A method and system for monitoring methane emissions from landfills by combined air and ground monitoring

Abstract

The present invention provides a method and system for monitoring methane emissions from landfills through combined ground and aerial monitoring. By considering the topographical features of the landfill, possible emission hotspots, and historical operation information, ground sampling points are selected. Areas that are difficult to reach by ground sampling can be achieved through aerial sampling by aerial survey. By integrating ground sampling and aerial survey, high-resolution methane concentration data can be obtained, while reducing the interference of flowing wind on the identification of hotspots. By combining surface sampling data and aerial survey data, the Getis-Ord Gi* statistic method and kernel density estimation method are used for bimodal hotspot area identification, which can more accurately locate the methane emission source area, significantly improving the accuracy and efficiency of methane emission monitoring in landfills, accurately and efficiently finding the methane emission source in the landfill and evaluating its emission volume, providing targeted suggestions for the operation of the landfill, and having important environmental protection and economic value.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring and relates to a methane emission monitoring method and system. Background Art

[0002] Landfills play an important role in the process of urban solid waste treatment. However, a large amount of methane is generated during the landfill and subsequent maintenance processes. Methane is a major greenhouse gas and has a significant impact on climate change. How to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts is of great significance for methane recovery and greenhouse gas emission reduction management in landfills.

[0003] Existing ground sampling methane emission monitoring methods generally include handheld device detection and fixed monitoring stations, etc. However, in large or complex terrain landfills, relying solely on ground monitoring means has problems such as insufficient sampling point density, limited coverage, and low operation efficiency. At the same time, due to the complex surface structure of landfills and uneven distribution of emission sources, traditional ground sampling monitoring is difficult to accurately locate and quantify methane emission sources. In recent years, with the development of unmanned aerial vehicle (UAV) remote sensing technology, using UAVs equipped with lidar, infrared cameras, methane detection sensors, etc. to observe the methane concentration in the air has become an emerging monitoring method. This method can provide high-resolution sampling data, quickly obtain the global methane concentration, and measure areas that are difficult to reach on the ground. However, if only relying on UAVs for aerial surveys, due to the interference of air flow over landfills, it is difficult to distinguish whether high-concentration areas are real emission sources, which may lead to missed judgments and misjudgments. All in all, with the current monitoring methods, it is difficult to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts, and it is difficult to provide targeted suggestions for the operation of landfills. Summary of the Invention

[0004] To solve the problem that the current monitoring methods in the background art are difficult to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts, the present invention provides a method and system for monitoring methane emissions from landfills by combining aerial and ground monitoring.

[0005] The method of the present invention includes:

[0006] Based on the aerial survey point cloud data and image data obtained for the landfill area, a three-dimensional model of the landfill is constructed;

[0007] Based on the three-dimensional model of the landfill, combined with the topographic features, possible emission hotspots, and historical operation information of the landfill, several ground sampling points are selected, and methane emission ground sampling is carried out according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill;

[0008] Based on the three-dimensional model of the landfill and several selected ground sampling points, determine the aerial survey height and the aerial survey route area for methane emission aerial sampling, and obtain the aerial survey methane concentration distribution data over the landfill;

[0009] Based on the three-dimensional model of the landfill, according to the longitude and latitude coordinates of the aerial survey sampling points, spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data, obtain the ground elevation and the aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data;

[0010] Use the Getis-Ord Gi* statistic method to analyze the surface methane concentration sampling data of the landfill to obtain the surface hot spot area, and use the kernel density estimation method to analyze the aerial survey average methane concentration data to obtain the aerial survey hot spot area;

[0011] Map the results of the surface hot spot area and the aerial survey hot spot area to the three-dimensional model of the landfill, and through the calculation of the local Jaccard coefficient, screen to obtain the methane emission source area;

[0012] Collect and obtain the environmental meteorological parameters of the landfill, combine the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data, and calculate the methane emission flux through the mass balance method.

[0013] Furthermore, for the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data over the landfill, perform data preprocessing: for the case of random data missing, use the interpolation method to supplement or directly delete; for the systematic data missing caused by including sampling detection equipment failures, mark it during statistics and re-sample and monitor if necessary; for data outliers, use statistical methods including 3 times the standard deviation, box plot method or setting thresholds according to physical background common sense to mark and remove the outliers.

[0014] Even further, the method for spatially registering the surface methane concentration sampling data and the aerial survey methane concentration distribution data includes: based on the three-dimensional model of the landfill, obtain the digital elevation model of the landfill through aerial survey software; the spatial coordinate systems used for methane emission ground sampling and aerial sampling are the same coordinate system, match the longitude and latitude coordinates of the aerial survey sampling points in the digital elevation model of the landfill, and obtain the ground elevation and the aerial survey elevation of the same sampling point;

[0015] Calculate the integration path length of the aerial survey methane concentration detection equipment according to the ground elevation and the aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration. The formula is as follows:

[0016] ,

[0017] ,

[0018] In the formula: is the average methane concentration measured by aerial survey at the sampling point; is the path integral concentration of the aerial survey methane concentration detection device at the sampling point, is the integral path length of the aerial survey methane concentration detection device; is the elevation of the take-off point of the aerial survey; is the flight altitude of the aerial survey; is the ground elevation of the sampling point.

[0019] Furthermore, the method for obtaining the surface hot spot area includes: calculating the weighted neighborhood sum for each ground sampling point; calculating the global mean and standard deviation; iteratively calculating the Gi* value for each ground sampling point; converting the Gi* value of each ground sampling point into a Z-score; obtaining the surface hot spot area according to the actual evaluation requirements of the Z-score;

[0020] When calculating the Getis-Ord Gi* statistic, a suitable neighborhood range needs to be set according to the distribution density of the ground data. The formula is as follows:

[0021] ,

[0022] In the formula, is the spatial weight between feature i and j ; is the attribute value of feature j ; is the neighborhood weighted sum; is the global mean; is the global standard deviation; is the total sample, that is, the total number of methane concentration data points collected by aerial survey.

[0023] The method for obtaining the aerial survey hot spot area includes: applying the kernel density estimation method to calculate the spatial density, using a Gaussian kernel, and its expression is:

[0024] ,

[0025] ,

[0026] In the formula, is the kernel function, indicating the density contribution intensity of the data point to the surrounding positions; is the standardized distance; is the bandwidth; is the target position; is the data point position;

[0027] Select the bandwidth according to Silverman's rule , the expression is:

[0028] ,

[0029] In the formula, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; is the total number of methane concentration data points collected by aerial survey;

[0030] For each grid point , calculate the density contribution of its surrounding points:

[0031] ,

[0032] In the formula, is the estimated value of methane concentration density at the spatial position ; is the total number of methane concentration data points collected by aerial survey;

[0033] Based on the calculated spatial density values, determine the aerial survey hotspots area based on empirical quantiles.

[0034] Furthermore, the screening method for the methane emission source area includes:

[0035] Generate binary grids for both the surface hotspot area result and the aerial survey hotspot area result to obtain the ground hotspot grid and the aerial survey hotspot grid;

[0036] Use the vector polygon file to define the boundary of the landfill;

[0037] Make the resolutions, coordinate systems, and spatial ranges of the ground hotspot grid and the aerial survey hotspot grid consistent;

[0038] Use the boundary of the landfill as a mask to crop the ground hotspot grid and the aerial survey hotspot grid to exclude external area interference;

[0039] Select the grid size according to the hotspot scale;

[0040] Generate a regular grid covering the landfill;

[0041] For each grid cell, count the number of aerial survey hotspot pixels and the number of overlapping pixels , and calculate the local Jaccard coefficient to quantify the overlapping degree between the two. The calculation formula is as follows:

[0042] ,

[0043] In the formula, is the Jaccard coefficient, is the grid the set of aerial survey hot pixels within; is the grid the set of ground hot pixels within;

[0044] Evaluate the spatial consistency of ground hot spots within the range of aerial survey hot spots according to the Jaccard coefficient, and screen to obtain the methane emission source area.

[0045] Furthermore, the calculation method of the methane emission flux is as follows:

[0046] Combined with the measured methane concentration distribution and the simultaneously obtained environmental meteorological parameters of the landfill, the mass balance method is used to calculate the methane emission flux, and the calculation formula is as follows:

[0047] ,

[0048] In the formula, F is the emission rate of the emission source; H is the integral height of the plane perpendicular to the wind direction; W is the integral width of the plane perpendicular to the wind direction; u is the wind speed perpendicular to the aerial survey plane; is the methane concentration signal enhancement value, with the upwind test value as the background value , and the downwind test value and the background value The difference is recorded as the methane concentration signal enhancement value.

[0049] Furthermore, use a portable methane analyzer to conduct ground sampling of methane emissions from the landfill; use a drone equipped with a laser methane concentration detector to conduct aerial sampling of methane emissions from the landfill; use a drone equipped with an airborne meteorological instrument to collect the environmental meteorological parameters of the landfill.

[0050] Based on the above method, the present invention proposes a landfill methane emission monitoring system for joint aerial and ground monitoring, including a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module.

[0051] The landfill three-dimensional model construction module is used to construct a landfill three-dimensional model according to the aerial survey point cloud data and image data obtained by aerial surveying the landfill area.

[0052] The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the three-dimensional model of the landfill, combined with the topographic features of the landfill, possible emission hotspot areas, and historical operation information, and conduct ground sampling of methane emissions according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill.

[0053] The aerial survey methane concentration distribution data acquisition module is used to determine the aerial survey height and aerial survey route area for aerial sampling of methane emissions based on the three-dimensional model of the landfill and the selected number of ground sampling points, and obtain the aerial survey methane concentration distribution data over the landfill.

[0054] The aerial survey average methane concentration data calculation module is used to spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the three-dimensional model of the landfill, according to the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data.

[0055] The hotspot area acquisition module is used to analyze the surface methane concentration sampling data of the landfill by using the Getis-Ord Gi* statistic method to obtain the surface hotspot area, and analyze the aerial survey average methane concentration data by using the kernel density estimation method to obtain the aerial survey hotspot area.

[0056] The methane emission source area screening module is used to map the results of the surface hotspot area and the aerial survey hotspot area into the three-dimensional model of the landfill, and screen the methane emission source area through the calculation of the local Jaccard coefficient.

[0057] The methane emission flux calculation module is used to collect and obtain the environmental meteorological parameters of the landfill, and calculate the methane emission flux by using the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data.

[0058] The present invention also provides an electronic device, including: a memory and a processor, which are communicatively connected to each other, the memory stores computer instructions, and the processor realizes a method for monitoring methane emissions from a landfill by means of combined air and ground monitoring as described above by executing the computer instructions.

[0059] The present invention also provides a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, it realizes a method for monitoring methane emissions from a landfill by means of combined air and ground monitoring as described above.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) Accurate data: By integrating ground sampling and aerial survey, high-resolution methane concentration data can be obtained, while reducing the interference of flowing wind on the identification of hot spots and improving the accuracy of the data.

[0062] (2) Optimization of sampling cost and safety: Considering the topographical features of the landfill, possible emission hot spots, and historical operation information, ground sampling points are selected. Areas that are difficult to reach by ground sampling can be sampled by aerial survey, reducing the sampling cost and improving the operation safety.

[0063] (3) Dual-modal hot spot identification: By combining surface sampling data and aerial survey data, the Getis-Ord Gi* statistic method and kernel density estimation method are used for dual-modal hot spot identification, which can more accurately locate the methane emission source area and improve the accuracy of emission source location.

[0064] (4) Wide applicability: The present invention is applicable to landfills with flat terrain and complex terrain, and can improve the accuracy of emission source location and flux quantification at low cost and high efficiency, providing a scientific basis for methane recovery and greenhouse gas emission reduction management.

[0065] (5) Targeted quantification of emission sources: The aerial survey sampling method of the present invention is different from the traditional full-field up-and-down profile flight aerial survey method, so that the methane emission flux can be quantified for a single emission source area, and the methane emission flux of the whole field can be obtained by summation, providing more accurate suggestions for the identification and treatment of potential high-emission areas in landfills.

[0066] (6) Provide a scientific basis: Through the combined sampling method of air and ground, quickly locate and accurately quantify the methane emission sources in landfills, provide a scientific basis for subsequent methane recovery and emission reduction management, and provide targeted suggestions for the operation management of landfills.

[0067] Generally speaking, the present invention significantly improves the accuracy and efficiency of methane emission monitoring in landfills through combined air-ground monitoring, dual-modal hot spot identification, and targeted emission source quantification, accurately and efficiently finds the methane emission sources in landfills and evaluates their emissions, provides targeted suggestions for the operation of landfills, and has important environmental and economic values. Brief Description of the Drawings

[0068] Figure 1 It is the overall flowchart of the method of the present invention.

[0069] Figure 2 It is the specific implementation flowchart of Embodiment 1.

[0070] Figure 3 It is the schematic diagram of ground sampling and UAV sampling in Embodiment 1.

[0071] Figure 4 Schematic diagram of aerial survey data spatial registration for Example 1.

[0072] Figure 5 Schematic diagram of bimodal hotspot identification and emission source localization for Example 1.

[0073] Figure 6 Schematic diagram of methane emission flux calculation for Example 1.

[0074] Figure 7 System architecture diagram of the present invention. Detailed implementation manners

[0075] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. Example 1

[0076] A method for monitoring methane emissions from a landfill by combining aerial and ground monitoring. The overall flowchart of the method is as Figure 1 shown, and the specific implementation flowchart of this example is as Figure 2 shown, and is specifically described as follows.

[0077] First, based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area, a three-dimensional model of the landfill is constructed.

[0078] Specifically, a drone can be used to carry a lidar ranging camera to conduct an aerial survey of the landfill area to obtain the shape and area of the landfill. Based on the digital surface model, through the post-processing and stitching of the aerial survey point cloud data and image data, a high-precision three-dimensional model file of the landfill is constructed, providing a basis for the reasonable layout of subsequent monitoring routes and the registration of ground observation data.

[0079] In this example, the construction process of the three-dimensional model of the landfill is as follows:

[0080] Aerial survey preparation: Select a drone platform and carry a lidar ranging camera. According to the terrain complexity, adjust the flight height and flight speed. For example, the flight height is 80 meters and the flight speed is 4 meters per second to ensure coverage of complex terrain areas such as hills and slopes.

[0081] Data acquisition: The drone covers the entire landfill area according to the pre-planned route and conducts multiple aerial surveys to obtain comprehensive point cloud data and image data. Each aerial survey should ensure an overlap rate of more than 60% to ensure the accuracy of data stitching.

[0082] Data Processing and 3D Model Construction: Use professional aerial survey software to post-process the acquired point cloud data and image data, including point cloud filtering, registration, stitching, and 3D reconstruction, to generate high-precision 3D model files of the landfill, such as LAS format or OBJ format. This model will be used for subsequent layout of monitoring points and flight routes and registration of ground observation data.

[0083] Then, based on the 3D model of the landfill, combined with the topographic features of the landfill, possible emission hotspots, and historical operation information, select several ground sampling points, and conduct ground sampling of methane emissions according to the ground sampling points to obtain surface methane concentration sampling data of the landfill.

[0084] Specifically, in the selection of ground sampling points, attention should be paid to the sampling interval and coverage area. Relative to the aerial survey monitoring resolution, the ground sampling points should consider reasonable intervals and position distributions at low resolution. Portable methane analyzers and other equipment can be used for ground sampling to measure the surface methane concentration, and preprocessing work should be carried out on the data obtained from ground sampling.

[0085] In this embodiment, the intervals of the selected several ground sampling points should ensure low-resolution coverage, with one sampling point set every 50 meters to balance the sampling density and monitoring cost; the sampling point intervals can be appropriately adjusted according to terrain changes, such as setting one sampling point every 30 meters to ensure methane concentration measurement coverage in complex terrains. At the selected ground sampling points, a handheld laser methane detector is used to measure the ground methane concentration. Each ground sampling point records: methane concentration value, measurement time, GPS coordinates, and environmental meteorological parameters, such as temperature, humidity, wind speed, and wind direction.

[0086] Based on the 3D model of the landfill and the selected several ground sampling points, determine the aerial survey height and aerial survey route area for methane emission aerial sampling, and obtain aerial survey methane concentration distribution data over the landfill.

[0087] Specifically, combined with the layout of ground sampling points and the 3D model of the landfill, and on the premise of meeting safety requirements, determine the aerial survey height and aerial survey route area for methane emission aerial sampling. Aerial surveys can use unmanned aerial vehicles (UAVs) equipped with methane concentration detection equipment, meteorological instruments, lidar, infrared imagers, and other sensors to obtain aerial survey methane concentration distribution data and environmental meteorological parameters at a certain height over the landfill, and preprocessing work should be carried out on the data obtained from UAV aerial survey sampling. In UAV aerial survey sampling, attention should be paid to flight area division and flight height.

[0088] In this embodiment, according to the three-dimensional model of the landfill and the layout of ground sampling points, the flight altitude and flight route of the unmanned aerial vehicle (UAV) are determined. The flight altitude is 80 meters, and the route design should cover the entire area of the landfill to ensure the comprehensiveness and high resolution of the data. The UAV is equipped with a laser methane concentration detector and an on-board weather station. The laser methane concentration detector is based on tunable diode laser absorption spectroscopy technology and samples and records the methane concentration value, measurement time, GPS coordinates, and environmental meteorological parameters such as temperature, humidity, wind speed, and wind direction.

[0089] The schematic diagrams of ground sampling and UAV sampling in this embodiment are as Figure 3 shown.

[0090] More specifically, for the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data over the landfill, data preprocessing is carried out: for the case of random data missing, interpolation method is used for supplementation or directly deleted; for the systematic data missing caused by including sampling detection equipment failure, it is marked during statistics and re-sampling monitoring is carried out if necessary; for data outliers, statistical methods including 3 times standard deviation, box plot method or setting threshold according to physical background common sense are used to mark and remove the outliers. However, due to the high variability of the methane concentration distribution in the landfill, the screened outliers also need to be distinguished in combination with expert experience.

[0091] Based on the three-dimensional model of the landfill, according to the longitude and latitude coordinates of the aerial survey sampling points, the surface methane concentration sampling data and the aerial survey methane concentration distribution data are spatially registered to obtain the ground elevation and aerial survey elevation of the same sampling point, and the average aerial survey methane concentration data is calculated.

[0092] Due to the certain elevation change on the surface of the landfill, it is difficult to plan terrain-following flight during the aerial survey of the UAV. Therefore, by performing spatial matching of the UAV aerial survey sampling data and the digital elevation model of the landfill at the same sampling point, that is, matching the longitude and latitude coordinates of the UAV aerial survey sampling points in the digital elevation model of the landfill, the ground elevation and UAV aerial survey elevation of the same sampling point are obtained.

[0093] In this embodiment, the schematic diagram of aerial survey data spatial registration is as Figure 4 shown.

[0094] Specifically, based on the three-dimensional model of the landfill, the digital elevation model of the landfill is obtained through aerial survey software; the spatial coordinate systems used for methane emission ground sampling and aerial sampling are the same coordinate system, such as the WGS84 coordinate system, and the longitude and latitude coordinates of the aerial survey sampling points are matched in the digital elevation model of the landfill to obtain the ground elevation and aerial survey elevation of the same sampling point.

[0095] Calculate the integrated path length of the aerial methane concentration detection device based on the ground elevation and aerial survey elevation at the same sampling point, and calculate the average aerial survey methane concentration. The formula is as follows:

[0096] ,

[0097] ,

[0098] In the formula: is the average aerial survey methane concentration at the sampling point; is the path integral concentration of the aerial methane concentration detection device at the sampling point, is the integrated path length of the aerial methane concentration detection device; is the elevation of the take-off point of the aerial survey; is the flight altitude of the aerial survey; is the ground elevation of this sampling point.

[0099] Next, use the Getis-Ord Gi* statistic method to analyze the surface methane concentration sampling data of the landfill to obtain the surface hot spot area, and use the kernel density estimation method to analyze the average aerial survey methane concentration data to obtain the aerial survey hot spot area.

[0100] In this embodiment, the schematic diagram of bimodal hot spot identification and emission source location is as Figure 5 shown.

[0101] The method for obtaining the surface hot spot area is as follows: calculate the weighted neighborhood sum for each ground sampling point; calculate the global mean and standard deviation; iteratively calculate the Gi* value for each ground sampling point; convert the Gi* value of each ground sampling point into a Z score; and obtain the surface hot spot area according to the actual evaluation requirements of the Z score.

[0102] In this embodiment, the classification of the Z score is as follows: Z ≥ 2.58: 99% confidence hot spot; Z ≥ 1.96: 95% confidence hot spot; Z ≤ -1.96: significant cold area.

[0103] When calculating the Getis-Ord Gi* statistic, it is necessary to set an appropriate neighborhood range according to the distribution density of the ground data to improve the accuracy of the analysis. For example, adjust the neighborhood size according to the distribution density of the ground data. The formula is as follows:

[0104] ,

[0105] In the formula, is the spatial weight between elements i and j ; is the attribute value of element j ; is the neighborhood weighted sum; is the global mean; is the global standard deviation; is the total sample, i.e., the total number of methane concentration data points collected by aerial survey.

[0106] The method for obtaining the hot spot area of aerial survey is as follows: Due to the high resolution and many sampling points of UAV data, the kernel density estimation method can be used to calculate the spatial density. The kernel density estimation method itself is a smooth density estimation method, which can help identify local concentration aggregation areas and is suitable for the high-resolution characteristics of UAV data. The Gaussian kernel is used in the kernel density estimation method, and its expression is:

[0107] ,

[0108] ,

[0109] In the formula, is the kernel function, representing the density contribution intensity of the data point to the surrounding positions; is the standardized distance; is the bandwidth; is the target position; is the data point position;

[0110] The bandwidth is selected according to Silverman's rule , and the expression is:

[0111] ,

[0112] In the formula, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; is the total number of methane concentration data points collected by aerial survey;

[0113] For each grid point x , calculate the density contribution of its surrounding points:

[0114] ,

[0115] In the formula, is the estimated value of methane concentration density at the spatial position ; is the total number of methane concentration data points collected by aerial survey;

[0116] For the calculated spatial density values, the hot spot area of aerial survey is determined based on the empirical quantile, such as the top 5% of the density values as the hot spot threshold.

[0117] Next, map the results of the surface hotspots and aerial survey hotspots to the 3D model of the landfill, and screen the methane emission source areas through the calculation of the local Jaccard coefficient.

[0118] The screening method for methane emission source areas includes:

[0119] Generate binary rasters for both the surface hotspot area results and the aerial survey hotspot area results to obtain the ground hotspot raster and the aerial survey hotspot raster;

[0120] Use the vector polygon file to define the boundary of the landfill;

[0121] Make the resolutions, coordinate systems, and spatial extents of the ground hotspot raster and the aerial survey hotspot raster consistent;

[0122] Using the boundary of the landfill as a mask, clip the ground hotspot raster and the aerial survey hotspot raster to exclude interference from external areas;

[0123] Select the grid size according to the hotspot scale;

[0124] Generate a regular grid covering the landfill;

[0125] For each grid cell, count the number of aerial survey hotspot pixels and the number of overlapping pixels , and calculate the local Jaccard coefficient to quantify the overlap degree between the two. The calculation formula is as follows:

[0126] ,

[0127] In the formula, is the Jaccard coefficient, is the set of aerial survey hotspot pixels in grid ; is the set of ground hotspot pixels in grid ;

[0128] Evaluate the spatial consistency of the ground hotspots within the aerial survey hotspots based on the Jaccard coefficient, and screen the methane emission source areas.

[0129] In this embodiment, the evaluation of the spatial consistency of the ground hotspots within the aerial survey hotspots can be represented by a heat map, and the specific content is shown in Table 1.

[0130] Table 1 Heat Map Interpretation Rules

[0131] Jaccard value Color Explanation Measure <![CDATA J i ≥0.7]]> Dark red Ground data highly supports drone hotspots (strong consistency) Select all drone hotspot areas as the areas for methane flux quantification <![CDATA 0.4≤ J i <0.7]]> Orange Ground data partially supports drone hotspots (medium consistency) Select the overlapping area of ground hotspots and drone hotspots as the methane flux quantification area <![CDATA J i <0.4]]> Blue Ground data insufficiently supports drone hotspots (low consistency) Ignore and do not participate in the analysis

[0132] According to the actual situation of the landfill, the methane emission source areas can be supplemented. Due to complex terrain, it may be difficult for ground monitoring to cover these potential emission source areas, which is likely to lead to missed judgment of ground hot spots. The geographical location information of potential emission sources, including pumping wells, gas collection wells, and drainage pipes in the landfill, can be marked by combining on-site surveys and landfill operation information. When the potential emission source area coincides with the aerial survey hot spot area, this area is considered to be a methane emission source. Since aerial survey monitoring is comprehensive, all aerial survey hot spot areas can be selected as the areas for the next step of methane flux quantification.

[0133] Finally, collect the environmental meteorological parameters of the landfill, and combine the methane emission source areas, the corresponding surface methane concentration sampling data, and the aerial survey average methane concentration data to calculate the methane emission flux through the mass balance method.

[0134] The idea of the mass balance method is as follows: Based on the measured spatial methane concentration distribution and meteorological parameters such as wind speed, the methane emissions of each emission source area are obtained by integrating the methane flux on the control surface; finally, the emissions from different source areas are superimposed to accurately quantify the overall methane emission of the landfill.

[0135] In this embodiment, the schematic diagram of methane emission flux calculation is as Figure 6 shown.

[0136] The calculation method of methane emission flux is as follows: Combine the measured methane concentration distribution and the simultaneously obtained environmental meteorological parameters of the landfill, and use the mass balance method to calculate the methane emission flux. The calculation formula is as follows:

[0137] ,

[0138] In the formula, F is the emission rate of the emission source; H is the integration height of the plane perpendicular to the wind direction; W is the integration width of the plane perpendicular to the wind direction; u is the wind speed perpendicular to the aerial survey plane; is the enhanced value of the methane concentration signal, with the upwind test value as the background value , and the downwind test value minus the background value is recorded as the enhanced value of the methane concentration signal.

[0139] In this embodiment, the methane emission flux quantification area is based on the screened methane emission source areas. For the area, all drone hot spot areas are selected as the areas for methane flux quantification; for the area, the overlapping area of the ground hot spot and the drone hot spot is selected as the methane flux quantification area; for the supplemented methane emission sources, all drone hot spot areas are selected as the areas for methane flux quantification.

[0140] In this embodiment, an unmanned aerial vehicle (UAV) aerial survey uses a laser methane detector based on tunable diode laser absorption spectroscopy (TDLAS) technology. Since the vertical column concentration of CH4 is detected, it is not necessary to integrate the vertical range of the emission plume when calculating the emission amount. The flux calculation formula is as follows:

[0141] ,

[0142] In the formula: F is the emission rate of the emission source, g / s; W is the integration width of the plane perpendicular to the wind direction, m; u is the wind speed perpendicular to the UAV aerial survey plane, m / s; is the enhanced value of the methane column concentration signal, ppm. Usually, the upwind test value is used as the background value , and the downwind test value and the background value The difference is recorded as the enhanced value of the methane column concentration signal.

[0143] Import the methane concentration distribution data sampled by the UAV aerial survey into geographic information processing software such as Arcgis pro. Through co-kriging interpolation by combining terrain elevation data and methane concentration distribution data, obtain the global methane concentration distribution map of the landfill. Map and screen the methane emission source area into the methane concentration distribution map of the landfill. Determine the upwind and downwind profiles and wind speeds of the methane emission source area during the aerial survey period. At a certain interval, such as 5 m, take 5 pairs of upwind and downwind profiles with the same length. Conduct calculations by the mass balance method and take the average value as the methane emission flux of this area.

[0144] Superimpose the methane emission fluxes of all methane emission source areas, which is the total methane emission of the entire landfill. Embodiment 2

[0145] A landfill methane emission monitoring system for combined air and ground monitoring, the architecture diagram is as Figure 7 shown, and it is composed of a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module.

[0146] The landfill three-dimensional model construction module is used to construct a landfill three-dimensional model based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area.

[0147] The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the three-dimensional model of the landfill, combined with the topographic features of the landfill, possible emission hotspot areas, and historical operation information, and conduct ground sampling of methane emissions according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill.

[0148] The aerial survey methane concentration distribution data acquisition module is used to determine the aerial survey height and aerial survey route area for aerial sampling of methane emissions based on the three-dimensional model of the landfill and the selected number of ground sampling points, and obtain the aerial survey methane concentration distribution data over the landfill.

[0149] The aerial survey average methane concentration data calculation module is used to spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the three-dimensional model of the landfill, according to the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data.

[0150] The hotspot area acquisition module is used to analyze the surface methane concentration sampling data of the landfill by using the Getis-Ord Gi* statistic method to obtain the surface hotspot area, and analyze the aerial survey average methane concentration data by using the kernel density estimation method to obtain the aerial survey hotspot area.

[0151] The methane emission source area screening module is used to map the results of the surface hotspot area and the aerial survey hotspot area into the three-dimensional model of the landfill, and screen the methane emission source area by calculating the local Jaccard coefficient.

[0152] The methane emission flux calculation module is used to collect and obtain the environmental meteorological parameters of the landfill, and calculate the methane emission flux by the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data.

[0153] The specific implementation methods of each module in this system are the same as those described in Embodiment 1, and will not be elaborated here. Embodiment 3

[0154] An electronic device includes: a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor realizes a method for monitoring methane emissions from a landfill by combined air and ground monitoring as described in Embodiment 1 above, and a system for monitoring methane emissions from a landfill by combined air and ground monitoring as described in Embodiment 2 by executing the computer instructions. Embodiment 4

[0155] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements a landfill methane emission monitoring method for joint air-ground monitoring as described in Embodiment 1 above, and a landfill methane emission monitoring system for joint air-ground monitoring as described in Embodiment 2.

[0156] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming languages such as Java, C++, Python, and interpreted scripting languages such as JavaScript.

[0157] The present application is described with reference to the flowcharts and / or block diagrams of methods, electronic devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing electronic devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing electronic devices generate a device for implementing the functions specified in Figure 1 one or more flows and / or Figure 1 blocks or multiple blocks.

[0158] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing electronic devices to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one or more flows and / or Figure 1 blocks or multiple blocks.

[0159] These computer program instructions can also be loaded onto a computer or other programmable data processing electronic devices, such that a series of operation steps are executed on the computer or other programmable electronic devices to generate a computer-implemented process, so that the instructions executed on the computer or other programmable electronic devices provide for implementing the functions specified in Figure 1 one or more flows and / or Figure 1Steps of the functions specified in one or more boxes.

[0160] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present application.

[0161] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A method for monitoring methane emissions from a landfill by combined air and ground monitoring, characterized in that, include: Based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area, a three-dimensional model of the landfill is constructed; Based on the three-dimensional model of the landfill, combined with the landfill's topographical features, possible emission hotspots, and historical operation information, several ground sampling points were selected, and ground sampling of methane emissions was carried out based on the ground sampling points to obtain the surface methane concentration sampling data of the landfill; Based on the three-dimensional model of the landfill and several selected ground sampling points, the aerial survey altitude and flight route area for aerial sampling of methane emissions were determined to obtain aerial survey methane concentration distribution data over the landfill; Based on the three-dimensional model of the landfill, the surface methane concentration sampling data and the aerial survey methane concentration distribution data are spatially registered according to the latitude and longitude coordinates of the aerial survey sampling points, the ground elevation and aerial survey elevation of the same sampling point are obtained, and the aerial survey average methane concentration data is calculated; The Getis-Ord Gi* statistic method was used to analyze the surface methane concentration sampling data of the landfill to obtain the surface hotspot areas, and the kernel density estimation method was used to analyze the aerial survey average methane concentration data to obtain the aerial survey hotspot areas; The results of the surface hot spots and aerial survey hot spots were mapped to the three-dimensional model of the landfill, and the methane emission source areas were screened out by calculating the local Jaccard coefficient. The environmental meteorological parameters of the landfill were collected and acquired, and the methane emission flux was calculated by the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and the average methane concentration data from aerial surveys.

2. The method for monitoring methane emissions from a landfill by combined air and ground monitoring according to claim 1, wherein: Data preprocessing is performed on the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data over the landfill: in the case of random missing data, interpolation method is used to supplement or directly delete the data; systematic missing data caused by sampling and detection equipment failure are marked during statistics, and re-sampling and monitoring are carried out if necessary; outliers are marked and eliminated using statistical methods including 3 times the standard deviation, box plot method or threshold setting based on common sense of physical background.

3. The method for monitoring methane emissions from a landfill by combined air and ground monitoring according to claim 1, characterized in that: The method for spatially registering the surface methane concentration sampling data and the aerial survey methane concentration distribution data comprises: based on the three-dimensional model of the landfill, obtaining the digital elevation model of the landfill through aerial survey software; using the same spatial coordinate system for the ground sampling and aerial sampling of methane emissions, matching the longitude and latitude coordinates of the aerial survey sampling points in the digital elevation model of the landfill, and obtaining the ground elevation and aerial survey elevation of the same sampling point; According to the ground elevation and aerial survey elevation of the same sampling point, the integral path length of the aerial survey methane concentration detection equipment is calculated, and the average aerial survey methane concentration is calculated. The formula is as follows: ， ， Where: is the average methane concentration measured by aerial survey at the sampling point; is the path integral concentration of the aerial survey methane concentration detection device at the sampling point; is the integral path length of the aerial survey methane concentration detection device; is the elevation of the take-off point of the aerial survey; is the flight altitude of the aerial survey; is the ground elevation of the sampling point.

4. The method for monitoring methane emissions from a landfill by combined air and ground monitoring according to claim 3, characterized in that: The method for obtaining the surface hotspot area includes: calculating the weighted neighborhood sum for each ground sampling point; calculating the global mean and standard deviation; iteratively calculating the Gi* value of each ground sampling point; converting the Gi* value of each ground sampling point into a Z score; and obtaining the surface hotspot area according to the actual evaluation requirements of the Z score; When calculating the Getis-Ord Gi* statistic, it is necessary to set an appropriate neighborhood range according to the distribution density of the ground data. The formula is as follows: ， In the formula, is the spatial weight between elements i and j ; is the attribute value of element j ; is the neighborhood weighted sum; is the global mean; is the global standard deviation; is the total sample, that is, the total number of methane concentration data points collected by aerial survey; The method for obtaining the aerial survey hot spot area includes: applying the kernel density estimation method to calculate the spatial density, using a Gaussian kernel, and its expression is: ， ， In the formula, is the kernel function, representing the density contribution intensity of the data point pair to the surrounding positions; is the normalized distance; is the bandwidth; is the target position; is the data point position; Select the bandwidth according to Silverman's rule , and the expression is: ， Wherein, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; is the total number of methane concentration data points collected by aerial survey; For each grid point , calculate the density contribution of its surrounding points: ， In the formula, represents the estimated value of methane concentration density at the spatial position ; is the total number of methane concentration data points collected by aerial survey; For the calculated spatial density values, determine the aerial survey hot spot area based on the empirical quantile.

5. The method for monitoring methane emissions from a landfill by combined air and ground monitoring according to claim 4, characterized in that: The method for screening the methane emission source area includes: Generate binary rasters for both the surface hot spot area result and the aerial survey hot spot area result to obtain the ground hot spot raster and the aerial survey hot spot raster; Use a vector polygon file to define the boundary of the landfill; Make the resolutions, coordinate systems, and spatial ranges of the ground hot spot raster and the aerial survey hot spot raster consistent; Using the boundary of the landfill as a mask, crop the ground hot spot raster and the aerial survey hot spot raster to exclude interference from external areas; Select the grid size according to the hot spot scale; Generate regular grids covering the landfill; For each grid cell, count the number of hot pixels in the aerial survey and the number of overlapping pixels , and calculate the local Jaccard coefficient to quantify the overlapping degree between the two. The calculation formula is as follows: ， Wherein, is the Jaccard coefficient, is the set of aerial survey hot pixels within the grid ; is the set of ground hot pixels within the grid ; Evaluate the spatial consistency of the ground hot spots within the aerial survey hot spot range based on the Jaccard coefficient, and screen to obtain the methane emission source area.

6. The methane emission monitoring method for landfill by combined air and ground monitoring according to claim 5, characterized in that: The method for calculating the methane emission flux is: Combined with the measured methane concentration distribution and the simultaneously obtained environmental meteorological parameters of the landfill, use the mass balance method to calculate the methane emission flux. The calculation formula is as follows: ， Where F is the emission rate of the emission source; H is the integrated height of the plane perpendicular to the wind direction; W is the integrated width of the plane perpendicular to the wind direction; u is the wind speed of the vertical aerial survey plane; is the enhanced value of the CH4 concentration signal, with the upwind test value as the background value , and the downwind test value and the background value The difference is denoted as the enhanced value of the CH4 concentration signal.

7. The method for monitoring methane emissions from a landfill by combined air and ground monitoring according to claim 1, characterized in that: Use a portable methane analyzer to conduct ground sampling of methane emissions from the landfill; use a drone equipped with a laser methane concentration detector to conduct aerial sampling of methane emissions from the landfill; use a drone equipped with an airborne meteorological instrument to collect the environmental meteorological parameters of the landfill.

8. A landfill methane emission monitoring system for joint air-ground monitoring that implements the method according to any one of claims 1-7, characterized in that: It includes a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module; The landfill three-dimensional model construction module is used to construct a landfill three-dimensional model based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area; The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the landfill three-dimensional model, combined with the topographic features of the landfill, possible emission hot spot areas, and historical operation information, and conduct ground sampling of methane emissions according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill; The aerial survey methane concentration distribution data acquisition module is used to determine the aerial survey height and aerial survey route area for aerial sampling of methane emissions based on the landfill three-dimensional model and the selected number of ground sampling points, and obtain the aerial survey methane concentration distribution data over the landfill; The aerial survey average methane concentration data calculation module is used to spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the landfill three-dimensional model, according to the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data; The hotspot area acquisition module is used to analyze the surface methane concentration sampling data of the landfill by using the Getis-Ord Gi* statistic method to obtain the surface hotspot area, and analyze the aerial survey average methane concentration data by using the kernel density estimation method to obtain the aerial survey hotspot area; The methane emission source area screening module is used to map the results of the surface hotspot area and the aerial survey hotspot area to the three-dimensional model of the landfill, and screen the methane emission source area by calculating the local Jaccard coefficient; The methane emission flux calculation module is used to collect the environmental meteorological parameters of the landfill, and calculate the methane emission flux by the mass balance method according to the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data.

9. An electronic device, characterized in that, It includes: A memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor realizes a method for monitoring methane emissions from a landfill with combined air and ground monitoring as described in any one of claims 1-7 by executing the computer instructions.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the processor, it realizes a method for monitoring methane emissions from a landfill with combined air and ground monitoring as described in any one of claims 1-7.

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