FOREST-FIRE PERCEPTION TOOLS

Transcription

1 FOREST-FIRE PERCEPTION TOOLS A. Ollero, B.C. Arrue, J.R. Martinez-de Dios Departamento de Ingeniería de Sistemas y Automática. Escuela Superior de Ingenieros. Universidad de Sevilla. Camino de los Descubrimientos, Sevilla (Spain). Fax: {aollero,barrue,jdedios}@cartuja.us.es. Abstract: This paper presents image-based perception tools for fire behaviour analysis. The tools can compute in real-time fire parameters and time evolution graphics of the fire automatically from the signals of the cameras, terrain information and other relevant data. The paper includes some field experiments carried out in Gestosa (Portugal) in the INFLAME project funded by the European Commission. INTRODUCTION Computers and communications, including portable systems, are modifying forest-fire fighting strategies and tactics providing updated information about the evolution of the fire and the existing resources. The use of GPS systems makes possible to know the current position of the resources. Telematic systems integrating headquarters computers, portable computers, sensors and communications are able to provide real-time field information and to transmit forest fire fighting commands [5]. Field information about predicted weather and wind also improve the perception of the forest-fire evolution. However, the information about fire spread, front length and fire line intensity is more difficult to obtain in real-time. This information is also important for fire behavior modeling. In fact, perceptions tools are also required to monitor fire behavior experiments and to provide accurate data to validate the models. It should be noted that traditional techniques to obtain data from fire behavior experiments demand extensive human resources before, during and after the experiments. This paper presents computer tools to monitor fire-behavior experiments including both laboratory and field experiments. These tools are also valuable for forest fire fighting. In the next section the requirements of these tools are considered. Then, some characteristic of the tools are summarised. Finally, the paper presents some preliminary results. 415

2 REQUIREMENTS OF FOREST-FIRE PERCEPTION SYSTEMS Forest-fire perception systems should provide the nearest idea of what is happening in a forest-fire that is being monitored[1][2]. These systems should include tools to locate the fire-front in a topography map. Besides, they should provide estimations of geometrical parameters of the fire such as length of the fire front and flames height, evolution of the firefront in time, and rate of spread. Forest-fire perception systems should be flexible in order to fit a wide number of situations. Image-based monitoring can be used for both laboratory experiments and in the field. It is important to determine the optimal position of the cameras taking into account the expected propagation of the fire. Furthermore, the calibration problems are very important and could require the placement of beacons of known dimensions in given locations if there is not enough information in the field of view of the cameras. Of course, the calibration problems and the uncertainty are greater in the field. Then, more equipment should be used to decrease this uncertainty and compensate unexpected events. Furthermore, computer-based perception systems should complement the actions carried out by operators helping their task in a wide range of situations. For instance, one of the major difficulties for the operator-based monitoring of a forest-fire takes place when the smoke hides the fire-front. In this situation, it is impossible to know where is the fire-line with accuracy. This difficulty can be solved using a monitoring system equipped with an infrared camera since smoke is transparent to frequencies in the near and middle infrared. Moreover, they can provide radiation and temperature measurements to estimate the severity of the fire. Since the higher temperatures of fire are around 1100º C, the adequate range of wavelength of infrared cameras for fire applications is the middle infrared (from 3µm. to5µm) according to the Wien law, λ=2898/t, where λ is expressed in µm., and T is temperature in Kelvin degrees. An infrared attenuator filter should be used in order to avoid the fire saturating the infrared images. The visual and infrared cameras could also be located in mobile terrestrial vehicles, helicopters and aeroplanes. In such cases it is necessary to apply image geo-referencing techniques. The GPS in the vehicles provide a very valuable information to perform this task. The application of other sensors has high relevance for fire monitoring. For instance, some meteorological information such as the wind direction can determine the position where 416

3 the cameras should be located in order to avoid that the smoke wind occults the fire-flames. Other data based on information such as wind intensity and direction, wind models and propagation models can be used to assign priorities in the monitoring in order to pay more attention to the most dangerous areas. PERCEPTION TOOLS In order to satisfy the requirements summarised in the previous section, several computer tools have been developed. These tools have interfaces for sensors, such as the visual and infrared cameras, and for input data such us terrain maps and particular experiment data. All this information is integrated in the system and processed to obtain dynamically the fire behaviour parameters and evolution graphics. Particularly, advanced image processing techniques with adaptive new thresholding [3] methods have been applied. Different experiments can be monitored (line and punctual ignition burns) and appropriated representations are used: rate of spread, evolution of the most advanced point in the time, flame height in the time, evolution of the lines of the fire front, middle radio in punctual ignition, width of the flame and others. Furthermore, the above tools integrate 3D visualisation functions in real time to improve the perception of the users of the evolution of the fire. On the other hand a tool to compute the optimal location of the cameras taking into account the terrain information and camera parameters has also been developed. EXPERIMENT RESULTS In this section some preliminary results obtained by the tools mentioned in the previous section are presented. Figures 1 to 3 show results obtained in field experiments carried out in Gestosa (Portugal) in May, 1998 [4]. Six plots were burnt in these experiments. The Figures show results of three of them. These burns were performed in the INFLAME project for fire behavior modelling. All these results were obtained automatically from the recorded tapes of the experiment. Fig. 1 presents the evolution of the fire front, and Fig. 2 the rate of spread. Fig. 3 shows the effect of the retardant on the rate of spread between 250 and 430 seconds. 417

4 Fig. 1. Temporal evolution of the fire-front in plot G8 of Gestosa 98. Fig. 2. Rate of spread of the fire versus time in plot G10 of Gestosa 98. Fig. 3. Effect of retardant on the fire rate of spread in plot G9 of Gestosa

5 CONCLUSIONS Computer, sensors and communications can be integrated in new tools very useful for the analysis of forest fire behaviour. This paper introduces new tools which can be applied to monitor in real-time fire experiments obtaining fire parameters and evolution graphics (rate of spread, evolution of the most advanced point in the time, flame height in the time, evolution of the lines of the fire front, middle radio in punctual ignition, width of the flame and others) automatically from the signals provided by the visual and infrared cameras. The tool could be also useful for forest fire fighting integrated in new telematic systems with appropriated communication, sensors and computers. ACKNOWLEDGEMENTS The work described in this paper has been partially funded by the INFLAME project Fire Behaviour Prediction Modelling and Testing (ENV4-CT ), partially funded by the European Commission (DG XII) in the Environment and Climate Program. REFERENCES [1] A.A. Brown, K.P. Davis, Forest fire: Control and Use. 2 nd edition. McGraw Hill. [2] C. Chandler, 1991 Forest-fire Management and Organization. (Fire in Forestry; Vol 2). Krieger Publishing Company, 1991 [3] J.R. Martinez-de Dios, A. Ollero, B. C. Arrue, 1999, Fuzzy logic and wavelets for visual monitoring of non-rigid objects. Application to fire monitoring. To be published in Signal Processing, [4] D.X. Viegas, GESTOSA 98. Shrunland Experimental Fire. Inflame Project General Report, [5] Wybo, J. L., G. Eftiquidis, D. Kotsouris, T. Manganas, D.X. Viegas, T. Apostolopoulos, E. Pelosio, G. Bovio, A. Ollero, D. Schmidt and A. Criado, DEDICS: A general framework for supporting management of forest fires. Proceedings of the III International Conference on Forest Fire Research. Vol. II, pp , Coimbra