A method of making-up tubular string components can include inputting to an image processor image data output from at least one camera, the image processor in response detecting positions of a tubular and a mark on another tubular, threading the tubulars with each other while inputting position data from the image processor to a controller, and the controller terminating the threading in response to the position of the mark relative to the position of the first tubular being within a predetermined range. Another method of making-up tubular string components can include, in response to inputting image data to an image processor, the image processor detecting longitudinal positions of two tubulars, threading the tubulars with each other, and a controller terminating the threading in response to the longitudinal position of one tubular relative to the longitudinal position of the other tubular being within a predetermined range.