CN104297117A - Scenic area road traffic pollution early-warning device based on remote sensing technique and scenic area road traffic pollution early-warning method based on remote sensing technique - Google Patents

Abstract

The invention discloses an early warning device for road traffic pollution in scenic spots based on remote sensing technology. Atmospheric laser measurement systems are installed at three to five commanding height measuring points, and the above atmospheric laser measurement systems are uniformly connected to a server; they will be used to detect the road traffic environment in scenic spots. The monitoring result device of the air roadside fixed conventional monitoring station for the concentration of pollutants is connected to the server; the monitoring device of the fixed conventional monitoring station for the comprehensive ambient air of the scenic spot is connected to the server. In view of the various advantages and disadvantages of the current regional environmental monitoring platform, and according to the West Lake The scenic spot has the geographical characteristics of "clouds and mountains on three sides and a city on one side". It is proposed to build an atmospheric remote sensing and telemetry platform at the commanding heights around the West Lake to monitor the NO ₂ and other chemical substances mainly produced by road traffic in the scenic spot in real time.

Description

Device and method for early warning of road traffic pollution in scenic spots based on remote sensing technology

technical field

The invention belongs to the cross field of environmental science and technology, public safety and disaster prevention and mitigation, and relates to a road traffic pollution early warning device and method for scenic spots based on remote sensing technology.

Background technique

With the improvement of economic conditions, the opportunities for Chinese people to travel during holidays have been greatly improved. Hangzhou West Lake Scenic Area, a world natural and cultural heritage of "heaven above and Suzhou and Hangzhou below", is attracting more and more visitors from home and abroad. However, the access and passage roads of the West Lake scenic spot are mostly positioned and designed according to the city's secondary arterial roads or even branch roads. With the continuous increase of tourist traffic, the dilemma of "difficult to drive and difficult to park" often occurs when entering and exiting the West Lake. The traffic jam during the Golden Week reached a blowout situation. Although this situation has been effectively alleviated by measures such as traffic restrictions and one-way lanes, as the number of private cars continues to rise, it is necessary to monitor the traffic flow in scenic spots and its impact on the atmosphere and acoustic environment, and inform tourists of the impact and even the degree of pollution. , Increase the intensity of traffic management to protect the tourism quality of West Lake.

The current situation of road traffic environmental impact and pollution in the West Lake Scenic Area exists in most scenic areas in my country to varying degrees.

At this stage, the research and control of regional traffic atmospheric environment carrying capacity, the macroscopic method is to conduct research on the static state of the largest motor vehicle total value in the region, and the focus is limited to providing scientific decision-making basis for controlling the total motor vehicle development . However, the environmental impact of motor vehicles is fluid and instantaneous. When the total amount does not exceed the total capacity of the urban environment, the distribution of pollution concentration in the area along the road is generally uneven, especially in small areas with heavy traffic and large traffic volume. Exhaust gas will have an impact on the environment, and the pollution concentration may even seriously exceed the standard. However, the air and acoustic environment in remote areas with less traffic and close to remote areas are of good quality. For the environmental impact along the road, it can be calculated and predicted through mathematical models and software through actual measurement and measurement of traffic flow, vehicle speed and large vehicle occupancy rate. However, the impact on the emission diffusion of automobile exhaust is also affected by the meteorological conditions at that time, as well as microscopic chemical reactions and changes, which will have a significant impact on the prediction and calculation results, and the use of historical meteorological data can only reflect the average results more accurately. Because it is difficult to obtain instantaneous meteorological parameters, and the changes of chemical processes are too complicated, they are generally simplified to be negligible, which makes the calculation results impossible or have large errors.

The actual measurement method is to establish multiple long-term fixed-point monitoring stations in the region and form a network. At present, the monitoring equipment of most stations for N0 ₂ , SO ₂ , PM, CO, THC, O ₃ and aerosols are ground-based point instruments. , for example, there are already several such stations in the West Lake Scenic Area; limited by personnel, investment and operating costs, the number of concentration observation data at ground stations is very limited, and the spatial distribution information of the atmosphere cannot be obtained. At present, the best spatial distribution data is traditionally acquired and realized through the remote sensing technology of balloon airship aircraft aviation and satellite aerospace airborne instruments, but its operation cost is higher, and the time and spatial resolution of the obtained data are poor.

The method of simultaneously observing the concentration of pollutants distributed in a wide atmospheric space from one location is usually to use wired or wireless methods to transmit data from many sensors located in a wide area to a remote measurement system for detection. However, the disadvantage of this method is that it cannot continuously measure the distribution state of the space. A better method is to use electromagnetic waves as "detectors" at the same location to continuously measure the distribution of space over a long distance. This is radar. Microwave radar has been widely used in the fields of aviation, navigation and meteorology. Now there are laser radars that use 4 to 5 orders of magnitude shorter wavelengths and are more directional.

Due to the short wavelength and good directionality of the laser, it has high measurement accuracy in space detection and can detect particulate and gaseous substances floating in the atmosphere. And because the laser belongs to the wavelength range absorbed by molecules and atoms, so when measuring the concentration of molecules and atoms in the atmosphere and the fluorescent objects floating on the sea surface and lake surface, as well as in the air of wind, temperature, humidity and other meteorological factors. It can be used for telemetry of atmospheric phenomena such as distribution of clouds and rainfall.

Since the spatial distribution information obtained by lidar has a large amount of data, with the development of computer and high-speed data processing technology, the application of lidar is more extensive.

The diffusion of air pollutants is seriously affected by meteorological conditions, and there are unavoidable chemical processes. The overall time and space of the transmission process is variable. At present, for the research and control of regional traffic atmospheric environment carrying capacity, simulation calculation is a method, but there are large errors in accuracy. Although the actual measurement method is the most reliable method, a network is formed by establishing multiple long-term monitoring stations in the region. At present, the monitoring equipment for N0 ₂ , PM and other chemical substances and gases at most stations are ground-based point instruments. For example, there are several such stations in the West Lake Scenic Area, but limited by personnel, investment and operating costs, the ground stations and concentration observation data, especially from the perspective of 3D spatial distribution, are very limited, so it is impossible to Obtaining the spatial distribution information of the atmosphere generally leads to small coverage and poor timeliness. At present, the best spatial distribution data is traditionally acquired and realized through the remote sensing technology of balloon airship aircraft aviation and satellite aerospace airborne instruments, but its operation cost is higher, and the time and spatial resolution of the obtained data are poor.

Conventional instruments for atmospheric remote sensing ground experiments include direct and indirect remote sensing equipment. Direct measurement also uses remote sensing instruments at fixed points, such as laser radar systems, with optical probes pointing at high altitudes, and differential absorption laser radars can measure the spatial distribution and concentration of pollutants such as NO ₂ . Indirect or non-remote sensing instruments, including air pollution automatic analyzers (automatic analyzers including NO ₂ and other pollutants), which can automatically measure the concentration of NO ₂ and other ambient air quality indicators; ambient air automatic monitoring system, equipped with meteorological parameter measurement and Converter (wind speed, wind direction, temperature and humidity, air pressure) sampling system, including measuring instrument system for factors such as _NO2 , as well as recorder, system controller and network transmission configuration, etc. for real-time online measurement of relevant parameters.

Contents of the invention

In view of the above-mentioned technical defects, the present invention takes the West Lake Scenic Area as an example, and proposes an early warning device and method for important road traffic pollution in the scenic area based on remote sensing technology.

In order to solve the problems of the technologies described above, the technical solution of the present invention is as follows:

The early warning device for road traffic pollution in scenic spots based on remote sensing technology sets up atmospheric laser measurement systems at three to five commanding height measuring points, and connects the above-mentioned atmospheric laser measurement systems to the server; it will be used to detect road traffic environment air in scenic spots and fixed on the roadside The monitoring result device of the concentration of pollutants at the conventional monitoring station is connected to the server; the monitoring device of the fixed conventional monitoring station for comprehensive ambient air in the scenic spot is connected to the server.

Further, a satellite receiving device is also included, the satellite receiving device receives satellite remote sensing signals, and the satellite receiving device is connected to the server.

Further, it also includes flying a tethered airship or balloon and a wireless device, the launching device of the tethered airship or balloon transmits the remote sensing signal, and the ground receiving device of the balloon receives the remote sensing signal and transmits it to the server.

The early warning method of road traffic pollution in scenic spots based on remote sensing technology includes the following steps:

41) Set up atmospheric laser measurement systems at three to five commanding height measuring points and collect data;

42) performing data fusion processing on the collected data;

43) Based on the fused data, make a prediction on the environmental quality;

Step 42) also includes the step of calibrating the collected data, specifically including:

51) Detect the concentration of pollutants in the air above the roadside fixed conventional monitoring stations of the road traffic environment air in the scenic area through the remote sensing of the laser measurement system;

52) Detect the concentration of pollutants in the sky above the conventional fixed monitoring station for comprehensive ambient air in the scenic spot through the remote sensing of the laser measurement system;

53) Compare the data detected in step 51) and the data detected in step 52) with the concentrations of relevant pollutants measured by these two types of fixed routine monitoring stations themselves, and use them to calibrate the collected data.

Further, the data fusion processing includes the following steps: N sets of atmospheric laser measurement systems are provided to measure the same scenic spot from different commanding heights, and the variance of each laser sensor is σ _i (i=0, 1, 2, ..., N -1), the true value to be estimated is X, and the measured values of each sensor are Xi ( _i =0, 1, 2, ..., N-1), which are independent of each other and are unbiased estimates of X, that is, each Atmospheric laser measurement systems assign weights w _i (i=0, 1, 2, ..., N-1), under the optimal condition of the minimum total mean square error σ ² , according to the measured values X _i of each atmospheric laser measurement system , find the optimal w _i in an adaptive way, so that the fused result best.

Further, it also includes the step of controlling the intensity of the laser for human eye safety.

The beneficial effects of the present invention are: in view of the various advantages and disadvantages of the current regional environmental monitoring platform, and according to the geographical characteristics of the West Lake scenic spot with "clouds on three sides and a city on one side", the present invention proposes to build an atmospheric remote sensing and telemetry platform at commanding heights around the West Lake , for the scenic spot, it is mainly due to NO ₂ and other chemical substances produced by road traffic (according to cost-effectiveness, such as adjustable wavelength, as much as possible to cover the characteristic factors of motor vehicle exhaust emissions, mainly CO, THC, O ₃ , aerosol, PM and SO ₂ etc.; but if the price investment is too high at this stage, it will not be considered for the time being) and the situation will be monitored in real time. For the three commanding heights of Beifeng Peak, Leifeng Pagoda and Santai Pavilion of Santai Mountain, the selected or designed atmospheric laser measurement system should have the ability to finely detect NO ₂ and other gas optical characteristics within 10km of the scenic spot. The constructed system should adopt low-cost equipment, for example, use Raman light source to make the output wavelength stable and reliable, and use pitch and azimuth scanning devices to perform inclination and two-dimensional scanning measurement. Compared with the active type, a passive laser system can also be used. The light source is changed to sunlight as the light source, and a high-precision imaging spectrometer is used to collect the solar spectrum. The solar spectrum at a certain time is selected as a reference, combined with the pollution gas concentration data at that time, and the differential absorption is applied. The principle is to invert the NO ₂ concentration at any other time; if the system is only considered as one of the environmental monitoring methods for the Golden Week and festivals, the passive laser system is easy to use during the day, which is very important for reducing investment and avoiding human eye safety. influence has advantages. The integrated implementation of the present invention, taking the West Lake scenic spot as an example, is of great significance for continuous, real-time, and large-scale monitoring of environmental air pollution and early warning.

Description of drawings

Fig. 1 is the distribution figure of 3 commanding height experimental measuring points that the present invention recommends as an example with West Lake "cloud mountain on three sides and city on one side";

Figure 2 is an effect map of observing the West Lake lakeside scenic spots, scenic spots and urban areas from three commanding heights (clouds and mountains on three sides);

Figure 3 is a two-dimensional scanning distribution display of NO ₂ or aerosol extinction coefficient (along the perspective of Santai Mountain);

Fig. 4 is the laser (spectrum) system inspection and calibration experiment design;

Fig. 5 is a schematic diagram of the steps and explanations of the steps of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific implementation examples.

At present, China already has the research and development and production capacity of vehicle-mounted pollution measurement lidar systems, such as the system developed by the Institute of Optics and Mechanics of the Chinese Academy of Sciences, which can perform three-dimensional spatial scanning measurements of atmospheric SO ₂ , NO ₂ and O ₃ . Using this system, the atmospheric SO ₂ , NO ₂ and O ₃ monitoring experiments were carried out in Beijing from December 2001 to January 2002, and the atmospheric SO ₂ , NO ₂ and O ₃ in the near-surface layer of Beijing were given for the first time. LiDAR measurement data. The measured data are compared with the monitoring data of ground instruments, and the results show that the measured data of the vehicle-mounted pollution measurement lidar system are reasonable and reliable.

Comparing the various advantages and disadvantages of the current regional environmental monitoring platform, and according to the geographical pattern characteristics of the West Lake scenic spot with "three clouds and mountains and one side city", the present invention proposes to build an atmospheric remote sensing and telemetry platform at the commanding heights around the West Lake to realize the main monitoring of the scenic spot. Real-time quantitative monitoring of NO ₂ or aerosols and other harmful gases produced by road traffic. The principles of point selection include: ① cover as many scenic spots as possible with the fewest points; ② can detect the position of long-term monitoring stations on the ground, so as to provide a way for the accuracy verification of measurement results; ③ avoid Motor vehicle roads, so that there is no road with a large traffic flow between the observation station and the monitored scenic spot, or as much as possible, to avoid the contribution of the middle road exhaust; ④ Each point can detect and cover the monitored scenic spot at the same time, so that Data averaging can offset to a certain extent the evaluation pollutants between the light source and the attention position, from non-concern roads or moving with the wind, which can improve the accuracy of measurement results; ⑤The environmental background concentration value at the selected observation point should be as close as possible Low.

As shown in Figure 1, considering the conditions that the instrument can be placed indoors for shelter from wind and rain, and convenient power supply, the three commanding heights of the North Peak, Leifeng Pagoda, and Santai Pavilion are recommended for site selection. The selected or designed atmospheric laser measurement system should have The ability to finely detect NO ₂ and aerosol optical characteristics within 10Km of the scenic area. The constructed system should adopt low-cost equipment, such as Raman light source, so that the output wavelength is stable and reliable, and the pitch and azimuth scanning devices can be used for tilt and two-dimensional scanning measurement. Among the 3 measuring points, Leifeng Pagoda has purchased 1 measuring point equipment, equipped with an azimuth device that can scan 360 degrees, and the other 2 measuring points have been developed twice, equipped with azimuth devices that can scan -90 degrees to +90 degrees. In order to improve the application of the system, other trace gases should be covered during the development process, mainly CO, SO2, O3, aerosol and other vehicle exhaust characteristic factors. In the case of confirming that the conditions may be met through experiments, low-power light sources such as micropulse and semiconductors can also be used to avoid the light source from affecting the safety of human eyes on the ground and reduce the overall investment. At the same time, a passive system can also be used, because the monitoring of the air quality of the tourist environment in the scenic spot is concentrated in the daytime, and sunlight can be used as the light source, without eye safety problems, and the cost of equipment can be reduced at the same time.

Principle of Atmospheric Environment Monitoring Laser System

①Active laser system

The ambient air monitoring laser system mainly consists of four major parts: a laser emitting system, an azimuth and elevation scanning device, an optical receiving system, and a data acquisition and control system.

Working principle: the general single-scattering laser equation can be expressed as

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; C</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; A\&eta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>\frac{\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; R</span>}}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, P(R) is the echo signal power at the distance received by the lidar, C is the laser constant, _P0 is the laser emission power, A is the receiving area of the telescope, η(R) is the geometric overlap factor of the laser, β( R) is the atmospheric backscattering coefficient, and α(R') is the atmospheric extinction coefficient.

Differential absorption measurement of NO ₂ : Differential Absorption Lidar (Differential Absorption Lidar) measurement uses two wavelengths, one wavelength (λ _on ) is selected on the absorption line of the pollutant gas molecules to be measured, and the other wavelength (λ _off ) is selected on the Gas molecules absorb outside the wings or lines. The wavelength should be selected so that the difference in absorption cross-section is as large as possible, and the difference between the two wavelengths is as small as possible. At this time, it can be considered that the influence of aerosol and other gases on the two wavelengths is basically the same and can be ignored. The difference yields the concentration of the detected pollutant gas molecules. The expression of the concentration N(z) of the measured possible pollutant gas molecules from the conventional dual-wavelength differential absorption lidar equation is:

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; dz</span>}}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; off</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}$

$\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; dz</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; off</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; off</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}$

In the formula, Δδ(T)—the absorption cross-section difference between the two wavelengths of the pollutant gas molecules at the temperature T; P(z) _λi —the echo power of the λ _i wavelength at the height of z; B, E _A , E _M —respectively Atmospheric backscattering (including atmospheric molecules and aerosols), atmospheric aerosol extinction, and correction items caused by atmospheric molecular extinction; β _λi (z)—the volume backscattering cross section of the _λi wavelength molecule and aerosol at z height; α _λi (z)—the extinction coefficient of wavelength _λi at height z (excluding the absorption of pollutant gas molecules).

Meter scattering method to measure aerosol: The Fernald method is a common method for dealing with non-uniformly distributed aerosols at this stage, that is, the extinction and backscattering of atmospheric molecules and aerosols are considered separately, and the extinction and backscattering ratio of molecules is taken as 8π/3, Assuming that the aerosol extinction and backscattering ratio at a certain calibration height is known, the distribution profile of the aerosol extinction coefficient and backscattering coefficient with height can be solved. The aerosol extinction coefficient formulas solved by the Fernald method are listed below.

Under the condition that the design function can be satisfied through the test, the active system can also use low-power light sources such as micro-pulse and semiconductor.

②Passive spectroscopy system

Active laser systems have the advantages of strong power, long range, and high sensitivity, but at the same time, they also have the disadvantages of large volume, heavy weight, and high price. If the passive laser system can be used instead, the size, weight and price can be reduced, which will have practical significance for improving the proposed technology to be accepted by relevant units.

One of the schemes is to replace the laser system with the spectral measurement system, and use sunlight as the light source, use a high-precision imaging spectrometer to collect the solar spectrum, select the solar spectrum at a certain moment as a reference, and combine the pollution gas concentration data at that time to apply the principle of differential absorption , to invert the NO ₂ concentration at any other time; the reference solar spectrum can use the drawn spectrum of the HITRAN database to analyze the absorption cross-section spectrum, embed it in a microcomputer or embedded system, and adjust the acquisition band to the corresponding wavelength during work.

The key to the above inversion process is to ensure that the spectral processing distortion is low, so as to achieve the characteristics of high accuracy of the inversion parameters, and thus improve the accuracy of the solar spectrum inversion of gas concentration to a certain extent. The feasibility of the method needs to be verified by comparing the experimental results with the measurement results of other equipment. If it is only considered to apply the system to one of the environmental monitoring methods for Golden Week and festivals, the scheme is feasible because it mainly works during the daytime.

System composition and configuration

Laser emission system: mainly composed of laser light source, frequency doubling crystal, Raman tube group, and beam expander. The fundamental wave of 1064nm and frequency-doubled light of 532nm of Nd:YAG laser pass through triple frequency crystal to produce 355nm light, and pump methane (CH ₄ ) and deuterium (D ₂ ) respectively with 355nm light to produce Raman frequency shift The first-order Stokes lines 395.60nm and 396.82nm are respectively used as the strong absorption line wavelength and weak absorption line wavelength for detecting NO2; if the 532nm light passes through the quadrupling frequency crystal and pumps H ₂ , CH ₄ , D ₂ respectively, The first-order Stokes lines 299.05, 288.39, and 289.04nm that produce Raman frequency shifts, select (289.04, 288.39nm) to detect the concentration distribution of SO ₂ , and select (288.39, 299.05nm) to detect the concentration distribution of O ₃ .

Azimuth and tilt scanning device: computer-driven stepping motor to achieve pitch and azimuth rotation, North Gaofeng and Santaishan pan tilt horizontal scanning angle -90°～+90°, vertical scanning angle -10°～+100°, angular velocity>5° per second, Leifeng Pagoda can rotate 360° horizontally and 90° vertically. Slope detection and scanning at different angles. The zero detection signal is set on the rotating disk of the scanning mirror, which is convenient for determining the position and preventing damage to the instrument caused by misoperation. The system is also equipped with good rainproof, dustproof and other devices.

Optical receiving system: mainly composed of receiving telescope, aperture diaphragm, eyepiece, filter, attenuation film and so on. Ultra-narrow-band, high-transmittance filters are selected for the filter, which can suppress background noise very well and improve the signal-to-noise ratio. The echo signal is received by the receiving telescope, limited by the field of view angle of the aperture diaphragm, expanded into parallel light by the eyepiece, and then reaches the photomultiplier tube through the attenuation sheet and the filter sheet. Different types of filters and attenuators are installed on two turntables, and the filters and attenuators that match the pollutants to be measured are selected by computer control to detect pollutants.

Signal acquisition and control system: The photomultiplier tube (PMT) is one of the key devices in the weak signal acquisition part. The Hamamatsu R374 photomultiplier tube from Japan can be used, which is equipped with a water-cooled refrigeration device and a high-voltage regulated power supply, which can convert light The signal is converted into an electrical signal. After the signal is amplified by a low-noise broadband amplifier, the data is collected by a 16bit high-speed data acquisition card. The work of each part of the lidar system is controlled by the embedded system/microcomputer/industrial computer, including the coordination and control of laser emission, echo signal reception, data acquisition, transmission and storage.

The result shows

Figure 2 is a rendering of the main scenic spots (lakeside), scenic spots (large-scale music fountain viewing platform) and urban areas of West Lake observed from three commanding heights (clouds and mountains on three sides).

Figure 3 is a schematic diagram of the distribution of extinction coefficients obtained by recommending that the laser system perform two-dimensional remote sensing scanning of NO ₂ or aerosols by rotating the pitch angle (from horizontal angle 0° to 50°) along the viewing angle of Mount Santai. The abscissa represents the horizontal distance, the ordinate represents the vertical height, and different colors represent the magnitude of the extinction coefficient, which very intuitively reflects the distribution of the concentration coefficient in this azimuth profile. At the same location, the concentration coefficient gradually decreases with the increase of height; at the same height, the concentration coefficient is roughly the same, indicating that the distribution in the horizontal direction is relatively uniform, and the slight difference reflects the fine structure of the atmospheric environment distribution.

Experiment and Calibration

While receiving the reflected laser signal, the laser system covers and accumulates the concentration of NO ₂ in the spatial distribution of non-observed targets. However, since the pollution sources near the observed scenic spot are mainly the motor vehicle roads, it is judged that the concentration value obtained by monitoring is mainly from road traffic. In this regard, the experiment shown in Figure 4 was designed to carry out necessary inspection and calibration of the system, specifically including: ① Detection of road traffic environment air in the scenic spot over the fixed conventional monitoring station on the roadside (near above the ground) by means of remote sensing with the laser measurement system ) concentration of pollutants; ②Through the remote sensing of the laser measurement system to detect the concentration of pollutants in the sky (near above the ground) of the comprehensive ambient air conventional fixed monitoring station in the scenic spot; ③The data and steps detected in step ① ② The detected data are compared with the concentration of relevant pollutants measured by the two types of fixed routine monitoring stations themselves, and used to calibrate the collected data. Among them, when setting up the atmospheric laser measurement system with the North Peak, Santai Mountain, and Leifeng Pagoda measuring points as examples, the above-mentioned atmospheric laser measurement system will be connected to the server at the same time; it will be used to detect the road traffic environment of the West Lake scenic spot The monitoring devices for NO ₂ and other concentrations at the monitoring stations are connected to the server; the monitoring devices of the fixed conventional monitoring station for comprehensive ambient air in the West Lake Scenic Area are connected to the server, and the satellite receiving device (referring to the gradual launch of China's environmental satellites into the network, which is located in Hangzhou The synchronous environmental satellite above the region), the satellite receiving device receives the satellite remote sensing signal, and the satellite receiving device is connected to the server. In addition, it also includes flying a tethered airship or balloon and a wireless device, the tethered balloon launching device transmits remote sensing signals, and the balloon ground receiving device is connected to the server.

Data Fusion Algorithm

Basic method of data fusion technology

As a data synthesis and processing technology, data fusion actually integrates and applies many traditional disciplines and new technologies, including communication, pattern recognition, decision theory, uncertainty theory, signal processing, estimation theory, optimization technology , computer science, artificial intelligence, and neural networks. In order to achieve data fusion, the information representation and processing methods adopted are from these fields. From the functional model of information fusion, we can see that the basic functions of fusion are correlation, estimation and identification, and the emphasis is on estimation and identification. Specifically, it mainly includes the following three aspects:

State estimation: State estimation is the use of multi-sensor combined data to determine the current position and velocity, future position and velocity, inherent characteristics or characteristic parameters of a moving target. Statistical estimators were first used to estimate planetary positions. In 1795, Gauss proposed the least squares method, which introduced the concept of using multiple observation data with estimation errors. In 1912, Fisher used the probability density function of the observation results in the maximum likelihood estimation method to maximize the logarithmic value of the estimated probability density function. In the 1940s, Kolmogrov and Winer supplemented the concept of statistical estimation for continuous or discrete measurement sequences. The current state estimation methods mainly include Kalman filter, insensitive Kalman filter, A-B filter and A-B-C filter, particle filter and related adaptive or extended methods.

Data association and track fusion: Correlation processing requires quantitative analysis of the correlation of multi-sensor or multi-source measurement information. According to a certain principle of discrimination, the information is divided into different sets, and the information in each set is related to the same source ( object or event) association. Techniques and algorithms for solving related problems, such as the nearest neighbor rule, maximum likeness method, optimal difference, statistical correlation and joint statistical correlation, etc. Related technologies were first used in radar automatic tracking in the 1960s. Before the 1970s, recursive estimators for continuous correlation and estimation were advanced, and by the 1980s, more complex multi-sensor target correlation systems were developed for more complex closed-space target correlation problems. The statistical track correlation algorithms in distributed multi-sensor data fusion mainly include: weighted and corrected track correlation algorithms, sequential track correlation algorithms, statistical double-threshold track correlation algorithms, etc.

Attribute recognition: Attribute recognition belongs to the category of pattern recognition. Taking radar radiation source identification as an example, the methods of attribute identification mainly include template matching method, artificial intelligence method, intrapulse analysis method, D-S evidence fusion method, gray relational theory and other identification methods. Attribute recognition is mainly through data mining or training and testing of existing prior information, and then calculating the closeness or similar membership with unknown types of targets to obtain the attributes of the target. The result of attribute identification provides auxiliary decision-making and information reference for the superior decision-making body.

Commonly used algorithms in data fusion technology, such as: weight coefficient method, parameter estimation information method, Demp-Ster evidence theory method, Kalman filter method, fuzzy neural network method, rough set theory method, cluster analysis method, etc.

In the measurement of the commanding height design of the present invention, the data of a single laser radar sensor is difficult to absolutely avoid relatively large randomness and contingency. Flying) data are jointly processed, and the air quality status of the scenic spots obtained is higher than that of a single sensor. Engineering and commercialization of existing fusion methods, development of processing hardware that can provide a variety of complex fusion algorithms, in order to complete fusion in real time while data is acquired. Multi-sensor data fusion is essentially a parameter estimation problem, and signal processing technology accounts for a considerable proportion in data fusion. Fusion method based on weight coefficient: also known as weighted average method, it is the simplest and intuitive fusion method to process information in real time. The basic process is as follows: Assuming that n sensors are used to measure a certain physical quantity, the output data of the i-th sensor is _Xi , where i=1, 2,...,n. The weighted average of the output measurement values of each sensor is carried out, and the weighted coefficient is w _i , and the obtained weighted average fusion result is: The weighted average method performs weighted average of the redundant information from different sensors, and the result is used as the fusion value. Applying this method must first analyze the system and sensors in detail to obtain the correct weights.

In view of the relatively large spatial range of the West Lake Scenic Area, the uneven distribution of its environmental parameters and the large influence of other factors, this invention recommends the application of the principle of least mean square weighted fusion algorithm. The system adopts simple and high-precision multi-sensor self-adaptive weighting Fusion algorithms process data to increase measurement credibility and system reliability. Others, such as fuzzy neural network-based fusion methods and data-related techniques, can be continuously applied, developed and supplemented.

There are N sets of laser radars to measure the same scenic spot from different commanding heights. The variance of each laser sensor is σ _i (i=0, 1, 2, ..., N-1), and the true value to be estimated is X. Each sensor The measured values of X _i (i=0, 1, 2, . . . , N−1) are independent of each other and are unbiased estimates of X. The basic principle of adaptive weighted fusion is: assign weight w _i (i=0, 1, 2, ..., N-1) to each sensor, and under the optimal condition that the total mean square error σ ² is the smallest, according to each sensor The measured value Xi, find the optimal w _i in an adaptive way, so that the fusion result best. This process is equivalent to nonlinear programming

For the objective function there is

In order to obtain w _i when the total mean square error σ _i ² is the smallest, according to the multivariate function seeking extreme value theory (Lagrangian theorem), we can know the conditions for the solution of the above formula, that is, the optimal weighting factor is

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

From formula (3), the variance σ _i (i=0, 1, 2, ..., N-1) of each sensor can be obtained, and the optimal estimate of X can be obtained ^X

$\stackrel{<span\; class="notranslate">\; ^</span>}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>$

The method is evaluated by taking the mean square error as the evaluation index of the algorithm fusion accuracy, and the calculation method of the mean square error corresponding to the optimal weighting factor is

${\stackrel{\&OverBar;}{\mathrm{\&sigma;}}}_{\min }^2=\frac{1}{k\underset{i=0}{\overset{N-1}{\mathrm{\&Sigma;}}}\frac{1}{{\mathrm{\&sigma;}}_i^2}}$ (K is the number of cycles)

Taking NO ₂ concentration measurement as an example (using the same equipment, it is not difficult to monitor SO ₂ and O ₃ synchronously), the actual monitoring and calculation steps are as follows: deploy 3 laser radar sensors at Beifeng Peak, Santai Mountain, and Leifeng Pagoda, and simultaneously monitor For the NO ₂ concentration in the lakeside large-scale water spray viewing area, data sampling is carried out every 15s, and 8 data within 2 minutes are selected for data fusion to verify the effectiveness of the data fusion method. Firstly, the average value and variance measured by each lidar sensor node are obtained, and the corresponding weight w _i is calculated, the fusion value is calculated, and the corresponding mean square error is obtained, and the fusion value and variance obtained by directly calculating the average. Generally, the estimated value after the data sampling adaptive fusion algorithm collected by multiple sensors/only sensors has smaller variance than the estimated value obtained by directly taking the average value of multiple sensors, that is, the effectiveness of the former will be significantly better than the arithmetic mean method. The actual monitoring cycle is repeated, and the data is transmitted to the main control point through the network or wireless system, where it is accumulated and the notification information is issued.

The laser pulse emitted by the laser radar from the commanding heights to the scenic spot may cause damage to the eyes of the tourists in the scenic spot when it irradiates on the ground, which is an important problem that the present invention must pay attention to and is difficult to avoid. Therefore, it is necessary to control the maximum value of the laser pulse energy emitted by the lidar to ensure that it is safe for the human eyes of scenic spot tourists.

① Eye safety requirements

The eyeball is an extremely sensitive light receiver, which is composed of different refractive media such as the lens and photoreceptors such as the retina. It can transmit light radiation of a certain frequency to the lens and make it image on the retina. The refractive medium in the eyeball has a strong converging effect, which can converge the incident light beam into a small spot, so that the light energy received by the retina per unit area is more than 100,000 times higher than the light energy incident on the cornea, so the high Focused laser light can easily cause damage to human eyes. The human eye has different transmittance and absorption characteristics for different frequencies of light radiation. Visible light waves with a wavelength of 400nm to 700nm will pass through the iris, lens and vitreous body of the eyeball, mainly causing damage to the retina of the eye; The near-infrared band of the laser can cause cataracts and retinal damage; however, lasers with wavelengths below 400nm and 1400nm have a high damage threshold to the human eye, and almost all of them are absorbed by the lens, so they generally do not cause damage to the inside of the eyeball.

② Calculation method and standard of human eye safety

The method of studying the impact of airborne lidar on the safety of human eyes on the ground is cited here to analyze the possible impact of commanding height lidar on the eyes of tourists in the West Lake Scenic Area.

Assume that the laser beams with two wavelengths of 532nm and 1064nm output by the Nd:YAG laser are both TEM00 mode, and the energy density I _fλ (r) of the laser beam transmitted to the ground footprint (foot Print) through the atmosphere is along the radius r of the footprint distributed as

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f\&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; t\&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a\&lambda;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: λ is the laser wavelength, respectively 532nm or 1064nm; T _fλ is the transmittance of the emitting optical unit at the wavelength λ; T _aλ is the transmittance of the atmosphere from the commanding height to the observed point to the wavelength λ; E _0λ is Nd : YAG laser output energy at wavelength λ (J); r _f is the radius of the footprint on the ground (m).

Obviously, at the center of the ground footprint where r=0, the incident laser energy density I _fλ (0) is maximum, and there is

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f\&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; t\&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a\&lambda;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

If the laser energy density will not cause damage to the eyes of the person in the center of the footprint, then the irradiated laser beam is also safe for the eyes of people in other positions within the footprint.

The diameter of the footprint on the ground is d _f =2r _f , and the divergence angle of the laser beam emitted by the laser radar from the commanding height to the observation point is θ _t (rad), then $\mathrm{\&theta;}{r}_f^2=\mathrm{\&theta;}{(d_f/2)}^2=\mathrm{\&theta;}{d}_f^2/4=\mathrm{\&theta;}{\left(Z{\mathrm{\&theta;}}_t\right)}^2/4.$ Then (2) can be expressed as

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f\&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 8</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; t\&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a\&lambda;</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Z</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In order to ensure the safety of the eyes of people in the ground footprint, the energy density I _fλ (r) of the laser pulse emitted by the commanding height lidar incident on the ground should meet the following conditions

$\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f\&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; MP</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}}<span\; class="notranslate">\; \&le;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

When the commanding height lidar emits the lasers of the above two wavelengths to the observation point at the same time, the total energy density incident on the ground must meet the following conditions

$\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 532</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 532</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1064</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 1064</span>}}}<span\; class="notranslate">\; \&le;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In the formula, MPE _λ (maximum permissible exposure) is the maximum permissible exposure corresponding to the wavelength λ _j , referring to the American ANSI standard, for 532nm wavelength, MPE ₅₃₂ =5×10 ^-3 J/m ² ; for 1064nm wavelength, MPE ₁₀₆₄ =5×10 ^-2 J/m ² . S _K is the eye safety factor, for the naked eye of the human eye, S _K =1. The left term of (5) represents the impact of laser pulses on the safety of human eyes on the ground, which can be simplified by S _L and called the laser pulse human eye safety factor

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 532</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 532</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1064</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 1064</span>}}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

It can be seen that the larger the value of _SL , the higher the safety performance of the laser pulse for human eyes.

③Atmospheric extinction mode and airborne lidar technical parameters

In the simulation calculation, the modes of atmospheric molecules and aerosol particles at wavelengths of 532nm and 1064nm are given by equations (7) and (8) respectively

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.54</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 532</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 8</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.47</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\\ \mathrm{<span\; class="notranslate">\; 5.13</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 6</span>}}\frac{\mathrm{<span\; class="notranslate">\; 532</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 36</span>}}<span\; class="notranslate">\; ]</span>\\ {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 50</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

The technical parameters of the commanding height atmospheric detection lidar are shown in Table 1.

Table 1 Main technical parameters of airborne atmospheric detection lidar

Eye safety when detecting aerosols

The relationship between laser beam divergence angle, laser pulse human eye safety maximum threshold energy and commanding height's nearest safe setting distance

When the commanding height lidar detects the aerosol mode atmosphere determined by formula (7) and formula (8), it can use laser pulses with a wavelength of 532nm or 1064nm alone, or simultaneously emit laser pulses with these two wavelengths for detection. When S _K in formula (5) = 1, namely

$\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 532</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 532</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1064</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; MPE</span>}}_{\mathrm{<span\; class="notranslate">\; 1064</span>}}}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Laser pulse eye safety maximum threshold energy is

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\frac{{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 532</span>}}}{\mathrm{<span\; class="notranslate">\; 0.005</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Z</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 1064</span>}}}{\mathrm{<span\; class="notranslate">\; 0.05</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Z</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

According to formula (10), the relationship between the laser pulse eye safety maximum threshold energy E _max and the distance during aerosol detection is established. It can be seen that E _max increases with the increase of height (because the maximum threshold energy of laser pulse eye safety varies with the distance from the commanding height to the observation point, the laser pulse energy can be adjusted to the required energy for detection); E _max is also related to the divergence angle of the laser beam, and the divergence angle of the laser beam also has a great influence on the value of E _max .

Relationship between laser pulse energy, commanding height and S _L

According to formula (3) and formula (6), the relationship between the output pulse energy of the laser and the distance from the commanding height to the observation point can be obtained. When performing aerosol detection, the distance Z _min is mainly determined by the maximum threshold energy of the 532nm laser pulse for human eye safety. When the distance needs to be adjusted to a large extent, the first consideration should be to adjust the energy of the 532nm laser pulse.

S _L /532nm＝S _L /1064nm＝2 When laser pulse eye safety maximum threshold energy and distance relationship

During atmospheric detection, the distance from the commanding heights to the observation points of different scenic spots varies greatly. In order to minimize the variation of laser pulse energy but meet the requirements of eye safety after adjustment, it is necessary to use lasers with wavelengths of 532nm and 1064nm Quantitative comparative analysis of the relationship between pulse energy and human eye safety factor. When the airborne lidar simultaneously emits 532nm and 1064nm laser pulses for detection, the ratio of the energy of these two wavelengths is a key factor, and the human eye safety factor is an important factor in determining this ratio. Due to the large difference in the extinction characteristics and backscattering characteristics of the two wavelengths of 532nm and 1064nm when detecting the atmosphere, the maximum irradiance energy density of 532nm for the human eye on the ground is an order of magnitude smaller than the maximum irradiance energy density of 1064nm , so it is necessary to simulate and analyze the respective laser pulse energies when the laser pulses of these two wavelengths are emitted simultaneously and their eye safety factors are equal to 2. The related results are as follows: when performing aerosol detection, the minimum safe distance from the commanding heights to the observation point is mainly determined by the energy of the laser pulse with a wavelength of 532nm. Laser pulse energy.

The above analyzes the problem of human eye safety when the laser system is used to detect air pollution through the theoretical model. Although the actual atmosphere and the model atmosphere are sometimes very different, relevant studies have shown that the human eye safety simulation analysis rules using the model atmosphere are also applicable. in various actual atmospheric conditions.

Therefore, the maximum threshold energy for human eye safety is a very important quantity when using commanding height lidar to detect air quality in scenic spots. It is not only related to the divergence angle of the laser beam, but also closely related to the distance from the commanding height to the observation point. The energy setting of the laser radar cannot exceed the maximum threshold energy of laser pulse human eye safety under certain conditions, so as not to cause damage to human eyes on the ground. When the human eye safety factors of the 532nm and 1064nm laser pulses are equal, the energy values of the maximum threshold energy of the two wavelengths are very different, because the extinction characteristics of the atmospheric components to the two wavelengths are very different.

Establish control of commanding height laser intensity through experimentation and use of passive lidar/micropulse/semiconductor laser sources

By using a higher power YAG laser radar from each commanding height to illuminate the air quality of all the scenic spots it observes, at all observed points, use a power meter to test the intensity of the laser light, and control the laser intensity of the scenic spots to reach the human eye Safety standards, establish a matrix corresponding to the safety strength and the location of the scenic spot, input the control program of each commanding height laser, and realize the control that avoids the influence on the human eye.

During the test, the unmanned time period is selected, and the staff also leave after positioning (no one enters the target area, and the entrants must wear laser protective glasses), and measure the maximum intensity at which the laser is forbidden to work, and the controlled sub-maximum intensity around the target area. , in order to grasp the buffer range (warning intensity) of beam intensity control.

During system development and operator training, laser safety procedures should be established for all personnel on the ground and at the vantage point. Standard operating procedures must be enforced to limit the movement of personnel near the laser or laser beam path to ensure that human exposure is limited to calculated allowable levels. The so-called unsafe area refers to the area that cannot be observed without protective glasses in the beam. To achieve safety management, the target surface should be placed in a position where there is no line of sight between the laser and the unrestricted, potentially occupied surface.

Prolonged observational stares at lasers may still be hazardous within the warning intensity range. The lower limit of continuous wave laser exposure for a long time is 1μW/cm ² , and appropriate corrections should be made according to the wavelength and laser output characteristics.

The issue of laser safety at commanding heights is also closely related to the reliability of aiming. The safety issue in lidar applications is mainly to ensure that the beam is not pointed directly at the ground or at non-target targets. In order to prevent the beam from pointing to the ground, all equipment should be equipped with a beam elevation lower limit switch or a mechanical baffle. It is best to use a mechanical baffle with high reliability. A position switch or fan-shaped flame-out device should also be used. Laser reflections from clouds, fog or rain do not pose a danger to ground observers even with binoculars. Laser aiming optics of modern common laser devices should be used, electronically controlled gimbal mirrors should be used, and the following safety measures should be taken to reduce emissions Mistakes and beam deflection: (a) protective master switch, automatic laser stop switch, stops laser operation when tracking is unstable; (b) automatic laser stop switch, stops laser operation at maximum angle of rotation; (c) working laser Fire switch "safety", the position that locks the laser when on the ground.

When repairing and testing lasers, appropriate protective measures must be taken, except that it is extremely dangerous for the laser beam to be aimed directly at people, and the laser output will produce dangerous diffuse reflections when it encounters objects. Therefore, there must not be any objects in the optical path, or all persons in the vicinity of the equipment should wear protective glasses. In the laboratory or maintenance test, a light-tight box can be used to inject all the laser output into the box. It must be ensured that the light beam always hits the test target within the controlled outdoor test distance.

Laser maintenance workers may be exposed to harmful radiation exceeding the exposure limit. Therefore, these workers should undergo eye examinations before and after assignments, and simple vision tests should be performed regularly during assignments.

Compared with the active high-power laser radar system, if the passive laser radar is used, because it avoids the high-intensity active laser emission, it can simultaneously relieve the possible impact of the laser on human eye safety. In addition, with the rapid advancement of science and technology, a laser emission system with significantly reduced laser intensity that will not affect the human eye can also be used. The application of a micro-pulse/semiconductor laser light source can also achieve the possibility of avoiding the impact of the commanding height lidar on the human eye.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Within the protection scope of the present invention.

Claims (6)

1. An early warning device for road traffic pollution in scenic spots based on remote sensing technology, which is characterized in that an atmospheric laser measurement system is installed at three to five commanding height measuring points, and the above atmospheric laser measurement system is uniformly connected to the server; it will be used to detect traffic in scenic spots The monitoring result device of the roadside fixed conventional monitoring station for ambient air on the road is connected to the server; the monitoring device of the fixed conventional monitoring station for comprehensive ambient air in the scenic spot is connected to the server. 2. The early warning device for road traffic pollution in scenic spots based on remote sensing technology according to claim 1, further comprising a satellite receiving device for receiving satellite remote sensing signals, and the satellite receiving device is connected to the server. 3. The early warning device for road traffic pollution in scenic spots based on remote sensing technology according to claim 1 is characterized in that it also includes flying moored airships or balloons and wireless devices, and the launching device of the moored airships or balloons transmits The remote sensing signal is received by the balloon ground receiving device and transmitted to the server. 4. The early warning method for road traffic pollution in scenic spots based on remote sensing technology is characterized in that it comprises the following steps: 41) Set up the atmospheric laser measurement system at the three commanding height measuring points and collect data; 42) performing data fusion processing on the collected data; 43) Based on the fused data, make a prediction on the environmental quality; Step 4) also includes the step of calibrating the collected data, specifically including: 51) Detect the concentration of pollutants in the air above the roadside fixed conventional monitoring stations of the road traffic environment air in the scenic area through the remote sensing of the laser measurement system; 52) Detect the concentration of pollutants in the sky above the conventional fixed monitoring station for comprehensive ambient air in the scenic spot through the remote sensing of the laser measurement system; 53) Compare the data detected in step 51) and the data detected in step 52) with the concentrations of relevant pollutants measured by these two types of fixed routine monitoring stations themselves, and use them to calibrate the collected data. 5. the road traffic pollution early warning method based on remote sensing technology in scenic spots according to claim 4, is characterized in that, described data fusion processing comprises the steps: N sets of atmospheric laser measurement systems are arranged to carry out the same scenic spot from different commanding height positions Measurement, the variance of each laser sensor is σ _i (i=0, 1, 2, ..., N-1), the true value to be estimated is X, and the measurement value of each sensor is _Xi (i=0, 1, 2,...,N-1), independent of each other and unbiased estimation of X, that is, to assign weight w _i (i=0,1,2,...,N-1) to each atmospheric laser measurement system, in the total average Under the optimal condition with the smallest square error σ ² , according to the measured values X _i of each atmospheric laser measurement system, the optimal w _i is searched in an adaptive way, so that the fused result best. 6. The early warning method for road traffic pollution in scenic spots based on remote sensing technology according to claim 4, further comprising the step of controlling the intensity of laser light for human eye safety.