Fleets of Small Unmanned Aerial Systems for Forest Fire Applications

2015 Forest Research Open Access  
Editorial Unmanned Aerial Systems (UAS) technologies experimented one of the strongest growths in the last decade. Advances in mechanics, sensing, communications and control systems together with a significant cost reduction are originating an explosion in the use of UAS in a growing number and variety of applications in a wide range of sectors including law enforcement, civil security and industry. Nowadays, the level of maturity of UAS technologies enables their use and effective exploitation
more » ... in a number of unprecedented applications, which were constrained to piloted aircrafts only some few years ago. All prospective reports, white books and strategic research agendas developed by the most relevant scientific and technology institutions agree in concluding that UAS is one of the technologies that will have deeper impact on society and economy in the near future. Airborne means have traditionally played a very important role in forest-fire fighting activities. In addition to transportation of brigades and fire extinguishing, they have also been widely used in forest surveillance and forest-fire monitoring, among others. Piloted aircrafts are also used by forest-fire services for measurement of the burnt area and evaluation of fire effects. UAVs have interesting potential advantages over piloted vehicles. First of all, UAS can effectively reduce the human risk level. Aerial vehicles are involved in many accidents during forest-fire extinguishing and other fire fighting activities, originating a high number of casualties every year. The use of unpiloted -remote controlled or autonomous-vehicles can help to reduce the risk also to the rest of personnel involved in fire fighting activities. Cost is another clear advantage. Forest-fire fighting activities employ extensive resources and a high number of aerial means. Many of them are directly involved in fire extinguishing and are very difficult to be substituted by UAS. However, others are used for data gathering in activities such as mapping, forest surveillance, fire detection and confirmation, fire monitoring and fire evaluation, among others, and, in these activities, the use of UAVs can involve important advantages. The high cost of piloted aerial vehicles frequently leads to schemes where each aircraft is equipped with all necessary sensors and devices for the missions it has been designed. This, in most cases, involves installing expensive equipment and requires well-trained personnel for their operation. Besides, these piloted aircrafts require significant infrastructure including long runways for taking-off and landing. This centralized scheme has been adopted by the first prototypes of UAS for forest-fire applications. One good example is the ALTUS UAV, an evolution of the Predator UAV, which was first demonstrated in fire experiments at the beginning of the last decade. However, the use of UAS instead of piloted aerial vehicles also provides higher flexibility. In the last years, in contrast to the centralized approach, the distributed paradigm is attracting more and more attention from the research community. Instead of one single high-performance UAS, this scheme comprises a fleet of simple, small, low-cost UAS that cooperate in order to perform the mission. Each of these small UAS could be equipped with different but complementary sensors. They can take off manually by throwing the UAS or using small catapults and require little infrastructure and lower training for their operators. The use of small UAS instead of high-performance UAS is also convenient in terms of costs and also to reduce the potential damage in case of accident. In contrast to the lower capabilities of each individual small UAS, the strengths of the distributed scheme come from the cooperation between usually different unmanned aerial systems. For instance, in forest-fire detection, one small UAS is equipped with a simple sensor to perform the first detection of potential alarms, which are transmitted to a Decision & Control Station. These alarms are used to dynamically command other small UAS equipped with specific fire sensors, which are sent to the location of the potential alarms for confirmation. The data of the alarm collected by all the small UAS is combined using fusion techniques in order to reliably confirm or discard the alarm and accurately locate it on a map. In forest-fire monitoring UAS equipped with visual and infrared cameras execute automatic image processing and geo-referencing techniques in order to compute in real-time the fire-front location, geometry and speed. Each UAS of the fleet is assigned to the detailed monitoring of the fire at a certain area. The perception of all the UAS is fused enabling forest-fire monitoring with higher spatial and temporal resolutions, which can significantly improve safety and efficiency of fire fighting. Besides, this decentralized approach has relevant advantages in terms of flexibility and robustness, which are very interesting in forest-fire fighting scenarios, potentially dangerous and prone to disturbances and unpredictable changes. This decentralized approach also has advantages in terms of modularity and scalability. These small UAS can organize into networks composed of as many nodes as necessary, enabling system extensibility, necessary for instance for the monitoring of large forest fires. Below is a brief description of the main forest-fire fighting activities that are or can be performed by fleets of small UAS. These activities refer not only to the direct tasks related to extinguishing. They include others that can be classified into pre-fire, during-fire and post-fire activities. Forest surveillance is a very important task in forest-fire fighting. People with profound knowledge of the terrain in watch towers are traditional and most extended way of forest surveillance. In the last twenty years a wide variety of systems for automatic forest-fire detection have been developed. They are installed in high visibility ground observation sites and use automatic processing techniques of images from infrared cameras to detect the radiation of the fire or from visual cameras to detect the smoke plume. Their main drawbacks are their limited coverage and the lack of reliability of the automatic detection, typically originating high false alarm rates. Other fire detection systems use images gathered by satellites. Satellite-based forest-fire detection has been successful in unpopulated, large and de Dios, Forest Res 2015, 4:1
doi:10.4172/2168-9776.1000e115 fatcat:scix2l7tr5awzk5rqdttnmi55i