Sphere anemometers are simple devices that use the wind drag force on a sphere to determine the wind speed by equating the weight of the sphere with the drag force in a pendulum like configuration. Modern versions of this device use ping-pong balls. By measuring the angle of deflection of the ball one can measure the wind velocity. There are 4 STL's files available with different scales: m/s (two scales: engraved and 3d) knots (engraved) mph (engraved) There's no need for a conversion table to measure the wind velocity. The dots on the scale are 5 degrees apart. Note the two vertical dots at zero angle. More details here: http://www.diale.org/Ping-Pong-Anemometer.html