Algorithm 1: Collision state estimation.

Notation: Circle radius $\mathcal{R}$, Object ${\mathit{o}}_{\mathit{i}}$, Object set $\mathit{O}$, Object dimension $s_o$, UAV dimension $s_u$, Object depth $\overline{\mathit{\lambda }}$, Environment depth $\overline{d},$ Boolean object collision state $collsion\_state.$

Input:$O$

for$o_i$ in $O$

if$\mathcal{R}<\overline{\mathit{\lambda }}$then

if$\mathcal{R}>s_o+s_u$&& $\mathcal{R}<\overline{d}-s_o$then

$collsion\_state⟵safe$

else

$collsion\_state⟵collision$

end if

else

$collsion\_state⟵collision$

end if

${\mathit{o}}_i⟵O$.next()

end for

return$\mathit{O}$