iliali16 0 Newbie Poster

Hi guys, I have the following problem. I am developing an application which will track movements of people the problem is that I am able to track markers in 2D and know their cordinates according to the picture but I need to make them in 3D which means that I can use my first image as a calibration one and have to compute the possiton of markers in 3D assuming that the first image has all the Z values 0. The thing is that i cannot find proper litriture and i am confused. I am attaching a picture so you can see what i am speaking about. Thanks for any info on literature or advice.