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From: NZTideMan <mulgor@gmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: How to synchronize two 3D Trajectories
Date: Sat, 13 Dec 2008 14:32:27 -0800 (PST)
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On Dec 14, 7:34=A0am, "smar " <smar...@yahoo.com> wrote:
> Hello
> Thanks for a very useful replay
>
> Yes there is a 4th dimension (time) too.
> But I guess, it can not be taken to compare A and B. Because there is a s=
mall time shift in both trajectories. Also:
> DeltaT of a certain pair of =A02 connective points in A could be differen=
t to -------- DeltaT of their corresponding points.
>
> I have implemented point matching (based on minimum 3D distance suggested=
 by NZTideMan ). It worked fine as all indices of all matching points are i=
n ascending order.
>
> But there could still be one thing:
> As there are small deviation between corresponding points. Minimum distan=
ce point matching may results some time in wrong matches (matching neighbou=
rhood points)
>
> How I can make this robust?
> Or there should be some alternative method?
>
> I would be very thankful for any further assistance.
> Regards
> Smar

Providing the times of each trajectory are accurate and have the same
start time, it doesn't matter that the time intervals are different:
you just use time as a parameter like this:
ti=3D[0:dt:tfin]';
xai=3Dinterp1(xa,ta,ti);
yai=3Dinterp1(ya,ta,ti);
zai=3Dinterp1(za,ta,ti);
xbi=3Dinterp1(xb,tb,ti);
ybi=3Dinterp1(yb,tb,ti);
zbi=3Dinterp1(zb,tb,ti);

devx=3Dxai-xbi;
devy=3Dyai-ybi;
devz=3Dzai-zbi;