CN111243212B - Forest fire monitoring system and method based on radio frequency technology - Google Patents
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Abstract
The invention belongs to the technical field of forest fire monitoring, and particularly relates to a forest fire monitoring system and method based on a radio frequency technology, a forest monitoring network and a control center; the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit is used for monitoring the change of the surrounding environment and sending the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions; besides the monitoring function, the forest fire occurrence position can be positioned, and in addition, the fire condition can be evaluated; the method has the advantages of accurate monitoring and high accuracy of the evaluation result.
Description
Technical Field
The invention belongs to the technical field of forest fire monitoring, and particularly relates to a forest fire monitoring system and method based on a radio frequency technology.
Background
Since the emergence of forests on earth, forest fires have been accompanied. Forest fires occur more than 20 ten thousand times every year all over the world, and the area of burning the forest occupies more than 1 per thousand of the total area of the forest all over the world. At present, China generates forest fires for about 1 million times every year on average, burns off hundreds of thousands of forests to millions of hectares, and occupies about 5-8 per thousand of forest area in China. It is a serious social hazard.
Forest fires occur more than 20 ten thousand times every year all over the world, and the area of burning the forest occupies more than 1 per thousand of the total area of the forest all over the world. At present, China generates forest fires for about 1 million times every year on average, burns off hundreds of thousands of forests to millions of hectares, and occupies about 5-8 per thousand of forest area in China. In 1987, in 5 months, Heilongjiang Daxing' an Ling, a super-huge forest fire also occurs, the fire passing area is 101 hectares, and the forest area accounts for 70 percent.
Forest fires not only burn trees to directly reduce the forest area, but also seriously destroy forest structures and forest environments, so that the forest ecological system is out of balance, the forest biomass is reduced, the productivity is weakened, animals and birds are benefited, and even people and livestock are killed. The strong fire can destroy the chemical and physical properties of soil, reduce the water retention and permeability of the soil, and raise the groundwater level of certain forests and low-lying lands to cause swampiness; in addition, due to carbonization and temperature increase of the soil surface, the drying of a burned land can be accelerated, positive weeds are gathered, and the forest is not updated favorably or low-value forest replacement resistant to extreme ecological conditions is caused.
The size of forest fires is often measured in terms of the area of the damaged forest, the area of the forest in which the forest is in disaster, and the number of plants. China regulations are as follows: when the forest trees (including mature forest, young forest and bamboo forest) are burned, the forest fire is caused when the damaged area is 10-1000 mu; the method is characterized in that the forest with the damaged area of 1000-10000 acres in the southern forest area and 1000-50000 acres in the northern forest area is a forest fire hazard; the area of damage exceeds 10000 mu in the south forest area and 50000 mu in the north forest area, which is a forest fire disaster. The unit area of the damaged forest is the area of the damaged forest, the number of plants burnt or killed by the forest is more than 30%, and the area of the young forest is more than 60%.
Disclosure of Invention
The invention mainly aims to provide a forest fire monitoring system and method based on a radio frequency technology, which not only have a monitoring function, but also can position the occurrence position of forest fire and evaluate the fire condition; the method has the advantages of accurate monitoring and high accuracy of the evaluation result.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
forest fire monitoring system based on radio frequency technology includes: a forest monitoring network and a control center; the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit is used for monitoring the change of the surrounding environment and sending the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions; the method for positioning the forest fire place by the control center through the data information sent by the monitoring points comprises the following steps: placing the radio frequency units of all monitoring points under a reference clock; the radio frequency unit of the target monitoring point sends signals to the radio frequency units of other monitoring points; the control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; the position of the target monitoring point can be calculated by using the following formula:
wherein the content of the first and second substances,
η＝[x-x1 y-y1 y1]T；
m＝[m2,1 … mM,1]T。
further, the method for the control center to judge whether forest fire occurs and to evaluate the fire condition comprises the following steps: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
Further, the method for calculating the farthest point of the boundary of the fire area from the center of gravity of the forest fire, wherein the farthest point is the fire point, comprises the following steps: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
Further, the simplified calculation of the barycenter of the polygon boundary uses the following formula:
where n is the number of sides of the polygon, xiAnd yiThe abscissa and ordinate of each fixed point of the polygon.
Further, the method for calculating the fire point performs the following steps: according to the gravity center G obtained by calculation and the position information of each monitoring point, obtaining the probability value of each monitoring point as a fire point as follows:
wherein the content of the first and second substances,
the mean value of the horizontal and vertical coordinates of the gravity center; σ is the standard deviation of normal distribution; siThe average value of the horizontal and vertical coordinates of each monitoring point is obtained; the point with the highest probability is the fire point.
Further, the algorithm comprises the following specific steps: two points with the maximum and minimum polygon abscissa values are taken and connected into a straight line AB; calculating a point C farthest from the AB among points on the left side of the AB in the polygon, and calculating a distance D between the point C and the AB; comparing the distance with a preset threshold value, if the distance is smaller than the threshold value, taking AB as the approximation of the broken line, and finishing the processing of the section; if the distance is larger than the threshold value, dividing the vector line into two segments of AC and BC by using C; when all the points on the left side of the AB are processed, the same operation is executed on the right side of the AB; and connecting the rest points in sequence to form the simplified polygon boundary.
A forest fire monitoring method based on radio frequency technology comprises the following steps: the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit monitors the change of the surrounding environment and sends the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions.
Further, the method for positioning the forest fire place by the control center through the data information sent by the monitoring point comprises the following steps: placing the radio frequency units of all monitoring points under a reference clock; the radio frequency unit of the target monitoring point sends signals to the radio frequency units of other monitoring points; the control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; the position of the target monitoring point can be calculated by using the following formula:
wherein the content of the first and second substances,
η＝[x-x1 y-y1 y1]T；
m＝[m2,1 … mM,1]T。
further, the method for the control center to judge whether forest fire occurs and to evaluate the fire condition comprises the following steps: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
Further, the method for calculating the farthest point of the boundary of the fire area from the center of gravity of the forest fire, wherein the farthest point is the fire point, comprises the following steps: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
Further, the simplified calculation of the barycenter of the polygon boundary uses the following formula:
where n is the number of sides of the polygon, xiAnd yiThe abscissa and ordinate of each fixed point of the polygon.
The forest fire monitoring system and method based on the radio frequency technology have the following beneficial effects: the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions. Besides conventional fire monitoring, the fire monitoring device can also monitor the fire intensity of forest fire and position the forest fire, and has multiple functions. Meanwhile, the invention uses the monitoring network formed by the radio frequency units of a plurality of monitoring points, and the positioning is more accurate by combining and positioning each monitoring point; in addition, the development direction and the fire size of the fire can be accurately judged through the image information acquired by the sensor unit, and forest fire extinguishment is facilitated.
Drawings
Fig. 1 is a schematic system structure diagram of a forest fire monitoring system based on radio frequency technology according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a method of a forest fire monitoring method based on radio frequency technology according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a comparison experiment curve of monitoring accuracy of a forest fire monitoring system and method based on a radio frequency technology provided by an embodiment of the invention and a monitoring system in the prior art; .
Wherein, 1-the experimental curve schematic diagram of the invention, 2-the experimental curve schematic diagram of the prior art.
Detailed Description
The method of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments of the invention.
Example 1
As shown in fig. 1 and 3, the forest fire monitoring system based on the radio frequency technology includes: a forest monitoring network and a control center; the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit is used for monitoring the change of the surrounding environment and sending the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions; the method for positioning the forest fire place by the control center through the data information sent by the monitoring points comprises the following steps: placing the radio frequency units of all monitoring points under a reference clock; the radio frequency unit of the target monitoring point sends signals to the radio frequency units of other monitoring points(ii) a The control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; the position of the target monitoring point can be calculated by using the following formula:
wherein the content of the first and second substances,
η＝[x-x1 y-y1 y1]T；
m＝[m2,1 … mM,1]T。
further, the method for the control center to judge whether forest fire occurs and to evaluate the fire condition comprises the following steps: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
Specifically, the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions. Besides conventional fire monitoring, the fire monitoring device can also monitor the fire intensity of forest fire and position the forest fire, and has multiple functions. Meanwhile, the invention uses the monitoring network formed by the radio frequency units of a plurality of monitoring points, and the positioning is more accurate by combining and positioning each monitoring point; in addition, the development direction and the fire size of the fire can be accurately judged through the image information acquired by the sensor unit, and forest fire extinguishment is facilitated.
Example 2
On the basis of the above embodiment, the method for calculating the farthest point of the boundary of the area with fire from the center of gravity of the forest fire, the farthest point being the fire point, performs the following steps: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
Specifically, the common forest fire monitoring methods in China mainly include ground patrol, watchtower monitoring, satellite remote sensing and the like. Wherein, the ground patrol monitoring range is small, and a plurality of places with inconvenient traffic are difficult to patrol; the observation effect of the lookout tower depends too much on the experience of lookout personnel, the lookout tower is low in accuracy, large in error, easy to be limited by terrain and topography, small in coverage range and dead angle for fire monitoring; and information such as the accurate range, the spreading direction, the speed, the acceleration and the like of the fire cannot be obtained and calculated, and practical decision reference information cannot be provided for forest fire early warning and fire fighting command work.
Example 3
On the basis of the above embodiment, the simplified calculation of the barycenter of the polygon boundary uses the following formula:
where n is the number of sides of the polygon, xiAnd yiThe abscissa and ordinate of each fixed point of the polygon.
Specifically, the center of gravity can be calculated more efficiently through the simplified polygon boundary, and the obtained center of gravity result is more accurate, so that the subsequent calculation result is more accurate.
Example 4
On the basis of the above embodiment, the method for calculating the fire point performs the following steps: according to the gravity center G obtained by calculation and the position information of each monitoring point, obtaining the probability value of each monitoring point as a fire point as follows:
wherein the content of the first and second substances,
the mean value of the horizontal and vertical coordinates of the gravity center; σ is the standard deviation of normal distribution; siThe average value of the horizontal and vertical coordinates of each monitoring point is obtained; the point with the highest probability is the fire point.
Specifically, after a forest fires, the fire spreads from the fire point to the upper, lower and surrounding areas. As early as the 18 th century, forest fire spread has been divided into two major categories: one type of fire that spreads quickly is known as a fast-moving fire, and the other type of fire that spreads slowly is known as a steady-fire. The number of fire fighters is determined by the size of the forest fire spreading area and the spreading speed in the early 20 th century. In the 70 s, various factors were used to determine a forest fire spread model to control forest fires.
The heat propagation modes for forest fire spreading are divided into the following two types: thermal convection: as the hot air rises, the ambient cold air replenishes, forming a convective plume above the combustion zone, accumulating approximately 3/4 heat of combustion. Thermal convection is often the primary cause of the conversion of surface fire to crown fire. Heat radiation: it propagates directly to each party in the form of electromagnetic waves. Its propagation is inversely proportional to the square distance of the center of the heat source. Thirdly, heat conduction: is that the combustibles transfer heat to the interior. The speed of heat transfer is determined by the magnitude of the thermal conductivity, which is the main mode of heat propagation of the underground fire.
The speed of spreading is fastest with the strongest fire, and the extended part is the fire head; the upwind spreading speed is low, the fire intensity is minimum, and the part opposite to the fire head is a fire tail; the part between the fire head and the fire tail is a fire wing. The part of the fire wing close to the fire head spreads quickly when the part of the fire wing spreads at a right angle with wind; while the portion of the wing near the tail spreads more slowly. On flat ground, when no wind exists, the fire spreads to the periphery at a constant speed and is circular or approximately circular; in strong wind, it is in the shape of an oblong with its long axis parallel to the main wind direction. The fan-shaped structure is in a fan shape when the main wind direction is not fixed (30-40 degrees) or when fire spreads on a hillside. When fire spreads over hilly terrain, it spreads faster towards the two ridges and more slowly in the valleys, which are concave. The spread rate of the fire is: linear velocity: dividing the straight-line distance from the ignition point to the end point by the time, and expressing the straight-line distance by the time in meters per minute or kilometers per hour; area velocity: dividing the area of the fire scene by the time to obtain the area of unit time, which is expressed by square meters per minute or hectare per hour; third, the peripheral speed of the fire scene: calculated in meters per minute or kilometers per hour.
Combustible material: the different types of the fuel have different physicochemical properties, structures and sizes, and the burning point and the burning speed have obvious differences. The direction of propagation of the fire tends to propagate more rapidly towards combustibles with a low ignition point and more slowly towards combustibles with a high ignition point. Fine combustible materials such as weeds and ground surface dead branches and fallen leaves, and the water content changes along with the humidity of the atmosphere; the moisture content change of the thicker combustible is closely related to the weather drought. The propagation of fine combustibles is faster and the propagation of coarse combustibles is slower. The terrain: the change in terrain not only affects the type and distribution of combustibles, but also affects the redistribution of ecological factors and thus the fire environment. The topography can affect the propagation of heat. If the fire is on a sunny slope or a ridge, the standing condition is dry, and the forest fire spreading speed is high; when fire is on a yin slope or a valley, the standing condition is wet, and the forest fire is slow to spread. The fire is fast spread from the mountain to the mountain, called as fire rushing, and is not easy to extinguish; the fire spreads slowly from the mountain to the mountain, so it is called sitting fire, and it is easy to put out fire. The slope size influences the forest fire spreading greatly, under general conditions, the forest fire spreading speed is accelerated along with the increase of the slope, but the forest fire spreading speed is seriously harmful to the forest in a gentle section, and the forest fire spreading speed is slightly harmful to the forest when the slope is increased. Thirdly, wind: the speed of the downwind spreading is fastest, the upwind spreading is slow, and the side wind spreading is between the two. The wind not only accelerates the evaporation and transpiration of water in the combustible material and accelerates the drying, thus promoting the combustible material to be more flammable, but also can change the heat transmission, thus changing the convection heat energy into heat advection and accelerating the forward spreading speed of forest fire. Under the action of wind, new oxygen can be continuously supplemented, and the combustion process is accelerated. In addition, the wind direction can determine the forest fire spreading direction. In a fire scene, when the wind direction changes suddenly, the fire can be weakened, and the fire fighting is beneficial to fighting. Other meteorological factors, such as temperature, humidity, precipitation, sunlight, etc., are all related to forest fire spread. Forest fire spreading is closely related to time, and the longer the time is, the larger the fire field spreading area is; conversely, the fire field spreading area is small.
Example 5
On the basis of the previous embodiment, the algorithm specifically comprises the following steps: two points with the maximum and minimum polygon abscissa values are taken and connected into a straight line AB; calculating a point C farthest from the AB among points on the left side of the AB in the polygon, and calculating a distance D between the point C and the AB; comparing the distance with a preset threshold value, if the distance is smaller than the threshold value, taking AB as the approximation of the broken line, and finishing the processing of the section; if the distance is larger than the threshold value, dividing the vector line into two segments of AC and BC by using C; when all the points on the left side of the AB are processed, the same operation is executed on the right side of the AB; and connecting the rest points in sequence to form the simplified polygon boundary.
Example 6
A forest fire monitoring method based on radio frequency technology comprises the following steps: the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit monitors the change of the surrounding environment and sends the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions.
Example 7
On the basis of the previous embodiment, the method for positioning the forest fire place by the control center through the data information sent by the monitoring point comprises the following steps: placing the radio frequency units of all monitoring points under a reference clock; the radio frequency unit of the target monitoring point sends signals to the radio frequency units of other monitoring points; the control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; the position of the target monitoring point can be calculated by using the following formula:
wherein the content of the first and second substances,
η＝[x-x1 y-y1 y1]T；
m＝[m2,1 … mM,1]T(ii) a The method for judging whether forest fire occurs and evaluating the fire condition by the control center comprises the following steps: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
Example 8
On the basis of the above embodiment, the method for calculating the farthest point of the boundary of the area with fire from the center of gravity of the forest fire, the farthest point being the fire point, performs the following steps: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
Specifically, the spread of fire is mainly related to 3 heat propagation forms such as heat convection, heat radiation and heat conduction. The hot convection is due to the rising hot air, supplemented by the cool ambient air, forming a convective plume over the combustion zone. The heat of combustion can be accumulated to 3/4. It is often the main reason for converting surface fire into crown fire under the action of strong wind. Thermal radiation is the primary means of heat transfer for the spread of surface fires. It is propagated straight around in the form of electromagnetic wave, and its heat transfer is inversely proportional to the square distance of heat source centre. The heat conduction is a heat transfer mode in the combustible, the heat transfer speed is determined by the heat conductivity coefficient of the combustible, and the heat transfer speed is a main reason for the underground fire spreading. The fire spreading speed is in direct proportion to the square of the wind speed, and the fire is fast spreading from bottom to top and strong in fire behavior under the condition of mountainous regions and is called as fire rushing; the downward spread from the mountain is called sitting fire, the fire is weak. The part with the fastest spreading speed and the strongest fire is a fire head; the part with the slowest spreading speed and the direction opposite to the fire head is a fire tail; the part between the fire head and the fire tail is a fire wing. The portion of the wing near the fire head spreads more quickly and the portion near the fire tail spreads more slowly. In a flat ground, the initial spread shape of a fire in the absence of wind is circular or nearly circular; the major axis of the oval shape is parallel to the main wind direction in strong wind; the fan shape is formed when the main wind direction is not constant (30-40 degrees change). When the hills spread over the terrain, the fire spreads faster towards the two ridges and slower in the valleys, often in the shape of a concave or chicken claw.
Example 9
On the basis of the above embodiment, the simplified calculation of the barycenter of the polygon boundary uses the following formula:
where n is the number of sides of the polygon, xiAnd yiThe abscissa and ordinate of each fixed point of the polygon.
Example 10
On the basis of the above embodiment, the method for calculating the fire point performs the following steps: according to the gravity center G obtained by calculation and the position information of each monitoring point, obtaining the probability value of each monitoring point as a fire point as follows:
wherein the content of the first and second substances,
the mean value of the horizontal and vertical coordinates of the gravity center; σ is the standard deviation of normal distribution; siThe average value of the horizontal and vertical coordinates of each monitoring point is obtained; the point with the highest probability is the fire point.
The above description is only an embodiment of the present invention, but not intended to limit the scope of the present invention, and any structural changes made according to the present invention should be considered as being limited within the scope of the present invention without departing from the spirit of the present invention.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process and related description of the system described above may refer to the corresponding process in the foregoing method embodiments, and will not be described herein again.
It should be noted that, the system provided in the foregoing embodiment is only illustrated by dividing the functional modules, and in practical applications, the functions may be distributed by different functional modules according to needs, that is, the modules or steps in the embodiment of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiment may be combined into one module, or may be further split into multiple sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not to be construed as unduly limiting the present invention.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes and related descriptions of the storage device and the processing device described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Those of skill in the art would appreciate that the various illustrative modules, method steps, and modules described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that programs corresponding to the software modules, method steps may be located in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. To clearly illustrate this interchangeability of electronic hardware and software, various illustrative components and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as electronic hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing or implying a particular order or sequence.
The terms "comprises," "comprising," or any other similar term are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (10)
1. Forest fire monitoring system based on radio frequency technology includes: a forest monitoring network and a control center; the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit is used for monitoring the change of the surrounding environment and sending the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions; the method for locating the forest fire place by the control center through the data information sent by the monitoring points is characterized by comprising the following steps: placing the radio frequency units of all monitoring points under a reference clock; the radio frequency unit of the target monitoring point sends signals to the radio frequency units of other monitoring points; the control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; and calculating the position of the target monitoring point by using the following formula:
wherein the content of the first and second substances,
η＝[x-x1 y-y1 y1]T；
m＝[m2,1…mM,1]T(ii) a m is an adjustment matrix, mM,1Is the value of an entry of the adjustment matrix; r isM,1The value range of the matrix is as follows: 2 to M, r2,1＝2…rM,1＝M。
2. The system of claim 1, wherein the method of the control center determining whether a forest fire is present and evaluating a fire condition performs the steps of: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
3. The system of claim 2, wherein the method of calculating the point at which the boundary of the area that has fired is furthest from the center of gravity of the forest fire, the furthest point being the point of fire performs the steps of: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
4. The system of claim 3, wherein the simplified polygon boundary centroid calculation uses the following formula:
where n is the number of sides of the polygon, xiAnd yiThe abscissa and ordinate of each fixed point of the polygon.
5. The system of claim 3, wherein the method of calculating the fire point performs the steps of: according to the gravity center G obtained by calculation and the position information of each monitoring point, obtaining the probability value of each monitoring point as a fire point as follows:
wherein the content of the first and second substances,
the mean value of the horizontal and vertical coordinates of the gravity center; σ is the standard deviation of normal distribution; siThe average value of the horizontal and vertical coordinates of each monitoring point is obtained; the point with the highest probability is the fire point.
6. The system of claim 3, wherein the method of simplifying forest fire boundaries to obtain simplified polygon boundaries performs the steps of: two points with the maximum and minimum polygon abscissa values are taken and connected into a straight line AB; calculating a point C farthest from the AB among points on the left side of the AB in the polygon, and calculating a distance D between the point C and the AB; comparing the distance with a preset threshold value, and if the distance is smaller than the threshold value, taking AB as the approximation of a broken line; if the distance is larger than the threshold value, dividing the vector line into two segments of AC and BC by using C; when all the points on the left side of the AB are processed, the same operation is executed on the right side of the AB; and connecting the rest points in sequence to form the simplified polygon boundary.
7. Forest fire monitoring method based on radio frequency technology based on a system according to one of the claims 1 to 5, characterized in that the method performs the following steps: the forest monitoring network consists of a plurality of monitoring points which are uniformly distributed in a forest area at equal intervals; the monitoring points comprise: a sensor unit, a radio frequency unit and a remote communication unit; the monitoring points realize information communication through a radio frequency unit; the monitoring point and the control center realize information communication through a remote communication unit; the sensor unit monitors the change of the surrounding environment and sends the monitored data to the control center; the control center judges whether forest fires occur or not through data information sent by each monitoring point, positions forest fire places and evaluates fire conditions.
8. The method of claim 7, wherein the method for locating forest fire locations by the control center through data information transmitted from the monitoring points comprises the following steps: placing the radio frequency units of all monitoring points under a reference clock; radio frequency of target monitoring pointThe unit sends signals to the radio frequency units of other monitoring points; the control center obtains the time of the signal reaching other monitoring points; definition of
Position coordinates of the target monitoring point, wherein
The experience height of the target monitoring point is obtained; definition of xi＝[xi,yi,zi]TSetting M other monitoring points for the position coordinates of other monitoring points, namely i is 1,2,3 … M; and calculating the position of the target monitoring point by using the following formula:
wherein the content of the first and second substances,
m＝[m2,1…mM,1]T(ii) a m is an adjustment matrix, mM,1Is the value of an entry of the adjustment matrix; r isM,1The value range of the matrix is as follows: 2 to M, r2,1＝2…rM,1＝M。
9. The method of claim 8, wherein the method of the control center determining whether a forest fire has occurred and evaluating a fire condition performs the steps of: comparing the size of a target area in the image information with a preset value according to the image information sent by the sensor unit, if the target area is smaller than the preset value, indicating that no fire is generated, and if the forest fire area is larger than the preset value, indicating that a fire point exists or the fire is generated, recording the row and column number of the corresponding target area; geometrically correcting the image, calculating the accurate coordinate of a fire point or a fire area according to the corrected image coordinate origin and the image resolution and by combining the row number and the column number of the target area, and if the fire point exists in the image, issuing forest fire early warning information; if there is an area that has already been on fire; calculating a point of the boundary of the area which has been ignited, which is farthest from the center of gravity of the forest fire, wherein the farthest point is an ignition point; according to the images continuously shot by the sensor unit, the position change of the fire point of the images at the adjacent shooting moments is calculated, the fire spreading direction is judged, and the speed and the acceleration of the fire spreading are calculated.
10. The method of claim 8, wherein the method of calculating the point at which the boundary of the area that has fired is furthest from the center of gravity of the forest fire, the furthest point being the point of fire, performs the steps of: extracting forest fire boundaries: scanning and identifying the corrected image line by line; extracting the maximum value and the minimum value of the unit temperature in the row, wherein the maximum temperature difference is the boundary of forest fire spreading to obtain the forest fire boundary, namely the position of a fire line; simplifying the forest fire boundary to obtain a simplified polygonal boundary; calculating the gravity center of the simplified polygon boundary; the fire spread is usually fastest in a certain direction, so that the simplified polygonal boundary formed by the fire scene is most convex in the direction, and the distance from the fire head to the center of gravity of the simplified polygonal boundary of the fire scene in the direction is also farthest, so that the point with the largest distance from the center of gravity to the simplified polygonal boundary of the fire scene is obtained as the fire starting point, and if the distances from all points to the center of gravity on the boundary of the fire scene are within a tolerance range, the fire spreads uniformly in all directions.
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