Highly accurate Electronic LCD display Reset button Built in compass Measuring wheel Measures up to 999 mm Works on straight curved or irregular lines Full instructions This handy measuring meter is a very accurate instrument for measuring distances between two points on a map plan or physical object. Simply trace the line to be measured with the serrated driving wheel & the length measured in either direction will be registered 11 in milimetres on the LCD display. With the aid of the built in calculator the actual distance can be calculated by multiplying this reading by the scale of the map or drawing