Re: what external 3d tracker is best ?

They're all pretty capable these days. I have only had experience with Boujou and Syntheyes, both of which work great (with Shake and the 3d software of your choice). I personally prefer Syntheyes, but that is just me. I suggest you download demos for all three and have a play to see which works best for you. I haven't used the demos/trial versions of them, but I would assume they will all allow you to track your own footage, solve then place a preset 3d stand in object into the scene so you can see how solid the track is (they won't let you export this camera data of course). I suggest you get some footage of a typical scene you are likely going to want to track, then you can use this footage to gauge the success of the potential matchmove software you are considering. You will probably find they all do the job fine, so then it will just come down to which interface you like and what your budget is.

Goodluck,

andrew