Algorithm 2 Grouping near altitudes algorithm.
1:  procedure FindNearAltitudes(WDb,alt,thres)	▹ Find altitudes in WDb close to alt.
2:    Counter = 0;
3:    for $i=1\leftarrow$WDb.Size do
4:       if alt-thres≤WDb(i).Altitude≤alt+thres then
5:          NearAlts(Counter++) = WDb(i);	▹ Store whole WDb.
6:       end if
7:    end for
8:    return NearAlts;
9:  end procedure