Here is a DYI frame to hold a camera (here doing a video) at a consistent height, but must move smoothly over a 5 foot square are.  This project as the making the credits section of a movie.  Credits were positioned in several areas of the desktop (typewriter, pad, newspaper) and the camera moved from one area to the next.  Two cranks mover the camera from one location to the next. We used 1/2″ EMT for the rails, but this could be increased to 3/4″ EMT for a heavier camera.  Pulleys were 1-1/2″ patio door wheels (Home Depot) pressed onto wooden dowels. Project cost less than $50 and can be disassembled for transporting.