In this paper, we focus mainly on formation control of a swarm of UAV's tracking a moving target on a non regular mountainous surface. The main objective is to show how to dispatch the whole swarm of the quadrotors around the target (climber) with respect to the natural environment (mountain) taking advantage as much as possible from the free space surrounding the climber. The formation shape adapts with the neighbour environment topology, so that it avoids the collision with the environment and the concealing of the target from the UAV's cameras sights, and ensures as well the formation compactness and its closure to the target respecting the agent-agent and the agent-target security distances. The algorithm to define the free and safe hovering space (SHS) is then demonstrated with other two-steps algorithm to determine for each agent its desired position within the SHS. This work, that is considered as an introduction for upcoming works, does not miss to provide a simple control for each individual agent based on an established and corrected approximate dynamic model. The main idea to resolve this problem is explained in 2D and will be expanded for 3D environment, with other necessary and complementary enhancements. Keywords: UAVs control, formation control, target tracking, surveillance, film-making, 3D reconstruction, monitoring, quadrotor modeling.