Algorithm 2 Changing satellite for VDOP improvement (n = 6)

1: void function changing satellite(azimuth_satellites, elevation_satellites)

2:  nz = 3;

3:  nu = 3;

4:  sat_me = find satellite of minimum elevation(elevation_satellites);

5:  sat_zenith = select satellite of high elevation(nz, azimuth_satellites);

6:  vec_s = generate vector of satellites(azimuth_satellites, elevation_satellites);

7:  vec_rp = generate vector of regular polygon(nu, sat_me);

8:  sat_uniform = select satellite of nearest regular polygon vector(vec_s, vec_rp);

9:  sat_selec = merge zenith and uniform satellites(sat_zenith, sat_uniform);

10:   case_selec = check case of selected satellite(sat_selec);

11:   if case_selec == 4

12:    sat_case8 = change satellite from case 4 to case 8;

13:    sat_case3 = change satellite from case 4 to case 3;

14:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case8, sat_case3);

15:   end

16:   if case_selec == 8

17:    sat_case7 = change satellite from case 8 to case 7;

18:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case7);

19:   end

20:   if case_selec == 3

21:    sat_case7 = change satellite from case 3 to case 7;

22:    sat_case2 = change satellite from case 3 to case 2;

23:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case7, sat_case2);

24:   end

25:   if case_selec == 5

26:    sat_case6 = change satellite from case 5 to case 6;

27:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case6);

28:   end

29:   if case_selec == 7

30:    sat_case6 = change satellite from case 7 to case 6;

31:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case6);

32:   end

33:   if case_selec == 2

34:    sat_case6 = change satellite from case 2 to case 6;

35:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case6);

36:   end

37:   if case_selec == 6

38:    sat_case1 = change satellite from case 6 to case 1;

39:    [case_selec, sat_selec] = compare case(case_selec, sat_selec, sat_case1);

40:   end

41:   return sat_selec, case_selec

42:  end function changing satellite

43:

44:  void function compare case(case_selec, sat_selec, sat_caseA, sat_caseB, …)

45:   flag_case = compare minimum VDOP(sat_selec, sat_caseA, sat_caseB, …);

46:   switch flag_case

47:    case case_selec

48:     return sat_selec, case_selec

49:    case A

50:     sat_selec = sat_caseA;

51:     case_selec = A;

52:     return sat_selec, case_selec

53:    case B

54:     …

55:   end

56:  end function case selection