Find the equivalent intersection point of multi lines in 3D space. HI everyone, I'm not a native english speaker, so I wonder you could understand my question very well. This question originates from my physics experiments. When I catch several lights from my equipment, the light source is far away, so I should caculate the position of the equivalent "light source". This comes the post title. Normally, all these light lines were skew each other. For two lines, this is very simple to get the answer, because we can easily define the equivalent point as the mid-point of the shortest distance of the two lines. Several algorthms can be found by Google. For more then two lines, How can I do? I have dig into some math stuff about linear algebra or algebra geometry. Each lines can be constrined by two equations of plans.like Ax+By+Cz=D. so, as n lines, we can get 2*n equations. Now, I wonder the best root of these equations. Normally, the least square method could be used, but I don't think this could applied to my case. The criterion is different, maybe, I want to find the point that the sum of distance to those lines are minimun. But this make the prolems get more complex to solve. Does anybody coulde give me some ideas to solve this? All what I want to is to get the equivalent point. I'd appreciate your reply! THANKS!