Wind speeds can be accurately measured using devices called anemometers. It was first developed in 1450 by the Italian artist Leon Battista Alberti, but was perfected much later in the 20th century. It is a common tool usually found in weather stations. Since the 15th century, their design has changed little. The most easily recognizable forms used in weather forecasting include Cup anemometers. Winged anemometers. The first determines the wind speed, depending on how fast the cup wheel rotates. Improvements to the design by Derek Weston in 1991 also allow them to determine wind directions from cyclical changes in the speed of the dishwheel wheel. Although simple in theory, other factors need to be taken into account before determining actual wind speeds. For example, turbulence caused by the device itself and friction from the mounting point need to be taken into account. A propeller anemometer, on the other hand, a propeller and the same tool combine a tail on the same axis to achieve accurate and precise wind speed and direction measurements. Wind speed is determined using a speed counter, which is then converted to wind speed.