At the moment I try to understand Bundle Adjustment on a level to be able to implement it on my own. The major point I'm still confused at is the management of the landmarks. So, let's think of a few frames, that all share some landmarks with each other (like in the image below).
I can triangulate the same corresponding feature in image 1 to image 2, from image 2 to image 3 and so forth. However, I get (slightly) different results for the same point in the world. I first tried it with fusing all the landmark estimates from the different triangulations (see an older post). But, I'm not sure if that is really the way to go.
If my question is still a bit to unclear, please let me know and I will improve it. I'm looking forward to interesting answers.