Input: The set of undetermined sensors ( 𝐼 2 ) in Phase 1.
Output: An initial set of sensors ( 𝐼 1 ) with distances between each other
known.
Step 1: Choose the first element in 𝐼 2 to be the first element in 𝐼 1 .
Step 2: Repeat:
   For each element in 𝐼 2 :
    If it has given distances to all the elements in 𝐼 1 ,
     add it into 𝐼 1 .
    End
   End
Algorithm 3: Choose an initial set in Phase 2.