Trajectory Triangulation

[MathematicalPhysicist]

im reading about the subject Trajectory Triangulation from here:
http://www.faculty.idc.ac.il/avidan/Traj-Trian-Pami.pdf

i havent finished reading (so perhaps it explained in further pages) and i encoutered to words 3D line.
now i presume D represents dimension so the next question is how can a line be a 3d if it's by definition is 1d?

perhaps it something with the terminology of the computer science any way what do you think?

[MathematicalPhysicist]

this T.T has connection to projective geometry. interesting...

[MathematicalPhysicist]

in page 3 it discuss about plucker coordinates and it states L(represents the line of intersection of the other lines you should read it, it's hard to explain))=P ^ Q
and it's have 4 coordinates wich is weird because they are discussing the trajectory of 3d line and not of a 4d so how can it be?

btw i think i have understood what they meant by 3d line the trajectory is in 3d not line itself.