A method for quickly positioning a thermal hazard zone of a mining face in a mine based on an infrared thermal image

Abstract

The present application relates to a kind of infrared thermal image-based underground mining face thermal damage area fast positioning method, belong to mine ventilation technical field;The present application is by measured mine strata thermal parameter data, mine fan data, mining equipment thermal data constructs complete mine ventilation system thermal parameter database, with mine ventilation three-dimensional well and roadway model thermal parameter matching, establishes mine ventilation system thermal model, dynamically simulates the actual working condition of mine ventilation system, predicts the wet bulb temperature anomaly point of mining face wind temperature mutation, uses infrared thermal imager to collect infrared thermogram in predicted anomaly point, draws the isotherm of thermogram, locates mining face thermal damage area, without relying on a large number of environmental monitoring in field, avoids the interference of mine environment to detection equipment, makes mining face thermal damage area positioning more quickly, accurately, efficiently, provides accurate data for mining face thermal damage area management, improves thermal damage area management efficiency.

Description

Technical Field

[0001] This invention relates to a method for rapid location of heat-hazard zones in underground mining faces based on infrared thermal imaging, belonging to the field of mine ventilation technology. Background Technology

[0002] With the increasing depth of mining of metallic and non-metallic minerals and the significant improvement in the level of mechanization in mining, high-temperature heat hazards at underground mining faces are becoming increasingly apparent, and have become one of the main problems restricting the safe and efficient mining of deep resources. Due to the large number of intermediate sections, mining faces, and electromechanical equipment in metallic and non-metallic mines, and the complexity of ventilation systems that change dynamically with mining operations, how to quickly and accurately locate heat hazard zones at underground mining faces has become a key focus and challenge in heat hazard prevention and control.

[0003] Chinese patent CN106837421A discloses a method for predicting mine airflow and controlling thermal hazards. This method, based on parameters from temperature sensors, humidity sensors, airflow state sensors, and related thermophysical parameters, uses a mine airflow and temperature prediction platform to perform numerical simulation calculations of underground airflow, obtaining the airflow temperature at various nodes underground. The predicted airflow temperature from the platform, along with parameters from the temperature, humidity, airflow state, and underground thermophysical parameter modules, is wirelessly transmitted to a mine thermal hazard control platform for numerical simulation analysis, thereby proposing an economical, effective, and reasonable thermal hazard control solution. However, this method requires the installation of numerous temperature, humidity, and airflow state sensors to collect data. Limited by the harsh environment of high temperature and humidity underground, the sensors are susceptible to environmental interference, resulting in a high failure rate. Furthermore, these sensors can only monitor the installation location or a small surrounding area, making it difficult to cover the entire underground system. Therefore, this method involves high investment and long construction time. Furthermore, because this method does not consider the coupling between the surrounding rock temperature field and the airflow temperature field at the mining face, as well as the movement trajectory of the mining equipment, the predicted airflow temperature is not accurate enough. Therefore, this method cannot quickly and accurately locate the heat hazard zone at the underground mining face. Summary of the Invention

[0004] To overcome the problems existing in the background technology, this invention constructs a complete thermal parameter database of the mine ventilation system by using measured thermal parameter data of mine rock strata, mine fan data, and thermal data of mining equipment. This database is then matched with the thermal parameters of a three-dimensional mine ventilation tunnel model to establish a thermal model of the mine ventilation system. This model dynamically simulates the actual working conditions of the mine ventilation system, predicts anomalous wet-bulb temperature points in the model where the wind temperature at the mining face changes abruptly, and uses an infrared thermal imager to collect infrared thermal images at the predicted anomalous points. The thermal image isotherms are then drawn to locate the heat hazard area at the mining face. This eliminates the need for extensive on-site environmental monitoring, avoids interference from the mine environment on the detection equipment, and makes the location of heat hazard areas at the mining face faster, more accurate, and more efficient. This provides accurate data for the treatment of heat hazard areas at the mining face and improves the efficiency of heat hazard treatment.

[0005] To overcome the problems existing in the background art and to solve the above problems, the present invention is achieved through the following technical solution: A method for rapid location of heat-hazard zones in underground mining faces based on infrared thermal imaging includes the following steps: S1. Establish a thermal parameter database for the mine ventilation system, including a three-dimensional mine ventilation tunnel model, thermal parameters of the mine rock strata, mine fan data, and thermal data of mining equipment; S2. Using the thermal parameter database of the mine ventilation system established in S1, perform thermal parameter matching on the three-dimensional shaft model of the mine ventilation system, establish a thermal model of the mine ventilation system, and assign corresponding mine parameters to improve the thermal model of the mine ventilation system. S3. Simulate the working conditions of the mine ventilation system based on the thermal model of the mine ventilation system, and predict the abnormal points in the model where the wind temperature at the mining face changes abruptly and the wet-bulb temperature of the airflow is greater than 27℃. S4. Set up an infrared thermal imager at the location of the tunnel corresponding to the abnormal wind temperature point at the mining face predicted by the thermal model of the mine ventilation system, and take visible light images and corresponding infrared thermal images. S5. Export the visible light image and the corresponding infrared thermal image, overlay the visible light image and the corresponding infrared thermal image, draw the thermal image isotherms, divide the overlay image of the visible light image and the infrared thermal image with 31℃ as the boundary, determine the heat hazard zone of the mining face above 31℃, and calculate the average temperature of each heat hazard zone of the mining face using a histogram.

[0006] A rapid location method for heat-hazard zones in underground mining faces based on infrared thermal imaging is characterized by: the mine rock thermal parameters collected in S1 include the thermal conductivity, specific heat capacity, thermal diffusivity, density, and geothermal gradient of various rock masses; the mine fan data includes the rated speed of the main fan and local fans, the maximum inner diameter of the diffuser outlet, the air volume and air pressure corresponding to the total pressure characteristic curve of the fan, the air volume and fan efficiency corresponding to the efficiency characteristic curve of the fan, the air volume and shaft power corresponding to the power characteristic curve of the fan, and the airflow density corresponding to the three curves.

[0007] Preferably, the process of perfecting the thermal model of the mine ventilation system described in S2 includes, S2.1, Based on the thermal parameter data of the rock strata, assign thermal parameter values ​​to the surrounding rock of each section of the three-dimensional mine ventilation tunnel model: Import the three-dimensional mine ventilation tunnel model into Ventsim Design or VUMA three-dimensional mine ventilation simulation software, determine the elevation and rock stratum type of each section of the tunnel from the surface wellhead to the deepest part, and use the software's thermal module to select each section of the three-dimensional tunnel and edit its attributes. Define the rock thermal conductivity, rock specific heat capacity, rock thermal diffusivity, rock density, and geothermal gradient of the rock strata at the corresponding elevation collected in S1 to the tunnel at the corresponding elevation.

[0008] S2.2, Based on the mine ventilation fan data, match the corresponding fan operation curves for the main and auxiliary fans in the thermal model of the mine ventilation system: Import the total pressure characteristic curves of the main and auxiliary fans into Ventsim Design or VUMA 3D mine ventilation simulation software. With the help of the fan digitization module, define the maximum air volume, minimum air volume, maximum air pressure, and minimum air pressure corresponding to the total pressure characteristic curves of the fans, obtain the digital plotting range of air volume and air pressure, and ensure that the imported total pressure characteristic curves of the fans completely overlap with the digital plotting range; calibrate the intersection points of the air volume and air pressure curves and efficiency characteristic curves corresponding to each blade angle of the fans in the digital plotting range, thereby digitizing the fan air volume-air pressure total pressure characteristic curves and air volume-efficiency characteristic curves; after selecting the 3D tunnel where the main fan and auxiliary fan are located, edit their fan attributes and match the corresponding main fan model and fan operation curves respectively.

[0009] S2.3, Based on the thermal data and activity areas of the mining equipment, establish the activity trajectories of the mining equipment in the ventilation network model. Use the flow-weighted method to match the heat release parameters of the mining equipment. Classify the underground mining equipment into diesel and electric types, and establish the utilization rate f, diesel engine point heat source power Nc, and motor power Nd for each type of equipment. Determine the average number of times each piece of mining equipment enters the activity trajectory range within the model per hour as t1, t2, t3, ..., t n The total number of iterations T = t1 + t2 + t3 + ... + t n The heat release of the mining equipment using the flow-weighted method for matching diesel equipment is: Qc=Nc1* t1*f / T+ Nc2* t2*f / T+……+ Nc n * t n *f / T (1) Qd=Nd1* t1*f / T+ Nd2* t2*f / T+……+ Nd n * t n *f / T (2) This allows for the matching of heat release values ​​from various mining equipment, thus constructing a thermal model of the mine ventilation system.

[0010] Preferably, the anomaly prediction process for the sudden change in wind temperature at the S3 mining face and the wet-bulb temperature of the airflow being greater than 27°C is as follows: the established thermal model of the mine ventilation system is imported into Ventsim Design or VUMA three-dimensional mine ventilation simulation software, the ambient temperature and humidity parameters are set, and the thermal parameters of the surrounding rock in the tunnel, the heat release parameters of the mining equipment, and the fan operation curve are kept consistent with the actual working conditions of the system. Thermal simulation calculation is performed using the thermal module. After the simulation is successful, the calculation results are called to display the wet-bulb temperature of the entire model tunnel, and anomalies are found in the model where the temperature difference between adjacent tunnels is greater than 3°C and the wet-bulb temperature of the high-temperature tunnel is greater than 27°C.

[0011] Preferably, the calculation process of the average temperature histogram of each mining face heat hazard zone in S5 is as follows: using IRSOFT, export the visible light image and the corresponding infrared thermal image of the mining area at the wind and temperature anomaly point; on the visible light image and the infrared thermal image of the mining area at the wind and temperature anomaly point, mark the four corner points of the image in the same clockwise order and at the same position; superimpose the visible light image and the corresponding infrared thermal image; draw isotherms of the thermal image at 31℃ and 45℃; divide the superimposed image of the visible light image and the infrared thermal image with 31℃ as the boundary; thereby locate the area above 31℃ as the heat hazard zone of the mining face; draw a histogram based on the proportion of pixel point cloud temperature values ​​in the entire temperature spectrum; and calculate the average temperature of the heat hazard zone of the mining area at the wind and temperature anomaly point by weighted average.

[0012] The beneficial effects of this invention are as follows: This invention constructs a comprehensive thermal parameter database for mine ventilation systems using measured thermal parameters of mine rock strata, mine fan data, and mining equipment thermal data. This database is then matched with thermal parameters from a three-dimensional mine ventilation tunnel model to establish a thermal model of the mine ventilation system. This model dynamically simulates the actual operating conditions of the mine ventilation system, predicts anomalous wet-bulb temperature points in the model where wind temperature changes abruptly at the mining face, and uses an infrared thermal imager to collect infrared thermal images at these predicted anomalous points. The resulting thermal isotherms are then plotted to locate heat-hazardous areas at the mining face. This method eliminates the need for extensive on-site environmental monitoring, avoiding interference from the mine environment on the detection equipment. It enables faster, more accurate, and more efficient location of heat-hazardous areas at the mining face, providing accurate data for heat-hazardous area management and improving the efficiency of heat-hazardous area management. Attached Figure Description

[0013] Figure 1 This is a diagram showing the rapid flow positioning process of the thermal hazard zone at the mining face in this invention. Figure 2 This refers to the three-dimensional mine ventilation tunnel model established in this embodiment of the invention; Figure 3 These are the predicted wind and temperature anomalies in this embodiment of the invention; Figure 4 This is an infrared thermogram of a point with abnormal wind and temperature in an embodiment of the present invention; Figure 5 This refers to the thermal hazard zone of the mining face located in this embodiment of the invention. Figure 6 This is a histogram showing the temperature distribution in the heat-affected area of ​​the mining face in an embodiment of the present invention. Detailed Implementation

[0014] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0015] from Figure 1 As shown, a method for rapid location of heat-hazard zones in underground mining faces based on infrared thermal imaging includes the following steps: S1. Establish a thermal parameter database for the mine ventilation system. Based on the measured CAD drawings of the mine's shafts, use the Ventsim Design 3D mine ventilation simulation system to create a 3D model of the mine ventilation shafts. Figure 2 As shown; the mine ventilation system thermal parameter database includes mine rock strata thermal parameters, mine fan data, and mining equipment thermal data; The types of rock strata in each section of the mine roadway are statistically recorded, and the thermal conductivity, specific heat capacity, thermal diffusivity, density, and geothermal gradient of various rock strata from the surface wellhead to the deepest roadway are measured to obtain the thermal parameter data of the mine rock strata. Based on the model of the main fan and local fans in the mine, find and determine the installed power, rated speed, maximum inner diameter of the diffuser outlet, total pressure characteristic curve, static pressure characteristic curve, efficiency characteristic curve, and power characteristic curve of the main fan and local fans to obtain the mine fan data. Based on the underground mining equipment in the mine, thermal data of the mining equipment was obtained by classifying it into diesel equipment and electric equipment. The thermal data of the mining equipment includes the utilization coefficient of diesel equipment, diesel particulate matter yield, nitrogen oxide yield, carbon monoxide yield, point heat source power of diesel equipment, and the utilization coefficient and power of electric equipment. S2. Using the thermal parameter database of the mine ventilation system established in S1, the thermal parameters of the three-dimensional mine ventilation tunnel model are matched. The specific steps are as follows: S2.1, Based on the thermal parameter data of the rock strata, assign thermal parameter values ​​to the surrounding rock of each section of the three-dimensional mine ventilation tunnel model: Import the three-dimensional mine ventilation tunnel model into Ventsim Design or VUMA three-dimensional mine ventilation simulation software, determine the elevation and rock stratum type of each section of the tunnel from the surface wellhead to the deepest part, and use the software's thermal module to select each section of the three-dimensional tunnel and edit its attributes. Define the rock thermal conductivity, rock specific heat capacity, rock thermal diffusivity, rock density, and geothermal gradient of the rock strata at the corresponding elevation collected in S1 to the tunnel at the corresponding elevation.

[0016] S2.2, Based on the mine ventilation fan data, match the corresponding fan operation curves for the main and auxiliary fans in the thermal model of the mine ventilation system: Import the total pressure characteristic curves of the main and auxiliary fans into Ventsim Design or VUMA 3D mine ventilation simulation software. With the help of the fan digitization module, define the maximum air volume, minimum air volume, maximum air pressure, and minimum air pressure corresponding to the total pressure characteristic curves of the fans, obtain the digital plotting range of air volume and air pressure, and ensure that the imported total pressure characteristic curves of the fans completely overlap with the digital plotting range; calibrate the intersection points of the air volume and air pressure curves and efficiency characteristic curves corresponding to each blade angle of the fans in the digital plotting range, thereby digitizing the fan air volume-air pressure total pressure characteristic curves and air volume-efficiency characteristic curves; after selecting the 3D tunnel where the main fan and auxiliary fan are located, edit their fan attributes and match the corresponding main fan model and fan operation curves respectively.

[0017] S2.3, Based on the thermal data and activity areas of the mining equipment, establish the activity trajectories of the mining equipment in the ventilation network model. Use the flow-weighted method to match the heat release parameters of the mining equipment. Classify the underground mining equipment into diesel and electric types, and establish the utilization rate f, diesel engine point heat source power Nc, and motor power Nd for each type of equipment. Determine the average number of times each piece of mining equipment enters the activity trajectory range within the model per hour as t1, t2, t3, ..., t n The total number of iterations T = t1 + t2 + t3 + ... + t n The heat release of the mining equipment using the flow-weighted method for matching diesel equipment is: Qc=Nc1* t1*f / T+ Nc2* t2*f / T+……+ Nc n * t n *f / T (1) Qd=Nd1* t1*f / T+ Nd2* t2*f / T+……+ Nd n * t n *f / T (2) This allows for the matching of heat release values ​​from various mining equipment, thus constructing a thermal model of the mine ventilation system.

[0018] S3. Simulating the actual working condition of the mine ventilation system according to the established thermal model of the mine ventilation system, predicting abnormal points where the air temperature at the mining face changes abruptly and the wet bulb temperature of the airflow is greater than 27°C in the model, importing the thermal model of the mine ventilation system established in step S2 into Ventsim Design or VUMA 3D mine ventilation simulation software, setting ambient temperature and humidity parameters, keeping the thermal parameter values of the surrounding rock of the roadway, the heat release parameter values of the mining equipment, and the operating curve of the fan consistent with the actual working condition of the system, performing thermal simulation calculation by means of the thermal module, calling the calculation result after successful simulation, displaying the wet bulb temperature of the roadway in the whole model, and finding out abnormal points in the model where the air temperature difference between adjacent roadways is greater than 3°C and the wet bulb temperature of the high-temperature roadway is greater than 27°C, as shown in Figure 3 , the dark area of the roadway where the wet bulb temperature of the airflow is higher than 27°C is the predicted abnormal air temperature point; S4. Installing an infrared thermal imager at the actual roadway position corresponding to the abnormal air temperature point predicted by the thermal model of the mine ventilation system, adopting a testos890 infrared thermal imager, 10m away from the stope face, determining that the surrounding rock is dolomite and setting the emissivity to 0.93, and shooting the visible light image of the stope at the abnormal air temperature point and the corresponding infrared thermal image, as shown in Figure 4 .

[0019] S5. Exporting the visible light image of the stope at the abnormal air temperature point and the corresponding infrared thermal image by means of IRSOFT, the matching analysis software for the testos890 infrared thermal imager, calibrating 4 corner points of the images in the same clockwise order and at completely identical positions on the visible light image and the infrared thermal image of the stope at the abnormal air temperature point, superimposing the visible light image and the corresponding infrared thermal image, drawing isotherms on the thermal image at 31°C and 45°C, and segmenting the superimposed image of the visible light image and the infrared thermal image with 31°C as the boundary, as shown in Figure 5 , so as to locate the area above 31°C as the thermal damage area of the mining face, drawing a histogram based on the proportion of the number of pixel cloud temperature values on the superimposed map ( Figure 5 ) in the total number of the entire temperature map, and obtaining the average temperature of the thermal damage area in the stope at the abnormal air temperature point by weighted average calculation.

[0020] Finally, it should be noted that the above descriptions are only the implementations of the present application, which are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the description and drawings of the present application, whether directly or indirectly applied in other relevant technical fields, shall similarly be included in the patent protection scope of the present application.

Claims

1. A method for rapid location of heat-hazard zones in underground mining faces based on infrared thermography, characterized in that, The method for rapid location of heat hazard zones at the mining face includes the following steps: S1. Establish a thermal parameter database for the mine ventilation system, including a three-dimensional mine ventilation tunnel model, thermal parameters of the mine rock strata, mine fan data, and thermal data of mining equipment; S2. Using the thermal parameter database of the mine ventilation system established in S1, perform thermal parameter matching on the three-dimensional mine ventilation tunnel model to establish a thermal model of the mine ventilation system, and assign corresponding mine parameters to improve the thermal model of the mine ventilation system, including the following steps: S2.1, Based on the thermal parameter data of the rock strata, assign thermal parameter values ​​to the surrounding rock of each section of the three-dimensional mine ventilation tunnel model: Import the three-dimensional mine ventilation tunnel model into Ventsim Design or VUMA three-dimensional mine ventilation simulation software, determine the elevation and rock stratum type of each section of the tunnel from the surface wellhead to the deepest part, and use the software's thermal module to select each section of the three-dimensional tunnel and edit its attributes. Define the rock thermal conductivity, rock specific heat capacity, rock thermal diffusivity, rock density, and geothermal gradient of the rock strata at the corresponding elevation collected in S1 to the tunnel at the corresponding elevation. S2.2, Based on the mine ventilation fan data, match the corresponding fan operation curves for the main and auxiliary fans in the mine ventilation system thermal model: Import the total pressure characteristic curves of the main and auxiliary fans into Ventsim Design or VUMA 3D mine ventilation simulation software. Using the fan digitization module, define the maximum air volume, minimum air volume, maximum air pressure, and minimum air pressure corresponding to the total pressure characteristic curves of the fans, obtain the digital plotting range of air volume and air pressure, and ensure that the imported total pressure characteristic curves of the fans completely overlap with the digital plotting range; calibrate the intersection points of the air volume and air pressure curves and the efficiency characteristic curves corresponding to each blade angle of the fans in the digital plotting range, thereby digitizing the fan air volume-air pressure total pressure characteristic curves and air volume-efficiency characteristic curves; after selecting the 3D tunnel where the main and auxiliary fans are located, edit their fan attributes, and match the corresponding main fan models and fan operation curves respectively. S2.3, Based on the thermal data and activity areas of the mining equipment, establish the activity trajectories of the mining equipment in the ventilation network model. Use the flow-weighted method to match the heat release parameters of the mining equipment. Classify the underground mining equipment into diesel and electric types, and establish the utilization rate f, diesel engine point heat source power Nc, and motor power Nd for each type of equipment. Determine the average number of times each piece of mining equipment enters the activity trajectory range within the model per hour as t1, t2, t3, ..., t n The total number of iterations T = t1 + t2 + t3 + ... + t n The heat release of the mining equipment using the flow-weighted method for matching diesel equipment is: Qc=Nc1* t1*f / T+ Nc2* t2*f / T+……+ Nc n * t n *f / T (1) Qd=Nd1* t1*f / T+ Nd2* t2*f / T+……+ Nd n * t n *f / T (2) This allows for the matching of heat release values ​​from various mining equipment, and the construction of a thermal model for the mine ventilation system. S3. Simulate the working conditions of the mine ventilation system based on the thermal model of the mine ventilation system, and predict the abnormal points in the model where the wind temperature at the mining face changes abruptly and the wet-bulb temperature of the airflow is greater than 27℃. S4. Set up an infrared thermal imager at the location of the tunnel corresponding to the abnormal wind temperature point at the mining face predicted by the thermal model of the mine ventilation system, and take visible light images and corresponding infrared thermal images. S5. Export the visible light image and the corresponding infrared thermal image, overlay the visible light image and the corresponding infrared thermal image, draw the thermal image isotherms, divide the overlay image of the visible light image and the infrared thermal image with 31℃ as the boundary, determine the heat hazard zone of the mining face above 31℃, and calculate the average temperature of each heat hazard zone of the mining face using a histogram.

2. The method for rapid location of heat hazard zones in underground mining faces based on infrared thermal imaging according to claim 1, characterized in that: The mine rock thermal parameters collected by S1 include the thermal conductivity, specific heat capacity, thermal diffusivity, density, and geothermal gradient of various rock masses; the mine fan data includes the rated speed of the main fan and local fans, the maximum inner diameter of the diffuser outlet, the air volume and air pressure corresponding to the total pressure characteristic curve of the fan, the air volume and fan efficiency corresponding to the efficiency characteristic curve of the fan, the air volume and shaft power corresponding to the power characteristic curve of the fan, and the airflow density corresponding to the three curves.

3. The method for rapid location of heat hazard zones in underground mining faces based on infrared thermal imaging according to claim 1, characterized in that: The process for predicting the anomaly point of sudden change in wind temperature and wet-bulb temperature of airflow greater than 27℃ at the S3 mining face is as follows: The established thermal model of the mine ventilation system is imported into Ventsim Design or VUMA 3D mine ventilation simulation software. The ambient temperature and humidity parameters are set, and the thermal parameters of the surrounding rock in the tunnel, the heat release parameters of the mining equipment, and the fan operation curve are kept consistent with the actual working conditions of the system. Thermal simulation calculation is performed with the help of the thermal module. After the simulation is successful, the calculation results are called to display the wet-bulb temperature of the entire model tunnel. Anomalies in the model where the temperature difference between adjacent tunnels is greater than 3℃ and the wet-bulb temperature of the high-temperature tunnel is greater than 27℃ are identified.

4. The method for rapid location of heat hazard zones in underground mining faces based on infrared thermal imaging according to claim 1, characterized in that: The calculation process of the average temperature histogram of each mining face heat hazard zone in S5 is as follows: Using IRSOFT, the visible light image and the corresponding infrared thermal image of the mining area at the wind and temperature anomaly point are exported. On the visible light image and the infrared thermal image of the mining area at the wind and temperature anomaly point, the four corner points of the image are marked clockwise in the same order and at the same position. The visible light image and the corresponding infrared thermal image are superimposed. The thermal image isotherms are drawn at 31℃ and 45℃. The superimposed image of the visible light image and the infrared thermal image is divided with 31℃ as the boundary, thereby locating the area above 31℃ as the heat hazard zone of the mining face. A histogram is drawn based on the proportion of the pixel point cloud temperature value in the entire temperature spectrum on the superimposed image. The average temperature of the heat hazard zone of the mining area at the wind and temperature anomaly point is obtained by weighted averaging.

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