A tachometric method which yields measurements of satisfactory precision for property surveys makes use of the subtense bar. In Europe where the method is mostly commonly used a horizontal bar with sighting marks on it, usually located 2 meters apart, is mounted on a tripod. The tripod is centred over one end of the line to be measured and the bar is levelled and turned so that it is made perpendicular to the line by sighting on the other end of the line with a small attached telescope.