WO2010015742A1 - Method and device for preventing and predicting the evolution of fires - Google Patents

Abstract

The invention relates to a system (1) for preventing fires, especially forest fires, comprising on the one hand a network of a plurality of geolocalized sensors (3) forming a grid in the area of forest to be monitored, each sensor (3) being able to detect locally an incipient fire and being provided with a radiofrequency transmitter connected by radio to a control terminal (5), so that the detection of an incipient fire in the vicinity of a sensor is transmitted automatically to its control terminal (5), which is able to generate an alert signal, the system being characterized in that it comprises a computer (9) provided with simulation software capable of predicting in advance in terms of physical time, on the basis of a plurality of parameters, the movement of a flame front away from the position of an incipient fire.

Description

 Method and device for preventing and predicting fire revolution

FIELD OF THE INVENTION The invention relates to methods and devices for the prevention and early detection of fires, and for modeling their evolution to better ensure the management of forest fires or sensitive public or private places.

For the purposes of this description, the term "forest" shall be broadly and simplistically referred to as any external environment containing vegetation that may be burned, it being understood that the designation "trees" of the said forest designates and includes simplifying for the purposes of this application, plants of any size and of any kind. The context is that of a general increase in the risk of forest fires, under the effect of several factors, such as climatic factors such as global warming, and sociological factors that lead to the development of land needs as a result of increased demand for housing and infrastructure. Indeed the development of needs leads to a fragmentation of wooded areas and the entry of more human activities, and therefore fire risks, into forest areas.

Increasing interface zones between forests and inhabited areas make global fire detection systems less effective, such as aerial surveillance or visual monitoring of fire departures, which are better suited to large areas of forest. .

As a result of these factors, it has been noted in recent years that forest fires cover millions of hectares every year throughout the world, including several hundred thousand in Europe and several tens of thousands in France. However, we know that the conditions of a forest fire, as well as its mode of propagation, depend on the conjugation of several elements, among which:

- the structure and composition of the vegetation: its level of flammability and combustibility is determined by:

- pre-existing climatic conditions, which condition the degree of plant drought;

- the general condition of the forest area, ie the stand conditions: layout of the strata, state of maintenance, density, species present, recent passage of fire;

- the chemical composition of vegetation: content of volatile organic compounds, especially terpenes;

- the surrounding conditions, such as:

- the weather conditions during the fire, which have a great influence on the nature of the forest fires: the force and the speed of the wind are an important factor of propagation, as well as the heat, hygrometry, the drought of the ground;

- the topography of the site (the relief and the exposure of the ground): in a zone without relief, a start of fire is easily subjected to the acceleration of the wind whereas in zone of irregular relief, the progression of the fire is accelerated in the climbs and slowed down on the descents.

It is clear that the current methods of forest fire prevention and control do not make use of all these parameters, or in a very partial and very empirical way, without however being able to deduce how a fire will evolve according to the nature of the fire. time.

It is also known that fire is a physico-chemical phenomenon of thermal degradation, and the combustion of the plant is accompanied by a strong emission of heat energy and can be broken down into several phases: - the evaporation of the water contained in the fuel;

- the emission of flammable gas by pyrolysis; - the ignition of these gases;

- combustion of the carbonaceous residue.

Under these conditions, the entire forest must be considered as a potential fuel. The spread of a fire breaks down as follows: the burning of the plant material causes an emission of heat, it is transferred to the fuel located in front of the flame front, the plants in this area absorb the heat and ignite in their turn. In addition to this, there is a phenomenon, unknown and yet frequent, namely the swings of fires in front of the front of the flames, which promote the spread of the fire and endanger the life of the firefighters already on the ground, by seclusion of secondary foci.

STATE OF THE ART

It is clear that in terms of prevention, the early detection of forest fires has long been the main concern of firefighting operatives. It is by intervening on the fires whose area is still reduced in the quarter of an hour which follows their detection, that the reliefs are the most effective. This objective of rapid intervention is all the more difficult to reach as the meteorological risk (wind, drought) is important.

But the response time is conditioned by the rapid knowledge of the most accurate information possible for effective location of the fire. The determination of suitable access to get closer to the fires is essential. This is why remote observations, not validated by information on the spot, do not always allow the exact location and the shortest and most adapted accesses.

In this sense, a process to visualize the exact location of the outbreak of fire and nearby forest roads is strongly desired by the intervention services. It is in this context that a first patent application was filed by the applicant, published under the number FR 2 893 743, in which is proposed a system using a network of geolocated temperature sensors and distributed over an area to be monitored these sensors being regularly interrogated by control terminals, and in the absence of a response from one or more sensors in an area, it can be concluded that there is a probable fire in this zone. An alarm signal is then generated by the control terminal and transmitted to the fire department by a radiofrequency signal.

We see that this system is a first significant progress over the state of the art as described in this previous patent application.

But it has become clear that it leaves some problems untreated.

Thus, the sensor network does not allow as such, when a fire is established, to predict and model the evolution of the flame front. Indeed, this system allows to know factually and precisely the location of the fire starts, and almost in real time, how the fire moves, since it is enough to follow the progressive disappearance of additional sensors to get a good idea of the displacement from the front of fire. But this system does not allow, as it stands, to accurately predict where the front of the fire will be in one hour, in two hours, which would of course be of the greatest interest so that firefighters can deploy their means of struggle against most appropriate places.

However, in the current state of control techniques, the knowledge of the position of the front of the fire makes it possible to get an idea only approximate of probable revolution of this position, according to the experience of the forces of fight against the fires in similar conditions.

But a simple error of estimation can have dramatic consequences. For example, the fire brigade command decides to send the fighting forces to a place too close to the front of the fire, and men are likely to be caught in reverse when there is a slight breeze. Either the forces of struggle are sent too far from the front of fire, and it is several additional hectares of forest that go up in smoke.

In addition, in the system already described in the aforementioned prior application, there is no clear method to best position the fire sensors. A homogeneous distribution of the sensors may not be the most appropriate, or cost too much, given the cost of the sensors and the cost of their installation in the trees.

Indeed, the mesh of sensors, control terminals (also called relays), and the concentrators recovering by a GSM or GPRS signal the information of the sensors, are an important investment for the public or private owners of the spaces to be secured, so that it would be useful to be able to parameterize the implementation of this infrastructure according to the real risks incurred. In order to better position the fire sensors, the system should be able to determine an optimal distribution according to the nature of the specific fire risks for each zone to be protected, according to the topography of the area in particular, and other additional useful parameters.

Of course, not all of these elements can be integrated into global satellite or airborne monitoring systems because there is a good deal of data that is partial and scalable.

GOALS OF THE INVENTION

An object of the invention is therefore to provide a method and a device for preventing forest fires without the disadvantages of known methods, and further improved over the aforementioned patent application of the same applicant.

Another object of the invention is to propose a method and a fire detection device which, in addition to being able to detect and locate a fire departure very quickly and to follow the fire front in real time, makes it possible to predict the most likely evolution of the fire front path in the minutes and hours after the start of fire, even in case of changing weather conditions.

Another object of the invention is to propose, upstream of the installation of the fire detection detection infrastructure, a method for optimizing the implantation of the sensors in the most appropriate locations of the forest area. monitor this as well to increase the efficiency of the system as to reduce its cost per hectare of protected forest.

Another object of the invention is to propose a method and a fire prevention system which is much better adapted to non-uniform forest areas interspersed with areas of human activities such as scattered settlements or forests crossed by road or other networks.

SUMMARY OF THE INVENTION

The invention is based on the assumption that the New Information and Communication Technologies (Noc) can help to move from a generalized global surveillance to a precise control, adapted to each place and which makes it possible to manage the surroundings difficult to control urban areas, road infrastructure, railways or energy transport, the limits of the areas of activity or recreation located in risky or exposed sites.

In particular, the development of specific sensors and the rapid transmission of their signals over a long distance will allow refining and supplementing, at a lower cost, important technological developments already in place. In principle, the invention therefore seeks to take advantage of the fact that, on the one hand, thanks to the micro-electronics and to a network of fire sensors adapted and well arranged on a forest area, and thanks to the means of modern wireless telecommunications, it must be possible to know in the vicinity of each sensor, and with a sufficiently high frequency, the state of a plurality of physical parameters which are known to influence the way in which a front of fire progresses according to the time. On the other hand, the invention seeks to take advantage of modeling and calculation means already used in other disciplines, such as in medicine, to predict how a characteristic, such as a pathogenic factor or an epidemic, will move. as a function of time, under the effect of various environment parameters.

The idea of the invention therefore consisted in adapting the calculation and modeling tools already known in very different situations to the problem of forest fires in order to be able to predict the evolution of a flame front. and this very early in relation to the flow of physical time.

In order to materialize this idea, the subject of the invention is a fire prevention system, in particular a forest fire system, comprising on the one hand a network of a plurality of geolocalised sensors constituting a mesh of the forest zone at monitor, each sensor being able to locally detect a fire departure and being associated with a radiofrequency transmitter connected by radio to a control terminal, so that the detection of a fire departure near a sensor is transmitted automatically to its control terminal, which is able to generate an alert signal. This system is characterized in that it comprises a computer equipped with a simulation software able to predict in advance with respect to the physical time, according to a plurality of parameters, the displacement of a fire front from detection of a fire start.

Preferably, said parameters include one or more of the following parameters: parameters related to the terrain (undulating, vegetation), the degree of hygrometry and the air temperature, and the characteristics of the wind, so as to simulate a few seconds or minutes, the configuration that the front of fire will have after several hours of fire.

Advantageously, the forecasting software is set to deliver a forecast in advance by a factor of 100 to 1000 with respect to the flow of physical time. According to an advantageous embodiment of the invention, said parameters also include at least one of the following parameters: the nature of the vegetation, the history of the fires in the zone, the proximity of risk factors. Ideally, the mesh of sensors and control terminals is optimized according to the characteristics of the area to be protected. Thus, it is preferably implanted with a variable density depending on the location of the sensors, said density being calculated according to a local fire risk and parameters representative of the nature and configuration of the area to be monitored.

According to a variant of the system, each sensor is sensitive to a gaseous component representative of a start of fire, so that when the concentration of said gaseous component exceeds a predetermined threshold in the vicinity of a sensor, this sensor sends a signal of alert at the control terminal. Alternatively, it is possible that a fire departure is signaled by the absence of response of a sensor to a query from its control terminal.

It will be advantageous for the control terminals to have programmed thresholds for at least one of said parameters, so as to be able to create an alert when one of these thresholds is exceeded by at least one of the sensors controlled by a control terminal. .

Some of said programmed thresholds are programmed directly into the sensors.

In order to facilitate the communication of the local parameter values from the sensors, the system comprises signal concentrators associated with a plurality of control terminals, said signal concentrators being able to shape the information collected from the control terminals. and transmit them via an antenna and a wireless telecommunications network, to a remote server of an Internet type network, also called "web" server. According to an advantageous embodiment of the transmission between the signal concentrators and the web server, it is done using a GSM or GPRS channel.

The invention also relates to a method for detecting and predicting fire in a wooded area, characterized in that it comprises the following steps: according to a prior analysis of the fire risk factors of said area determining a mesh of fire sensors optimized for said zone, each fire sensor being provided with a radiofrequency transmitter capable of transmitting identification and / or location information of each sensor; dispose in the vicinity of each of the nodes of the mesh thus determined, a fire sensor; detecting at each fire sensor the state of absence or presence of fire, and in the event of fire in the vicinity of a fire sensor, causing said sensor to emit a warning signal comprising a identification information and / or a signal locating said sensor towards a control terminal; transmit the alert signal from the control terminal to a hub capable of communicating with a remote web server, using wireless communication, in particular GSM or GPRS type; allow fire detection process clients to view fire detection information through an internet-like network attacking the web server. Advantageously, the method further comprises a step of providing the fire detection information from the fire sensors to a prediction software capable of simulating the evolution of a fire front in advance of the actual evolution of the fire front as a function of physical time. In addition, the method preferably comprises a step of displaying the simulated evolution of a fire front on a terminal connected to said web server.

The parameters taken into account by the prediction software to simulate the anticipated advance of a fire front, are at least one of the following parameters: the starting positions of fire, the degree of undulating terrain, the nature of the vegetation, the history of the fires in the area, the proximity of risk factors, the hygrometry of the air, the temperature of the air, the characteristics of the wind.

DETAILED DESCRIPTION

Other features and advantages of the invention will appear on reading the detailed description of the accompanying drawings in which: - Figure 1 illustrates a block diagram of a detection system known from the aforementioned prior patent of the applicant, using sensors distributed fairly evenly in an area to be protected;

FIG. 2 illustrates the meaning of the graphic symbols of the components of the system of FIG. 1; FIG. 3 illustrates the plan of a site along a highway, with a particular fire risk, and in which the system according to FIG. 4 can be used;

FIG. 4 illustrates a schematic diagram of the improved device according to the invention, using a set of sensors distributed according to the risks, and an information processing chain making it possible to make available to the users of the system the situation of the risks, and the foreseeable evolution of a fire in the event of a fire in the covered area.

FIG. 5 is a photograph showing in graphical form a fire front evolution forecast made on a real case, using the simulation system according to the invention. Referring to FIG. 1. This figure schematically shows a basic cell of a system 1 for early and automatic detection of a forest fire, substantially equivalent to the above-mentioned prior patent application. as regards the acquisition of local fire departure information which is carried out using fire sensors.

This system 1, whose main constituent elements will now be recalled, comprises on the one hand a plurality of sensors 3 able to detect and transmit the local evolution of a physical or chemical quantity whose sudden variation is able to indicate a fire start. Alternatively, the sensors can signal a probable start of fire, by their silence when periodically interrogated by a control terminal, also called relay. Indeed, when a fire starts near a sensor, the sensor ends up burning and in any case can no longer communicate with its control terminal when the surrounding temperature becomes higher than its operating temperature, which is lower at 100 ^° C.

This network of sensors 3 constitutes a mesh of the forest area to be monitored, with a density, that is to say a number of sensors per unit area, relatively regular in the general case where the risk of fire does not occur. is not very differentiated within the same area covered by the mesh of sensors.

But it has been understood that the density of the sensor network will have to be higher in a rather dry wooded area often exposed to strong winds, such as the South of France or Portugal, and it may be lower in an area more northern woodland. Thus, it has been previously determined that a detection system according to the invention is already quite effective as soon as it comprises between 3 and 5 sensors per hectare of forest, the network being constituted for example by square meshes comprising a sensor at each corner of a square, and a control terminal in the center of a mesh. Sensor operation: It is of course possible to operate the sensors 3 and the control terminals 5 according to a positive logic, in which the state of all the sensors is continuously monitored, and a sudden change in the quantity measured by a sensor (temperature , hygrometry) is interpreted as a start of potential fire. But this approach requires a lot of computation and an important bandwidth for the transmissions of information starting from the sensors.

It is therefore preferable to operate the sensors 3 and the control terminals 5 in a negative logic, in which only the stopping of the capture of a detection signal of a sensor by a control terminal 5 is signaled, with the coordinates of the sensor or sensors 3 which have just stopped transmitting. This solution has the advantage of directly focusing on the likely starting fire zone.

In order to precisely locate the fire departure zone, it is provided that each sensor 3 comprises a unique identification, which is associated with positioning information of the sensor (or of the nearest control terminal), in particular of the GPS type ( acronym for "Global Positioning System"). Thus, it suffices that each sensor 3 transmits by radio information including its identification number, and a database makes it possible to link the identification of each sensor, and its geographical location.

Preferably, in order to extend the life of its internal battery, each sensor does not transmit continuously, but transmits a periodic identification signal, so that the absence of an identification signal for a period greater than one or a few periods of the signal, be interpreted by the control terminal as a potential fire start at the location of the reported missing sensor.

In order to reduce the risk of false alarm, it can be further provided that each control terminal is configured to emit an alarm signal only in the event of simultaneous absence of an identification signal of two or more neighboring fire sensors. The probability that two or more neighboring sensors fail simultaneously for any cause being small, this near-simultaneous failure or in a short time interval will make it possible to determine with very little error that the origin of the absence of signal is in fact a start of fire . Raising sensor information:

It is essential for the proper functioning of the system according to the invention, that the local detection information of a fire departure by one of the sensors 3 of the system, is relayed as quickly as possible to a control terminal 5 of the information from the sensors, in order to be able to generate an alert and set up a device for fighting against fire.

In this respect, the system of FIG. 1 is also improved with respect to the version described in the previous patent application, at the level of the retrieval chain of the warning information, insofar as the information does not is more simply delivered to the firefighting forces by a radiofrequency signal, but the control terminals are connected, by means of concentrators 7, one of which is shown schematically, to a remote web server 9, by means of an antenna 11.

The web server 9 is connected at the input to a telecommunication stage compatible with the wireless telephone networks, in particular of the GSM or GPRS type, which are known in themselves and can be easily implemented with the help of a mobile telecommunications operator.

Thus, the information coming from the sensors 3 is relayed by means of the control terminals or relays 5, the concentrators 7, the antennas 11 and a wireless telecommunications network, up to the web server 9. At this level, they are made available, via the internet and an appropriate client application, not only to firefighters, but to any interested party, whatever its location, provided that the administration of the web server has given him access rights to the server . In this way, the system according to the invention can be parameterized so that public parts (town halls, departments, regions, ...) but also private parties (private owners of land or forests) may exercise, via the acquisition chain described above and via the Internet, fire surveillance information issued by the system 1 according to the invention. Since the web server is connected to the internet, any authorized user will be able to consult the alert information transmitted by the hubs, using an appropriate client program installed on a personal computer or even on a mobile phone or any other communication terminal. mobile having access to the web server. In this way, access to the alert information is no longer restricted to firefighters as in the previous application, and the system can therefore be extended to a wider range of use, including fire surveillance private forests or other private areas. Of course, the development of application programs of the server and client stations to ensure the consideration and formatting of the information from the sensors, does not present a problem for a computer scientist and will not be described in more detail. Positioning of the sensors: As can be seen in FIG. 1, the sensors and the relays are uniformly distributed over the surface of the zone to be protected, which makes it impossible to correctly differentiate the treatment of the risk as a function of the possible the variability of fire risk in relation to the proximity of risk zones, or according to the topography and in particular the hilly terrain, or depending on the nature of the vegetation, or other factors that may be recognized. to be later influence on fire starts.

But it should be noted that the determination of the density of sensors was until now rather empirical, which can lead to too many sensors per unit area, leading to a high cost of the system, while having no -be not enough sensors in areas where the risk of fire is highest and where the mesh should be tighter. According to one aspect of the invention, the density of the number of sensors can now be determined more rationally using a mathematical model implemented by software, which is given a whole series of parameters, and which delivers at the output, for each zone considered, not only a density, but above all an optimal positioning of the sensors 3 according to said input parameters.

The input parameters are notably taken from parameters related to the terrain (undulating, vegetation), the degree of hygrometry and air temperature, the usual characteristics of the wind, the proximity of specific risk factors, such as this will be explained in more detail in connection with FIG.

In Figure 3, there is shown schematically an area to be equipped with a prevention system according to the invention, in the case where this area presents an increased risk of fire. We will now describe the operating principle of the algorithm and simulation software that determines the best installation positions of fire sensors, in a case where there is a non-homogeneous risk of fire starting.

In the example chosen, the additional risk factor is linked to the presence of a highway 13, since it is known that fire starts are greatly increased in this type of zone, due to the negligence or voluntary acts of certain users. , who for example do not hesitate to throw a cigarette butt still lit by the window of their car.

In the vicinity of Highway 13, there is shown an area 15 to be protected as a priority. It is typically an inhabited area, such as a village or city district.

The usual direction 17 and the strength of prevailing winds in this area are also shown. Finally, an area 19 200 meters wide, downwind of the highway, has been determined in which the probability of fire is highest given this context. The software also has access to a topographic database of the entire area, and a database of vegetation in this area.

On the basis of all these parameters attached to the risk zone, the software, based on a so-called "small-world" model, will determine the number and the optimized position of the sensors, in the zone 19 of high probability. starting fire or between that zone and the zone to be protected 15.

For this purpose, the software will take as a sorting criterion the possible positions of the sensors 3, the fact that the fire front must necessarily pass close to a sensor, regardless of the starting point of fire in the risk zone. . As a result, the software cuts the increased risk area 19 into square elementary cells 20, each of which, for example, is 50 meters apart.

Applying the hypothesis of a fire departure to each of the elementary cells 20, a simulated fire contour line 21 is thus obtained, located for example at t-15 minutes, where the instant t is the moment when the fire would arrive. on the area to be protected 15, which would allow the forces of struggle 15 minutes to intercept the front of fire, in this example. It is then sufficient to distribute the sensors 3 along the line 21, and it will be certain that a fire that will start in the increased risk zone 19, will necessarily be detected by the sensors, while reducing the number thereof.

We can see that this system is much more efficient than that which would have consisted of distributing sensors in a homogeneous and non-targeted way throughout the area represented, rather than on a line of passage through the fire front to reach the area to be protected.

A further important aspect of the invention will now be described in connection with FIGS. 4 and 5.

In the system known from the aforementioned prior application, it was possible to detect automatically, and almost in real time, the start of a forest fire, which already represented a significant advantage over the then known detection techniques. However, the system according to the previous application, even if it allowed a faster detection of a fire, could not predict the evolution of a fire as a function of time, with an accelerated speed over time physical. Consequently, the redisposition of the means of fight against the fire could be determined only from the real observation of the evolution of the fire, which did not allow the forces of fight against the fire, to anticipate revolution Fire with several hours in advance.

However, it is clear that such a possibility would be ideal, since it would allow, if the reliability of the fire evolution forecasts is sufficient, to position the control means at the optimized locations according to the evolution of the fire within hours. to come, and depending on the nature of the areas to be protected.

One aspect of the invention has therefore consisted of transposing and adapting a prediction algorithm, the propogation of a fire and the accelerated prediction of its evolution according to the parameters of the environment (topography, vegetation) and climatic parameters. .

For this purpose, the modified system according to the invention provides for coupling the output of the concentrators 7 relaying the information coming from the sensors 3, to means for predicting the evolution of the fire, capable of calculating in advance of the phase. evolution of the fire according to a variety of parameters, including naturally the location of a fire departure, but also a plurality of information concerning the protected area, this information being stored in advance in a database and regularly updated.

Among the information used by the calculation module executing the prediction algorithm, it will be noted, without limitation:

- the three-dimensional cartography of the areas to be monitored, since we know that the fire does not evolve at the same speed on a flat area, on an ascending slope that accelerates the progression of the fire, or on a downward slope that slows down the progression of fire; - vegetation type mapping, since it is known that different species of plants or trees do not have the same combustion characteristics at all;

- a mapping of the humidity rate of the air and / or the moisture content of the vegetation, since it is known that these parameters affect both the probability of a fire departure and its speed of evolution ;

a table of locations of the sensors, in order to be able to connect a fire departure or a front of fire to its position on the ground;

- a table of "customers" of the system, which will make the link between the sensors, and the private or public persons (firefighters, town halls, private individuals, companies) customers of the system and who will be able to have access to the information on the situation of the fire and its forecast of evolution;

- a map showing the characteristics of the wind: direction, direction, speed, since we know that a fire does not propagate in the same way in the presence or absence of wind.

Of course, some poorly scalable parameters will not need frequent updating (eg topographic data), but other highly scalable parameters such as air humidity will need to be updated frequently. , or almost continuously, in order to improve the reliability of the predictions delivered by the calculation module.

The calculation module is in the form of a server 9 which of course comprises a processor (not shown) having access to the memory 23 in which are stored databases containing the values of the parameters above, and software application based on a stochastic model called "small world" documented in the scientific literature.

The computation module provided with its algorithm constitutes a numerical modeling system able, from a departure or a front of fire, to predict its evolution taking into account, in particular, the topography of the ground, the vegetation, and wind, and to deduce its potential power in a given place. The engine of the modeling system is a stochastic model of propagation. This type of model is able to predict a characteristic's revolution according to the parameters of the medium, and the transmissibility parameters of the characteristic. This type of model, known per se, is used in particular in the field of human health, for predicting the spread of viral epidemics according to the virulence and characteristics of a virus.

This is an extension of the social network model called "small-world network" which, through, for example, only four input data, takes into account the basic phenomena that govern the spread of a fire, such as the radiation of flames, the thermal degradation of the plant and its combustion, or the emission of firebrands. It differs from deterministic models that can not describe the erratic revolution of a real fire, but also existing stochastic models that do not take into account long-range effects, beyond the nearest neighbors (trees, bushes, etc.). ) a site on fire.

The so-called "small world" social network model has been successfully applied to the spread of epidemics or internet viruses. It has been extended by the invention to forest fires. In this model, to connections to the trees that are closest neighbors are added long-distance connections, which are induced by the heat radiation and the effect of the firebrands, which are at the origin of the swings of fire.

In addition, the "small world" network model, by its very nature, supports the heterogeneous conditions associated with meteorology, vegetation and topography, making it a predictive tool for the "fractal" propagation of large fronts. of fire.

This modeling tool is very fast, with a simulation time of 100 to 1000 times shorter than the physical time. As a result, the system makes it possible to anticipate the evolution of a fire between 100 and more than 1000 times faster than the passage of time physical, depending on the number of data to be processed and the power of the processor running the forecasting software. In the case of a factor of 1000, this amounts for example to having the position at which will probably be a fire after 3 hours of fire (3 * 3600 = 11800 seconds), but after about only 11 seconds of calculation.

FIG. 4 shows the architecture of an exemplary embodiment of the system 1 according to the invention. In addition to the fire sensors 3, control terminals 5 and concentrators 7 already described above, the system comprises a web server 9, operating for example under Linux, and having access to the databases 25, 27, 29 stored locally or in a centralized remote memory location.

The databases contain, in particular, sensor installation tables giving the correspondence between fire sensor serial numbers and their GPS position. The databases also contain, for areas under the protection of the system, the tables 27 of the parameters that may affect the propagation of a possible fire in the area, namely topographic tables, vegetation data tables, the winds, the hygrometry rate etc. In addition, a table 29 of clients or users is stored, with their access rights, so that each authorized user of the system can have access to monitoring and monitoring data concerning the area for which he is responsible.

Of course, an application application software 31 is provided to be able to feed and update the databases.

At the remote level, the computer stations 33 clients can transmit to the central server 9 information, including map, the area they are responsible for monitoring. This transmission is done in a known manner, in particular via Internet servers 35. As a concrete example of the performance of the system, the prediction software used by the invention has made it possible to model the evolution of the fire. Lançon in France which, in 2005, ravaged nearly 700 hectares in 6 hours. The simulation by the prediction software lasted only 64 seconds.

FIG. 5 shows a screen shot of the computer used for the simulation of the Lançon fire from the starting points of fire and the topographic, climatic and other parameters entered in the software.

From two starting points of fire, the fire evolved at an intermediate time along a front of fire indicated by a line 37 (line delimiting a perimeter of smaller size), then several hours later, the real front of fire had arrived at a new front of fire indicated by line 39. On the same screen shot, on line 41, the simulated fire front, in 64 seconds, was represented by the prediction software used in the system and the process according to the invention.

As can be seen, the correspondence between the real fire front (line 39) and the simulated fire front (line 41) is striking. There is a gap in a certain rather steep area (lower part of the photo), but this is explained by the fact that the actual fire front in this area has been imprecisely identified in this area due to Difficulties of physical access to this area by firefighters who make the actual survey of the front of fire.

ADVANTAGES OF THE INVENTION

The method and system according to the invention serve the intended purposes. They represent an original concept combining a new forest fire propagation modeling system with a low-cost sensor network.

The modeling system makes it possible to optimize the in situ location of the sensor network and, in a crisis phase, to predict the evolution of a fire by using the information sent in real time by these sensors using a wireless communication infrastructure. The sensors will make it possible to evaluate the local fire risk, to detect early a fire and to follow the spatio-temporal evolution of a fire front in the risk zones equipped with the system according to the invention.

This system is an adaptable, modular tool, complementary to global systems but can replace them on critical areas, particularly along road or other infrastructures, or for the protection of specific equipment (power plants, recreational areas or activities).

In addition, the system allows the protection of a sensitive area through modeling that will test a fire at each point of the mesh of the area, to determine the most relevant distribution of fire sensors. According to the prevention time predefined by the operator (15, 30,

40 ... minutes notice), the sensors will be installed preferentially on a line matching the contours that have been determined scientifically by the modeling system.

Claims

1. System (1) for preventing fire, in particular forest fire, comprising on the one hand a network of a plurality of geolocated sensors arranged in a forest area to be protected and (3) constituting a mesh of the forest area to be monitored, each sensor (3) being able to locally detect a fire departure and being associated with a radiofrequency transmitter connected by radio to a control terminal (5), so that the detection of a fire departure near a sensor is automatically transmitted to its control terminal (5), which is capable of generating an alert signal, characterized in that it comprises a computer (9) equipped with a simulation software capable of predicting in advance with respect to the physical time, according to a plurality of parameters, the displacement of a fire front from the position of a fire start detected by at least one of the sensors of the sensor network. 2. System according to claim 1, characterized in that said parameters include one or more parameters among the following: parameters related to the terrain (hilly, vegetation), the degree of hygrometry and the air temperature, and characteristics of the wind, so as to simulate in seconds or minutes, the configuration that will have the front of fire after several hours of fire. 3. System according to claim 2, characterized in that the forecasting software is set to deliver a forecast in advance by a factor of 100 to 1000 with respect to the flow of physical time. 4. System according to claim 3, characterized in that said parameters further include at least one of the following parameters: the nature of the vegetation, the history of fires in the area, the proximity of risk factors. 5. System according to claim 4, characterized in that the sensor array (3) is implanted with a variable density according to the location of the sensors, said density being calculated according to a risk. local fire and parameters representative of the nature and configuration of the area to be monitored. 6. System according to claim 4 or claim 5, characterized in that the control terminals (5) have thresholds programmed for at least one of said parameters, so as to be able to create an alert when one of these thresholds is exceeded by at least one of the sensors controlled by a control terminal. 7. System according to any one of the preceding claims, characterized in that it comprises signal concentrators (7) associated with a plurality of control terminals (5), said signal concentrators being able to shape the information collected from the control terminals and transmitting them via an antenna (11) and a wireless telecommunications network to a remote server (9). 8. System according to claim 7, characterized in that the transmission between the signal concentrators (7) and the remote server (9) is done using a GSM or GPRS channel. 9. A method for detecting and predicting fire in a wooded area, characterized in that it comprises the following steps: - based on a prior analysis of the fire risk factors of said zone, determine a mesh of fire sensors (3) optimized for said zone, each fire sensor being provided with a radiofrequency transmitter capable of emitting identification and / or location information of each sensor; - provide the nodes of the mesh thus determined, with fire sensors; detecting at each fire sensor the state of absence or presence of fire, and in the event of the presence of a fire in the vicinity of a fire sensor, having said sensor transmit an alert signal comprising identification information and / or a signal locating said sensor, to a control terminal. 10. The method of claim 9, characterized in that it further comprises a step of providing the fire detection information from the fire sensors to a simulation software capable of simulating the evolution of a front of fire in advance compared to the actual evolution of the fire front as a function of physical time. 11. The method of claim 10, characterized in that said simulation software implements a stochastic propagation model. 12. The method of claim 11, characterized in that it comprises a step of displaying the simulated evolution of a fire front on a terminal connected to said web server. 13. Method according to any one of claims 11 to 12, characterized in that the parameters taken into account by the simulation software to simulate the anticipated progression of a fire front, are at least one of the parameters among the set following: fire starting positions, degree of undulating terrain, nature of vegetation, history of fire in the area, proximity of risk factors, air humidity, temperature of the fire air, the characteristics of the wind. 14. A method according to claim 9, characterized in that to determine an optimized fire sensor mesh, a simulation software is used, using a stochastic propagation model able to determine the optimal positions of the sensors between said at risk zone. fire and an area to protect. 15. Method according to any one of claims 9 to 14, characterized in that it further comprises steps of: - transmitting the warning signal from the control terminal (5) to a concentrator (7) fit communicating using a wireless communication, in particular of the GSM or GPRS type, with a remote server (9). - Allow customers of the fire detection process to view the fire detection information via a client station (33) and an internet type network attacking said remote server (9).