Algorithm 1. RLS operation.

1: if sensor senses an event then

2: broadcast (localizationMSG) // including node-ID, TS, depth

3: end if

4: for each beacon receive (localizationMSG) do

5: localizationMSG.insert (TR, B(x, y))

6: send LocalizationMSG toward sink

7: end for

8: for sink receive (localizationMSG) do

9: dist = (TR - TS) * v

10: r = sqrt (distˆ2 - depthˆ2)

11: localizationMSG.insert(r)

12: Sink.table.addrecord (LocalizationMSG)

13: m = m + 1

14: If m ≥ 3 then

15: Select 3 records which (r < others)

16: PS = Trilaterate((x1,y1,r1), (x2,y2,r2), (x3,y3,r3))

17: end if

18: end for