Input: The positions of the anchors, the distances .
Output: The positions of a set of determined sensors.
Step 1: Phase 1:
    Set the anchors to be the initial set of sensors.
    Apply the extended geometric buildup algorithm.
Step 2: If the percentage of the undetermined sensors is greater than TH.
    Phase 2:
     Find and determine an initial set of sensors.
     Apply the extended geometric buildup algorithm.
Step 3: Align the sensors determined in the two phases.
Algorithm 4: The two-phase geometric buildup algorithm.