth decomposition level in the wavelet tree structure.

[0108] Step 250 - 2 , screening the second node whose corresponding detail coefficient is greater than the screening threshold as the third node not disturbed by noise.

[0109] According to the disclosed embodiment, each second node in the wavelet tree structure may be screened according to the calculated screening threshold, and the second node having a detail coefficient greater than the screening threshold is retained, and the second node is defined as the third node.

[0110] Step 260: Reconstruct the signal using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal.

[0111] After threshold screening, the laser echo signal can be reconstructed using the retained approximate coefficients and the denoised detail coefficients:

[0112]

[0113] In the formula, represents a second laser echo signal obtained by signal reconstruction; represents the approximation coefficient of the jth layer, That is, all approximate coefficients are summed to represent the low-frequency approximate part in the second laser echo signal; m is the total level of the wavelet coefficients retained after screening; represents the approximation coefficient of the jth layer, To sum the detail coefficients corresponding to the third node, that is, to sum the part of non-continuous second nodes retained in the m second nodes, the high-frequency detail part in the second laser echo signal is represented.

[0114] Step 270: Perform laser ranging processing on the field line based on the second laser echo signal.

[0115] For the embodiments of the present disclosure, the propagation time of the optical signal can be calculated by measuring the time difference between the laser emission signal and the second laser echo signal, and the line distance can be calculated in combination with the speed of light. The average value can be taken after multiple measurements to complete the laser ranging of the on-site line.

[0116] In summary, the technical solution in the present application, after obtaining the first laser echo signal in the laser ranging process, can firstly perform wavelet transform processing on the first laser echo signal to obtain multiple wavelet coefficients including approximate coefficients and detail coefficients at each decomposition level; then a wavelet tree structure corresponding to multiple wavelet coefficients can be constructed, the wavelet tree structure includes a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, and the first node and the second node in the wavelet tree structure are sorted according to the decomposition level respectively; further, the third node that is not disturbed by noise can be selected in the second node according to the noise characteristics; finally, the detail coefficient corresponding to the approximate coefficient and the third node is used to reconstruct the signal to obtain the second laser echo signal, and the laser ranging processing is performed on the field line based on the second laser echo signal. The present invention can deeply analyze the time domain and frequency domain characteristics of the laser echo signal through the combination of wavelet transform and tree structure, select the feature nodes that are not disturbed by noise according to the attributes of the nodes, and use the feature nodes that are not disturbed by noise to reconstruct the signal of the laser echo signal, which can remove the interference of noise on the laser echo signal, improve the accuracy of signal analysis, and make the data of line measurement more accurate and reliable.

[0117] Based on the same inventive concept as the above method, an embodiment of the present invention also provides a laser ranging system for a field line, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned laser ranging methods for a field line are implemented.

[0118] In summary, the embodiments of the present invention provide a laser ranging method and system for field lines. On the one hand, the laser echo signal is analyzed by wavelet transform, and a tree structure is established to organize different frequency components of the signal at different levels, which is convenient for analyzing and understanding the characteristics of the signal, wherein each node represents different frequency and time characteristics, which is helpful for analyzing the detailed changes, trends and noise distribution of the signal. On the other hand, through the combination of wavelet transform and tree structure, the time domain and frequency domain characteristics of the laser echo signal can be deeply analyzed, and feature nodes that are not interfered by noise can be selected according to the attributes of the nodes. The signal of the laser echo signal is reconstructed using the feature nodes that are not interfered by noise, which can remove the interference of noise on the laser echo signal, improve the accuracy of signal analysis, and make the line measurement data more accurate and reliable.

[0119] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0120] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0121] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser ranging method for an on-site line, characterized in that: The method comprises: Performing wavelet transform processing on the first laser echo signal in the laser ranging process to obtain a plurality of wavelet coefficients, wherein the wavelet coefficients include approximate coefficients and detail coefficients at each decomposition level; Constructing a wavelet tree structure corresponding to the plurality of wavelet coefficients, wherein the wavelet tree structure includes a first node corresponding to the approximate coefficient and a second node corresponding to the detail coefficient, and in the wavelet tree structure, the first node and the second node are respectively sorted according to the decomposition level; selecting a third node that is not disturbed by noise from the second nodes according to the noise characteristics; Among them, the method for screening the third node that is not disturbed by noise is: determining frequency domain images and time domain images obtained after a plurality of the first laser echo signals are processed by wavelet transform, the frequency domain image is used to characterize the frequency domain characteristics of the first laser echo signal, and the time domain image is used to characterize the time domain characteristics of the first laser echo signal; by analyzing the frequency domain image and the time domain image, calculating the noise standard deviation of the detail coefficient; based on the noise standard deviation, screening the third node that is not disturbed by noise in the second node; The method for calculating the noise standard deviation of the detail coefficient is as follows: calculating the environmental interference factor caused by climate environment change based on the signal curve in the frequency domain image; determining the multipath interference factor caused by the multipath effect based on the signal curve in the time domain image; and calculating the noise standard deviation of the detail coefficient according to the environmental interference factor and the multipath interference factor. The method for calculating the environmental interference factor caused by climate and environmental changes is as follows: determining the amplitude difference and phase difference between different first laser echo signals according to the signal curve in the frequency domain image; calculating the frequency energy of the first laser echo signal near the reference frequency according to the amplitude difference, the phase difference, the reference frequency and the preset statistical frequency range; calculating the environmental interference factor based on the frequency energy of the first laser echo signal near the reference frequency and the theoretical frequency domain energy; Reconstructing a signal using the approximate coefficient and the detail coefficient corresponding to the third node to obtain a second laser echo signal; Laser ranging processing is performed on the field line based on the second laser echo signal.

2. The method according to claim 1, characterized in that: Before performing wavelet transform processing on the first laser echo signal in the laser ranging process, the method further includes: According to a preset sampling time and a preset sampling frequency, a laser receiver is used to collect a plurality of initial laser echo signals of the laser beam; The initial laser echo signal is filtered, normalized, and signal enhanced to obtain a plurality of the first laser echo signals.

3. The method according to claim 1, characterized in that The first laser echo signal in the laser ranging process is subjected to wavelet transform processing to obtain a plurality of wavelet coefficients, including: Determining the number of decomposition layers of wavelet transform according to the signal length of the first laser echo signal; The first laser echo signal is decomposed at multiple scales to obtain approximate coefficients and detail coefficients corresponding to each decomposition level under the number of decomposition levels.

4. The method according to claim 1, characterized in that: The step of constructing a wavelet tree structure corresponding to the plurality of wavelet coefficients comprises: With the first laser echo signal as the vertex, the approximate coefficient as the first node, and the detail coefficient as the second node, a wavelet tree structure corresponding to the plurality of wavelet coefficients is constructed in descending order of the decomposition levels.

5. The method according to claim 1, characterized in that The determining of a multipath interference factor caused by a multipath effect based on a signal curve in the time domain image comprises: Screening out similar laser echo signals from a plurality of first laser echo signals based on a signal curve in the time domain image; Calculating the time delay difference between the similar laser echo signals using a cross-correlation function; A multipath interference factor caused by the multipath effect is calculated based on the time delay difference.

6. The method according to claim 1, characterized in that The step of selecting a third node that is not disturbed by noise from the second nodes based on the noise standard deviation includes: Calculate a screening threshold corresponding to the noise feature based on the noise standard deviation; The second node corresponding to the detail coefficient greater than the screening threshold is screened as the third node not interfered by the noise.

7. A laser ranging system for a field line, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is executed by a processor, a laser ranging method for a field line is implemented as described in any one of claims 1 to 6.

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