阅读说明：本技术 一种多通道激光雷达极浅水测深数据处理方法 (Multichannel laser radar ultra-shallow water sounding data processing method ) 是由 梁琨 徐杨睿 郑永超 杨颂 于 2020-11-18 设计创作，主要内容包括：本发明公开了一种多通道激光雷达极浅水测深数据处理方法,属于激光雷达水下测绘领域,包括：获取多通道激光雷达的浅水通道无回波波形数据的均值和方差,分别作为均值参考值和方差参考值；将浅水通道的回波波形数据减去均值参考值后,提取出持续Tns(T>0)大于方差参考值的数据作为有效回波数据；对有效回波数据进行高斯拟合,得到第一拟合曲线,以根据第一拟合曲线确定海底回波相对时间T-1；对有效回波数据与第一拟合曲线的差值进行高斯拟合,得到第二拟合曲线,以根据第二拟合曲线确定海表回波相对时间T-2；按照H＝v*(T-2-T-1)计算极浅水域的水深H。本发明能够利用多通道激光雷达测深数据准确计算极浅水域的实际水深,并效减少提高计算速度。(The invention discloses a multichannel laser radar ultra-shallow water depth measurement data processing method, which belongs to the field of laser radar underwater surveying and mapping and comprises the following steps: acquiring the mean value and the variance of the shallow water channel echo-free waveform data of the multi-channel laser radar, and respectively taking the mean value and the variance as a mean value reference value and a variance reference value; subtracting the mean value reference value from the echo waveform data of the shallow water channel to extract the continuous Tns (T)>0) Data larger than the variance reference value is used as effective echo data; performing Gaussian fitting on the effective echo data to obtain a first fitting curve so as to determine the relative time T of the sea bottom echo according to the first fitting curve 1 (ii) a Performing Gaussian fitting on the difference value of the effective echo data and the first fitting curve to obtain a second fitting curve so as to determine the sea chart echo relative time T according to the second fitting curve 2 (ii) a According to H ═ v [ (T) ] 2 ‑T 1 ) And calculating the water depth H of the ultra-shallow water area. The invention can utilize the multi-channel laser radar depth measurement data standardThe actual water depth of the ultra-shallow water area is calculated, and the calculation speed is effectively reduced and improved.)

1. A multi-channel laser radar ultra-shallow water sounding data processing method is used for calculating the water depth of an ultra-shallow water area; the method comprises the following steps:

acquiring the mean value and the variance of the shallow water channel echo-free waveform data of the multi-channel laser radar, and respectively taking the mean value and the variance as a mean value reference value and a variance reference value;

subtracting the mean value reference value from the echo waveform data of the shallow water channel, and extracting data with duration Tns larger than the variance reference value as effective echo data; t > 0;

performing Gaussian fitting on the effective echo data to obtain a first fitting curve so as to determine the relative time T of the sea bottom echo according to the first fitting curve₁；

Carrying out Gaussian fitting on the difference value of the effective echo data and the first fitting curve to obtain a second fitting curve so as to determine the sea table echo relative time T according to the second fitting curve₂；

According to H ═ v [ (T) ]₂-T₁) Calculating the water depth of the ultra-shallow water area;

wherein v is the propagation speed of the laser in the water, and H is the water depth of the ultra-shallow water area; the first fitted curve and the second fitted curve reflect the relation of the intensity of the laser reflection signal with the change of the relative position.

2. The method for processing the data of the multi-channel lidar ultra-shallow water sounding as recited in claim 1, wherein T is 5. ltoreq. T.ltoreq.20.

3. The method of claim 2, wherein T is 7.

4. The method for processing the data of the multi-channel lidar of any of claims 1 to 3, wherein a fitting interval for Gaussian fitting of the effective echo data is T before a maximum value of the effective echo data₃ns to data at the end of the valid echo data;

wherein, 0<T₃≤10。

5. The method of claim 4, wherein T is T₃＝10。

6. The method of any of claims 4, wherein the seafloor echo relative time T is determined from the first fitted curve₁The method comprises the following steps:

determining the relative position corresponding to the peak point of the first fitting curve as the relative position of the sea bottom echo, and determining the time corresponding to the relative position of the sea bottom echo as the relative time T of the sea bottom echo₁。

7. The method as claimed in claim 4, wherein the difference between the effective echo data and the first fitting curve is subjected to Gaussian fitting, and the fitting interval is from the starting position of the difference to the position corresponding to the peak point of the first fitting curve.

8. The method of claim 7, wherein determining the sea surface echo relative time T from the second fitted curve₂The method comprises the following steps:

determining the relative position corresponding to the peak point of the second fitting curve as the sea surface echo relative position, and determining the time corresponding to the sea surface echo relative position as the sea surface echo relative time T₂。

9. The method for processing the ultra-shallow depth sounding data of the multi-channel lidar as recited in any one of claims 1 to 3, wherein the shallow-water channel echo-free waveform data of the multi-channel lidar is a part of data at the beginning or the end of the echo waveform data of the shallow-water channel;

or the shallow water channel of the multi-channel laser radar has no echo waveform data and is waveform data which is received by a detector and does not enter water.

10. A computer-readable storage medium comprising a stored computer program;

the computer program, when executed by a processor, controls an apparatus on which the computer-readable storage medium is located to perform the method of processing the ultra-shallow water sounding data of the multi-channel lidar recited in any of claims 1-9.

Technical Field

The invention belongs to the field of underwater surveying and mapping of laser radars, and particularly relates to a method for processing ultra-shallow water sounding data of a multi-channel laser radar.

Background

The laser radar has the characteristics of strong energy, good directivity, short wavelength and high resolution, and plays an important role in the field of marine topographic mapping application, particularly in the depth measurement of shallow water areas near coastal zones and island reefs.

The sea water has strong attenuation to the laser energy, so that the dynamic range of the underwater echo signal received by the laser radar is very large, and the sea surface and shallow water echo signals are very easy to cause the saturation of a detector while the detection of the deep water weak signal is realized. Therefore, in order to expand the detection dynamic range in the actual laser radar depth measurement system, the depth measurement echo adopts two channels of a shallow water view field and a deep water view field to carry out view field division simultaneous detection. When the multi-channel ranging laser radar is used for measuring the actual water depth in an extremely shallow water area, the deep water field, namely the deep water channel, can be directly saturated due to the close distance and the strong energy, and the practical significance is not achieved; the shallow water field, i.e. the shallow water channel, causes aliasing of the sea bottom and the sea surface echo because the sea surface is close to the sea bottom, and the sea surface and the sea bottom cannot be directly separated to obtain the sea surface and the sea bottom position for calculating the depth.

In order to calculate the depth of an extremely shallow water area by using multi-channel laser radar sounding data, the Shanghai precision optics research proposes an RLD deconvolution (Chadson-Lucy deconvolution) echo separation method, and the method can obtain a result approximate to a maximum likelihood solution in a time domain and is derived from Bayes' theorem. When RLD is used, iteration is carried out on the 1 multiplied by N one-dimensional signals for N times, and a deconvolution result is obtained. The method can calculate the actual water depth of the ultra-shallow water area, but the time consumption is long in the iteration process, and the method cannot be applied to the application with high real-time requirements.

Disclosure of Invention

Aiming at the defects and the improvement requirements of the prior art, the invention provides a method for processing the ultra-shallow water sounding data of a multi-channel laser radar, aiming at calculating the actual water depth of an ultra-shallow water area by using the sounding data of the multi-channel laser radar and effectively improving the calculation speed.

To achieve the above object, according to one aspect of the present invention, there is provided a method for processing depth measurement data of an ultra-shallow water area by using a multi-channel laser radar, for calculating a water depth of the ultra-shallow water area; the method comprises the following steps:

acquiring the mean value and the variance of the shallow water channel echo-free waveform data of the multi-channel laser radar, and respectively taking the mean value and the variance as a mean value reference value and a variance reference value;

subtracting the mean value reference value from the echo waveform data of the shallow water channel, and extracting data with duration Tns larger than the variance reference value as effective echo data; t > 0;

performing Gaussian fitting on the effective echo data to obtain a first fitting curve so as to determine the relative time T of the sea bottom echo according to the first fitting curve₁；

Performing Gaussian fitting on the difference value of the effective echo data and the first fitting curve to obtain a second fitting curve so as to determine the sea chart echo relative time T according to the second fitting curve₂；

According to H ═ v [ (T) ]₂-T₁) Calculating the water depth of the ultra-shallow water area;

wherein v is the propagation speed of the laser in water, and H is the water depth of the ultra-shallow water area; the first fitted curve and the second fitted curve reflect the relation of the intensity of the laser reflection signal with the change of the relative position.

Firstly, acquiring the mean value and the variance of the shallow water channel echo-free waveform data as reference values, wherein the shallow water channel echo-free waveform data does not contain water body reflection information, so that the reference values obtained by the method reflect system noise; according to the method, effective echo data are extracted from the shallow water channel based on the reference value, and the relative time of the submarine echo is determined based on the Gaussian fitting result of the effective echo data, so that the influence of system noise on the fitting result can be avoided, and the accuracy of the determined relative time of the submarine echo is ensured; the invention determines the sea surface echo relative time based on the difference value of the effective echo data and the Gaussian fitting result, and the sea surface echo relative time can be accurately obtained because the difference value only contains the sea surface echo information; according to the invention, the sea bottom echo relative time and the sea surface echo relative time are accurately obtained from the sounding data of the multichannel laser radar in a fitting mode, so that the actual water depth of the ultra-shallow water area can be accurately calculated, and related calculation can be completed only through simple fitting, the calculation time is effectively reduced, and the calculation speed is improved.

Further, T is more than or equal to 5 and less than or equal to 20.

According to the method, after the mean value is subtracted from the shallow water channel echo waveform data of the multi-channel laser radar, the data which lasts for 5-20 ns and is larger than the variance reference value is extracted, the situation that effective information contained in the extracted data is too little and the calculation accuracy is influenced due to the fact that the time interval is set to be too short can be avoided, and meanwhile the situation that the effective information is lost and the calculation amount is increased and the calculation accuracy and the calculation speed are influenced due to the fact that the time interval is set to be too long can be avoided.

Further, T ═ 7.

According to the invention, after the mean value of the shallow water channel echo waveform data of the multi-channel laser radar is subtracted, the data which lasts for 7ns and is greater than the variance reference value is extracted, so that the water body reflection signal can be retained, and the noise data can be removed as much as possible.

Further, the fitting interval for performing Gaussian fitting on the effective echo data is T before the maximum value of the effective echo data₃ns to the data at the end of the valid echo data;

wherein, 0<T₃≤10。

Research shows that the sea bottom reflection peak value is near the maximum value of the echo signal; effective echo data is formed by superposing seabed reflection echoes and sea surface reflection echoes, the theoretical water depth corresponding to 10ns before the peak value of the effective echo data is 1.0 m, in order to reduce the influence of the sea surface reflection echo peak value on the fitting of the seabed echoes, only the data 10ns before the seabed reflection peak value is taken, and the data after the seabed reflection peak value has no interference of other factors and can be adopted, therefore, the invention utilizes the T before the maximum value of the effective echo data to realize the effective echo data₃ns(0<T₃Less than or equal to 10) to the end of the effective echo data to form a fitting interval, thereby ensuring the accuracy of the submarine echo relative to time.

Further, T₃＝10。

Further, determining the sea bottom echo relative time T according to the first fitted curve₁The method comprises the following steps:

determining the relative position corresponding to the peak point of the first fitting curve as the relative position of the sea bottom echo, and determining the time corresponding to the relative position of the sea bottom echo as the relative time T of the sea bottom echo₁。

In the reflected echo, the point with the maximum intensity is the position of the reflecting surface; according to the method, the relative position corresponding to the peak point of the first fitting curve obtained by Gaussian fitting of the effective echo data is determined as the sea bottom echo relative position, and the time corresponding to the sea bottom echo relative position is determined as the sea bottom echo relative time, so that the accuracy of the calculation result is ensured.

Further, the difference value between the effective echo data and the first fitting curve is subjected to Gaussian fitting, and the fitting interval of the difference value is data from the starting position of the difference value to the position corresponding to the peak point of the first fitting curve.

According to the invention, effective echo data is formed by superposing a sea floor reflection echo and a sea surface reflection echo, and the influence of the sea surface reflection echo is eliminated from a first fitting curve obtained by performing Gaussian fitting on the effective echo data, so that the difference value of the effective echo data and the first fitting curve reflects the information of the sea surface reflection echo.

Further, determining the sea-table echo relative time T according to the second fitting curve₂The method comprises the following steps:

determining the relative position corresponding to the peak point of the second fitting curve as the sea surface echo relative position, and determining the time corresponding to the sea surface echo relative position as the sea surface echo relative time T₂。

In the reflected echo, the point with the maximum intensity is the position of the reflecting surface; according to the invention, the relative position corresponding to the peak point of the second fitting curve is determined as the sea surface echo relative position, and the time corresponding to the sea surface echo relative position is determined as the sea surface echo relative time, so that the accuracy of the calculation result is ensured.

Furthermore, the shallow water channel of the multi-channel laser radar has no echo waveform data and is a part of data at the beginning or the end of the echo waveform data of the shallow water channel;

or the shallow water channel of the multi-channel laser radar has no echo waveform data, and the shallow water channel is waveform data which is received by the detector and does not enter water.

In the shallow water channel echo waveform data of the multi-channel laser radar, the first part of data is data before laser enters water, is data in air, does not contain information reflected by a water body, and can be regarded as system noise; in the shallow water channel echo waveform data of the multi-channel laser radar, a part of tail data is received completely because the detector is opened for a long time, and water body reflection information is not included any more, so that the data can be regarded as system noise; therefore, the method can acquire the echo-free waveform data of the shallow water channel of the multi-channel laser radar and accurately acquire the system noise.

According to another aspect of the present invention, there is provided a computer readable storage medium comprising a stored computer program;

when the computer program is executed by the processor, the device on which the computer readable storage medium is positioned is controlled to execute the method for processing the ultra-shallow water sounding data of the multichannel laser radar provided by the invention.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

(1) according to the invention, the sea bottom echo relative time and the sea surface echo relative time are accurately obtained from the sounding data of the multi-channel laser radar in a fitting mode, so that the actual water depth of an ultra-shallow water area can be accurately calculated, and related calculation can be completed only through simple fitting, thereby effectively reducing the calculation time and improving the calculation speed. Experiments show that in an extremely shallow water area with the water depth within 2 meters, the calculation speed of the method is obviously improved compared with the existing RLD deconvolution echo separation method while the calculation accuracy of the water depth is ensured.

(2) According to the invention, the fitting interval of Gaussian fitting is specially set, so that the calculation accuracy is further ensured, and the calculation speed is further improved.

Drawings

Fig. 1 is a flowchart of a method for processing multi-channel lidar sounding data according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a Gaussian fit of a sea floor echo according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a gaussian fitting of a sea-table echo according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

The invention provides a method for processing ultra-shallow water sounding data of a multi-channel laser radar, which aims to solve the technical problems that the conventional method for extracting depth information from the ultra-shallow water sounding data of the multi-channel laser radar has long calculation time and cannot meet the real-time requirement, and the overall thought of the method is as follows: by the fitting method, the sea bottom echo relative time and the sea surface echo relative time are respectively extracted from the shallow water channel echo data of the multi-channel laser radar, so that the actual water depth of the ultra-shallow water area is calculated by using the difference between the sea bottom echo relative time and the sea surface echo relative time and the speed of laser propagation in water, complex calculation is avoided on the basis of ensuring calculation accuracy, and the calculation speed is greatly improved. The following are examples.

Example 1:

a multi-channel laser radar ultra-shallow water sounding data processing method is used for calculating the water depth of an ultra-shallow water area; as shown in fig. 1, the method comprises the steps of:

a system noise obtaining step:

acquiring the mean value and the variance of the shallow water channel echo-free waveform data of the multi-channel laser radar, and respectively taking the mean value and the variance as a mean value reference value and a variance reference value;

because the shallow water channel echo-free waveform data does not contain water body reflection information, the reference value reflects system noise;

and effective data extraction:

subtracting the mean value reference value from the echo waveform data of the shallow water channel, and extracting data with duration Tns larger than the variance reference value as effective echo data; t > 0;

the echo waveform data of the shallow water channel comprises system noise, a seabed reflection signal, a sea surface reflection signal and a water body attenuation signal, and an effective echo signal in the ultra-shallow water echo signal is formed by superposing the seabed reflection echo and the sea surface reflection echo;

in the invention, the value T is set to be more than or equal to 5 and less than or equal to 20, so that the influence of too little effective information contained in the extracted data and the influence of the calculation accuracy caused by too short time interval setting on the effective echo data can be avoided in the process of extracting the effective echo data, and the influence of the effective information loss and the increase of the calculated amount caused by too long time interval setting on the calculation accuracy and the calculation speed can be avoided;

as a preferred implementation, in this embodiment, T ═ 7, experiments show that after subtracting the mean value from the echo waveform data of the shallow water channel of the multichannel laser radar, data lasting for 7ns and greater than the variance reference value are extracted, so that the water body reflected signal can be retained, and the noise data can be removed as much as possible;

sea bottom echo fitting:

performing Gaussian fitting on the effective echo data to obtain a first fitting curve so as to determine the relative time T of the sea bottom echo according to the first fitting curve₁(ii) a The first fitted curve reflects the variation of the laser reflection signal intensity with the relative position, which, in this embodiment,the effective echo data, the first fitted curve and the difference between the two, as shown in figure 2;

since the laser reflection waveform is gaussian linear, the present embodiment performs gaussian fitting on the effective echo data to determine the sea bottom echo relative time T₁；

Since the effective echo data is formed by overlapping the sea floor reflection echo and the sea surface reflection echo, in order to avoid the influence of the sea surface reflection echo on the fitting of the sea floor echo, in this embodiment, the fitting interval for performing gaussian fitting on the effective echo data is T before the maximum value of the effective echo data₃ns to the data at the end of the valid echo data;

research shows that the sea bottom reflection peak value is near the maximum value of the echo signal; the theoretical water depth corresponding to 10ns before the peak value of the effective echo data is 1.0 m, only the data of 10ns before the peak value of the sea surface reflection is taken to reduce the influence of the sea surface reflection echo peak value on the fitting of the sea bottom echo, and the data after the peak value of the sea bottom reflection is free from the interference of other factors and can be adopted, so that the embodiment utilizes the T before the maximum value of the effective echo data₃ns(0<T₃Less than or equal to 10) to the end of the effective echo data to form a fitting interval, so that the accuracy of the submarine echo relative to time can be ensured; as an optional implementation manner, in this embodiment, T is₃＝10；

As an alternative implementation, in this embodiment, the seafloor echo relative time T is determined according to the first fitted curve₁The method comprises the following steps:

determining the relative position corresponding to the peak point of the first fitting curve as the relative position of the sea bottom echo, and determining the time corresponding to the relative position of the sea bottom echo as the relative time T of the sea bottom echo₁As shown in fig. 2;

in the reflected echo, the point with the maximum intensity is the position of the reflecting surface; in the embodiment, the relative position corresponding to the peak point of the first fitting curve obtained by Gaussian fitting of the effective echo data is determined as the sea bottom echo relative position, and the time corresponding to the sea bottom echo relative position is determined as the sea bottom echo relative time, so that the accuracy of the calculation result is ensured;

sea surface echo fitting:

performing Gaussian fitting on the difference value of the effective echo data and the first fitting curve to obtain a second fitting curve so as to determine the sea chart echo relative time T according to the second fitting curve₂(ii) a The second fitting curve reflects the relationship that the intensity of the laser reflection signal changes with the relative position, and in this embodiment, the difference between the effective echo data and the first fitting curve, and the second fitting curve are shown in fig. 3;

as a preferred embodiment, performing gaussian fitting on the difference value between the effective echo data and the first fitted curve, wherein the fitted interval is data from the starting position of the difference value to the position corresponding to the peak point of the first fitted curve;

in the embodiment, the effective echo data is formed by superposing the sea floor reflection echo and the sea surface reflection echo, and the influence of the sea surface reflection echo is eliminated from the first fitting curve, so that the difference value of the effective echo data and the first fitting curve reflects the information of the sea surface reflection echo; it should be noted that the setting of the fitting interval of the second fitted curve is only a preferred setting manner of the present invention, and in other embodiments of the present invention, the fitting interval may also be expanded to be after the peak point of the first fitted curve;

as an alternative implementation, in this embodiment, the sea table echo relative time T is determined according to the second fitted curve₂The method comprises the following steps:

determining the relative position corresponding to the peak point of the second fitting curve as the sea surface echo relative position, and determining the time corresponding to the sea surface echo relative position as the sea surface echo relative time T₂As shown in fig. 3;

similarly, in the reflected echo, the point with the maximum intensity is the position of the reflecting surface; according to the invention, the relative position corresponding to the peak point of the second fitting curve is determined as the sea surface echo relative position, and the time corresponding to the sea surface echo relative position is determined as the sea surface echo relative time, so that the accuracy of the calculation result is ensured;

water depth calculation step:

according to H ═ v [ (T) ]₂-T₁) Calculating the water depth of the ultra-shallow water area;

wherein v is the propagation velocity of the laser in water, the propagation velocity of the laser in water is slightly different due to different refractive indexes of water, generally, the propagation velocity is about 0.1 m/nanosecond, and in practical application, the propagation velocity is calculated according to the refractive index of water in a specific ultra-shallow water area; h is the water depth of the ultra-shallow water area.

Generally speaking, in the embodiment, the seabed echo relative time and the sea surface echo relative time are accurately obtained from the sounding data of the multichannel laser radar in a fitting manner, so that the actual water depth of an ultra-shallow water area can be accurately calculated, the related calculation can be completed only through simple fitting, the calculation time is effectively reduced, and the calculation speed is improved.

As an optional implementation manner, in this embodiment, any one of the following data may be used as the shallow water channel echo-free waveform data of the multi-channel lidar:

the waveform data is a part of the data at the beginning or the end of the echo waveform data of the shallow water channel, or the waveform data which is received by a detector and does not enter water is utilized.

In the shallow water channel echo waveform data of the multi-channel laser radar, the first part of data is data before laser enters water, is data in air, does not contain information reflected by a water body, and can be regarded as system noise; in the shallow water channel echo waveform data of the multi-channel laser radar, a part of tail data is received completely because the detector is opened for a long time, and water body reflection information is not included any more, so that the data can be regarded as system noise; therefore, in the embodiment, the shallow water channel echo-free waveform data of the multi-channel laser radar is acquired in the above manner, and the system noise can be accurately acquired.

Example 2:

a computer readable storage medium comprising a stored computer program;

when the computer program is executed by the processor, the apparatus on which the computer readable storage medium is located is controlled to execute the method for processing the ultra-shallow water sounding data of the multi-channel laser radar provided in embodiment 1.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.