## 1 Introduction  
The Mediterranean area is a region experiencing strong ecological variations due to global climate change: wildland and forest fires represent there an important cause of natural hazards and disasters for assets and human lives every year. Early detection and accurate tracking of the fire front propagation are key points in fire fighting strategies to minimize the damage and possible casualties. According to fire managers, the delay in detecting a fire ignition in the open is considered as one of the main factors increasing the response time of the first fire fighting actions. The resulting size of the fire to be managed as the final burning area strongly depends on this response time of the first fire fighting action (FFFA). According to the Promethee database--the inventory of fires in the Mediterranean region in the South of France since 1973--only the alerts given by operational services (firemen, forest patrolols) lead to aFFFA response time lower than 15 minutes due to the quality of information on the accurate location of the fire: this database reports that 66% of all fire detections are performed by civilians. Furthermore, reference [1] mentions that the increase in the number of fire lookout towers and patrolols of forest managers significantly decreases the final size of burned areas. In both cases, the decrease of the burned vegetation area can be attrbuted to shortFFFA response times. Moreover, in standard models for fire fight and forest manager, the fire power. i.e., the amount of heat release by time and length units of fire front is linearly dependant on the fire rate of spread (ROS). This means that the accurate tracking of the fire front spread leads to information of first rate importance in terms of fire fighting.  
The present study aims to illustrate that a device for detecting the presence of a fire and for tracking its space and time evolution can be designed from a Wireless Sensor Network. Indeed, a Wireless Sensor Network (WSN) meets the technical needs to provide accurate environmental data and robustness for use in a fire environment. Advances in Micro-Electro-Mechanical-System (MEMS) based sensor devices and miniaturization of processors and radios as sensor packages have led to the emergence of sensor networks. A sensor node must support the following abilities: computing, communicating and sensing. The sensor sends collected data, usually via a radio transmitter, to a command center (sink or base station) either directly or through a data concentration center (gateway). In a sensor network, different functionalities can be associated with the sensor nodes. The sensor nodes are usually scattered in a sensor field. Each of these scattered sensor nodes is able to collect data and route this data back to the sink/base station using a multihop infrastructureless architecture. The sink may also communicate with the task manager node via Internet or satellite. The design of the sensor network is influenced by many factors, including fault tolerance, scalability, production costs, operating environment, sensor network topology, hardware constraints, transmission media, and power consumption.  
Our contribution in this framework was to design a new tool for monitoring wildland and forest fires using a WSN. We show in this paper that a Wireless Sensor Network can perform the following sequence of tasks:  
1. sensing thermal data in the open: the system must be able to sense accurate critical environmental data (the air hygrometry for instance) for zoning a risk of fire ignition;2. detecting a fire ignition: the sensing of thermal data must be sufficiently adapted and accurate to the detection of a fire environment as a temperature elevation due to the presence of a gaseous flame;
3. tracking the fire spread during its spatial and temporal evolution.  
In the following, we present a short description of the state-of-art of existing WSN systems in fire monitoring in order to underline the originality of the present contribution.