# UAV Deployment Using Two Levels of Stigmergy for Unstructured Environments
## 3 Methods
### Sematectonic Pheromone Deployment (SEPHE)  
#### 3.3.1 Behavior Description  
As observed in the previous section, the slant beacon deployment behavior requires not special capacity for implementation. Any current UAV can fulfill all the hardware requirements, including communication. Therefore, it is appropriate behavior for implementation in large swarms, where individuals are simple. This type of behavior is therefore especially suitable for a swarm  
Figure 8: State diagram for the Sematectonic Pheromone Deployment (SEPHE) behavior of individuals of type _active_. In each processing step, any individual in this role will execute the steps listed in the diagram.  
Figure 7: Behavioral trace for different simulation steps. Each simulation step is equivalent to 1/2 s. An enlarged area of the simulation is shown when the target case (95% coverage of the map area) is reached. The figure shows the robots (in red), their communication area \(RF_{max}\) (yellow), the angles recommended by the _beacon_ robots (black concentric lines around the robot) and their visual or coverage area (blue).  
of microdrones, such as those presented above. If we have individuals with more sensory and processing capabilities, we can take greater advantage of the benefits of the use of stigmergy for swarm communication and the emergence of useful behaviors.  
In this section, we will present a behavior called sematectonic pheromone deployment (SEPHE) that has the same purpose as that of SLABE, that is, to cover an unstructured and a priori complex environment. For this behavior, the drones will be required to be able to perform local localization among themselves. In [3], the authors present a sensor that can be used to effectively perform local localization among agents. Like SLABE, there will be two differentiated states. _Active_ agents will take off and navigate via an obstacle-avoidance algorithm until the signal from the farthest _beacon_ vehicle is within the safety limit. Then, the _active_ vehicle will transition to the _beacon_ state, as in the previous case.  
The fundamental difference with SLABE behavior is that while an _active_ drone navigates, it will emit pheromones that will be collected by the _beacon_ vehicles through which it travels. The _beacon_ drones will therefore serve as the local location mechanism of the swarm as well as stores of local pheromone maps. These local maps will be communicated to any drone within range.  
The repeater drones will therefore be responsible for the communication, both direct and indirect, of the swarm. They must also maintain their virtual pheromone map, communicate it to their nearby robots, and adjust it, if necessary. The repeater drones should also apply the intensity decrement to the map, so that, among other tasks, areas that have not been explored for a long time can be re-verified.  
This behavior is therefore a variation of the use of quantitative sematectonic stigmergy, which requires more communication than that required by the SLABE behavior but which is more similar to the standard implementations of community-based pheromone robotic systems, in addition to providing much more information to the active robots for making decisions in flight. The following describes the behavior in detail.