Yo yo,
 
I have many questions so let me tell you what I am trying to accomplish.  We are using MatchMover to try and recreate a vehicle accident at an intersection.  If this goes well, well try it on some other cases in the future.  This is our big test run.  
 
We went out and filmed on location.  Three cameras, all different; one on a moving vehicle and two fixed tripod shots on opposite corners of the intersection.  We also took many still shots throughout the afternoon.  We placed stakes with tennis balls on top for markers and we measured most everything.  
 
 Ok, I can solve the camera for the vehicle camera easily enough.  Plenty of parallax.  Now I want to solve for the fixed cameras on either corner. (fixed meaning it does not move)  I really don't know where to start.  I at first had them as additional sequences in my project but then ended up deleting them because it was easier to solve for my vehicle cam without them.  But I want them in there because I thought there was a way to have all three cameras in the project and then when I exported it to Lightwave, in this case, I would have all three cameras in my scene and could build from there.  But if I keep working like I am I will just have a different scene for each of my cameras, and I don't want to do that if I don't have to.  
 
This brings me to my second issue.  How can I solve for a fixed camera?  I have helper images and other cameras but all my efforts have proved that I don't quite understand how to use other sequences and images correctly in my project.  
 
Thirdly, I want to know if I was going about this wrong: I solved my vehicle camera and then I imported another sequence from one of the fixed cameras.  I proceeded to place tracks in the new squence, but Matchmover did not like that and I got plenty of red X's.  Then what was already solved went to crap.  
 
Forthly, I am not too wise on focal length and all that lies within, which may be causing a lot of my problems.  I read the MM manual, but don't quite have the hang of it.  If you could tell me a bit on how to figure that out and apply it to my project.
 
I think that's it, and I appriciate all of your help.  This is what happens when your boss tells you to learn a program you've never heard of before.  
 
Later,
 
Audioman

Hello,
 

 
If you have MatchMover 3.1, the fixed camera constraint is available, and this will definitely help your project:
 
The best thing to do here is the following:
 
- First solve for your moving sequence if it solves fine.
 
- Load one additional helper sequence, and specify "Fixed" for its motion, or at least "Nodal Pan" if you do not have version 3.1
 
- If you're using 3.1, you then simply have to click the tracks on one frame (as the camera is fixed). Else you have track the features on the additional sequence (which should still be easy). Make sure the tracks which represent the same features are shared between additional sequences and the first sequence
 
- Simply try to do an "Extend Camera Fixed", which means you want to solve only the frames / features that are not yet initialized. Depending on your footage, you may need before doing that to lock the keyframes (by clicking the locker on the right end side of the track view), and manually set the keyframes on the helper sequence
 
- Then you can repeat this with any number of additional sequences
You'll end up with 3 cameras in the same 3D world.  
 

 
If you do not know anything about your focal length, you can simply let the initial value as it is (should be 50 mm). It will be refined by the solver. The more accurate initial value you provide, the easier the solve will be. Smaller focal length provide wider angle of view, bigger of course lead to smaller angle of view. You can see in the 3D view of MatchMover in real time the effect of focal length: just load your footage, switch to 3D mode, and edit the focal length in the camera parameters. You still can specify if you zoomed in (then the focal length is variable) or if it stayed fixed.
 
If you want a deeper help, do not hesitate to make your project available to us and we'll make a better investigation
 
Thanks