Terrestrial detection systems

2.1Terrestrial detection systems

2.1.1Fixed ground surveillance - Lookout towers

Usually the cabins on the lookout towers have the following equipment: a) Azimuth circle / angle table or an alidade – it allows to precisely determine the smoke/fire direction; b) Area map; c) Binoculars; d) radio station / cellular phones; e) clock.

According to the Conservation FAO Book related to wildfire Protection of Forests (FAO, 2001), the visibility limit in kilometres by the lookouts can reach up to 20/25 km, but can drop to 10 km with bad visibility conditions like fog, haze, little contrast, among others.

Figure 1 – Lookout tower in Mafra – Portugal Figure 2 – Instruments inside a lookout tower

a) Advantages of the fixed ground surveillance

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  Large field of vision due to location and height of post;
  
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  Almost permanent observation (depends on surveillance shifts);
  
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  An experienced observer detects easily any change of the landscape without moving from his working place.
  

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  Sighting required by at least two posts for exact location of fire;
  
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  Existence of shadow areas (areas not visible);
  
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  High initial installation cost;
  
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  Visibility difficulties with dust clouds and other factors referred above;
  
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  Ineffective when smoke from large fires in the area, “smoke” in their viewing area;
  
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  It is very difficult to contract personnel, especially with experience, when the observers are seasonal workers.
  

2.1.2Mobile ground surveillance – mobile brigades

The mobile brigades can use 4x4 vehicles, motorcycles, bicycles, horses, boats or travel by foot. These brigades are very useful as a complement of lookout towers surveillance. Besides their role of fire detection, they inform the public, can control the fire hazard human activities in the forest, and finally they can sometimes dissuade people or suppress initial fires.

Usually the patrols have a radio to inform the detection coordination centre, a map of the area and binoculars. Some of the mobile brigades have a fire first attack kit in there vehicle (water container, motor pump, etc).

Figure 3 – Surveillance vehicle with a extinguish set from Poland

a) Advantages of the mobile ground surveillance

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  Complement the lookout towers moving through the shadow areas;
  
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  Enables first attempt at putting out fire;
  
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  Provides accurate information on fire;
  
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  Especially effective after lightning storms;
  
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  Very effective in verifying alerts from fixed posts when existence of fire has not been confirmed;
  
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  This system can have an important role of infraction dissuasion (psychological effect).
  

b) Disadvantages

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  Surveillance not continuous;
  
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  Reduced field of vision;
  
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  High cost if the surveillance is performed 24h/day.
  

2.2Aerial detection

The aerial surveillance can be divided in two types according to their specific goals. The first one has the objective to detect fires at their initial stage and communicate to the control centres. The second one is the armed aerial detection. In this last case, besides the detection and communication of the occurrence, the airplanes have a water reserve and can perform a first attack to the detected fire. Usually the aerial detection uses small airplanes like Cessnas or Pipers models among others. Helicopters, due to their high flight and maintenance costs are not very common in aerial detection. However, this is a mean that some countries, such as Spain, use to detect wildfires. At the same time, this is a very effective transport mean to perform a first assault, transporting highly trained fire brigades minutes after fire alert.

Figure 4 – Cessna airplane for aerial surveillance in Coimbra - Portugal

a) Advantages of the aerial detection system:

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  Large instantaneous field of vision with no shadow areas;
  
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  Its ability to concentrate surveillance over areas of particular high risk such as recreation areas on weekends or on paths followed by recent lightning storms;
  
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  The reduction of detection costs when detection is not required: air patrols can be eliminated or greatly reduced on days of low fire danger;
  
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  Great flexibility;
  
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  Provides accurate and exact information on location of fire;
  
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  May act as surveillance aircraft and first assault;
  
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  Effective discriminating false alarms.
  

b) Disadvantages:

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  Cannot operate in adverse weather conditions and at night;
  
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  The costs associated with this kind of detection can be elevated;
  
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  Observation interrupted by long time lapse between two flights in the same area.
  

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