Velocity-Preserving Trajectory Compression Based on Retrace Point Detection

Algorithm 1

Retrace point detection process.

 Input: trajectory , ratio threshold , inscribed angle threshold .

 Output: retrace points RP.

1. i=1, j=3, RP = Φ.

2. while j<n do

3. Calculate Maximum direction deviation ;

The selected pair of the anchor point and float point (with the maximum direction deviation);

4. if then

5.  Calculate inscribed angle θ and ratio threshold ;

6.  if θ>= and >= then

7.    RP∪;

8.    r=dis;

9.    while e+1<=n

10.     k=e+1;

11.     if dis(,)<=r then

12.      RP∪;

13.      e=e+1;

14.     else:

15.      break;

16.     end if

17.    end while

18.   else:

19.    i=e;

20.    j=i+2;

21.   end if

22.  end if

23. else

24.   j=j+1;

25. end if

26.end while

Return retrace points set RP.