阅读说明：本技术 一种雾区能见度反演方法及系统 (Method and system for inverting visibility in fog region ) 是由 胡树贞 陶法 张雪芬 王志成 茆佳佳 何平 于 2021-08-16 设计创作，主要内容包括：本公开实施例公开了一种雾区能见度反演方法及系统,该方法包括：控制激光雷达和毫米波雷达时空同步扫描,获取扫描区域的激光回波信号和毫米波回波信号；针对每个扫描方向,根据激光回波信号,获取激光雷达消光系数廓线,确定激光雷达有效探测区域；对毫米波回波信号进行处理,获取毫米波雷达反射率因子；根据毫米波雷达反射率因子,识别扫描区域中的雾区；将重叠区域内的激光雷达消光系数与毫米波雷达反射率因子进行数据融合,获取毫米波雷达等效消光系数,重叠区域为激光雷达有效探测区域和毫米波雷达识别出的雾区之间的重叠区域；根据毫米波雷达等效消光系数确定毫米波雷达识别出的雾区的能见度。该技术方案能够实现雾区能见度的精确反演。(The embodiment of the disclosure discloses a method and a system for inverting visibility in a fog area, wherein the method comprises the following steps: controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning, and acquiring a laser echo signal and a millimeter wave echo signal in a scanning area; aiming at each scanning direction, acquiring a laser radar extinction coefficient profile according to a laser echo signal, and determining an effective detection area of the laser radar; processing the millimeter wave echo signal to obtain a millimeter wave radar reflectivity factor; identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor; performing data fusion on the laser radar extinction coefficient and the millimeter wave radar reflectivity factor in the overlapping region to obtain the millimeter wave radar equivalent extinction coefficient, wherein the overlapping region is the overlapping region between the laser radar effective detection region and the fog region identified by the millimeter wave radar; and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar. The technical scheme can realize accurate inversion of visibility in the fog region.)

1. A fog region visibility inversion method is characterized by comprising the following steps:

controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning, and acquiring a laser echo signal and a millimeter wave echo signal in a scanning area;

aiming at each scanning direction, acquiring a laser radar extinction coefficient profile according to the laser echo signals, wherein the laser radar extinction coefficient profile is a curve representing the corresponding relation between the distance from each scanning position to the scanning center point and the laser radar extinction coefficient of each scanning position;

determining an effective detection area of the laser radar according to the extinction coefficient profile of the laser radar;

processing the millimeter wave echo signal to obtain millimeter wave radar base data, wherein the millimeter wave radar base data comprises millimeter wave radar reflectivity factors;

identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor;

performing data fusion on a laser radar extinction coefficient and a millimeter wave radar reflectivity factor in an overlapping region to obtain a millimeter wave radar equivalent extinction coefficient, wherein the overlapping region is an overlapping region between the laser radar effective detection region and a fog region identified by the millimeter wave radar;

and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar.

2. The method of claim 1, wherein determining a lidar effective detection region based on the lidar extinction coefficient profile comprises:

performing 5-level sym8 wavelet transformation on the laser radar extinction coefficient profile sigma to obtain a transformed laser radar extinction coefficient profile;

determining the mean value of the transformed laser radar extinction coefficient profile as a signal-to-noise ratio threshold value sigma_avgTaking the maximum value of the extinction coefficient in the profile of the extinction coefficient of the laser radar after transformation as the maximum value sigma of the extinction coefficient_max；

Maximum value sigma of the extinction coefficient_maxThe position corresponding to the zero-crossing point of the first extinction coefficient in the descending process is used as the boundary position of the effective detection area, and the zero-crossing point is the signal-to-noise ratio threshold value sigma_avgThe intersection point of the laser radar extinction coefficient profile line and the transformed laser radar extinction coefficient profile line;

and determining the effective detection area of the laser radar according to the boundary position in each scanning direction.

3. The method of claim 1, wherein the millimeter wave echo signal comprises: the millimeter wave radar scans a first millimeter wave echo signal obtained by the target azimuth in a range height display (RHI) scanning mode; and the millimeter wave radar displays a second millimeter wave echo signal obtained by scanning in the PPI scanning mode at a plane position.

4. The method of claim 3, wherein the processing the millimeter wave echo signal to obtain millimeter wave radar base data in the scan region comprises:

presetting the first millimeter wave echo signal and the second millimeter wave echo signal respectively to obtain a first millimeter wave radar reflectivity factor Z on a target azimuth vertical plane in an RHI scanning mode_RHIAnd a second millimeter wave radar reflectivity factor Z on the plane in PPI scanning mode_PPIThe preset processing comprises coherent accumulation, fast Fourier transform and spectrum average processing.

5. The method of claim 4, wherein the pre-conditioning process further comprises a median filtering and a corrosion dilation process.

6. The method of claim 4, wherein identifying fog regions in the scanned region from the millimeter wave radar base data comprises:

according to the first millimeter wave radar reflectivity factor Z_RHIAnd the echo bottom height H of the first millimeter wave echo signal_bEcho height H_tAnd identifying the fog region in the vertical direction of the scanning region in the target direction by using an identification formula as follows:

Fog_area_V＝Z_RHIH_bH_t|Z_RHI≤Z₀，H_b≤H_B，H_t≤H_T；

wherein the Fog _ area _ V represents a vertical Fog zone range at the target orientation, the Z₀、H_B、H_TIs a preset initial threshold value;

obtaining a most proximal boundary position a and a most distal boundary position b of the vertical fog region in the PPI scanning mode according to the projection of the vertical fog region in the target direction on the PPI scanning mode;

according to the second millimeter wave radar reflectivity factor Z_PPIAnd a and b, identifying the fog region in the horizontal direction of the scanning region by using an identification formula as follows:

wherein the Fog _ area _ H is expressed as a second millimeter wave radar reflectivity factor Z on the plane in PPI scanning mode_iLess than or equal to Z₀And the communication area is communicated with the interval from the position a to the position b, and the communication area is a fog area in the horizontal direction.

7. The method of claim 6, wherein the target position comprises at least one position, and accordingly, for each position, one fog region in the horizontal direction is identified, and the fog regions in the scanning area are obtained by combining at least one fog region in the horizontal direction corresponding to the at least one position.

8. The method according to any one of claims 1 to 7, wherein the data fusion of the laser radar extinction coefficient and the millimeter wave radar reflectivity factor in the overlapping region to obtain the millimeter wave radar equivalent extinction coefficient comprises:

the fusion factor μ is calculated according to the following formula:

μ＝γ_avg/Z_avg；

wherein, γ_avgIs the mean value of the laser radar extinction coefficients in the overlap region, Z_avgThe mean value of the reflectivity factors of the second millimeter wave radar in the overlapping area is obtained;

calculating the equivalent extinction coefficient gamma of the millimeter wave radar according to the fusion factor and the following formula_m-ladr：

γ_m-ladr＝μ×Z_m；

Wherein, Z is_mThe factor of the reflectivity of the millimeter wave radar on the mth range bin in the fog region identified by the millimeter wave radar in the PPI scanning mode.

9. The method as claimed in claim 8, wherein said determining visibility in fog region according to said millimeter wave radar equivalent extinction coefficient comprises:

calculating the visibility VIS of the fog area according to the following formula_m-ladr：

VIS_m-ladr＝3.912/γ_m-ladr。

10. A fog region visibility inversion system, comprising: laser radar, millimeter wave radar, servo platform and processor, wherein,

the servo platform is connected with the laser radar and the millimeter wave radar and is used for controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning;

the processor is connected with the servo platform, the laser radar and the millimeter wave radar, and is used for indicating the servo platform to control the laser radar and the millimeter wave radar to perform space-time synchronous scanning and receiving a laser echo signal returned by the laser radar and a millimeter wave echo signal returned by the millimeter wave radar; aiming at each scanning direction, acquiring a laser radar extinction coefficient profile according to the laser echo signals, wherein the laser radar extinction coefficient profile is a curve representing the corresponding relation between the distance from each scanning position to the scanning center point and the laser radar extinction coefficient of each scanning position; determining an effective detection area of the laser radar according to the extinction coefficient profile of the laser radar; processing the millimeter wave echo signal to obtain millimeter wave radar base data, wherein the millimeter wave radar base data comprises millimeter wave radar reflectivity factors; identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor; performing data fusion on a laser radar extinction coefficient and a millimeter wave radar reflectivity factor in an overlapping region to obtain a millimeter wave radar equivalent extinction coefficient, wherein the overlapping region is an overlapping region between the laser radar effective detection region and a fog region identified by the millimeter wave radar; and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar.

Technical Field

The disclosure relates to the field of atmospheric detection and atmospheric remote sensing, in particular to a method and a system for inverting visibility in a fog region.

Background

When fog occurs, the horizontal visibility on the ground is often reduced, and certain influence is caused on the production and the life of human beings. Traditionally, fog is monitored mainly by using a forward scattering visibility meter to carry out single-point observation, but for industries such as airports and ports with higher requirements on visibility observation, single-point observation carried out by the forward scattering visibility meter is simply relied on, the observation data representativeness is lower, the application requirement of production service cannot be met, and therefore, the realization of remote sensing observation of the visibility in a fog area has important practical value.

At present, there are two main ways for remote sensing observation of visibility in a fog area, one way is to use a millimeter wave radar to invert visibility in the fog area, and the millimeter wave radar can acquire relevant information of an meteorological target in a scanning area according to the scattering effect of a fog droplet spectrum on electromagnetic waves, identify the vertical boundary and horizontal distribution of fog, analyze and invert the intensity information and horizontal and vertical airflow distribution conditions of the fog, and monitor the generation and elimination evolution process of the fog. However, when the visibility of a fog region is quantitatively inverted based on the millimeter wave radar, inversion is generally performed by establishing an empirical formula between the visibility and a reflectivity factor of the region where the radar is located in fog weather, and an inversion result depending on the empirical formula is easily affected by multiple factors such as the cause and the type of fog, the distribution of a fog droplet spectrum and the like, so that the error of the inversion result is large. The other mode is that the atmospheric visibility is inverted by using a laser radar, the laser radar is more sensitive to a droplet spectrum and can obtain an atmospheric aerosol extinction coefficient in a scanning area, the relation between the aerosol extinction coefficient and the visibility is relatively clear, and the visibility information can be inverted relatively accurately, but the laser radar has a short wavelength and is seriously attenuated in low-visibility weather, and the meteorological information in a large enough space range cannot be obtained. Therefore, how to realize the remote large-area accurate inversion of the visibility in the fog area has important research significance.

Disclosure of Invention

The embodiment of the disclosure provides a method and a system for inverting visibility in a fog area.

In a first aspect, an embodiment of the present disclosure provides a method for inverting visibility in a fog region, including:

controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning, and acquiring a laser echo signal and a millimeter wave echo signal in a scanning area;

aiming at each scanning direction, acquiring a laser radar extinction coefficient profile according to the laser echo signals, wherein the laser radar extinction coefficient profile is a curve representing the corresponding relation between the distance from each scanning position to the scanning center point and the laser radar extinction coefficient of each scanning position;

determining an effective detection area of the laser radar according to the extinction coefficient profile of the laser radar;

processing the millimeter wave echo signal to obtain millimeter wave radar base data, wherein the millimeter wave radar base data comprises millimeter wave radar reflectivity factors;

identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor;

performing data fusion on a laser radar extinction coefficient and a millimeter wave radar reflectivity factor in an overlapping region to obtain a millimeter wave radar equivalent extinction coefficient, wherein the overlapping region is an overlapping region between the laser radar effective detection region and a fog region identified by the millimeter wave radar;

and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar.

Further, the determining the effective detection area of the laser radar according to the laser radar extinction coefficient profile includes:

performing 5-level sym8 wavelet transformation on the laser radar extinction coefficient profile sigma to obtain a transformed laser radar extinction coefficient profile;

determining the mean value of the transformed laser radar extinction coefficient profile as a signal-to-noise ratio threshold value sigma_avgTaking the maximum value of the extinction coefficient in the profile of the extinction coefficient of the laser radar after transformation as the maximum value sigma of the extinction coefficient_max；

Maximum value sigma of the extinction coefficient_maxThe position corresponding to the zero-crossing point of the first extinction coefficient in the descending process is used as the boundary position of the effective detection area, and the zero-crossing point is the signal-to-noise ratio threshold value sigma_avgThe intersection point of the laser radar extinction coefficient profile line and the transformed laser radar extinction coefficient profile line;

and determining the effective detection area of the laser radar according to the boundary position in each scanning direction.

Further, the millimeter wave echo signal includes: the millimeter wave radar scans a first millimeter wave echo signal obtained by the target azimuth in a range height display (RHI) scanning mode; and the millimeter wave radar displays a second millimeter wave echo signal obtained by scanning in the PPI scanning mode at a plane position.

Further, the processing the millimeter wave echo signal to obtain the millimeter wave radar base data in the scanning area includes:

presetting the first millimeter wave echo signal and the second millimeter wave echo signal respectively to obtain a first millimeter wave radar reflectivity factor Z on a target azimuth vertical plane in an RHI scanning mode_RHIAnd a second millimeter wave radar reflectivity factor Z on the plane in PPI scanning mode_PPIThe preset processing comprises coherent accumulation, fast Fourier transform and spectrum average processing.

Further, the preset treatment also comprises median filtering and corrosion expansion treatment.

Further, the identifying the fog region in the scanning region according to the millimeter wave radar base data includes:

according to the first millimeter wave radar reflectivity factor Z_RHIAnd the echo height of the first millimeter wave echo signalH_bEcho height H_tAnd identifying the fog region in the vertical direction of the scanning region in the target direction by using an identification formula as follows:

Fog_area_V＝Z_RHIH_bH_t|Z_RHI≤Z₀，H_b≤H_B，H_t≤H_T；

wherein the Fog _ area _ V represents a vertical Fog zone range at the target orientation, the Z₀、H_B、H_TIs a preset initial threshold value;

obtaining a most proximal boundary position a and a most distal boundary position b of the vertical fog region in the PPI scanning mode according to the projection of the vertical fog region in the target direction on the PPI scanning mode;

according to the second millimeter wave radar reflectivity factor Z_PPIAnd a and b, identifying the fog region in the horizontal direction of the scanning region by using an identification formula as follows:

wherein the Fog _ area _ H is expressed as a second millimeter wave radar reflectivity factor Z on the plane in PPI scanning mode_iLess than or equal to Z₀And the communication area is communicated with the interval from the position a to the position b, and the communication area is a fog area in the horizontal direction.

Further, the target position comprises at least one position, correspondingly, for each position, a fog area in the horizontal direction is identified, and the fog areas in the horizontal direction corresponding to the at least one position are combined to obtain the fog area in the scanning area.

Further, the data fusion of the laser radar extinction coefficient in the overlapping area and the millimeter wave radar reflectivity factor to obtain the millimeter wave radar equivalent extinction coefficient includes:

the fusion factor μ is calculated according to the following formula:

μ＝γ_avg/Z_avg；

wherein, γ_avgIs the mean value of the laser radar extinction coefficients in the overlap region, Z_avgThe mean value of the reflectivity factors of the second millimeter wave radar in the overlapping area is obtained;

calculating the equivalent extinction coefficient gamma of the millimeter wave radar according to the fusion factor and the following formula_m-ladr：

γ_m-ladr＝μ×Z_m；

Wherein, Z is_mThe factor of the reflectivity of the millimeter wave radar on the mth range bin in the fog region identified by the millimeter wave radar in the PPI scanning mode.

Further, the determining the visibility in the fog region according to the equivalent extinction coefficient of the millimeter wave radar includes:

calculating the visibility VIS of the fog area according to the following formula_m-ladr：

VIS_m-ladr＝3.912/γ_m-ladr。

In a second aspect, an embodiment of the present invention provides a visibility inversion system in a fog region, including: laser radar, millimeter wave radar, servo platform and processor, wherein,

the servo platform is connected with the laser radar and the millimeter wave radar and is used for controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning;

the processor is connected with the servo platform, the laser radar and the millimeter wave radar and used for indicating the servo platform to control the laser radar and the millimeter wave radar to perform space-time synchronous scanning, receiving laser echo signals returned by the laser radar and millimeter wave echo signals returned by the millimeter wave radar, and acquiring a laser radar extinction coefficient profile according to the laser echo signals in each scanning direction, wherein the laser radar extinction coefficient profile is a curve representing the corresponding relation between the distance from each scanning position to a scanning central point and the laser radar extinction coefficient of each scanning position; determining an effective detection area of the laser radar according to the extinction coefficient profile of the laser radar; processing the millimeter wave echo signal to obtain millimeter wave radar base data, wherein the millimeter wave radar base data comprises millimeter wave radar reflectivity factors; identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor; performing data fusion on a laser radar extinction coefficient and a millimeter wave radar reflectivity factor in an overlapping region to obtain a millimeter wave radar equivalent extinction coefficient, wherein the overlapping region is an overlapping region between the laser radar effective detection region and a fog region identified by the millimeter wave radar; and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar.

The technical scheme provided by the embodiment of the disclosure can have the following beneficial effects:

the method for inverting the visibility in the fog area effectively combines the advantages of high detection sensitivity of a laser radar and long detection distance of a millimeter wave radar, and realizes accurate inversion of the visibility in the fog area.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

Other features, objects, and advantages of the present disclosure will become more apparent from the following detailed description of non-limiting embodiments when taken in conjunction with the accompanying drawings. In the drawings:

FIG. 1 shows a flow diagram of a method for fog region visibility inversion according to an embodiment of the present disclosure;

FIG. 2 illustrates a schematic diagram of an acquisition process of an overlap region according to an embodiment of the present disclosure;

FIG. 3 illustrates a correlation graph for determining an effective detection zone of a lidar in accordance with an embodiment of the present disclosure;

fig. 4 shows a schematic structural diagram of a visibility inversion system in a fog region according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. Also, for the sake of clarity, parts not relevant to the description of the exemplary embodiments are omitted in the drawings.

In the present disclosure, it is to be understood that terms such as "including" or "having," etc., are intended to indicate the presence of the disclosed features, numbers, steps, actions, components, parts, or combinations thereof, and do not preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof are present or added.

It should be further noted that the embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

The details of the embodiments of the present disclosure are described in detail below with reference to specific embodiments.

Fig. 1 shows a flowchart of a method for inverting visibility in a fog area according to an embodiment of the present disclosure, and as shown in fig. 1, the method for inverting visibility in a fog area includes the following steps S101 to S107:

in step S101, controlling the laser radar and the millimeter wave radar to perform space-time synchronous scanning, and obtaining a laser echo signal and a millimeter wave echo signal in a scanning area;

in step S102, for each scanning direction, obtaining a lidar extinction coefficient profile according to the laser echo signal, where the lidar extinction coefficient profile is a curve representing a correspondence between a distance from each scanning position to a scanning center point and a lidar extinction coefficient at each scanning position;

in step S103, determining an effective detection area of the lidar according to the laser radar extinction coefficient profile;

in step S104, processing the millimeter wave echo signal to obtain millimeter wave radar base data, where the millimeter wave radar base data includes a millimeter wave radar reflectivity factor;

in step S105, identifying a fog region in the scanning region according to the millimeter wave radar reflectivity factor;

in step S106, performing data fusion on the laser radar extinction coefficient and the millimeter wave radar reflectivity factor in an overlap region to obtain a millimeter wave radar equivalent extinction coefficient, where the overlap region is an overlap region between the laser radar effective detection region and a fog region identified by the millimeter wave radar;

in step S107, the visibility of the fog region identified by the millimeter wave radar is determined according to the equivalent extinction coefficient of the millimeter wave radar.

The method can control the laser radar and the millimeter wave radar to perform space-time synchronous periodic scanning, an effective detection area of the laser radar is determined by a laser echo signal obtained by scanning of the laser radar, a fog area in the scanning area of the millimeter wave radar is identified by the millimeter wave echo signal obtained by scanning of the millimeter wave radar, for example, fig. 2 shows a schematic diagram of an acquisition process of an overlapping area according to an embodiment of the method, as shown in fig. 2, the laser radar has high detection sensitivity but poor penetration force, so that the obtained effective detection area Q1 is smaller, the millimeter wave radar has far detection distance and large scanning area, so that the identified fog area Q2 is larger, the overlapping area Q12 between the effective detection area Q1 and the fog area Q2 is an observation effective overlapping area of two radars, and because an empirical formula inversion visibility error between a reflectivity factor of the millimeter wave radar and the visibility is large, the inversion result of the empirical formula correspondence between the extinction coefficient and the visibility is more accurate, so that the laser radar extinction coefficient and the millimeter wave radar reflectivity factor in the overlapping area Q12 are subjected to data fusion to obtain a fusion factor, the fusion factor can reflect the corresponding relation between the millimeter wave radar reflectivity factor and the laser radar extinction coefficient to a certain extent, and the equivalent extinction coefficient in the fog area identified by the millimeter wave radar can be obtained according to the fusion factor and the reflectivity factor in the fog area identified by the millimeter wave radar; and then, the visibility of the fog area identified by the millimeter wave radar can be determined by inversion through the equivalent extinction coefficient of the millimeter wave radar, so that the visibility of the obtained fog area is relatively accurate.

Therefore, the fog region visibility inversion method provided by the embodiment effectively combines the advantages of high detection sensitivity of the laser radar and long detection distance of the millimeter wave radar, and realizes accurate inversion of the fog region visibility.

In an embodiment of the present disclosure, the step S103 in the method for inverting visibility in a fog area may be implemented as the following steps a1 to a 4:

in step a1, performing 5-level sym8 wavelet transform on the laser radar extinction coefficient profile σ to obtain a transformed laser radar extinction coefficient profile;

in step A2, determining the mean value of the transformed lidar extinction coefficient profile as the signal-to-noise ratio threshold σ_avgTaking the maximum value of the extinction coefficient in the profile of the extinction coefficient of the laser radar after transformation as the maximum value sigma of the extinction coefficient_max；

In step A3, the extinction coefficient maximum value σ is set_maxThe position corresponding to the zero-crossing point of the first extinction coefficient in the descending process is used as the boundary position of the effective detection area, and the zero-crossing point is the signal-to-noise ratio threshold value sigma_avgThe intersection point of the laser radar extinction coefficient profile line and the transformed laser radar extinction coefficient profile line;

in step a4, the lidar effective detection area is determined based on the boundary position in each scanning direction.

In this implementation, the lidar extinction coefficient and the method of defining and obtaining the lidar extinction coefficient profile are well understood by those skilled in the art and will not be described in detail herein.

FIG. 3 is a graph illustrating a correlation curve for determining an effective detection region of a lidar according to an embodiment of the present disclosure, as shown in FIG. 3. FIG. 3 shows a lidar extinction coefficient profile σ in a scanning direction and a transformed lidar extinction coefficient profile obtained by performing a 5-level sym8 wavelet transform on the lidar extinction coefficient profile σ. As can be seen from FIG. 3, the SNR threshold σ is_avgThe intersection points of the laser radar extinction coefficient profile after the transformation are multiple, such as a zero crossing point 1, a zero crossing point 2 and the like, wherein the zero crossing point 2 is a zero crossing point of a descending process of a first extinction coefficient after the maximum value point of the extinction coefficient, and then the boundary position of an effective detection area of the laser radar in the direction isThe positions corresponding to the horizontal axis x1 corresponding to the zero crossing point 2, that is, the positions within the distance x1 from the scanning center point in the scanning direction all belong to the effective detection area of the laser radar.

Therefore, the boundary positions of the laser radar effective detection areas in all scanning directions can be obtained through the method, and the laser radar effective detection areas are further obtained.

In an optional implementation manner of this embodiment, the millimeter wave echo signal includes: the millimeter wave radar scans a first millimeter wave echo signal obtained by the target azimuth in a range height display (RHI) scanning mode; and the millimeter wave radar displays a second millimeter wave echo signal obtained by scanning in the PPI scanning mode at a plane position.

In this implementation, the RHI scan mode and PPI scan mode are well known to those skilled in the art and will not be described in detail herein.

It should be noted that, in the fog region detection of the present embodiment, in order to improve the scanning efficiency and save time, the maximum elevation angle of the millimeter wave radar scanned in the RHI scanning mode is controlled within 30 °, which may be set according to specific situations.

In an optional implementation manner of this embodiment, step S104 in the above-mentioned fog region visibility inversion method may be implemented as the following step B1:

in step B1, the first millimeter wave echo signal and the second millimeter wave echo signal are respectively subjected to preset processing, so as to obtain a first millimeter wave radar reflectivity factor on a target azimuth vertical plane in the RHI scanning mode and a second millimeter wave radar reflectivity factor on a plane in the PPI scanning mode, where the preset processing includes coherent accumulation, fast fourier transform, and spectrum averaging.

In this alternative implementation, the processes of coherent accumulation, fast fourier transform and spectral averaging in the preset process are well known to those skilled in the art, and will not be described in detail here.

In this optional implementation manner, after performing the preset processing on the first millimeter wave echo signal, a first millimeter wave radar reflectivity factor on a vertical plane of a target azimuth in the RHI scanning mode may be obtained, and after performing the preset processing on the second millimeter wave echo signal, a second millimeter wave radar reflectivity factor on a plane in the PPI scanning mode may be obtained.

In an optional implementation manner of this embodiment, the preset processing in step B1 in the above-mentioned fog region visibility inversion method may further include median filtering and corrosion expansion processing.

In this implementation manner, coherent accumulation, fast fourier transform, and spectrum averaging may be performed on the first millimeter wave echo signal and the second millimeter wave echo signal, respectively, to obtain a first standby millimeter wave radar reflectivity factor and a second standby millimeter wave radar reflectivity factor; the first standby millimeter wave radar reflectivity factor and the second standby millimeter wave radar reflectivity factor obtained here may contain clutter, and at this time, median filtering and corrosion expansion processing need to be performed on the standby reflectivity factor containing the clutter, so that the standby reflectivity factor is more suitable for actual conditions, and further, subsequent visibility inversion is more accurate. And carrying out median filtering and corrosion expansion treatment on the first standby millimeter wave radar reflectivity factor and the second standby millimeter wave radar reflectivity factor respectively to obtain the first millimeter wave radar reflectivity factor and the second millimeter wave radar reflectivity factor.

In this alternative implementation, the median filtering and erosion dilation in the default process are well known to those skilled in the art and will not be described in detail herein.

In an optional implementation manner of this embodiment, the step S105 in the above-mentioned fog region visibility inversion method may be implemented as the following steps C1 to C3:

in step C1, according to the first millimeter wave radar reflectivity factor Z_RHIAnd the echo bottom height H of the first millimeter wave echo signal_bEcho height H_tAnd identifying the fog region in the vertical direction of the scanning region in the target direction by using an identification formula as follows:

Fog_area_V＝Z_RHIH_bH_t|Z_RHI≤Z₀，H_b≤H_B，H_t≤H_T；

wherein the Fog _ area _ V represents a vertical Fog zone range at the target orientation, the Z₀、H_B、H_TIs a preset initial threshold value;

in step C2, obtaining a most proximal boundary position a and a most distal boundary position b of the vertical fog region in the PPI scanning mode according to the projection of the vertical fog region in the target orientation on the PPI scanning mode;

in step C3, according to the second millimeter wave radar reflectivity factor Z_PPIAnd a and b, identifying the fog region in the horizontal direction of the scanning region by using an identification formula as follows:

wherein the Fog _ area _ H represents that the reflectivity factor of the second millimeter wave radar on the plane in the PPI scanning mode is less than or equal to Z₀And a communication area communicated with the interval from the position a to the position b.

In this implementation, the connected domain is a fog region in the horizontal direction, and Z is_iIs less than or equal to Z₀The second millimeter wave radar reflectivity factor.

In this implementation, the vertical Fog region range Fog _ area _ V at the target azimuth and the first millimeter wave radar reflectivity factor Z_RHIAnd the echo bottom height H of the first millimeter wave echo signal_bEcho height H_tCorrelation according to Z_RHI、H_bAnd H_tA vertical Fog region Fog _ area _ V in the target orientation may be determined, which is a solid area Q3 in the vertical direction in the target orientation.

In this implementation manner, the millimeter wave radar scans one circle at an elevation angle in the PPI scanning mode, the scanning corresponds to a planar area, and the vertical Fog region Fog _ area _ V is projected on the planar area scanned in the PPI scanning mode, so as to obtain the vertical Fog region Fog _ area _ VThe boundary position a of the nearest end of the straight fog region in the horizontal direction and the boundary position b of the farthest end of the straight fog region in the horizontal direction. Then the echo connected domain Z can be obtained according to the a, b_iAnd Z or less on the plane in the PPI scanning mode₀Second millimeter wave radar reflectivity factor Z_iAnd identifying the Fog region in the horizontal direction of the scanning region to obtain a connected region Fog _ area _ H, wherein the connected region is the Fog region in the horizontal direction, and the Fog region range in the horizontal direction is the Fog region identified by the millimeter wave radar.

In an optional implementation manner of this embodiment, in steps C1 to C3 in the above-mentioned method for inverting visibility of a fog region, the target position includes at least one position, and accordingly, at least one fog region in the horizontal direction corresponding to the at least one position is identified, and the at least one fog region in the horizontal direction is combined to obtain the fog region in the scanning region.

In this implementation, the target orientation may be one orientation or may be two or more different orientations. When the target azimuth is an azimuth, a horizontally oriented fog region may be determined as the fog region recognized by the millimeter wave radar according to the above steps C1 to C3. When the target orientation is two or more different orientations, for each orientation, a horizontal fog region may be determined according to the above steps C1 to C3, and the fog regions in the scanning area may be obtained by combining the at least one horizontal fog region.

In this implementation, performing RHI scans in multiple orientations is beneficial to improving the accuracy of the identification range of the fog region in the horizontal direction.

In an optional implementation manner of this embodiment, the step S106 in the above-mentioned fog region visibility inversion method may be implemented as the following steps D1 to D2:

in step D1, the fusion factor μ is calculated according to the following formula:

μ＝γ_avg/Z_avg；

wherein, γ_avgIs the mean value of the laser radar extinction coefficients in the overlap region, Z_avgThe mean value of the reflectivity factors of the second millimeter wave radar in the overlapping area is obtained;

in step D2, the millimeter wave radar equivalent extinction coefficient γ is calculated according to the following formula according to the fusion factor_m-ladr：

γ_m-ladr＝μ×Z_m；

Wherein, Z is_mAnd the millimeter wave radar reflectivity factor of the millimeter wave radar in the mth range bin in the fog region identified by the millimeter wave radar in the PPI scanning mode is obtained.

In this implementation, both the millimeter wave radar reflectivity factor Z and the laser radar extinction coefficient γ are proportional to the droplet number concentration N and the diameter D of the droplet spectrum, and the formula can be expressed as:

in this implementation, the second millimeter wave radar reflectivity factor Z for each location within the overlap region may be determined_PPICalculating the mean value to obtain Z_avgCalculating the mean value of the laser radar extinction coefficients gamma of all the positions in the overlapping area to obtain gamma_avgThe ratio of the two was used as the fusion factor μ.

In this implementation, the fusion factor

The fusion factor mu is only in proportional relation with the mist droplet spectrum diameter D, and for each single mist weather process, the mist droplet spectrum diameter can be approximately considered to be kept unchanged, so that the fusion factor mu can be considered as a constant related to the mist weather process. The corresponding relation between the millimeter wave radar reflectivity factor and the laser radar extinction coefficient can be reflected to a certain degree, so that the equivalent extinction coefficient of the fog region identified by the millimeter wave radar can be obtained according to the millimeter wave radar reflectivity factor in the fog region identified by the millimeter wave radar in the PPI scanning mode and the fusion factor.

In this alternative implementation, the definition of the distance library is well known to those skilled in the art and will not be described in detail herein. And calculating the equivalent extinction coefficient on the whole plane in the fog region according to the second millimeter wave radar reflectivity factor and the fusion factor on each range bin in each scanning direction.

In an optional implementation manner of this embodiment, step S107 in the above-described fog region visibility inversion method may be implemented as the following step E1:

in step E1, the visibility VIS of the fog region is calculated according to the following formula_m-ladr：

VIS_m-ladr＝3.912/γ_m-ladr。

The following are embodiments of the disclosed apparatus that may be used to perform embodiments of the disclosed methods.

Fig. 4 shows a schematic structural diagram of a fog region visibility inversion system, which may be implemented as part or all of a system by software, hardware, or a combination of both, according to an embodiment of the present disclosure. As shown in fig. 4, the visibility inversion system for fog areas includes: laser radar 401, millimeter wave radar 402, servo platform 403, and processor 404, wherein:

the servo platform 403 is connected with the laser radar 401 and the millimeter wave radar 402 and is used for controlling the laser radar 401 and the millimeter wave radar 402 to perform space-time synchronous scanning;

the processor 404 is connected to the servo platform 403, the laser radar 401 and the millimeter wave radar 402, and is configured to instruct the servo platform 403 to control the laser radar 401 and the millimeter wave radar 402 to perform time-space synchronous scanning, and receive a laser echo signal returned by the laser radar 401 and a millimeter wave echo signal returned by the millimeter wave radar 402; acquiring a laser radar extinction coefficient profile in the scanning area according to the laser echo signal, processing the laser radar extinction coefficient profile, extracting an extinction coefficient signal-to-noise ratio threshold value and an extinction coefficient maximum value, and determining an effective detection area of the laser radar; processing the millimeter wave echo signals to obtain millimeter wave radar base data, and identifying a fog region in the scanning region according to the millimeter wave radar base data, wherein the millimeter wave radar base data comprise millimeter wave radar reflectivity factors; performing data fusion on a laser radar extinction coefficient and a millimeter wave radar reflectivity factor in an overlapping region to obtain a fusion factor, wherein the overlapping region is an overlapping region between the laser radar effective detection region and a fog region identified by the millimeter wave radar; calculating the equivalent extinction coefficient of the millimeter wave radar according to the fusion factor; and determining the visibility of the fog region identified by the millimeter wave radar according to the equivalent extinction coefficient of the millimeter wave radar.

In this embodiment, the visibility inversion method of the fog region executed by the processor in the visibility inversion system of the fog region is consistent with the visibility inversion method of the fog region, and specific details may be referred to the description of the visibility inversion method of the fog region, which is not described herein again.

The foregoing description is only exemplary of the preferred embodiments of the disclosure and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention in the present disclosure is not limited to the specific combination of the above-mentioned features, but also encompasses other embodiments in which any combination of the above-mentioned features or their equivalents is possible without departing from the inventive concept. For example, the above features and (but not limited to) the features disclosed in this disclosure having similar functions are replaced with each other to form the technical solution.